Product-related increases in diastolic blood pressure 8. Exercise was perceived as being less strenuous after consumption of the product. Due to the poly-alkaloidal and protoalkaloidal nature of this product, the factor or factors responsible for the effects on blood glucose and diastolic blood pressure cannot be determined.

Seifert et al. The product contained 13 mg p -synephrine as Advantra Z ® , mg caffeine as guarana , and The study involved 14 females and 9 males in a placebo-controlled, crossover design.

Subjects ingested one capsule with each of three meals on day one of treatment, and one more capsule on the morning of the second day. Data were collected 60 min after the last administration of the product.

No differences were observed in heart rate or blood pressure following treatment. This was an acute study which did not provide information on long-term effects, but did demonstrate an increase in energy expenditure.

Stohs et al. The study was a randomized, placebo-controlled, double blind design with the vehicle for the p -synephrine being one ounce of tomato juice. The amount of p -synephrine in the product was verified by independent analysis. Measurements were taken at baseline prior to consuming the product and at 75 min.

At this time point, a 6. No significant effects were observed with respect to blood pressure or heart rate, nor were there any significant differences in responses to a 10 item self-report questionnaire which addressed such issues as nervousness, tension, anxiety, hunger, energy, headache, general discomfort, and sleepiness.

Longer term safety and efficacy studies involving p -synephrine alone are warranted. The amount of p- synephrine in the capsules was determined by high pressure liquid chromatographic analysis. Electrocardiograms, blood pressures, heart rates, blood chemistries and blood cell counts with differentials were determined at baseline, 30 min, 60 min, 90 min, 2 hours, 4 hours, 6 hours and 8 hours, as well as after 5, 10 and 15 days.

Blood samples were drawn after 2 hours after the first dose as well as at 5, 10 and 15 days to measure p -synephrine levels to ensure compliance. p -Synephrine had no significant effect on heart rate, blood pressure, blood chemistries, or blood cell counts, and caused no cardiovascular abnormalities.

Bloomer et al. Methyl-synephrine is purported to occur in nature, does not occur in bitter orange extract, and is of synthetic origin in this product and other products that have been marketed.

For the sake of completeness, the results of these studies will be summarized, but these results will not be incorporated into the general discussion of bitter orange extract and p -synephrine provided below.

Both studies examined the effects of the product on metabolic rate, and plasma free fatty acids, glycerol, norepinephrine and epinephrine levels. The initial study [ 38 ] measured changes over a 90 min time frame in 10 healthy male subjects.

The second study [ 39 ] measured the same parameters over a six hour time frame in 10 healthy male and 10 healthy female subjects. Increases in each of the parameters were observed, with a It is also important to note that significant increases in heart rate as well as systolic and diastolic blood pressure occurred in both studies in response to the consumption of the product.

The authors note that the product may be useful in healthy, normotensive, closely monitored individuals.

However, it is not a product that should be recommended to the general public. In a study similar to those reported by Bloomer et al. Over a three hour time period following ingestion of the product significant increases in resting oxygen uptake and caloric expenditure were occurred.

However, increases in heart rate, systolic blood pressure, tension and confusion were also observed, confirming the highly undesirable properties of this synthetic product. Stohs [ 41 ] has reviewed and assessed the 22 FDA adverse event reports AERs from April through October associated with bitter orange C.

aurantium -containing products, as well as 10 clinical case reports published during this time interval regarding the possible involvement of bitter orange-containing weight management products with cardiovascular incidents and other adverse events.

In all reported AERs and case cases, the products involved were poly-herbal, poly-alkaloidal and poly-protoalkaloidal. Adverse events that have been purported in conjunction with the published clinical case reports included: acute lateral-wall myocardial infarction, exercise-induced syncope associated with QT prolongation, ischemic stroke, ischemic colitis, vasospasm and stroke, variant angina, coronary vasospasm and thrombosis, exercise induced rhabdomyolysis, ST segment myocardial infarction, and ventricular fibrillation [ 41 ].

In one case report it was suggested that a bitter orange-containing dietary supplement may have masked bradycardia and hypotension while exacerbating weight loss in an individual with anorexia nervosa, although no evidence was provided that an adverse event had actually occurred.

Although the products consumed were all multi-ingredient, in each case reference was specifically made to C. aurantium, bitter orange or p -synephrine as the most likely causative agent. A more probable culprit for at least some of these effects may have been the high caffeine intake associated with the products in question.

Another factor to be considered is the occurrence of up to mg p -synephrine per quarter liter of various Citrus juices [ 42 , 43 ] which are widely consumed without the report of adverse events. Millions of individuals ingest p -synephrine and bitter orange-containing food products as orange juices and marmalades as well as dietary supplements on a daily basis.

Therefore, although these case reports should raise the level of awareness with regard to the use of complex weight management products, it is not possible to extrapolate the cause of these adverse effects to the p -synephrine which may have been present in the products.

No evidence showing a direct link between bitter orange extract and the adverse events is provided [ 41 ]. A total of 23 published and unpublished studies involving a total of approximately total human subjects were reviewed.

The authors located information regarding the unpublished studies through presentations at scientific meetings and availability of research reports on the internet, as well as information from the investigators involved in the studies.

Seven of the studies were not published in peer reviewed journals [ 17 - 20 , 25 , 33 , 37 ] Table 2. However, six of these studies were presented at national meetings [ 18 - 20 , 25 , 33 , 37 ], and one of these six studies is in the process of being submitted for consideration for publication [ 37 ].

As noted in the references, information including presentations and final reports are available on the internet regarding these unpublished studies. The results associated with these unpublished studies Table 2 in general are consistent with the results of the published studies Table 1.

Five published studies [ 6 , 24 , 27 , 31 , 36 ] and two unpublished studies [ 33 , 37 ] reported no cardiovascular effects when using p -synephrine bitter orange only containing products. The published studies involved a total of subjects with a total of 31 subjects in the two unpublished studies.

However, in one of these studies [ 24 ] consisting of 12 subjects it is not clear that effects on heart rate and blood pressure were specifically examined, with the authors simply reporting that no adverse effects were observed.

Five published studies [ 15 , 21 , 22 , 26 , 30 , 35 ] using p -synephrine in combination with other ingredients reported no cardiovascular effects.

A total of 88 subjects were involved in these studies. Small cardiovascular effects were reported by Bui et al. Small cardiovascular effects were reported for three studies that involved subjects consuming p -synephrine plus caffeine [ 28 , 32 , 34 ]. reported an increase in heart rate [ 28 ] and diastolic blood pressure [ 34 ] 10 subjects.

Upon careful review, the study of Haller et al. p -Synephrine Advantra Z ® alone had no effect on systolic or diastolic blood pressure. The authors reported an increase in heart rate six hours after treatment.

The half-life of p -synephrine is two to three hours [ 28 , 34 , 45 ]. As a consequence, an increase in heart rate after two to three half-lives when the p- synephrine blood levels will have dropped to one-fourth to one-eighth the peak blood levels would not be expected.

Furthermore, a major complicating factor is that all subjects consumed a meal three hours after ingesting the p -synephrine The cardiovascular and thermic effects of food are well known [ 31 ], and an increase in heart rate in the control group was also observed.

Thus, it is not plausible to attribute the increase in heart rate to p -synephrine, or an increase in heart rate and blood pressure to a product that contained very little p -synephrine 5.

This study did show that the commercial product Xenadrine EFX® which contained only 5. This product was reported to also contain 5.

aurantium extracts are either devoid of octopamine or contain only trace amounts [ 3 ], thus the product being used [ 28 ] appears to have been adulterated.

Hansen et al. These doses represent over 13 times the usual daily dose for p -synephrine and the equivalent of the caffeine in about three cups of coffee given together as a single bolus dose to these animals. When caffeine was added, increases in heart rate and blood pressure were observed [ 46 ].

These studies indicate that in rats at very high doses of p -synephrine the combination with caffeine may result in cardiovascular effects. However, due to the highly inequivalent dosing between this study in rats and typical dosing in humans, the results of this study in rats cannot be directly extrapolated to humans.

A dose of 3. Various studies indicate that the lipolytic activity of p -synephrine is due to binding to β-3 adrenergic receptors in adipose tissues [ 10 ]. These same β-3 adrenergic receptors are also associated with cardiovascular tissues, and their activation results in a down-regulation of cardiovascular stimulation [ 48 , 49 ].

Thus, p -synephrine stimulation of β-3 adrenoreceptors in the cardiovascular system does not result in an increase in blood pressure or heart rate but may exhibit a modulating rather than a stimulatory effect.

This cardiovascular receptor response may explain why an increase in heart rate or blood pressure is not seen in most cases when p -synephrine is used alone or in combination with caffeine in dietary supplements, in spite of the fact that caffeine alone may produce modest increases in these parameters under some conditions [ 50 , 51 ].

Approximately half of the clinical studies involved the use of commercial products. In only one case [ 28 ] was the actual amount of p -synephrine and other protoalkaloids determined, while in the remaining studies involving commercial products the reported amounts of p -synephrine and caffeine were simply based on label claim.

The amount of p -synephrine was independently determined in two studies in which bitter orange extract was used as a single ingredient product [ 36 , 37 ].

Various studies have shown that there are not always good correlations between the label claim of marketed products or the product data sheet and the amount of p -synephrine shown to be present by independent analysis [ 52 - 56 ].

Therefore, the actual amount of p -synephrine consumed in the majority of the studies was not verified. Finally, nine studies involving the administration of bitter orange extract alone or in combination with other constituents have demonstrated an increase in metabolic rate without an increase in heart rate or blood pressure [ 18 - 20 , 26 , 30 - 32 , 35 , 36 ].

These results suggest that bitter orange extract and p -synephrine may be beneficial in weight management. The results involving both published and unpublished clinical studies indicate that p -synephrine alone or in combination with caffeine does not appear to produce significant adverse cardiovascular effects or pose a risk to human health at doses commonly ingested orally.

No adverse effects have been directly attributable to bitter orange extract or p- synephrine. The results indicate that bitter orange extract and p -synephrine increase metabolism and energy expenditure. The data accumulated to date do not support hypothesized concerns regarding potential adverse effects of p -synephrine particularly with respect to the cardiovascular system due to a paucity of binding to α-, β-1 and β-2 adrenergic receptors while exhibiting modest binding to β-3 adrenergic receptors.

All authors have served as consultants for Nutratech, Inc. Nutratech Inc. provided some of the unpublished research reports. Chen JK, Chen TT.

Zhi Shi Fructus Aurantii Immaturus. Chinese Medical Herbology and Pharmacology. City of Industry, CA USA: Art of Medicine Press. Stohs SJ, Shara M. A review of the safety and efficacy of Citrus aurantium in weight management. In: ed.

Bagchi D, Preuss HG. Obesity: Epidemiology, Pathophysiology, and Prevention. Boca Raton, FL, USA: CRC Press. Pellati F, Benvenuti S. Chromatographic and electrophoretic methods for the analysis of phenethylamine alkaloids in Citrus aurantium.

J Chromatog A. Sander LC, Putzbach K, Nelson BC. et al. Certification of standard reference materials containing bitter orange. Analyt Bioanalyt Chem. Evans RL, Pho AN, Roman MC, Betz JM. Penzak SR, Jann MW, Cold JA.

Seville sour orange juice: synephrine content and cardiovascular effects in normotensive adults. J Clin Pharmacol. Bent S, Padula A, Neuhaus J. Safety and efficacy of Citrus aurantium for weight loss. Amer J Cardiol. Nasir JM, Durning SJ. Exercise-induced syncope associated with QT prolongation and ephedra-free Xenadrine.

Mayo Clinic Proceed. Stephensen TA, Sarlay JrR. Ventricular fibrillation associated with use of a synephrine containing dietary supplement.

Military Med. Stohs SJ, Preuss HG, Shara M. A review of the receptor-binding properties of p -synephrine as related to its pharmacological effects. Oxid Med Cell Long. Stohs SJ, Preuss HG. Stereochemical and pharmacological differences between naturally occurring p -synephrine and synthetic p -synephrine.

J Funct Foods. McGuffin M. Media spins numbers on bitter orange AERs based on erroneous information from FDA. The Safety of bitter orange Citrus aurantium and its primary protoalkaloid p -synephrine.

The safety of Citrus aurantium bitter orange and its primary protoalkaloid p -synephrine. Phytother Res. Colker CM, Kalman DS, Torina GC, Perlis T, Street C. Effects of Citrus aurantium extract, caffeine, and St.

John's wort on body fat loss, lipid levels, and mood states in overweight healthy adults. Curr Therap Res. Dulloo AG, Duret C, Rohrer D. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing h energy expenditure and fat oxidation in humans.

Amer J ClinNutr. Kendall-Reed P. Study on the effectiveness of Ultra Slim Down ® for the reduction of body weight. Unpublished report.

Other data were analyzed by one-way analysis of variance ANOVA. A P -value less than 0. As demonstrated in Figures 1 , 2 , Western blot results of CYP1A2, CYP2E1, and CYP3A4 indicated visible upregulation of protein expression in rat liver compared to saline-treated group.

CYP1A2 and CYP3A4 protein expression was significantly induced in all treatment conditions. Similarly, the protein expression of CYP2E1 was significantly up-regulated. FIGURE 1. Grayscale plot of protein expression ration of CYP1A2, CYP3A4, and CYP2E1 in rat liver determined by Western Blot.

FIGURE 2. Relative protein expression ration of CYP1A2, CYP3A4, and CYP2E1 in rat liver determined by Western Blot. The effects of FA on CYP1A2, CYP2E1, and CYP3A4 mRNA expression in rat liver were determined by RT-PCR method.

As shown in Figure 3 , compared with the control group, the mRNA expression of CYP1A2 was significantly induced, especially at the high dosage group; FA seemed to increase CYP3A4 mRNA expression in a dose-dependent manner and statistically significant increase were observed at all treatment conditions, which is consistent with the corresponding CYP protein expression.

However, there were not significant changes in CYP2E1 mRNA expression. FIGURE 3. CYP1A2, CYP3A4, and CYP2E1 mRNA expression in rat liver after orally administration of FA. The concentrations of caffeine, dapsone, and chlorzoxazone in rat plasma were determined by a sensitive and simple UPLC method.

CYP1A2, CYP3A4, and CYP2E1 activities were evaluated by comparing pharmacokinetic parameters of caffeine, dapsone, and chlorzoxazone in control and experimental group. The main pharmacokinetic parameters of caffeine, dapsone, and chlorzoxazone in rats are presented in Table 3.

Mean plasma concentration—time curves of caffeine, dapsone, and chlorzoxazone are presented in Figure 4. The results indicated that the metabolisms of caffeine and dapsone in experimental group were evidently accelerated and that potential induction of rat hepatic CYP1A2 and CYP3A4 activities was evidence-based in presence of FA.

TABLE 3. Main pharmacokinetic parameters of caffeine, dapsone, and chlorzoxazone in rat plasma. FIGURE 4. Blank control group BCG received saline for 7 days; HLG experimental group received 30 g kg -1 day -1 FA extraction. Error bars represent SD. The UPLC chromatogram implied that there were complex components with several peaks at different retention times in the FA-medicated serum Figure 5 , those components including prototype drug component and their metabolites.

The retention time of reference standards meranzin hydrate, naringenin, and hesperetin was 5. With regard to retention time and UV wavelength of reference substances, it was verified that the FA-medicated serum contained meranzin hydrate, naringenin, and hesperetin.

FIGURE 5. UPLC-PAD chromatograms of sulfamethoxazole 1 , meranzin hydrate 2 , naringenin 3 , and hesperetin 4 in serum. A Blank serum, B FA-mediated serum, and C blank serum added the standard substances. The MTT assay was applied to assess the effect of FA-medicated serum on HepG2 cell viability, which was presented in Table 4.

Thus, the serum could be used for further study. The RT-PCR analysis, which was shown in Figure 6 , was performed to determine the effects of FA-medicated serums on CYP1A2, CYP3A4, and CYP2E1 mRNA expression in HepG2 cells. FA-medicated serum seemed to increase CYP1A2 mRNA expression in a dose-dependent manner; statistically significant increase was observed at the high dosage group.

However, there was very small, not significant change in CYP2E1 mRNA expression. FIGURE 6. CYP1A2, CYP3A4, and CYP2E1 mRNA expression in HepG2 cells cultured with FA-mediated serum using real-time PCR.

In other word, Herbal medicines play important roles in the primary health care of individuals and communities. But there is a potential risk of unexpected drug—drug interactions when patients administrate herbs and prescribed modern medication simultaneously without informing their physician of their herb use Ooi et al.

The classical herb implicated with drug—drug interactions is St. Pharmacokinetic interaction is one category of drug—drug interaction Pal and Mitra, , which mainly attributed to the induction or inhibition of specific CYPs.

The CYPs superfamily is one of the most important drug-metabolizing enzyme systems and involves in the biotransformation of a large number of exogenous and endogenous compounds Wang et al. Depending on how the drugs interact with CYPs, it can be beneficial by enhancing blood levels or detrimental leading to therapeutic failure Pal and Mitra, Such interactions may lead to lower bioavailability and subtherapeutic plasma drug concentrations Kumar et al.

In this study, we investigated the effects of the herb FA on hepatic CYP1A2, CYP2E1, and CYP3A4. In our study, FA significantly induced CYP2E1 protein expression, but did not appear to have significant effect on the corresponding mRNA expression in rat liver. Previous studies have proved that the expression of specific mRNAs and subsequent accumulation of corresponding proteins are not always in accordance Nakaminami et al.

The research has demonstrated that the CYP3A4 mRNA level correlated significantly to the CYP3A4 protein level, which was not the case for CYP2E1 Sumida et al. It has also been demonstrated that CYPs in the liver usually are regulated at the transcriptional level except for CYP2E1.

Despite that the mRNAs are the source of protein content, protein expression, namely CYP2E1, can be regulated at various levels including pre-transcription, transcription, pre-translation, translation, and post-translation Sumida et al.

This may explain our results that CYP2E1 mRNA expression and its corresponding protein expression is not completely consistent. It is reported that the most common mechanism of CYP induction is transcriptional activation resulting in the increased protein synthesis of CYP enzymes Døssing et al.

Thus, For CYP2E1, our result indicates that FA is unlikely to significantly affect CYP2E1 until the clinical researches are conducted. For CYP1A2 and CYP 3A4, the present results showed that FA up-regulated CYP1A2 and CYP3A4 significantly not only from the protein expression but also from the mRNA expression in rat liver.

This suggests that FA is potential to induce CYP1A2 and CYP3A4 before completing the clinic trial. Another reason for our conclusions was based on the fact that FA had the potential to induce rat hepatic CYP1A2 and CYP3A4 activities responsible for relevant alterations of probe drug plasma levels, and was not able to induce or inhibit rat hepatic CYP2E1 activity in the experiment.

These imply that the potential risk of drug—drug interaction will occur when FA is consumed accompanied with CYP1A2 or CYP3A4 substrates. Conversely, there is low probability of pharmacokinetic interaction between FA and substrates of CYP2E1.

The CYPs mRNA expression in HepG2 cell is based on HepG2 cell model, serum pharmacological method, UPLC method, and MTT assay for reasons as follow: first, HepG2 cells, the human liver cancer cell with different gene expression profiles, are known to constitutively express CYP1A2, CYP2E1, and CYP3A4 Ooi et al.

Besides, HepG2 cell model is easy to obtain, control, and perform without the inter-individual and inter-species variation and interpretation difficulties, which could accurately evaluate the potential inductive effect for drugs Cui et al.

Second, Serum pharmacological method is frequently adapted to the study of herb medicines, as it not only eliminates the interferences of the physical and chemical characters of crude drugs on the experimental results, but also provides the experimental conditions similar to the in vivo environment Yin et al.

It has been reported that the AUC0-t of naringenin and hesperetin were much higher than those of flavanone glycosides in rat plasma following oral administration of FA extract, which might result from the hydrolysis of flavanone glycosides naringin, hesperidin, and neohesperidin Tong et al.

Meranzin hydrate was considered as one major component of FA and induced similar effect to FA on intestinal motility Huang et al. Hence, in our present study, naringenin, hesperetin, and meranzin hydrate were selected to be detected as the bioactive compounds in FA-mediated rat serum Figure 1.

Fourth, the result of MTT assay showed that FA-medicated serum at the three different concentrations did not exhibit significant cytotoxicity against HepG2 cells, which exclude the effect of the variable-the activity and number of HepG2 cells on the result of PCR analysis.

In our study, FA-medicated serum increased CYP1A2 and CYP3A4 mRNA expression with statistically significant difference compared to the control group, while there was not significant change in CYP2E1 mRNA expression.

This result supported the conclusion get in rat above. A previous study showed that water extract of FA immature increased CYP3A4 protein expression and ethanol extract of FA immature induced CYP3A4 expression via induction of PXR expression Okada et al.

They speculated that narirutin might be the key constituent increasing PXR expression and CYP3A4 protein expression. It is well known that the efficacy of herbs is significantly correlated with active constituents in herbs. Narirutin is also one of the major flavonoids in FA and thought to be biological active Huang et al.

It has similar effects to FA to some extent Huang et al. Thus, narirutin might be a main compound contributing to the slight induction of FA on CYPs. This needs further experiments to test the hypothesis. The CYP enzyme induction, one of the common cases of metabolic enzymes related to drug—drug interaction beside the drug metabolism inhibition, causes serious clinical consequences Cui et al.

For drugs that produce therapeutic effects primarily by the prototype drug, induction may result in a reduced therapeutic efficacy of co-administrated drugs, or even lead to therapy failure Lin, For that, the dosage of drugs should be modified within their safe range clinically.

For example, rifampin interacts with warfarin resulted from its enzyme inducer activity on CYP2C9, CYP3A4, CYP1A2, and CYP2C There was a case report that a female on anticoagulation increased warfarin dose from Multiple dose adjustment may occur when FA is combined with CYP1A2 or CYP3A4 substrates with a narrow therapeutic index.

Besides, induction may increase the risk of metabolite-induced toxicity by increasing reactive metabolite formation, such as CYP1A induction Lin, Our study shows that FA may be a potential inducer of CYP1A2, CYP3A4, and may not be able to affect CYP2E1 until the clinic researches are performed.

Thus, caution should paid to reduce adverse drug—drug interaction when FA is administrated combined with CYP1A2 or CYP3A4 substrates.

XQ contributed the conception and the design of this study. LZ and MC conducted the experiments. LZ and XQ wrote the main manuscript text. All the authors participated in performing the laboratory analyses and interpreting the data.

All the authors read and approved the final manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. This research was supported by the China Postdoctoral Science Foundation Grant No.

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Springerplus Fan, R. The right adrenal tissue stored in acetic acid was used for analysis. The subsequent steps were performed as previously described From each tissue, non-serial sections 5 μm thick were obtained microtome Microtec-CUT , SC, USA.

Digital images were acquired randomly TIFF format using an Olympus DP71 camera coupled to an Olympus BX40 light microscope Olympus, Japan. Ten photomicrographs per animal were used. BAT digital images were analyzed, and their areas were calculated.

All photomicrographs were measured with Image-Pro Plus 5. Total RNA was extracted from BAT samples using the RNeasy Lipid Tissue kit Qiagen, Germantown, Maryland following the protocol described by the manufacturer.

cDNA was synthesized using a reverse transcription kit Applied Biosystems Thermo Fisher Scientific, Massachusetts, USA , and the samples were incubated in a thermocycler Applied Biosystems Veriti 96 Well Thermal Cycler.

The primers were purchased from TaqMan Thermo Fisher Scientific Supplementary Table 2. In each reaction plate, the negative control without sample C- , the negative control without enzyme RT- , and the standard curve of serial dilution corresponding to the gene of interest were added.

The results were expressed in relation to the expression values of their control groups, which were 1 and normalized to the standard curve. Subsequently, we used these values for statistical analysis. The efficiencies of each test were calculated from a serial dilution curve present on each plate, using only plates whose efficiencies were between 85 and Brown adipose tissue respiration was determined as previously described 40 , 41 with minor modifications.

BAT was prepared for measurements of respiratory flux rates by mechanic dissection with sharp forceps in relaxing buffer BIOPS; in mM: CaK2EGTA 2. After that, the interscapular brown adipose tissues were washed in ice-cold respiration medium MIR05—in mM: EGTA 0.

The respiratory rates of BAT were determined with the Oroboros 2k-Oxygraph Oroboros Instruments, Innsbruck, Austria in 2 ml of MIR05 at 37°C with continuous stirring. Before adding the tissue into the chamber, wet weight measurements were taken, and a sample of 5—7 mg was used per chamber.

All measurements were taken at oxygen concentrations above nmol ml-1 in the chamber. DatLab software Oroboros Instruments, Innsbruck, Austria was used for data acquisition and analysis. Digitonin is used to permeabilize the cell membranes while leaving the mitochondrial membranes intact because of its specificity for solubilizing cholesterol, which exists in much higher concentrations in the plasma membrane.

The study was carried out with two groups of independent substrates in each chamber: chamber A, in mM glutamate 10, pyruvate 5, malate 2, ADP 1 and succinate 10, for the analysis of carbohydrate-related oxidation with electron entry through complexes I and II of the respiratory chain and chamber B, in mM palmitoyl-carnitine 0.

The addition of cytochrome c 10 μM allowed for the evaluation of the integrity of the mitochondrial membrane because an increase in respiration with the addition of cytochrome c indicates a defect in the outer mitochondrial membrane Statistical analyses were performed using GraphPad Prism software version 6.

The body weights of normal litters NL and small litters SL during lactation PND21 are shown in Figure 2. The small litter group SL had a higher body weight than the normal litter group NL on PND4 until weaning PND21, SL: 3.

NL: 2. Figure 2. Evolution of body weight during the lactation period 21 days of mice raised in normal NL and small SL litters. The SL group had a higher body weight NL: SL: SL: 3.

aurantium and synephrine did not show significant differences in fat mass with the NL groups Figure 3D.

Figure 3. Effect of treatments with C. aurantium and synephrine on body weight A,C , body composition by Nuclear Magnetic Resonance B,D and tissue weight of visceral WAT E and BAT F of mice raised in normal and small litters in the pre-treatment A,B and post-treatment C—F period.

NL A,B. NL-Syn C,D. SL-Syn E,F. The accumulated body weight from PND30 to PND49 is depicted in Figure 4. The SL groups treated with C. Figure 4. Accumulated weight gain of mice raised in normal and small litters submitted to treatment with C.

There was no significant difference in heart rate Supplementary Figure 1A , systolic blood pressure Supplementary Figure 1B , and diastolic blood pressure Supplementary Figure 1C in the normal and small litter groups treated with C.

aurantium and synephrine or vehicle. There was no significant difference in the OGTT Supplementary Figure 2A or the area under the curve AUC of the OGTT Supplementary Figure 2B in the normal and small litter groups treated with C. The plasma concentration of leptin in the SL groups treated with C.

aurantium and synephrine was not different from that in the NL groups or SL vehicle group Figure 5A. Figure 5. Effect of treatment with C.

aurantium and synephrine in hormonal dosages. Plasma leptin A , Total T3 B and Free T4 C. There was no significant difference in the absolute catecholamine content in the adrenal gland Figure 6A.

There was no significant difference in plasma corticosterone Figure 6C. Figure 6. aurantium and synephrine on the medulla adrenal and plasma corticosterone.

aurantium and synephrine 2-fold-increase vs. NL -Syn; 2-fold-increase vs. Treatment with C. aurantium and synephrine was able to restore the lipid droplet size and quantity of nuclei in the small litter groups.

Figure 7. BAT histology by Hematoxylin—Eosin HE staining with 40× magnification. Quantitative analysis of lipid droplets and nucleus number of the BAT. Figure 8 shows biomarkers related to thermogenesis in BAT. The NL groups did not show differences in gene expression in BAT.

aurantium and synephrine showed increased gene expression of UCP-1, PRDM16, PGC-1α, and PPARγ. Treatment of the SL group with C. SL groups treated with C. The SL-Syn group showed higher relative mRNA expression of PRDM than the SL and NL groups 2.

No significant difference was observed in the gene expression of CPT Figure 8D , ADRβ-3 Figure 8E , or BMP7 Figure 8G. However, treatment with C. Figure 8. aurantium and synephrine on thermogenic factors in BAT. Also, SL-Syn group presented no changes in all parameters of BAT mitochondrial function evaluated.

Figure 9. High resolution respirometry of brown adipose tissue from overfeed mice. Flux per mass with substrates pyruvate, glutamate, malate, and succinate A. Flux per mass with substrates palmitoyl-L-carnitine, malate, and ADP B.

It is well known that overfeeding early in life causes metabolic effects in the short- and long-term, but such effects are poorly investigated in adolescence.

The reduction in litter size is an effective and reproducible model of obesity 12 , 15 , Our results demonstrated that both overweight and metabolic changes typical of obesity persist from lactation to adolescence.

Moreover, the administration of Citrus aurantium or its active compound, synephrine, proved efficacious in ameliorating certain metabolic dysfunctions induced by postnatal overfeeding, employing distinct mechanisms.

Conceicao et al. We find at PND30, overweight and high body fat in SL group by body composition NMR analyses. Furthermore, we showed that the SL group showed higher body weight from PND4 until adolescence. Studies were carried out upon utilization of products derived from medicinal plants and nutraceuticals for the management of obesity and metabolic disorders Until this moment, no studies have demonstrated the effects of C.

aurantium and synephrine at the same doses and period adolescence used in the current investigation. Here, we used a smaller dose than the one usually used in other studies because it would not be interesting to use elevate adrenergic agonist dose in adolescent animals.

Hansen and collaborators 30 demonstrated, in adult female rats, that the administration of C. In agreement, we also observed that the SL group treated with C. aurantium or synephrine did not show significant differences in body weight and body fat on PND Synephrine, due to it is an adrenergic agonist effect and its similarity to ephedrine, has potential adverse effects upon the cardiovascular system However, we did not show changes in heart rate or systolic or diastolic blood pressure in the treatments with C.

aurantium extracts and synephrine. Citrus aurantium has been associated with improvement in hyperglycemia Although obese, the SL group had no changes in glucose homeostasis, with no significantly different in TOTG compared to the NL group.

Litter size reduction programming impairs leptin signaling and causes leptin resistance at PND 37 , Corroborating these findings, the SL group showed hyperleptinemia, indicating leptin resistance in these animals as early as 50 days old.

However, C. aurantium and synephrine slightly reduced this hyperleptinemia induced by overfeeding. In the literature, no studies were found about the effect of C.

aurantium and synephrine on leptin secretion and signaling. Thus, precocious treatment with C. aurantium may prevent those animals from developing future glucose intolerance since leptin resistance can be one contributor factor to insulin resistance.

Rodrigues and collaborators 37 showed that, in PND21, the SL group had high TSH and serum thyroid hormone concentrations.

However, on PND, this group showed normal TSH and lower T3 and T4 in serum. Here, treatment with C. aurantium increased total T3 and free T4 compared to all NL groups in this study, and synephrine SL-Syn increased even more because it was higher than in the SL group.

As there are no studies focusing the interplay between thyroid function and C. aurantium or synephrine , more studies are needed to better understand the mechanisms involved.

aurantium , other than synephrine, can increase adrenal catecholamines, which can occur either by greater synthesis or by accumulation due to deficient secretion. We measured only tissue catecholamines, and this increase was not enough to alter cardiovascular parameters. However, this change may have resulted in a slight increase in circulating adrenaline, inducing lipolysis in white and brown adipocytes, through their interaction with β-3 adrenergic receptors Only one in vitro study has reported the influence of C.

aurantium on the differentiation and activation of brown adipocytes through anti-adipogenic and thermogenic mechanisms In the current study, we explored the in vivo anti-obesity potential of C. aurantium extracts and its main active component, synephrine, in brown adipose tissue dysfunction of adolescent mice programmed by early postnatal overfeeding.

The whitening of BAT occurs in obesity. In this process, BAT has increased tissue mass with large lipid droplets, low vascularization, high pro-inflammatory cytokine expression, and low UCP-1 and other thermogenesis marker expression 13 , 48 , causing dysfunction.

In the qualitative and quantitative analyses of BAT, we demonstrated a reduction in its mass and in the content of lipid vesicles and an increase in the number of nuclei in the SL groups treated with C.

aurantium and synephrine, showing that the treatments normalized the BAT structure and recovered its original phenotype. We investigated some important markers of thermogenesis and activity in BAT, such as UCP-1, PRDM16, PCG-1α, CPT-1, beta-3AR, PPARγ, and BMP-7 Furthermore, we found, in general, higher gene expression of UCP1, PRDM 16, PGC-1α, and PPARγ, demonstrating the thermogenic action of both C.

aurantium and its active compound, synephrine. β-3 adrenergic receptor expression in BAT was unchanged, but we cannot ignore the effect of synephrine β-3 adrenergic ligand on adrenergic receptors. PPARγ is responsible for positively regulating genes involved in lipid oxidation CPT-1 and thermogenesis, such as UCP-1 and PGC-1α responsible for mitochondrial biogenesis and stimulation of UCP-1 gene expression In addition, PPARγ participates in several physiological functions, such as glucose metabolism control, adipocyte differentiation regulation, and inflammatory response regulation.

This receptor is considered a primary regulator of adipogenesis, controlling cell differentiation of preadipocytes into mature adipocytes 51 and acting in the direction of white and brown adipocyte differentiation UCP-1 is a key marker of thermogenesis in BAT.

In experimental models, the absence of UCP-1 is associated with increased body weight and decreased thermogenesis in BAT In our model of obesity induced by litter size reduction, we observed BAT dysfunction and UCP-1 gene expression reduction.

aurantium on BAT was better than synephrine alone that only caused a higher gene expression for PRDM16, a known transcriptional co-regulator capable to directing brown adipogenesis. Mitochondria primarily produce ATP for cellular energy by directing proton flow to ATP synthase.

This occurs when protons, temporarily stored in the intermembrane space, are released into the mitochondrial matrix by uncoupling proteins, reducing the membrane potential, and producing heat rather than ATP Thus, the induced decrease in proton flux is mediated by an increase in UCP1 in adipose tissue, increasing heat production and potentiating weight loss.

This mechanism is important as a therapeutic target in the regulation of body weight.

Controlled Labs. Core Nutritionals. Das Labs Bucked Up. G Fuel. I Prevail Supplements. Innova Pharm. Insane Labz. Iron Rebel. Like A Pro Supplements. Mark Bell Slingshot. Muscle Force. Nature's Best IsoPure.

Nutra Bio. Nuts N More. Oh Yeah! Optimum Nutrition. Pride Foods. Pro Supps. Project AD. Rule 1. Unbound Supplements. Bitter Orange: The Metabolism Boosting Fruit Did you know a specific fruit could help you drop some unwanted weight?

Those include: Synephrine Limonene Octopamine Vitamin C Flavonoids These natural compounds are extracted from the fruit and peel of bitter oranges for higher potency. How Does Bitter Orange Help You Lose Weight? References: U. Department of Health and Human Services.

Bitter orange. National Center for Complementary and Integrative Health. Cleveland Clinic. Stohs, S. A review of the human clinical studies involving citrus aurantium bitter orange extract and its primary protoalkaloid p-synephrine. International journal of medical sciences.

Effects of p-synephrine during exercise: A brief narrative review. A 60day double-blind, placebo-controlled safety study involving citrus aurantium bitter orange extract. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association.

Previous article Next article. Preuss 2 , Mohd Shara 3. Dean Emeritus, Creighton University Medical Center, Omaha, NE , USA; 2. Departments of Biochemistry, Medicine and Pathology, Georgetown University Medical Center, Washington, DC , USA; 3. Faculty of Pharmacy, Jordan University of Science and Technology, Irbid , Jordan.

Preuss, M. This review summarizes the published as well as unpublished human studies involving Citrus aurantium bitter orange extract and its primary protoalkaloid p -synephrine, providing information and an assessment of the safety and efficacy of these widely used products.

The results of over 20 studies involving a total of approximately subjects that consumed p -synephrine alone or in combination with other ingredients are reviewed and critiqued. In general, bitter orange extract alone p -synephrine or in combination with other herbal ingredients did not produce significant adverse events as an increase in heart rate or blood pressure, or alter electrocardiographic data, serum chemistry, blood cell counts or urinalysis.

Longer term studies are needed to further assess the efficacy of these products and affirm their safety under these conditions.

Citrus aurantium extract and its primary protoalkaloidal constituent p -synephrine Figure 1 are extensively used in weight management products and as thermogenic agents. They are also used in sports performance products to enhance stamina. aurantium extract is widely known as bitter orange extract, a product that is derived from the immature green fruits of the Seville orange.

Bitter orange extract is used in weight management products due to its purported effects on metabolic processes, including an increase in basal metabolic rate and lipolysis as well as mild appetite suppression [ 2 ].

Uncertainty has existed concerning the safety of bitter orange extract and p -synephrine. In general, both the lay public and scientific communities have failed to differentiate between p- synephrine which is a phenylethylamine derivative that has the hydroxy group in the para position on the benzene ring and the synthetic m -synephrine phenylephrine which has a hydroxyl group in the meta position on the benzene ring Figure 2.

m -Synephrine exhibits cardiovascular effects but is not a constituent of bitter orange [ 3 - 5 ]. Properties possessed by m -synephrine are inappropriately attributed to bitter orange extract and p- synephrine, and clinical case study reports and reviews involving bitter orange extract frequently make inappropriate references to m -synpephrine see for example [ 6 - 9 ].

A limited number of studies have been conducted with p -synephrine and bitter orange extracts without the addition of various other ingredients and herbal products.

The issue of safety and efficacy is further clouded and complicated by the structural similarity of p -synephrine to ephedrine Figure 3 and other biogenic amines, in spite of the fact that the pharmacokinetics of the these compounds and their receptor binding specificities are vastly different due to significant structural and stereochemical differences [ 10 , 11 ].

As a consequence, markedly different pharmacological properties should be anticipated. Other issues have also obfuscated the picture with respect to the safety and efficacy of bitter orange extract. Some of the extracts that are used are either non-standardized or poorly standardized, making it difficult if not impossible to establish reproducibility.

In some cases, lack of knowledge of the chemical composition of the extracts being used precludes useful comparisons.

Products containing bitter orange extract in most cases contain a variety of other herbal extracts, many of which are caffeine containing. A final issue that has added to the overall confusion regarding bitter orange has been the release of erroneous adverse events information by governmental agencies.

Statements implying that large numbers of adverse events and even deaths due to the use of products containing bitter orange extract have clearly been shown to be incorrect and misleading [ 12 ], but are still widely reported. Several reviews have addressed the safety of bitter orange extract based on animal, in vitro and receptor binding studies as well as some human studies [ 2 , 10 , 13 ].

This review addresses data associated with published human studies, clinical case reports, and unpublished clinical studies. Information with respect to unpublished studies is derived from final research reports available on the internet, presentations at national meetings of professional organizations, and presentations and research reports from the investigators directly involved.

References are cited based on the origin of the information. A limited number of well-designed and controlled human studies have been conducted with bitter orange extracts assessing efficacy and safety.

The majority of studies have been conducted using products that contain not only an extract of C. aurantium , but other ingredients such as caffeine, green tea, ginkgo, ginseng, guarana, and yerba mate'. The incorporation of bitter orange extract into products containing other potentially active ingredients makes comparative analyses difficult.

However, several human safety and efficacy studies have been conducted on bitter orange extract p -synephrine alone. Colker et al. The product which was consumed on a daily basis contained mg C.

John's wort. The total daily intake of phenylethylamine-related protoalkaloids was approximately After six weeks, the treated group lost small but significant amounts of body weight 1.

No significant changes in blood pressure, heart rate, electrocardiographic findings, serum chemistry or urinalysis were noted and no significant changes were observed in the results of the Profile of Mood States Questionnaire for fatigue or vigor.

The treated group also experienced a significant increase in basal metabolic rate as compared to the placebo group. The amount of caffeine consumed daily in the product mg is equivalent to approximately four cups of coffee or over five cups of tea, and is a well-known thermogenic agent [ 16 ].

It is not clear whether the weight loss and increase in basal metabolic rate were due to the caffeine, the bitter orange extract, exercise, caloric restriction or a combination thereof. This combination of ingredients and protocol appeared to be effective and safe for promoting modest fat and body weight loss in healthy, overweight adults, although the number of subjects in the study was small [ 15 ].

Kendall-Reed [ 17 ] conducted a 10 week unpublished study on a system Ultra Slim Down ® that consisted of two products Table 2. The final report of the study is available on line. One product contained mg hydroxycitric acid Citrimax TM , mg bitter orange extract Advantra Z ® and 50 mg kola nut extract, while the second product contained mg chitosan.

Thirty-two overweight subjects were divided into three groups and either given the two products one capsule of each in conjunction with each meal , a diet and exercise program, or the products in conjunction with the diet and exercise program.

At the end of the study no adverse side effects were observed or reported. The group consuming the product-only lost an average of 4.

In summary, consumption of the products alone was more effective than diet and exercise, while consuming the products in combination with diet and exercise was most effective. No adverse effects were reported. This study was not published and subjected to peer review. Possible cardiovascular effects of Seville sour orange juice in normotensive adults were assessed by Penzak et al.

Twelve subjects consumed 8 ounces of orange juice approximately 13 mg p -synephrine and water in a crossover design followed by repeat ingestion 8 hours later.

Hemodynamic parameters including heart rate and blood pressure did not significantly differ between control and treated groups. In spite of the lack of evidence, the authors concluded that individuals with tachyarrhythmias, severe hypertension and narrow angle glaucoma as well as monoamine oxidase inhibitor receptors should avoid Seville orange juice.

The warning was based on the erroneous assumption that the form of synephrine present in the orange juice was m -synephrine [ 6 ]. Kalman and associates have conducted three unpublished studies using a commercial weight loss product Xenadrine EFX ® Table 2.

The product contained a proprietary blend of extracts from C. aurantium bitter orange , yerba mate, grape seed, green tea and ginger root in addition to several vitamins and amino acids.

The product contained 6 mg p -synephrine, mg caffeine and mg catechin polyphenols in capsule form. The results of these studies were presented at various scientific meetings, but were never published in a scientific journal and subjected to peer review. In each of these studies it is not possible to determine the role of p -synephrine in the observed effects.

A double blind cross-over study involving 6 healthy human subjects who received two capsules of Xenadrine EFX ® 12 mg p -synephrine Kalman et al. A significant increase 2. No effects on heart rate or blood pressure were observed, and no subjective complaints or adverse events were reported.

Kalman et al. Basal metabolic rates were determined at baseline, four hours after a standardized meal at which time two capsules of Xenadrine EFX ® or the placebo were ingested, and hourly for the next five hours.

At the two and three hour time points after ingestion of the product relative to the control, No significant differences in heart rate or blood pressure were observed in response to the product relative to baseline and control values.

No significant effects of the product were noted as compared to the placebo group with respect to blood pressure, heart rate, electrocardiographic data, fasting blood glucose, renal function, hepatic function or complete blood count with differentials over the 14 days of the study.

The treated group experienced a significant reduction in fatigue levels, while sleep quality was negatively impacted. At the end of the study, the treated group experienced a reduction in diastolic blood pressure as compared to the placebo group The authors concluded that the product was safe over the course of the study [ 20 ].

No weight loss was observed over the two weeks of the study. Half of the subjects were randomly assigned to either the treatment or control group.

After 8 weeks the experimental group had lost a significantly greater amount of weight than the control group 3. The daily intake of p -synephrine 10 mg was small, and its relative contribution to the overall weight loss cannot be determined.

The study was a 14 day, placebo-controlled double-blinded crossover protocol where subjects received two capsules of the product or placebo for the first seven days and four capsules per day for the next seven days.

Analyses were conducted at baseline, and days seven and No significant differences were observed at any time point between treated and placebo control with respect to systolic and diastolic blood pressures, heart rate, or heart valve function and left ventricular ejection fraction as determined by serial echocardiograms or Doppler echocardiograms.

The maximum amount of p -synephrine 10 mg per day was small compared to the maximum amounts of ephedrine 40 mg per day and caffeine mg per day. A statistically larger proportion of subjects taking the product reported minor adverse effects as dry mouth, increased activity, and sleep disorders, but there were no serious adverse events and no significant difference with regard to cardiovascular measurements heart rate, blood pressures, serial echocardiograms and Doppler echocardiograms between the treated and placebo groups.

Gurley et al. The daily consumption of p -synephrine was The authors concluded that a supplement containing C. aurantium extract did not appear to significantly modulate cytochrome P enzyme activities in human subjects, and therefore posed minimal risk for cytochrome Pmediated, herb-drug interactions.

The bitter orange extract had no significant effect on CYP1A2, CYP2D6, CYP2E1 or CYP3A4, the major drug-metabolizing cytochrome enzymes. No adverse effects were observed. The authors did not assess the possible effects on body weight or blood chemistry.

The study was not published Table 2 , but a copy of the final report is available on line. Of the 65 adults enrolled, 54 completed the study with 6 dropouts from the placebo group and 5 subjects from the product treatment group.

The product contained extracts of bitter orange, guarana and green tea as well as 7-oxo-dehydroandrostenedione DHEA , conjugated linoleic acid and chromium picolinate. The daily consumption of bitter orange extract was mg but the p -synephrine content was not noted.

At the completion of the 8 week study, the treated group lost an average of 2. No significant differences occurred between the treatment and placebo groups with respect to systolic and diastolic blood pressures, heart rate or temperature. Furthermore, there were no significant differences in serum chemistry profiles and complete blood counts between the two groups.

There was also no difference in the reported incidence of adverse events between the two groups and no serious adverse events were reported [ 25 ]. It is not possible to determine the role of p- synephrine and the bitter orange extract in the observed effects. This was a randomized, double-blind placebo-controlled study involving healthy, overweight adults.

A total of 35 subjects completed the 8 week study. Each adult received three capsules of the weight-loss product twice daily or a placebo in conjunction with a calorie-restricted diet and an exercise program. The product also contained 3-acetyloxo-dehydroepiandrosterone 17 mg , Coleus forskohlli extract 50 mg extract, 10 mg forskolin , yerba mate extract mg , guarana extract mg extract, 51 mg caffeine , piperine 1.

The most significant finding of the study was a 7. No significant differences were noted between the treated and the placebo-controlled groups with respect to body weight, body fat, or lean tissue [ 26 ]. No changes in heart rate or blood pressure were observed and no serious adverse events were reported.

The relative role of each of the ingredients cannot be determined. Min et al. This randomized, placebo-controlled, double blind and crossover study involved 18 healthy subjects.

The rate-corrected QT QTc interval and blood pressure were measured before dosing and at 1, 3, 5 and 8 hrs after dosing. The bitter orange extract did not significantly alter the QTc interval or the systolic or diastolic blood pressures at any time point.

Haller et al. The protocol consisted of a randomized, double blind, placebo-controlled crossover design involving 10 subjects with a one-week washout between treatments.

The results showed that the dietary supplement but not the p- synephrine-containing bitter orange extract increased both systolic and diastolic blood pressures at two hours post-treatment, while heart rate increased at six hours by The authors concluded that the pressure effects were not likely caused by the C.

aurantium alone since no blood pressure effect was observed with an 8-fold higher dose of p -synephrine. The authors also concluded that the increase in blood pressure may be attributable to caffeine and other stimulants in the dietary supplement.

The increase in heart rate reported for p -synephrine at 6 hours is not consistent with the pharmacokinetics of p- synephrine or a number of other studies, and is discussed in detail below.

The amounts of the ingredients in the products were verified by analytical analysis. Bui et al. Heart rate and blood pressure were measured every hour for six hours. These investigators reported small but clinically insignificant increases in heart rate, and systolic and diastolic blood pressures for up to five hours.

The difference in the results between this study and the study of Min et al. However, these effects on heart rate and blood pressure were small and have not been observed in other studies. Sale et al. As noted above, this product contained bitter orange, guarana and green tea extracts.

Subjects received either the placebo or the product and were followed for seven hours or exercised on a treadmill for 60 min. The product had no effect on ATP utilization under resting or exercise conditions relative to control.

Fatty acid oxidation to ATP decreased while plasma levels of fatty acids increased in response to the product. The product had no effect on resting heart rate or blood pressure. Gougeon et al. No other ingredients were present in the product. The thermic effect of food on a 1. Five capsules of the C.

aurantium extract provided 26 mg p -synephrine, and 4 mg or less each of other phenethylamines Advantra Z ®. The thermic effect of food was determined on an initial 30 subjects. A subset of 11 men and 11 women were additionally studied after ingestion of the bitter orange extract in conjunction with the protein meal, while a another subset of 12 women and 8 men were studied a third time following ingestion of the C.

aurantium -containing capsules alone. The thermic effect of the bitter orange extract was greater in men than women in the absence of a meal. A significant increase in the respiratory quotient occurred in both sexes in response to the bitter orange extract alone.

No significant changes occurred in systolic and diastolic blood pressures or pulse rates when compared with base line values following exposure to the bitter orange extract.

Hoffman et al. aurantium extract, Garcinia cambogia and chromium JavaFit TM over a three hour period of time in a randomized, double blind study which involved 10 healthy, physically active subjects Table 1. The enriched coffee product contained mg caffeine, Significant increases were observed in responders with respect to resting metabolic rate and respiratory exchange ratio.

No significant differences were observed in average heart rate or diastolic blood pressure while a 3 mm Hg increase was observed in the systolic blood pressure. The modest effect on blood pressure is not surprising based on the amount of caffeine in the product.

Talbott et al. aurantium extract product Advantra Z ® while the other half of the subjects received the placebo Table 2. Heart rate and blood pressures were determined at the start of the study and after six weeks. No significant differences were observed between the treated and placebo control groups at the conclusion of the study with respect to these cardiovascular parameters.

No effects on body weight were reported. This study represents the highest dose of p -synephrine for the longest period of time that has been reported. The study was presented at a scientific meeting but never published.

The product Ripped Fuel Extreme Cut TM contained 21 mg p -synephrine and mg caffeine, as well as other ingredients including herbal extracts of green tea, ginger root, cocoa seed, willow bark, and wasabi. The product or placebo was taken one hour prior to 30 min of moderately intense exercise.

No significant treatment-related differences in systolic blood pressure, heart rate or body temperature were observed. Product-related increases in diastolic blood pressure 8. Exercise was perceived as being less strenuous after consumption of the product.

Due to the poly-alkaloidal and protoalkaloidal nature of this product, the factor or factors responsible for the effects on blood glucose and diastolic blood pressure cannot be determined. Seifert et al. The product contained 13 mg p -synephrine as Advantra Z ® , mg caffeine as guarana , and The study involved 14 females and 9 males in a placebo-controlled, crossover design.

Subjects ingested one capsule with each of three meals on day one of treatment, and one more capsule on the morning of the second day. Data were collected 60 min after the last administration of the product.

No differences were observed in heart rate or blood pressure following treatment. This was an acute study which did not provide information on long-term effects, but did demonstrate an increase in energy expenditure.

Stohs et al. The study was a randomized, placebo-controlled, double blind design with the vehicle for the p -synephrine being one ounce of tomato juice. The amount of p -synephrine in the product was verified by independent analysis.

Measurements were taken at baseline prior to consuming the product and at 75 min. At this time point, a 6.

No significant effects were observed with respect to blood pressure or heart rate, nor were there any significant differences in responses to a 10 item self-report questionnaire which addressed such issues as nervousness, tension, anxiety, hunger, energy, headache, general discomfort, and sleepiness.

Longer term safety and efficacy studies involving p -synephrine alone are warranted. The amount of p- synephrine in the capsules was determined by high pressure liquid chromatographic analysis.

Electrocardiograms, blood pressures, heart rates, blood chemistries and blood cell counts with differentials were determined at baseline, 30 min, 60 min, 90 min, 2 hours, 4 hours, 6 hours and 8 hours, as well as after 5, 10 and 15 days.

Blood samples were drawn after 2 hours after the first dose as well as at 5, 10 and 15 days to measure p -synephrine levels to ensure compliance. p -Synephrine had no significant effect on heart rate, blood pressure, blood chemistries, or blood cell counts, and caused no cardiovascular abnormalities.

Bloomer et al. Methyl-synephrine is purported to occur in nature, does not occur in bitter orange extract, and is of synthetic origin in this product and other products that have been marketed. For the sake of completeness, the results of these studies will be summarized, but these results will not be incorporated into the general discussion of bitter orange extract and p -synephrine provided below.

Both studies examined the effects of the product on metabolic rate, and plasma free fatty acids, glycerol, norepinephrine and epinephrine levels.

The initial study [ 38 ] measured changes over a 90 min time frame in 10 healthy male subjects. The second study [ 39 ] measured the same parameters over a six hour time frame in 10 healthy male and 10 healthy female subjects.

Increases in each of the parameters were observed, with a It is also important to note that significant increases in heart rate as well as systolic and diastolic blood pressure occurred in both studies in response to the consumption of the product.

The authors note that the product may be useful in healthy, normotensive, closely monitored individuals. However, it is not a product that should be recommended to the general public.

In a study similar to those reported by Bloomer et al. Over a three hour time period following ingestion of the product significant increases in resting oxygen uptake and caloric expenditure were occurred.

However, increases in heart rate, systolic blood pressure, tension and confusion were also observed, confirming the highly undesirable properties of this synthetic product. Stohs [ 41 ] has reviewed and assessed the 22 FDA adverse event reports AERs from April through October associated with bitter orange C.

aurantium -containing products, as well as 10 clinical case reports published during this time interval regarding the possible involvement of bitter orange-containing weight management products with cardiovascular incidents and other adverse events. In all reported AERs and case cases, the products involved were poly-herbal, poly-alkaloidal and poly-protoalkaloidal.

Adverse events that have been purported in conjunction with the published clinical case reports included: acute lateral-wall myocardial infarction, exercise-induced syncope associated with QT prolongation, ischemic stroke, ischemic colitis, vasospasm and stroke, variant angina, coronary vasospasm and thrombosis, exercise induced rhabdomyolysis, ST segment myocardial infarction, and ventricular fibrillation [ 41 ].

In one case report it was suggested that a bitter orange-containing dietary supplement may have masked bradycardia and hypotension while exacerbating weight loss in an individual with anorexia nervosa, although no evidence was provided that an adverse event had actually occurred.

Although the products consumed were all multi-ingredient, in each case reference was specifically made to C. aurantium, bitter orange or p -synephrine as the most likely causative agent.

A more probable culprit for at least some of these effects may have been the high caffeine intake associated with the products in question. Another factor to be considered is the occurrence of up to mg p -synephrine per quarter liter of various Citrus juices [ 42 , 43 ] which are widely consumed without the report of adverse events.

Millions of individuals ingest p -synephrine and bitter orange-containing food products as orange juices and marmalades as well as dietary supplements on a daily basis.

Therefore, although these case reports should raise the level of awareness with regard to the use of complex weight management products, it is not possible to extrapolate the cause of these adverse effects to the p -synephrine which may have been present in the products.

No evidence showing a direct link between bitter orange extract and the adverse events is provided [ 41 ]. A total of 23 published and unpublished studies involving a total of approximately total human subjects were reviewed. The authors located information regarding the unpublished studies through presentations at scientific meetings and availability of research reports on the internet, as well as information from the investigators involved in the studies.

Seven of the studies were not published in peer reviewed journals [ 17 - 20 , 25 , 33 , 37 ] Table 2. However, six of these studies were presented at national meetings [ 18 - 20 , 25 , 33 , 37 ], and one of these six studies is in the process of being submitted for consideration for publication [ 37 ].

As noted in the references, information including presentations and final reports are available on the internet regarding these unpublished studies. The results associated with these unpublished studies Table 2 in general are consistent with the results of the published studies Table 1.

Five published studies [ 6 , 24 , 27 , 31 , 36 ] and two unpublished studies [ 33 , 37 ] reported no cardiovascular effects when using p -synephrine bitter orange only containing products.

The published studies involved a total of subjects with a total of 31 subjects in the two unpublished studies. However, in one of these studies [ 24 ] consisting of 12 subjects it is not clear that effects on heart rate and blood pressure were specifically examined, with the authors simply reporting that no adverse effects were observed.

Five published studies [ 15 , 21 , 22 , 26 , 30 , 35 ] using p -synephrine in combination with other ingredients reported no cardiovascular effects. A total of 88 subjects were involved in these studies. Small cardiovascular effects were reported by Bui et al. Small cardiovascular effects were reported for three studies that involved subjects consuming p -synephrine plus caffeine [ 28 , 32 , 34 ].

reported an increase in heart rate [ 28 ] and diastolic blood pressure [ 34 ] 10 subjects.