Synephrine and Its Derivative Compound A: Common and Specific Biological Effects.

This review is focused on synephrine, the principal phytochemical found in bitter orange and other medicinal plants and widely used as a dietary supplement for weight loss/body fat reduction. We examine different aspects of synephrine biology, delving into its established and potential molecular targets, as well as its mechanisms of action. We present an overview of the origin, chemical composition, receptors, and pharmacological properties of synephrine, including its anti-inflammatory and anti-cancer activity in various in vitro and animal models. Additionally, we conduct a comparative analysis of the molecular targets and effects of synephrine with those of its metabolite, selective glucocorticoid receptor agonist (SEGRA) Compound A (CpdA), which shares a similar chemical structure with synephrine. SEGRAs, including CpdA, have been extensively studied as glucocorticoid receptor activators that have a better benefit/risk profile than glucocorticoids due to their reduced adverse effects. We discuss the potential of synephrine usage as a template for the synthesis of new generation of non-steroidal SEGRAs. The review also provides insights into the safe pharmacological profile of synephrine.

Review of Case Reports on Adverse Events Related to Pre-workout Supplements Containing Synephrine.

The use of pre-workout supplements has become increasingly popular, including the use of supplements containing synephrine. Synephrine might stimulate weight loss and improve sports performance by its proposed adrenergic properties. However, with its increasing popularity, numerous cases of adverse events related to synephrine use have been reported. This study provides a comprehensive overview and analysis of current case reports related to the supplemental use of synephrine. The scientific literature on cases of adverse events related to synephrine intake was collected through August 2021 using Pubmed and Google Scholar and subsequently reviewed and analysed. We obtained 30 case reports describing a total of 35 patients who suffered from medical complaints following use of synephrine-containing supplements. The patients most often presented with chest pain, palpitations, syncope and dizziness. Commonly raised diagnoses were ischaemic heart disease, cardiac arrhythmias and cerebrovascular disease. Five patients were left disabled or remained on medication at last follow-up. We here show an association between the use of pre-workout supplements containing synephrine and adverse events, mainly related to the cardiovascular system. However, we cannot exclude a role of possible confounding factors such as caffeine. Thus, the use of pre-workout supplements containing synephrine may lead to serious adverse health events, and therefore, caution is needed.

Effects of p-Synephrine during Exercise: A Brief Narrative Review.

The p-synephrine is the principal phytochemical found in bitter orange (Citrus aurantium). This substance is widely included in dietary supplements for weight loss/body fat reduction due to its potential benefits of increasing fat oxidation. For years, p-synephrine-containing dietary supplements have been marketed without proper knowledge of their true effectiveness to enhance fat utilization, especially when combined with exercise. However, the effects of p-synephrine on fat oxidation during exercise have been investigated in the last few years. The aim of the current discussion is to summarize the evidence on the effects of p-synephrine intake on fat oxidation and performance during exercise. Previous investigations have demonstrated that the acute intake of p-synephrine does not modify running sprint performance, jumping capacity, or aerobic capacity. However, the acute intake of p-synephrine, in a dose of 2-3 mg/kg of body mass, has been effective to enhance the rate of fat oxidation during incremental and continuous exercise. This effect has been observed in a range of exercise workloads between 30% and 80% of peak oxygen uptake (VO2peak). The p-synephrine has the ability to increase the maximal rate of fat oxidation during exercise of increasing intensity without affecting the workload at which maximal fat oxidation is obtained (Fatmax). The effect of p-synephrine on fat oxidation is normally accompanied by a concomitant reduction of carbohydrate utilization during exercise, without modifying the energy expended during exercise. The shifting in substrate oxidation is obtained without any effect on heart rate during exercise and the prevalence of adverse effects is negligible. Thus, the acute use of p-synephrine, or p-synephrine-containing products, might offer some benefits for those individuals seeking higher fat utilization during exercise at low to moderate intensities. However, more research is still necessary to determine if the effect of p-synephrine on fat oxidation during exercise is maintained with chronic ingestion, in order to ascertain the utility of this substance in conjunction with exercise programs to produce an effective body fat/weight loss reduction.

[Synephrine in dietary supplements and specialized foodstuffs: biological activity, safety and methods of analysis].

Synephrine is a natural protoalkaloid of the bitter orange Citrus aurantium L., it has structural similarity to ephedrine and adrenaline. Synephrine in the form of bitter orange extract is widely used as an ingredient of dietary supplements (DS) and specialized foodstuffs (SF) intended for weight loss and fitness improvement. Along with thermogenic and lipolytic effects, synephrine can cause cardiovascular side effects, especially when combined with caffeine and physical activity. This aspect is important, insofar as the main consumers of weight loss products are overweight people who are at risk of developing cardiovascular diseases. The aim of the research is a hygienic assessment of the usage of bitter orange extract and synephrine in DS and SF, which includes an analysis of approaches to technical regulation in the Russian Federation and abroad, a review of data on biological activity, safety, types of adulteration and methods for the determination of citrus protoalkaloids. Results. The adrenergic effect of bitter orange is caused by the presence of R-(-)-psynephrine, making up about 90% or more of the total protoalkaloids. Dry bitter orange fruit extracts, standardized to synephrine content, which can vary from 4 to 98%, are used in the production of DS and SF. Synephrine is a weak adrenergic agonist, acting primarily through ß3-adrenergic receptors, stimulating lipolysis. Because of insufficient safety data, the consumption of synephrine is regulated in the Russian Federation and abroad. The upper permissible level of synephrine consumption in the Russian Federation is 30 mg per day. Various cases of adulteration of DS and SF for weight loss and sport nutrition have been revealed: undeclared addition of synephrine in the form of bitter orange extract, addition of synthetic synephrine, its isomers or analogs. The main method for the determination of synephrine and other biogenic amines in DS and SF is high performance liquid chromatography with ultraviolet and/or mass detection. Conclusion. The data presented in the review confirm the feasibility of developing an official method for determination of main protoalkaloids and monitoring of DS and SF for the content of synephrine and other citrus protoalkaloids on its basis.

Review of Published Bitter Orange Extract and p-Synephrine Adverse Event Clinical Study Case Reports.

p-Synephrine is the primary active ingredient in bitter orange (Citrus aurantium) extract and is present in other citrus species. This review summarizes all known case reports that have been published regarding adverse events associated with multi-ingredient dietary supplements containing bitter orange extract. A common characteristic of all the case studies was the assumption that if bitter orange extract is listed on the label of the product it is the most likely cause of any adverse effect, although in no case was the presence of p-synephrine determined or a direct link demonstrated. No case study reviewed the existing published literature, and all failed to note that numerous clinical studies have not demonstrated adverse effects at commonly used doses. Most studies did not indicate the composition of the product involved, and no study analyzed the product in question. In no case was a direct correlation between the event and p-synephrine made. Although p-synephrine and ephedrine have some structural similarity, the structural differences result in markedly different pharmacokinetic, physiological, and pharmacological effects, and thus the effects produced by ephedrine cannot be extrapolated to p-synephrine.

Phytochemical compounds in sport nutrition: Synephrine and hydroxycitric acid (HCA) as examples for evaluation of possible health risks.

Numerous food supplements contain phytochemical compounds as active ingredients. Although such supplements are often perceived by consumers as being risk-free, the safety of many of them is currently uncertain. The present review provides two examples for risk assessment for phytochemical ingredients that are used in certain supplements marketed for sportspeople-synephrine (extracted from fruits of Citrus aurantium) and hydroxycitric acid (HCA, isolated from fruits of Garcinia cambogia). Animal and human studies, as well as case reports, provide evidence for cardiovascular effects due to ingestion of high synephrine doses, especially in combination with caffeine and physical exertion. A dose of up to 6.7 mg synephrine/day, however, which is equivalent to the median dietary intake from conventional foods in Germany, is presumed to represent a safe intake from supplements. In subchronic animal studies, administration of high doses of certain HCA-containing preparations led to testicular toxicity (i.e., testicular atrophy and impaired spermatogenesis), yielding a no observed adverse effect level of 389 mg HCA/kg bw/day. In view of lack of adequate human data on the safety of HCA preparations, particularly with respect to the human male reproductive system, substantial uncertainties exist regarding the safety of supplements containing high amounts of HCA.

[Risk assessment of synephrine in dietary supplements]. / Gesundheitliche Risiken von Synephrin in Nahrungsergänzungsmitteln.

Synephrine is a sympathomimetic phenylethylamine derivative that occurs naturally in citrus fruits. It is often added to dietary supplements intended for weight loss and enhancement of sports performance, typically in the form of Citrus aurantium extracts and in many cases in combination with caffeine. The health risks of synephrine were evaluated on the basis of the available toxicological data and in accordance to the EFSA guidance on the safety assessment of botanicals and botanical preparations intended for use in food supplements. In animal studies, orally applied synephrine induced adrenergic effects on the cardiovascular system (increase of blood pressure, ventricular arrhythmias), which were enhanced by the concomitant application of caffeine as well as physical activity. Some human intervention studies investigating the acute effects of synephrine on blood pressure and heart rate of healthy, normotensive test persons indicate that synephrine can induce cardiovascular effects in humans. A series of published case reports of adverse cardiovascular effects (hypertension, cardiac arrhythmia, myocardial infarction) were associated with consumption of synephrine- and caffeine-containing dietary supplements. In conclusion, consumption of high amounts of synephrine, especially in combination with caffeine and physical exercise, is associated with an increased risk of adverse effects on the cardiovascular system. According to the assessment by the BfR (Bundesinstitut für Risikobewertung), daily intake of synephrine through dietary supplements should not exceed the median intake from conventional foods.

Synephrine-containing dietary supplement precipitating apical ballooning syndrome in a young female.

Apical ballooning syndrome (ABS) is a unique reversible cardiomyopathy that is frequently precipitated by emotional or physical stress. In addition, the few drugs reported to precipitate ABS were either illegal or strictly controlled for medical use. This paper reports a case of ABS precipitated by a dietary supplement. Our case accentuates the potential risk of dietary supplements containing synephrine, which is uncontrolled and available to the general public. Therefore, the Korea Food and Drug Administration should regulate these dietary supplements, and warn healthcare workers and the general public of the potential hazards of the indiscriminate abuse of dietary supplements.

Synephrine-containing dietary supplement precipitating apical ballooning syndrome in a young female

Apical ballooning syndrome (ABS) is a unique reversible cardiomyopathy that is frequently precipitated by emotional or physical stress. In addition, the few drugs reported to precipitate ABS were either illegal or strictly controlled for medical use. This paper reports a case of ABS precipitated by a dietary supplement. Our case accentuates the potential risk of dietary supplements containing synephrine, which is uncontrolled and available to the general public. Therefore, the Korea Food and Drug Administration should regulate these dietary supplements, and warn healthcare workers and the general public of the potential hazards of the indiscriminate abuse of dietary supplements.

The safety of Citrus aurantium (bitter orange) and its primary protoalkaloid p-synephrine.

Citrus aurantium (bitter orange) extract and its principal protoalkaloidal constituent p-synephrine are widely used in weight loss and weight management as well as in sports performance products. However, questions are raised frequently regarding the safety of these ingredients. The potential inherent dangers associated with the use of products containing C. aurantium extract are frequently touted, while conversely, millions of doses of dietary supplements have been consumed by possibly millions of individuals in recent years. Furthermore, millions of people consume on a daily basis various juices and food products from Citrus species that contain p-synephrine. This review summarizes current information regarding the safety of C. aurantium (bitter orange) extract and p-synephrine based on human, animal and in vitro assessments as well as receptor binding and mechanistic studies. The data indicate that based on current knowledge, the use of bitter orange extract and p-synephrine appears to be exceedingly safe with no serious adverse effects being directly attributable to these ingredients.

Ventricular fibrillation associated with use of synephrine containing dietary supplement.

As the prevalence of obesity increases in the United States, military personnel are turning to unregulated dietary supplements to aid in weight loss. Some of these supplements may cause more harm than benefit. We report the case of a 27-year-old active duty female who experienced an episode of ventricular fibrillation associated with the use of a dietary supplement containing synephrine. Recommendations for both physicians and the military regarding monitoring the use of these substances by active duty personnel are then provided.

STEMI in a 24-year-old man after use of a synephrine-containing dietary supplement: a case report and review of the literature.

Billions of dollars are spent annually in the United States in the largely unregulated market of dietary supplements. Many of these supplements are marketed as weight-loss and athletic-performance-enhancement products. The association of various ephedra-containing products with adverse cardiovascular events has led to a ban on the sale of these products by the U.S. Food and Drug Administration. The result has been the emergence of new formulations marketed for weight loss and athletic-performance enhancement that are "ephedra-free" but contain other sympathomimetic substances, the safety of which has not been established. We present the case of a previously healthy 24-year-old man who presented with an ST-segment-elevation myocardial infarction (STEMI) within hours of taking the ephedra-free product Nutrex Lipo-6x. Emergent coronary angiography revealed the presence of extensive, diffuse thrombus in the left anterior descending coronary artery. The patient had no risk factors for coronary artery disease or myocardial infarction; this includes the absence of a hypercoagulable state and the absence of a history of illicit drug use. This case of STEMI--associated as it is with the use of a synephrine-containing product by a person without risk factors for coronary artery disease--is to our knowledge the 1st reported in the literature. We discuss the patient's evaluation and clinical course, and we review the literature with respect to synephrine-containing dietary supplements. On the basis of synephrine's chemical composition and mechanism of action, we propose a direct association between this patient's use of Nutrex Lipo-6x and his STEMI.

A case of severe exercise-induced rhabdomyolysis associated with a weight-loss dietary supplement.

In response to questions about the safety of ephedra-based dietary products, ephedra-free products are now available. Many contain synephrine, a sympathomimetic amine with structural similarities to ephedra. We present a 22-year-old, previously healthy, African American male with sickle cell trait who developed rhabdomyolysis after ingestion of a synephrine-containing dietary supplement. The patient developed fatigue, dehydration, and myalgias while exercising. He developed severe rhabdomyolysis, with a peak creatine phosphokinase level of 2.8 million U/L, complicated by pulmonary edema, acute renal failure, disseminated intravascular coagulation, and bilateral compartment syndromes in his lower extremities. He required prolonged hospitalization for hemodialysis, multiple wound debridements, hyperbaric oxygen therapy, and physical therapy. He has permanent sensory and motor neurological deficits in his distal lower extremities. Military physicians should routinely inquire about the use of dietary supplements, educate patients about the potential adverse reactions associated with these agents, and encourage healthy diets and exercise for weight loss.

Ischemic stroke associated with use of an ephedra-free dietary supplement containing synephrine.

In response to concerns regarding the safety of ephedra-containing dietary supplements, manufacturers have marketed "ephedra-free" products. Many of these contain synephrine, a sympathomimetic amine from the plant Citrus aurantium. Synephrine is structurally similar to ephedrine and has vasoconstrictor properties. We describe a 38-year-old patient with ischemic stroke associated with an ephedra-free dietary supplement containing synephrine and caffeine. The patient presented with memory loss and unsteady gait after taking 1 or 2 capsules per day of a dietary supplement (Stacker 2 Ephedra-Free) for 1 week. He had no notable medical history or major atherosclerotic risk factors and took no other medications. Physical examination showed a mildly ataxic gait and substantial Impairment of both concentration and memory. Computed tomography and magnetic resonance Imaging of the brain showed subacute infarctions in the left thalamus and left cerebellum in the distribution of the vertebrobasilar circulation. Other causes of ischemic stroke were evaluated, and findings were unremarkable; a vasospastic origin was considered most likely. The patient was discharged with nearly complete resolution of symptoms. Synephrine, a sympathomimetic amine related to ephedrine, may be associated with Ischemic stroke. Consumers and clinicians need to be Informed about the potential risks of ephedra-free products.