[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 β₃-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.