Contents of ephedrine-like alkaloid synephrine in traditional Chinese decoctions
The FDA's ban on ephedra has led to an increase in the use of the ephedrine-like alkaloid synephrine, in dietary supplements for the purpose of body loss. Synephrine naturally occurs in bitter-orange (Citrus aurantium L.) and other Citrus species. Concerns have been raised about the safety of products containing synephrine. Tangerine peel (Citrus reticulata Blanco; Chenpi) is a herbal drug used in traditional Chinese medicine (TCM) and also contains small amounts of synephrine . Traditional decoctions  of this drug are evaluated: i.e. the extraction yields for synephrine in dependence to extraction time. Thereof, an assumed daily intake is calculated for synephrine.
Results showed a content of synephrine of 3.0mg/g in the herbal drug (batch 1). Traditional decoction resulted in extraction yields of 69% synephrine, referred to dried drug. An extraction profile over time showed similar yields (about 67%) also after 3 hours of decoction. Maceration in cold water was about the same effective, yielding up to 71% of synephrine after 3h. The analysis of a second herbal drug batch showed a synephrine content of 1.7mg/g. Traditional decoction of it resulted in an extraction yield of 75% synephrine. A longer decoction lasting 2 hours lead to extraction yields up to 93%.
It can be concluded that, assuming a daily dose of Chenpi of 3–9g, there could result a daily intake of up to 19mg synephrine. Such doses are below the levels exhibiting pharmacological effects, which are reported to be of 100 to 150mg .
Acknowledgement: We thank Lian Chinaherb, Switzerland, for the supply of herbal drug material.
References: 1. EDQM (2010) Mandarin epicarp and mesocarp (draft monograph), In: Pharmeuropa 22.4
2. EDQM (2010) Preparation of drugs for traditional Chinese medicines, In: Pharmeuropa 22.2
3. Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit (2009) Illegale Schlankheitsmittel, In: LGL Jahresbericht 2009