Structural Characterization of Yohimbine-type Alkaloids from Pausinystalia yohimbe by UPLC-QTOF

Pausinystalia yohimbe (Yohimbe), formerly known as Corynanthe yohimbe, is an evergreen tree native to Africa. Chemical constituents from Yohimbe bark include tannins and indole alkaloids. Yohimbe bark contains about 6% total alkaloid in which yohimbine represents 10–15% [1]. The tryptamine alkaloid yohimbine is a prescription medicine that has been used to treat erectile dysfunction and explored as a remedy for type-II diabetes in animal and human models carrying polymorphisms of the α2A-adrenergic receptor gene [2]. P. yohimbe is widely distributed over-the-counter as an herbal aphrodisiac.

With the aim of discovering a fast method in quality control of Yohimbe products, an UPLC-QTof method was developed for separation and structural characterization of yohimbine-type alkaloids from P. yohimbe. The separation was achieved by using C-18 column material with a gradient system composed of 50 mM ammonium formate and acetonitrile. According to tandem mass spectra of yohimbine, the cleavage occurred between C2-C3 and C5-C6, and gave the product ions at m/z 144 and 212 Da. The ions at m/z 212 further yielded ions at m/z 194, 180, 162 and 134 corresponding to fragments [212-H₂O]⁺, [212-MeOH]⁺, [212-MeOH-H₂O]⁺, [212-H₂O-HOAc]⁺, respectively. The fragmentation pathway of yohimbine is proposed in Figure 1. This method is useful for monitoring yohimbine-type alkaloids from Yohimbe and its related products.

Fig.1: Proposed fragmentation pathway of yohimbine

Acknowledgements : This research is supported in part by Science Based Authentication of Dietary Supplements funded by the Food and Drug Administration grant No. 1U01FD004246–01; the United States Department of Agriculture, Agricultural Research Service, Specific Cooperative Agreement No. 58–6408–2-0009, and the Global Research Network for Medicinal Plants (GRNMP), King Saud University. References: [1] Beta JM, White KD, et al., (1995)J AOAC Int 78: 1189–1194. [2] Rosengren AH, Johubka R, et al. (2010) Science 327: 217–220.