GAS-CHROMATOGRAPHIC DETERMINATION OF YOHIMBINE IN COMMERCIAL YOHIMBE PRODUCTS

The bark of Pausinystalia yohimbe [K. Schumann] Pierre (Rubiaceae), lo ng valued as an aphrodisiac in West Africa, recently has been promoted in the United States as a dietary supplement alternative to anabolic steroids for enhancement of athletic performance. As the number of yoh imbe products on the retail market increases, concerns about their saf ety are raised because of the reported toxicity of yohimbine (the majo r alkaloid of the plant). Although plant materials are usually identif ied microscopically, we were unable to identify them in many of the pr oducts, because as their labels indicated, the products were mixtures of various botanicals or were bark extracts and contained little or no plant material. A method for extraction and capillary gas chromatogra phic (GC) separation of the alkaloids of P. yohimbe was, therefore, de veloped and used to analyze a number of commercial yohimbe products. T he method involved solvent extraction and partitioning in chloroform-w ater followed by separation on a methyl silicone capillary GC column ( N-P detection). Comparisons of chromatograms of extracts of authentic bark with those of commercial products indicated that, although many p roducts contained measurable quantities of the alkaloid yohimbine, the y were largely devoid of the other alkaloids previously reported in th is species. Concentrations of yohimbine in the commercial products ran ged from <0.1 to 489 ppm, compared with 7089 ppm in the authentic mate rial. Authentic bark has been reported to contain up to 6% total alkal oids, 10-15% of which are yohimbine. The possible presence of undeclar ed diluents in the products was indicated by peaks in product chromato grams but not in those of authentic bark.