Extracts from the roots and rhizomes of black cohosh (Cimicifuga racemosa) are widely used as dietary supplements
to alleviate menopausal symptoms. State-of-the-art quality control measures involve phytochemical fingerprinting of
the triterpene glycosides for species identification and chemical standardization by HPLC. In the course of developing
materials and methods for standardization procedures, the major C. racemosa triterpene glycoside (1) was isolated and
initially thought to be cimicifugoside (2). Detailed HR-LC-MS and 1D and 2D NMR analysis of 1 and 2 unambiguously
revealed that 1 is the chlorine-containing derivative of 2, namely, 25-chlorodeoxycimigenol-3-O-â-D-xyloside. Accordingly,
HPLC profiles of black cohosh preparations require revision of the assignments of the chlorinated (1) and nonchlorinated
(2) pair. Besides explaining the substantial shift in polarity (∆tR[RP-18] ca. 20 min), 25-deoxychlorination opens a new
pathway of structural diversification in triterpene glycoside chemistry. As chemical conversion of 2 into 1 could be
demonstrated, deoxychlorination may be interpreted as artifact formation. Simultaneously, however, it is a potentially
significant pathway for the gastric in ViVo conversion (“nature’s prodrug”) of the relatively polar triterpene glycosides
into significantly less polar chlorinated derivatives with altered pharmacological properties.