Identification of a series of C21O2 pregnanes from fecal extracts of a pregnant black rhinoceros (Diceros bicornis minor)

Fecal extracts from a pregnant black rhinoceros, Diceros bicornis, were ana lyzed by radioinununoassay, HPLC, and by GC-mass spectrometry. From 40 g of dried feces a total of 33 pregnanes in the C21O2 series, including a numbe r of novel 17 alpha epimers were identified. No progesterone was recovered. The principal progesterone metabolite by mass was 5 alpha -pregnan-3 beta ,20 alpha -diol (44.5%), which did not cross react with the antibody used i n our RIA. The antibody recognized progesterone and pregnanes with 20-one c onfiguration, which when combined made up less than 15% of the total C21O2 steroid mass. Of the 33 pregnanes in the C21O2 Series identified, 81%, by m ass, were in the 5 alpha -configuration. These results are compared with st udies in other rhinoceros species (Asian and Sumatran) in which pregnanes i n the 5 beta -configuration are the major fecal metabolites, and the white rhinoceros in which pregnanes in the 5 alpha -configuration are the dominan t form. (C) 2001 Elsevier Science Inc. All rights reserved.