Steroidal and triterpenoidal sapogenins from rhoicissus revoilii, sesbania keniensis and albizia gummifera from Kenya

Abstract

A system has been developed for the fractionation, purification for the free triterpenes, sugars and steroids of the tuber of Rhoicissus revoilii PLANCH. (Vitaceae). Hydrolysis of saponins using sodium periodate has been employed and found to be (Chapter 1) gentler than acid hydrolysis. Structural elucidation of the main triterpenes employing modern chemical and instrumental techniques was successfully accomplished and the triterpenes concluded to be 33, 23-dihydroxyolean-12-en-28-oic acid (hederagenin) and 23, 33-dihydroxyolean-12-en-23,28- dioic acid (medicagenic acid). The two main steroids in the tuber of Rhoicissus revoilii have been fully analysed and found to be a-spinasterol and chondrillasterol. The minor steroids detected in R.revoili tuber have been shown by mass spectrometry to be A^-steroids * The free sugar from R.revoilii tuber has been 1. proved to be sucrose from mass and H NMR spectroscopic analysis. . Several free fatty acids have been detected from the same plant. - . mm*. iv A scheme for the fractionation of Sesbania keniensis (Leguminoseae) seeds has also been developed. Purification of the principal triterpene and steroid in the seeds of Sesbania Keniensis has been accomplished. The triterpene was structurally elucidated and found to be oleanolic acid, while the main sterol was proved to be stigmasterol. Finally, the stem bark of Albizia gummifera (Leguminoseae) has been investigated both for biological activity of the extracts and chemical constituent of the isolated sapogenin(s). The sapogenin was found to be oleanolic acid from direct spectral comparison with authentic oleanolic acid.