Phytochemical studies on certain South African species of the rutaceous genera Agathosma Willd. and Zanthoxylum L

Abstract

Selected species of two South African rutaceous genera, Agathosma Willd. and Zanthoxylum L., were phytochemically studied. Two species of the former genus, A. puberula (Steud.) Fourc . and A. elavisepala R. A. Dyer, yielded a novel O-prenylcoumarin, puberul in, the structure of which was fully elucidated as 6,8- dimethoxy-7-prenyloxycoumarin. This represents the first report of a coumarin from that endemic genus. In another study the alkaloids in three species of Zanthoxylum, Z. davyi (Verdoorn) Waterm., Z. thorneroftii (Verdoorn) Waterm. and Z. humile (E .A. Bruce) Waterm . , were investigated. Chelerythrine, nitidine, (-) -α-N-methylcanadine, (+)-laurifoline and (+)-magnoflorine were isolated and characterized in the stem and root bark of Z. davyi, while the root bark of Z. thorneroftii contained skimmianine and decarine in addition to the alkaloids present in Z. davyi. Skimmianine, decarine, N-norchelerythrine, chelerythrine, (-)-α-N-methylcanadinc, candicine and tembetarine were identified in the root bark of Z. humile. The chemotaxonomic significance of these alkaloids occurring in the South African taxa in relation to other African Zanthoxylum taxa, is discussed. Several non-alkaloids (lupeol, β-sitosterol and (-)-sesamin) were also isolated and characterized in Z. davyi and Z. humile. Horizontal cellulose column chromatography and low pressure liquid chromatography have been applied to the separation of quaternary alkaloids