A CONTRIBUTION TO THE PHYTOCHEMISTRY OF THE EAST-AFRICAN TETRAPLOID SHRUBBY ALOES AND THEIR DIPLOID ALLIES

Compounds in the leaf exudates of a group of shrubby aloes from EAch AFrica have been re-examined by two-dimensonal thin-layer chromatography using Fast Blue B as a revealing reagent. Exudates from the most abundant taxa, the two subspecies [nyeriensis and kedongensis] of Aloe nyeriensis, were found to contain substances giving four distinct chromatographic patterns. One was distinguished by the presence of the anthrone C-glycoside barbaloin while two others contained instead homonataloin with or without aloenin. The fourth group contained of these but a similar compound of unknown constitution. Exudate patterns from the neighbouring but localized tetraploid species A. cheranganiensis, the more remote A. dawei and A. elonica, together with the diploid A. yavellana, related to one or other of the groupings of A. nyeriensis. Some plants of a localized diploid species, A. morijensis, also yielded a similar pattern but other plants of rather more slender form contained quite different compounds resembling those in the diploids A. fibrosa and A. babatiensis. This supports the hypothesis that A. morijensis is close to the putative ancestor of the tetraploid East African shrubby aloes. The other widespread shrubby species in this locality, the diploid A. rabaiensis, is unrelated taxonomically and chemically.