The cathedulin alkaloids.

Abstract

Studies on fresh and dried leaf and shoot material of Catha edulis (khat) collected in Ethiopia, Kenya and the Yemen Arab Republic have led to the isolation, separation and characterization of new celastraceous alkaloids, the cathedulins, with molecular weights in the 600-1,200 range. All the cathedulins whose structures have been investigated prove to be polyesters or lactones of a sesquiterpene polyol core and fall into three groups: (a) low molecular weight esters of pentahydroxydihydroagarofuran; (b) cathedulins of medium molecular weight characterized by the possession of a euonyminol core and an evonimic acid dilactone bridge; and (c) high molecular weight, more complex esters of euonyminol. Chemical evidence and spectral data were used in assigning structures to the cathedulins studied as well as in placing the various esterifying acids on the different hydroxyl positions of the sesquiterpene core. In addition to cathedulins, neutral products isolated from khat include beta-sitosterol and its glycoside, friedeline, and hydroxylated delta 4-exo-relatives of the latter. Moreover, the pigmented root-bark contains triterpenoid quinones including celastrol, pristimerin, iguesterin and tingenone (tingenin A and B).