Bioactive Pentacyclic Triterpenes from the Stems of Combretum laxum

Abstract

Two new triterpene glucosides, beta-D-glucopyranosyl 2alpha,3beta,24-trihydroxyolean- 12-en-28-oate and beta-D-glucopyranosyl 2alpha,3beta,23,24-tetrahydroxyurs-12-en-28-oate, in addition to nine known compounds belonging to three different triterpene classes (oleanane-, ursane- and lupane-type) have been isolated from the stems of a specimen of Combretum laxum growing in the "Pantanal" of the central-western region of Brazil. Among the known triterpenes, beta-D-glucopyranosyl 2alpha,3beta,6beta-trihydroxyolean-12-en-28-oate is reported for the first time in the Combretaceae, while bellericoside and asiatic acid are described for the first time in the genus Combretum. The structures of the isolated compounds have been established on the basis of spectral techniques (1D-, 2D-NMR and MS). Their in vitro antifungal activities against standard strains of Candida albicans, C. krusei and Cryptococcus neoformans were also evaluated in this work.