Investigations on antimycobacterial activity of some ethiopian medicinal plants

Fifteen crude extracts prepared from seven Ethiopian medicinal plants used to treat various infectious diseases were assessed for their ability to inh ibit the growth of Mycobacterium tuberculosis, A preliminary screening of t he crude extracts against M. tuberculosis typus humanus (ATCC 27294) was do ne by dilution assay using Lowenstein-Jensen medium. None of the tested ext racts except the acetone fraction obtained from the stem bark of Combretum molle (R, Br. ex G. Don,) Engl & Diels (Combretaceae) showed significant in hibitory action against this strain, The acetone fraction of the stem bark of C, molle caused complete inhibition at concentrations higher than 1 mg/m L. Phytochemical analysis of the bioactive fraction led to the isolation of a major tannin and two oleanane-type pentacyclic triterpene glycosides, Th e tannin was identified as the ellagitannin, punicalagin, whilst the saponi ns were characterized as arjunglucoside (also called 4-epi-sericoside) and sericoside, All the pure compounds were further tested against the ATCC str ain. Punicalagin was found to inhibit totally growth of the ATCC and also o f a patient strain, which was fully sensitive to the standard antituberculo sis drugs, at concentrations higher than 600 mug/mL and 1.2 mg/mL, respecti vely, On the other hand, the saponins failed to show any action on the ATCC strain. It appears that our findings are the first report of tannins exhib iting antimycobacterial activity, Copyright (C) 2001 John Wiley & Sons, Ltd .