title: Investigations on antimycobacterial activity of some Ethiopian medicinal plants.
abstract: Fifteen crude extracts prepared from seven Ethiopian medicinal plants used to treat various infectious diseases were assessed for their ability to inhibit the growth of Mycobacterium tuberculosis. A preliminary screening of the crude extracts against M. tuberculosis typus humanus (ATCC 27294) was done by dilution assay using Löwenstein-Jensen medium. None of the tested extracts except the acetone fraction obtained from the stem bark of Combretum molle (R. Br. ex G. Don.) Engl & Diels (Combretaceae) showed significant inhibitory action against this strain. The acetone fraction of the stem bark of C. molle caused complete inhibition at concentrations higher than 1 mg/mL. Phytochemical analysis of the bioactive fraction led to the isolation of a major tannin and two oleanane-type pentacyclic triterpene glycosides. The tannin was identified as the ellagitannin, punicalagin, whilst the saponins were characterized as arjunglucoside (also called 4-epi-sericoside) and sericoside. All the pure compounds were further tested against the ATCC strain. Punicalagin was found to inhibit totally growth of the ATCC and also of a patient strain, which was fully sensitive to the standard antituberculosis drugs, at concentrations higher than 600 microg/mL and 1.2 mg/mL, respectively. 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 exhibiting antimycobacterial activity.
authors.affiliation: Department of Pharmacognosy, School of Pharmacy, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.
authors.forename: K
authors.initials: K
authors.lastname: Asres
authors.forename: F
authors.initials: F
authors.lastname: Bucar
authors.forename: S
authors.initials: S
authors.lastname: Edelsbrunner
authors.forename: T
authors.initials: T
authors.lastname: Kartnig
authors.forename: G
authors.initials: G
authors.lastname: Höger
authors.forename: W
authors.initials: W
authors.lastname: Thiel
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D005002:Ethiopia; D006801:Humans; D016488:Medicine, African Traditional; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology; D018547:Plant Stems; D010946:Plants, Medicinal; D019685:Rosales
chemical_list: D000995:Antitubercular Agents; D010936:Plant Extracts