African Journal of Biotechnology Vol. 4 (10), pp. 1167-1171, October 2005          
ISSN 1684–5315 © 2005 Academic Journals

Full Length Research Paper

Isolation of an antibacterial stilbene from Combretum woodii (Combretaceae) leaves

J N Eloff*, J O Famakin and D R P Katerere

Programme for Phytomedicine, Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa.

*Corresponding authors E-mail: kobus.eloff@up.ac.za. Phone: +27-12-529-8244. Fax: +27-12-529-8525.

Accepted 28 September, 2005

Acetone extracts of C. woodii leaf powder was separated by solvent-solvent partition into six fractions. The highest total activity was in the chloroform fraction. This fraction contained mainly one compound active against S. aureus. This compound was isolated by bioassay-guided fractionation using silica gel open column chromatography and identified by nuclear magnetic resonance (NMR) and mass spectroscopy (MS) as the stilbene 2’,3’,4-trihydroxyl-3,5,4’-trimethoxybibenzyl (combretastatin B5) previously isolated from the seeds of C. kraussii. It showed significant activity against S. aureus with an MIC of 16 mg/ml but with lower activity towards P. aeruginosa (125 mg/ml), E. faecalis (125 mg/ml) and slight activity against E. coli. This is the first report of the antimicrobial activity of combretastatin B5. Its concentration in the leaves was in the order of 5-10 mg/g which makes the use of non-polar leaf extracts a viable proposition in treating some infections, particularly in resource-poor settings.

Key words: Combretastatin B5, bibenzyl, stilbene, antibacterial, Combretaceae.