Extraction of antibacterial compounds from Combretum microphyllum (Combretaceae)

The aim of this investigation was to simplify extracts to facilitate the isolation of antibacterial compounds from the complex mixture of chemicals in the plant by using different extractants. Intact dried leaves were extracted with acetone and 1% aqueous sodium bicarbonate and ground leaves were extracted by hexane, carbon tetrachloride, di-isopropylether, ethyl ether, methylene dichloride, tetrahydrofuran, acetone, ethanol, ethyl acetate, methanol and water. TLC was used to determine chemical composition and antibacterial activity of extracts was determined by a microplate serial dilution method. The different solvents extracted from 2.6 to 17.4% of the dry weight. Methanol, methylene dichloride and tetrahydrofuran extracted the most components. The chemical composition of the non-polar components of the different extracts were remarkably similar. The minimum inhibitory concentration for the different extractants varied from 0.01 to 1.25 mg/ml with the four test organisms used (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis). The extracts had similar activity towards Gram-negative and Gram-positive bacteria. Di-isopropyl ether, ethanol, ethyl ether, acetone and ethyl acetate extracted high antibacterial activity with a lower quantity of other non-active compounds and could be useful for isolating bioactive compounds.