Effects of fractionation on antibacterial activity of crude extracts of Tamarindus indica
Column chromatographic fractionation of the crude ethanolic extract of the stem bark of Tamarindus indica yielded six fractions (TiA - TiF). Among these, TiB showed about five tracks: TiC, TiD and TiE, two tracks each, on thin layer chromatography (TLC). Fractions TiC, TiD and TiE were re-eluted with different solvent systems and each yielded two sub-fractions, while fraction TiB yielded four. All fractions and sub-fractions tested for antibacterial activity in vitro using the agar well diffusion technique. TiA showed activity against 100% of the test gram negative bacterial strains and 60% of the gram positive strains; TiB, TiC, and TiD each showed activity against 71.4% of the gram negative test strains and 100, 80 and 60%, respectively, of the gram positive strains. Fractions TiE and TiF, respectively, showed activity against 42.9 and 14.3% of the gram negatives and 60 and 20% against the gram positives bacteria. The crude extract and Ciprofloxacin (control), respectively, were active against 57.1 and 100% of the gram negatives; and 80 and 100% of the gram positives. The activities of the subfractions of TiB, TiC, TiD and TiE against the test strains varied from those of the parent fractions. The phytochemistry of these fractions showed varied contents of tannins, saponins, flavonoids, alkaloids, antroquinone, glycosides and terpene.
Key words: Fractionation, chromatography, plant extract, Tamarindus indica, antibacterial activity,