IN VITRO ANTIMICROBIAL ACTIVITIES OF CRUDE EXTRACTS OF LEAVES, BARKS AND FRUITS OF TAMARIND (Tamarindus indica L.) AGAINST SELECTED PATHOGENIC BACTERIA

Abstract

Because of the rapid development of drug resistance and high cost of the new generation antibiotics, lots of efforts are being made to discover new antimicrobial agents mainly from medicinal plants. This study was undertaken to evaluate the phytochemical composition and evaluate the antibacterial activities of aqueous, methanolic and hexane crude extracts of the leaves, barks and fruits of Tamaridus indica against some human pathogenic bacteria (S. aureus, S. pyogenes, E. coli and S. Typhi) using the disc diffusion method. The minimum inhibitory concentrations (MIC) of the extracts were also assessed using the broth dilution method. In the determination of antimicrobial activities, the antibiotic Amoxicillin and sterilized distilled water were used as positive and negative controls, respectively. The results of the qualitative analysis of the chemical composition of the crude extracts revealed the presence of tannins, alkaloids, flavonoids, saponins, steroids, terpenoids, anthraquinnones and, glycosides. Of the three solvents, methanol and aqueous performed better than hexane in the extraction of bioactive compounds. With regard to the antibacterial activities of the crude extracts, methanolic crude extracts of fruits,barks and leaves showed better antibacterial activities than the crude extracts obtained using other solvents. The methanolic fruit extract showed 16, 14.16, 13.16 and 13.00mm of the zone of inhibitions against S. aureus, S. pyogenes, E. coli and S. Typhi, respectively, at a concentration of 150 mg/ml. Of the four tested bacterial species S. aureus and S.Typhi were the most and least susceptible, respectively. The inhibitory effects of the crude extracts were significantly different at p<0.05. The MIC of the crude extracts was generally in the range of 12.50 to 66.66 mg /ml against the four tested bacterial species. However, the minimum bactericidal concentrations (MBC) values ranged from 25 to 100 mg/ml against the four tested bacterial species. In general, the present investigation has shown that the leaf, bark and fruit extracts of T. indica have the potential to be selected as candidates in the search for antimicrobial agents. However, further research is needed for isolation and quantification of the specific bioactive compounds to authenticate the most important chemical component that is responsible for the antibacterial activity