Comparative study of in vitro antibacterial activity of leaves, bark, heart wood and seed extracts of Caesalpinia sappan L.

To evaluate and compare the maximum antimicrobial activity by screening different parts of Caesalpinia sappan L. extracted in different solvents against Salmonella ebony (MTCC 3384) (S. ebony), Klebsiella pneumoniae (MTCC 432) (K. pneumoniae), Escherichia coli (MTCC 443) (E. coli) and Bacillus subtilis (MTCC 10619) (B. subtilis). Dried plant parts were extracted with petroleum ether, methanol, chloroform and water by Soxhlet extraction method. The extracts were tested against S. ebony, K. pneumoniae, E. coli and B. subtilis by using the agar well diffusion method. Among the above solvents, the methanol and chloroform and aqueous extracts of leaves, seeds, bark and heart wood showed strong antibacterial activity. The inhibition zone for heart wood extracts against K. pneumoniae was (30.333 ± 0.330) mm in methanol, chloroform (28.166 ± 0.730) mm and aqueous extract (28.166 ± 0.170) mm; for B. subtilis, that was (27.333 ± 0.440) mm in methanol, (27.166 ± 0.170) mm in chloroform, (26.166 ± 0.440) mm in aqueous extract and least in petroleum ether (12.660 ± 0.170) mm. The leaf extracts in methanol showed maximum antibacterial activity against S. ebony as seen by the inhibition zone (16.000 ± 0.290) mm and K. pneumoniae (13.000 ± 0.290) mm. The maximum antibacterial response of the seed extract against K. pneumoniae was observed in chloroform solvent (14.000 ± 0.580) mm followed by aqueous extract (13.833 ± 0.600) mm. No response was observed in petroleum ether and methanol. The heart wood extracts showed the highest antibacterial activity having a minimal inhibition concentration of 2 mg/mL in all three solvents against the four bacterial strains, except petroleum ether where MIC was 5 mg/mL against E. coli and B. subtilis. The aqueous and methanolic extracts of bark showed minimal inhibition concentrations of 5 mg/mL and 2 mg/mL against K. pneumoniae respectively whereas aqueous extract of bark showed a minimal inhibition concentration of 5 mg/mL against E. coli.