Evaluation Of In Vitro Antibacterial Activity of Some Sri Lankan Medicinal Plants

This study evaluated in vitro antibacterial activity and their minimum inhibitory concentration of five plants (stem of Stereospermum suaveolens, Oroxylum indicum and roots of Clitoria ternatea, whole plant of Bacopa monnieri and Alysicarpus vaginalis) used in traditional and folk medicine of Sri Lanka for treatment of various bacteria induced infectious diseases. This was performed using aqueous extracts against two gram positive [Staphylococous aureus (ATCC 25923); Bacillus cereus (ATCC 11778)] and three gram negative [Pseudomonas aeruginosa (ATCC 9027); Escherichia coli (ATCC 35218); and Salmonella typhimurium (ATCC 13311)], clinically important bacterial pathogens, using Kirby-Bauer disk diffusion test and broth micro-dilution technique. The results showed, for the first time, that the water extract of roots of C. ternatea exhibits dose-related potent antibacterial activity (MIC: 128 mu g/ml) against bacterial pathogen, B. cereus. Whilst the extracts of other four plants possessed no antibacterial activity against any of the bacterial strains tested. The antibacterial activity of C. ternatea roots is attributed to flavonoids, polyphenols including tannins, and saponins present in the extract. It is concluded that roots of Sri Lankan medicinal plant C. ternatea can function as a potent antibacterial agent against common food poising bacterial pathogen, B. cereus.