Evaluation of Antibacterial Activity of the Stem Bark of Alstonia scholaris Linn. R.Br

Alstonia scholaris Linn. R. Br. also called as Devil's tree and Dita bark belongs to the family Apocyanaceae. It is a large, ever green tree, found almost throughout India up to an altitude, 600m. The bark was collected and authenticated by Dr. Madhava Chetty, Sri Venkateshwara University, Tirupathi. The antibacterial activity of the stem bark of Alstonia scholaris Linn. R. Br. was investigated as there is a necessity for the search of new antibiotics as the infectious diseases continue to be the major concern for health institutions, pharmaceutical companies and Governments all over the world, especially with the current increasing trends of multidrug resistance among emerging - reemerging bacterial pathogens to the available modern drug or antibiotics. The plants are the cheapest and safe alternative source of antimicrobials. The powder of the dried stem bark was extracted with different solvents in increasing order of the polarity by soxhelation. Antibacterial activity was tested against both Gram positive (Staphylococcus aureus, Bacillus subtilis) and Gram negative (Pseudomonas aeruginosa, Escherichia coli) organisms using agar disc diffusion method. The methanol and benzene extracts exhibited significant antibacterial activity against Gram negative bacteria and ethanol extract against Gram positive bacteria. Chloroform and acetone extracts exhibited less activity, while petroleum ether and aqueous extracts showed no zone of inhibition. The results were compared with the standard drug, Ampicillin.