IN-VITRO ANTIMYCOBACTERIAL ACTIVITY OF SELECTED INDIAN MEDICINAL PLANTS TO RESISTANT STRAINS OF MYCOBACTERIUM TUBERCULOSIS

Tuberculosis (TB) remains a highly significant infection of microbial origin causing death of human in developing countries. The anti-tubercular drugs are less effective because of the emergence of multi-drug resistant strains and ineffective to extensively drug resistant strains of Mycobacterium tuberculosis. Plants are being an alternative source of anti-microbial compounds; the aim of this study was to investigate anti-mycobacterial potential of the few Indian medicinal plants and isolated compound from these to standard avirulent Mycobacterium tuberculosis H37Ra, standard virulent H37Rv and isoniazid resistant clinical isolates using Broth Microdilution Method. Methods and Results: Lyophilised ethanolic, aqueous and aqueous ethanolic extracts of four Indian medicinal plants viz. Coleus amboinicus, Glychirrhiza glabra, Pongamia pinnata and Terminalia chebula  were screened for their in vitro antimycobacterial activity by Broth microdilution method (BMM) after 14 days of incubation at 37°C. The ethanolic extract of G. glabra was active against the tested strains of M. tuberculosis in primary screening with a MIC of 500µg/ml. The other extracts failed to exhibit inhibition at the tested concentrations. Glycyrrhizin a major and active constituent of the root of G. glabra was hence evaluated for its anitmycobacterial activity to the tested strains of M. tuberculosis. The isolated pure compound Glycyrrhizin exhibited a MIC value of 100µg/ml to the tested strains of M. tuberculosis. Conclusion: Our findings provide scientific support for ethno medical uses of Glycyrrhiza glabra to cure coughs and chest related ailments with the establishment of glycyrrhizin as a molecule for antimycobacterial activity and indicate a promising potential of this plant for the development of safer and efficacious anti-tuberculosis therapy.