Detection of anti-tuberculosis activity in some folklore plants by radiometric BACTEC assay

The anti-tubercular drugs are less effective because of the emergence of multi-drug resistant (MDR) and extensively drug resistant (XDR) strains of M. tuberculosis, so plants being an alternative source of anti-microbial compounds. The aim of this study was to investigate anti-tuberculosis potential of the plants using Mycobacterium smegmatis as a rapid screening model for detection of anti-mycobacterial activity and further to evaluate the active plants for anti-tuberculosis activity against M. tuberculosis using radiometric BACTEC assay.

The 15 plants were screened for anti-mycobacterial activity against M. smegmatis by the disk diffusion assay. The ethanolic extracts of Mallotus philippensis, Vitex negundo, Colebrookea oppositifolia, Rumex hastatus, Mimosa pudica, Kalanchoe integra and Flacourtia ramontchii were active against M. smegmatis in primary screening. The anti-tuberculosis potential was identified in the leaves extracts of Mallotus philippensis by radiometric BACTEC assay. The ethanolic extract of M. philippensis showed anti-tuberculosis activity against virulent and avirulent strains of M. tuberculosis H(37) Rv and M. tuberculosis H(37) Ra with minimum inhibitory concentration 0·25 and 0·125 mg ml(-1), respectively. The inhibition in growth index values of M. tuberculosis was observed in the presence of ethyl acetate fraction at a minimum concentration of 0·05 mg ml(-1).

We found that BACTEC radiometric assay is a valuable method for detection of anti-tuberculosis activity of the plant extracts. The results indicate that ethanolic extract and ethyl acetate fraction of M. philippensis exhibited significant anti-mycobacterial activity against M. tuberculosis.

These findings provide scientific evidence to support the traditional medicinal uses of M. philippensis and indicate a promising potential of this plant for the development of anti-tuberculosis agent.