Antimycobacterial screening of selected medicinal plants against Mycobacterium tuberculosis H ₃₇ Rv using agar dilution method and the microplate resazurin assay

Background: Tuberculosis (TB), has been serious disease to the global human population causing millions of deaths worldwide. The recent increase in the number of multi-drug resistant clinical isolates of Mycobacterium tuberculosis has created an urgent need for the discovery and development of new anti-TB drugs. Medicinal plants have had a great influence on the daily lives of people living in developing countries, particularly in India. Medicinal plants were selected, and they were evaluated for its anti-TB activity against the pathogenic strain of M. tuberculosis H₃₇Rv.

Methods: Eleven medicinal plants were selected on the basis of its literature survey, and three different extracts were prepared. Antimycobacterial activities were screened using two in vitro assays, namely agar dilution assay and microplate resazurin assay against M. tuberculosis H37Rv at different concentrations of prepared extracts. We analyzed minimal inhibition concentrations and percentage of inhibition of the used strain of Mycobacteria. Isoniazid was used as a standard anti-TB drug.

Results: The results of this study showed that aqueous extracts four selected medicinal plants Ocimum sanctum, Adhatoda vasica, Leptadenia reticulata, and Cocculus hirsutus having minimum inhibitory concentration at 500 μg/ml, 500 μg/ml, 250 μg/ml, and 250 μg/ml, respectively, and O. sanctum (60.24%), A. vasica (62.89%), L. reticulata (74.26%), and C. hirsutus (81.67%) showed significant anti-TB activity against M. tuberculosis.

Conclusion: This study helps society to found new anti-TB agents having better anti-TB activity with lesser or no side effects.

Keywords: 11 selected medicinal plants; Agar dilution method; Mycobacterium tuberculosis; isoniazid; microplate resazurin assay.