Ethnopharmacological relevance: Ocimum basilicum belongs to the genus Ocimum (Lamiaceae). Many species of this genus including O. basilicum have been traditionally used for the treatment of a variety of diseases including respiratory diseases and symptoms of tuberculosis.

Aim of study: The aim of the study was to evaluate the activity of pure constituents of O. basilicum, a plant used in traditional medicine to treat respiratory diseases including symptoms of tuberculosis, against Mycobacterium tuberculosis H37Rv.

Materials and methods: The crude methanolic extract from the aerial parts (leaves, fruits and flowers) of the plant was separated into EtOAc and water subextracts and the EtOAc subextract was further divided into acidic and neutral fractions. Each of these was subjected to fractionation through column chromatography followed by prep. TLC. Several pure compounds were thus isolated and their activity was determined against M. tuberculosis H37Rv using MABA assay.

Results: Nine compounds were assayed for antituberculosis activity which exhibited upto 49% inhibition of M. tuberculosis H37Rv at 6.25 μg/mL. These include one new compound bacilicin, the structure of which was elucidated based on 2D-NMR (HSQC, HMBC, COSY and NOESY) and Ms spectral analysis. The known compounds were identified on the basis of comparison of their spectral data with those reported earlier.

Conclusions: Inhibition of M. tuberculosis by pure compounds from O. basilicum supports the use of this plant in ethnomedicine as a remedy for symptoms of tuberculosis. The results also suggest that the activity of the plant may be due to a synergistic effect of active compounds including those investigated in the present studies, and hence this plant is a potential candidate for obtaining further new antituberculosis natural products.