Isolation and Characterization of Antimycobacterial Compounds from Fruits of Aegle marmelos (L.) Correa

Abstract

Root extracts of Aegle marmelos, an evergreen tree indigenous to India, is an important ingredient in Ayurvedic preparations used for the treatment of pulmonary tuberculosis. Leaves of the tree are used as a remedy for respiratory ailments in folk medicine. The fruit is extensively used in the treatment of various bacterial diseases such as dysentery, diarrhea, etc. The present study was designed to screen organic solvent extracts of fruits of A. Marmelos for their inhibitory activity on Mycobacterium tuberculosis (M. tuberculosis), and to isolate and identify the compounds responsible for antimycobacterial activity. The minimum inhibitory concentration (MIC) of the extract and purified molecules on virulent laboratory strain M. tuberculosis H37Rv was determined by resazurin microtiter assay (REMA). Structural elucidation of the compounds was carried out employing NMR. Cytotoxicity of the compounds was evaluated against human monocyte THP1-derived macrophages by MTT assay. The hexane extract of A. marmelos fruits inhibited the growth of M. tuberculosis at an MIC of 50 μg/mL. Fractionation of the hexane extract by column chromatography led to the isolation of imperatorin, β-sitosterol, plumbagin, marmesin, marmin, and stigmasterol which individually inhibited the growth of M. tuberculosis. In vitro cytotoxicity assay revealed that the compounds are not cytotoxic at the concentrations that inhibited the growth of M. tuberculosis.