Activity of Medicinal Plant Extracts on Multiplication ofMycobacterium tuberculosisunder Reduced Oxygen Conditions Using Intracellular and Axenic Assays

Abstract

Aim.Test the activity of selected medicinal plant extracts on multiplication ofMycobacterium tuberculosisunder reduced oxygen concentration which represents nonreplicating conditions.Material and Methods.Acetone, ethanol and aqueous extracts of the plantsAcorus calamusL. (rhizome),Ocimum sanctumL. (leaf),Piper nigrumL. (seed), andPueraria tuberosaDC. (tuber) were tested onMycobacterium tuberculosisH37Rv intracellularly using an epithelial cell (A549) infection model. The extracts found to be active intracellularly were further studied axenically under reducing oxygen concentrations.Results and Conclusions.Intracellular multiplication was inhibited ≥60% by five of the twelve extracts. Amongst these 5 extracts, in axenic culture,P. nigrum(acetone) was active under aerobic, microaerophilic, and anaerobic conditions indicating presence of multiple components acting at different levels andP. tuberosa(aqueous) showed bactericidal activity under microaerophilic and anaerobic conditions implying the influence of anaerobiosis on its efficacy.P. nigrum(aqueous) andA. calamus(aqueous and ethanol) extracts were not active under axenic conditions but only inhibited intracellular growth ofMycobacterium tuberculosis, suggesting activation of host defense mechanisms to mediate bacterial killing rather than direct bactericidal activity.