Study of Anti Mycobacterial Activity of Selected Medicinal Plants and Target Site Identification

Abstract

The rapid emergence of drug-resistant Mycobacterium tuberculosis (Mtb) has significantly reduced the effectiveness of existing anti-tubercular therapies, highlighting an urgent need for novel antimicrobial agents with new mechanisms of action. Medicinal plants, long utilized in traditional healthcare systems, represent a promising and underexplored source of bioactive compounds. The central hypothesis of this study was that selected medicinal plants possess potent anti-mycobacterial compounds capable of inhibiting mycobacterial growth through specific molecular target interactions. To achieve this, a total of 36 plants were selected with the assistance of previously reported literature and the medicinal knowledge of the tribes in the Rajnandgaon district of Chhattisgarh state. Extracts of the selected plants were prepared using suitable solvents and their primary anti-bacterial activity was evaluated against Mycobacterium smegmatis (M. smegmatis) using the disc diffusion assay. All extracts exhibited some level of activity against M. smegmatis, with Swertia chirayita, Cinnamomum tamala, Piper betle and Piper nigrum (P. nigrum) showing the most potent activity. Further analysis focused on the seed extract of P. nigrum and five different extracts of P. nigrum seeds were prepared using ethanol, methanol, acetone, n-hexane and ethyl acetate solvent. The acetone extract of P. nigrum seed demonstrated significant anti-bacterial activity against Mycobacterium phlei (M. phlei), M. smegmatis and Mycobacterium fortuitum (M. fortuitum). Phytochemical analysis with conventional qualitative phytochemical analysis methods and thin layer chromatography (TLC) of different extracts of P. nigrum seed showed no major differences in the phytochemical profiles. Further Gas chromatography-mass spectra (GC-MS) analysis of the acetone extract of P. nigrum seed identified ten major compounds, including Alpha-copaene, Caryophyllene, Alpha-bisabolene, Piperine and others. Silica column chromatography of the acetone extract of P. nigrum see