Cytotoxicity and gene expression studies in understanding the mechanism on antimycobacterial properties of methanolic leaf extract of Acalypha indica Linn.

Abstract

Despite the availability of effective antituberculosis medication, tuberculosis (TB) remains a serious global health concern, raising the demand for low-after effect drug alternative. This study aims to explore the anti-mycobacterial potency of Acalypha indica Linn. on Mycobacterium tuberculosis using Mycobacterium smegmatis as a model and thereby uncover its mechanism. Characterization of bioactive phytocompounds and their cumulative effects were studied through both biochemical and molecular approaches. The antimycobacterial efficacy was screened by cell viability assay and IC50. FE-SEM and qRT-PCR were used to study the effect of A. indica leaf methanolic extract (AILME) on cell integrity and mycolic acid synthesis pathway. This study reports AILME to be the most effective solvent-extract combination which showed >40 % cell inhibition from 25 µg mL−1 onwards at 24 hr. AILME showed >80 % antioxidant potential, lowest IC50 of 48.24 µg mL−1 and a MIC value of 200 µg mL−1 at 24 hr. The FE-SEM analysis of the AILME treated bacterial cells showed significant morphological damage which supports the results of antimycobacterial activity. The gene expression study revealed that AILME inhibited the expression of inhA and mtrA genes involved in mycolic acid biosynthesis pathway and cell wall integrity, respectively. The bioactive phytocompounds characterised through GCMS and HR-LCMS revealed about nineteen potent anti-TB compounds like malic acid, catechin, pyrrolidine, hexadecanoic acid, quercetin etc. that might supervise the role behind the antimycobacterial effect of the herb. This study reveals that AILME possesses strong antimycobacterial action by impeding the formation of mycolic acid biosynthesis pathway and disorganization of cell wall. Presence of anti-TB phytocompounds in abundance suggest its potential chemotherapeutic nature against M. tuberculosis.