Sesamol exhibits potent antimycobacterial activity: Underlying mechanisms and impact on virulence traits

Novel strategies to overcome multidrug resistance (MDR) in Tuberculosis (TB) still remain a concern. Usage of natural compounds nowadays to surmount the increasing burden of MDR-TB has shown promising results. The aim of this study was to evaluate the antimycobacterial potential of sesamol (Ses) a natural phenolic compound against Mycobacterium smegmatis, a surrogate for MTB and its underlying mechanism of action along with its effect on mycobacterial virulence traits.

Cell surface phenotypes were estimated microscopically and spectrophotometrically respectively. Membrane parameters were assessed using propidium iodide (PI) uptake, passive diffusion of drug with substrate EtBr and phenotypic susceptibility assay. Changes in lipid profiles were estimated by lipase assay. Oxidative and genotoxic damage were studied using fluorescent probes DCFDA and DAPI. Biofilm formation was studied using crystal violet and calcoflour white staining probes along with biomass measurement. Cell adherence was estimated using buccal epithelial cells.

We observed that antimycobacterial activity of Ses was 6mM and it enhances the efficiency of known anti-TB drugs. Ses affects cell surface phenotypes as displayed by altered colony morphology, impaired sliding motility and enhanced cell sedimentation rate. Membrane perturbation was revealed by hypersensitivity against SDS, reduced PI uptake, enhanced passive diffusion and lipase activity. In addition, Ses leads to oxidative and DNA damage along with abrogated iron homeostasis. Furthermore, we uncover phenotypes related to virulence like inhibited biofilm formation and cell adherence to buccal epithelial cells.

This study for the first time establishes the anti-mycobacterial potential of Ses that may be further exploited for improving the therapeutic strategies and warrants further attention.