Inhibition of mycobacterial CYP125 enzyme by sesamin and β-sitosterol: An in silico and in vitro study

Background: Cholesterol degradation pathway is one of the important pathways in survival of Mycobacterium tuberculosis (Mtb) bacilli, and steroid C26-monooxygenase (CYP125) enzyme of Mtb associated with this pathway is reported to be novel drug target. This study aims to find out novel, safe, and effective inhibitors against CYP125 from natural phytochemicals with reported anti-tubercular activity. Methods: Bioinformatics approach such as homology modeling, virtual screening, and molecular dynamics (MD) simulation was applied to identify best hits among all the shortlisted 148 compounds. The Mtb H37Ra bacilli growth was measured at optical density at 600 nm in minimal media supplemented with cholesterol and monitored for 10 days. Two promising compounds, namely, sesamin and β-sitosterol, were studied to determine their effective minimum inhibitory concentrations (MICs) in Mtb H37Ra bacilli culture. Results: In virtual screening, 15 compounds showed comparatively better binding affinity than natural substrate (choletst-4-en-3-one). In MD simulation study, the protein structure was observed to be stable in alls the interaction complexes, i.e., with choletst-4-en-3-one, sesamin, and β-sitosterol. The MICs of sesamin and β-sitosterol were observed to be 2 μg/ml, inhibiting the growth of the Mtb bacilli by 51% and 53%, respectively. Conclusions: From the above experimental findings, sesamin and β-sitosterol may be proposed as safe and potential inhibitors of CYP125 resulting in diminished growth of Mtb bacilli.