Functional analysis of quinovic acid derivatives from Sarcocephalus pobeguinii as inhibitors of hepatitis C virus NS3/4A protease

Abstract

This study assessed compounds from Sarcocephalus pobeguinii as potential inhibitors of HCV-NS3/4 A. Ten compounds isolated from S. pobeguinii were initially screened for their inhibitory activity against HCV-NS3/4 A through the fluorescence resonance energy transfer assay. The 50 % inhibitory concentration (IC₅₀) and the inhibition mechanism of active compounds were determined through concentration-response and enzyme-kinetics studies, respectively. The physical interactions between the enzyme and inhibitors were analyzed by thermal shift assay and surface plasmon resonance, while molecular interactions were predicted using molecular docking. The antiviral activity of the hit compounds was tested in a cell-based assay. Three inhibitors of HCV-NS3/4 A: Quinovic acid, Quinovic acid 3-O-[α-D-quinovopyranoside], and Quinovic acid 3-O-[β-D-quinovopyranoside] with IC₅₀ in the micromolar range were successfully identified. They displayed their inhibitory activity through a non-competitive inhibition mechanism and bound to the HCV-NS3/4 A protease in a real-time manner through 1:1 binding and steady-state affinity models, inducing its instability by lowering its melting temperature. The lead compounds effectively inhibited HCV replication at non-toxic concentrations. These results contribute to the valorization of S. pobeguinii as a potential source of efficient inhibitors to reinforce the current therapeutic arsenal for the treatment of HCV infection.