In silico prediction of gallic acid binding to Zika virus NS3/RdRp proteins and in vitro confirmation of its antiviral activity

Abstract

The global health threat posed by the Zika virus (ZIKV), characterized by its association with severe neurological sequelae and congenital malformations, is exacerbated by the current lack of clinically approved antiviral interventions. This study aimed to identify a benzoic acid–derived anti-ZIKV candidate through in silico–in vitro screening of derivatives and to characterize the selected lead compound. Gallic acid (GA), a naturally occurring phenolic compound, emerged as the most suitable candidate and was selected for further analyses. Molecular docking and 100 ns molecular dynamics (MD) simulations demonstrated that GA formed stable interactions with the catalytic domains of ZIKV NS3 and RdRp, with conformational perturbations in RdRp. This suggests that GA inhibits protein activation through active-site occlusion and/or structural destabilization. Treatment with non-cytotoxic concentrations of GA significantly suppressed viral replication in ZIKV-infected Vero E6 cells, with >98% inhibition of plaque formation and NS1 mRNA expression at concentrations of 100–200 μM, and modulated the expression of innate immune response genes including TNF-α, IFIT, IFITM, OAS, and PKR. Collectively, these findings indicate that GA exerts potent antiviral activity through the direct inhibition of viral non-structural proteins, underscoring its potential as a promising lead compound for the development of anti-ZIKV therapeutics.