Bioactive galloylquinic acids from Copaifera lucens as dual inhibitors of SARS-CoV-2 Spike and RdRp proteins

Abstract

The persistent global burden of SARS-CoV-2 underscores the urgent need for new antiviral agents. In this study, we evaluated the antiviral efficacy and underlying molecular mechanisms of galloylquinic acids (GQAs) extracted from Copaifera lucens leaves against SARS-CoV-2 using in vitro and in silico approaches. Cytotoxicity assays revealed a CC50 value of 387.7 µg/mL, while antiviral testing demonstrated an IC50 of 3.81 µg/mL, resulting in a high selective index (SI) of 102. Plaque reduction assays confirmed concentration-dependent virucidal effects, with up to 93% viral inhibition at 200 µg/mL. GQAs significantly disrupted key stages of the viral life cycle, including adsorption (80% inhibition at 250 µg/mL) and replication (up to 85.6% inhibition). Western blot analysis supported these findings, showing dose-dependent suppression of viral protein expression. Moreover, GQAs inhibited papain-like protease (PLpro) and the spike protein receptor binding domain (RBD) with notable potency, approaching the efficacy of reference antivirals remdesivir and molnupiravir. Molecular docking studies revealed strong binding affinities between the tri-substituted GQA and both the spike RBD and RNA-dependent RNA polymerase (RdRp), mediated by salt bridges, hydrogen bonding, and electrostatic interactions. These findings highlight GQAs from Copaifera lucens as promising multi-target antiviral candidates against SARS-CoV-2, exhibiting both direct virucidal effects and inhibition of viral entry and replication machinery.