Fisetin and rutin as 3C protease inhibitors of enterovirus A71

Enterovirus A71 (EV-A71) causes severe complications: encephalitis, pulmonary edema, and death. No effective drug has been approved for clinical use. This study investigated the antiviral effects of flavonoids against EV-A71. An in vitro inhibitor screening assay using recombinant EV-A71 3C protease (3Cpro) demonstrated fisetin and rutin inhibiting 3Cpro enzymatic activity in a dose-dependent manner. Cell-based fluorescence resonance energy transfer (FRET) assay with an EV-A71 3Cpro cleavage motif probe also confirmed that fisetin and rutin inhibited the replication of EV-A71 in cells. A virus replication assay indicated that fisetin and rutin reduced significantly the EV-A71-induced cytopathic effect and viral plaque titers in RD cells culture. The IC50 values of plaque reduction against EV-A71 were 85 μM for fisetin and 110 μM for rutin. Therapeutic indices (CC50/IC50 of plaque reduction assays) of fisetin and rutin exceeded 10. The study suggests that fisetin and rutin inhibit the replication of EV-A71.

► Recombinant EV71 3C protease assays were used for screening 3C inhibitors.
► Fisetin and rutin showed inhibitory effects on 3C protease activity.
► IC50 values against EV71 were 84.48 μM for fisetin and 109.63 μM for rutin.
► The study suggested fisetin and rutin as anti-EV71 agents.