Design, synthesis, and activity evaluation of C-8 arylated luteolin derivatives as influenza endonuclease inhibitors.

The polymerase acidic (PA) subunit of the influenza virus, an endonuclease of the RNA-dependent RNA polymerase, represents a viable target for anti-influenza therapies, as evidenced by the efficacy of the FDA-approved drug Xofluza. A characteristic feature of endonuclease inhibitors is their ability to chelate Mg or Mn ions within the enzyme's catalytic site. Previously, our studies identified luteolin and its C-8-glucoside orientin as potent endonuclease inhibitors. This report details our subsequent investigation into the structural modifications of the phenyl moiety attached to the C-8 position of luteolin. The inhibitory potencies (IC values) quantified with AlphaScreen technology indicated that substituting the C-8 glucose moiety of orientin resulted in compounds with comparable inhibitory potency. From a series of eighteen compounds, acid 12 with 3-carboxylphenyl moiety at the C-8 position was the most potent inhibitor with nanomolar potency.