Biflavonoids and glucopyranoside derivatives from Ouratea polygyna (Ochnaceae) and their inhibition of the SARS-CoV-2 3CLPro main protease.

Ouratea polygyna is a plant endemic to Brazil whose phytochemical and/or biological properties have not yet been studied. Studies point to flavonoids and phenols as inhibitors of the proliferation of coronaviruses. Therefore, we proceeded to the identification of compounds present in the extracts of this plant and evaluated their potential for viral inhibition on SARS-CoV-2 3CLPro. The results showed that the bioflavonoids fractions with amentoflavone and robustaflavone inhibited the viral protease at the levels of a synthetic inhibitor at all concentrations evaluated (10, 25 and 50 µM). Fractions with glucopyranoside derivatives (1-O-(4-hydroxyphenyl)-6-O-(4-hydroxybenzoyl)-β-D-glucopyranoside and 4-hydroxyphenyl-(6'-O-benzoyl)-O-β-glucopyranoside) also showed inhibition of this enzyme at all concentrations, with an increase in inhibition above the positive control when used at 50 µM concentration. These results demonstrate an important role of amentoflavone, robustaflavone, and glycopyranoside derivatives in the inhibition of viral replication and transcription.