Fig. 2.

Underlying of the most important structural proteins of CoV are spike protein (S), membrane protein (M), envelop protein (E), and the nucleocapsid protein (N), the RNA genome of CoV is packed in the nucleocapsid protein and further covered with envelope. The hydroxyl group of flavonoids at 7-position looks important to bind at the binding site against 3-chymotrypsin-like protease (3CLpro), and papain-like protease (PLpro). Flavonoids as a vast reservoir of therapeutically active constituents as antiviral candidates against RNA viruses, adopted from Rasouli et al. (2017), Solnier et al. (2020), and Pillaiyar, Meenakshisundaram, and Manickam (2020).