Food phytochemicals, epigallocatechin gallate and myricetin, covalently bind to the active site of the coronavirus main protease in vitro

Abstract

SARS-CoV-2 main protease is a possible target for protection against viral infection. This study examined the inhibitory effect of food phytochemicals on the main protease of SARS-CoV-2 by determining a cleaved product after chromatographic separation. First, 37 phytochemicals, including glycosides and metabolites, were screened at 20 µM; epigallocatechin gallate, myricetin, theaflavin, herbacetin, piceatannol, myricitrin, and isothiocyanates inhibited the enzyme in varying degrees. The IC50 values were estimated from 0.4 to 33.3 µM against the 0.5-µM enzyme. The dose-dependent adduction of epigallocatechin gallate and myricetin was confirmed by quinone staining of protein blotted onto a membrane. The enzyme activity was decreased by increasing the concentration of the two phytochemicals, accompanied by increasing the respective adducted molecule estimated by intact mass spectrometry. Reduced glutathione canceled the formation of conjugate and the inhibitory effect of epigallocatechin gallate or myricetin on the enzyme, suggesting that the formation of the quinone moiety in the phytochemicals is critical for the inhibition. The covalent binding of epigallocatechin gallate or myricetin to the cysteine residue at the active site was confirmed by analyzing peptides from the chymotrypsin-digested main protease.

COVID-19 and per capitagreen tea consumption: update

“…There is mounting evidence suggesting the therapeutic potential of green tea catechins in prevention/treatment of COVID19. In particular, in addition to numerous docking studies (for instance, [1-7]) there is growing number of studies showing direct antiviral activity of at least one catechin epigallocatechin-3-gallate (EGCG) against SARS-CoV-2 in in vitro experiments ([8-17] see also [18-20] for review). Moreover, a recent work [21] reports that EGCG from green tea effectively blocks infection of SARS-CoV-2 and new variants .…”