Quercetin is a natural polyphenol belonging to the flavonol class. It inhibits 3-chymotrypsin-like protease (3CLpro) and PLpro. The likely antiviral properties are challenged by its poor oral bioavailability profile.
When looking for new antiviral compounds aimed to counteract the COVID-19, a disease caused by the recently identified novel Coronavirus (SARS-CoV-2), the knowledge of the main viral proteins is fundamental. The major druggable targets of SARS-CoV-2 include 3-chymotrypsin-like protease (3CLpro), papain-like protease (PLpro), RNA-dependent RNA polymerase, and spike (S) protein. Molecular docking studies have highlighted that quercetin, a natural polyphenol belonging to the flavonol class, inhibits 3CLpro, PLpro and S proteins. Biophysical technics have then very recently confirmed that quercetin is reasonably a potent inhibitor of 3CLpro. The likely antiviral properties of quercetin are anyway challenged by its very poor oral bioavailability profile and any attempt to overcome this limit should be welcome. A phospholipid delivery form of quercetin (Quercetin Phytosome