Tannic acids and proanthocyanidins in tea inhibit SARS-CoV-2 variants infection

The COVID-19 pandemic has caused hundreds million cases and millions death as well as continues to infect human life in the world since late of 2019. The breakthrough infection caused from mutation of SARS-CoV-2 is rising even the vaccinated population has been increasing. Currently, the severe threat posed by SARS-CoV-2 has been alleviated worldwide, and the situation has transitioned to coexisting with the virus. The dietary food with antiviral activities may improve to prevent virus infection for living with COVID-19 pandemic. Teas containing enriched phenolic ingredients such as tannins have been reported to be antitumor agents as well as be good inhibitors for coronavirus. This study developed a highly sensitive and selective ultra-high performance liquid chromatography-high resolution mass spectrometric method for quantification of tannic acids, a hydrolysable tannin, and proanthocyanidins, a condense tannin, in teas with different levels of fermentation. The in vitro pseudoviral particles (Vpp) infection assay was used to evaluate the inhibition activities of various teas. The results of current research demonstrate that the tannins in teas are effective inhibitors against infection of SARS-CoV-2 and its variants.