Studies have previously shown that tea catechins -- biologically active chemicals in tea -- effectively deactivated the virus SARS-CoV-2.
In the new study, published in the journal Scientific Reports, healthy volunteers consumed a candy containing green tea or black tea, and saliva collected from them immediately after the candy consumption significantly decreased virus infectivity in vitro.
“We found that all the Omicron subvariants that we tested were efficiently inactivated by treatment with green tea, Matcha green tea, and black tea,” said Osam Mazda, from the Department of Immunology, at Kyoto Prefectural University of Medicine in Japan.
“The study may suggest a molecular basis for potential usefulness of these compounds in suppression of mutant viruses that could emerge in the future and cause the next pandemic,” Mazda said.
It has been reported that viruses infect salivary glands and other oral tissues to propagate. However, the virus inactivating effect was not demonstrated in the saliva collected from healthy volunteers 5 or 15 min after the cessation of the candy consumption. This may be due to high flow rates of saliva in healthy volunteers.
“A candy containing green tea or black tea may be useful for inactivating virus if infected persons consume it, to decrease virus load in the oral cavity and gastrointestinal tract of the infected person, as well as to prevent spread of the virus from the infected persons to nearby non-infected persons,” the researchers said.
The team showed that the tea catechins, particularly (-)-epigallocatechin gallate (EGCG) and its derivative theaflavin-3,3'-di-O-digallate (TFDG), strongly suppressed infectivity of BA.1 and XE subvariants, while effect on BA.2.75 was weaker.
Neutralisation assay showed that EGCG and TFDG inhibited interaction between BA.1’s spike protein RBD (receptor-binding domain) and ACE2.
In-silico analysis suggested that N460K, G446S and F490S mutations in RBDs crucially influenced the binding of EGCG/TFDG to the RBDs.
The results indicate specific amino acid substitutions in RBDs that crucially influence the binding of EGCG/TFDG to the RBDs and different susceptibility of each Omicron subvariant to EGCG/TFDG. IANS/KB
