Abstract
Saliva plays major roles in the human-to-human transmission of SARS-CoV-2. If the virus in saliva in SARS-CoV-2-infected individuals can be rapidly and efficiently inactivated by a beverage, the ingestion of the beverage may attenuate the spread of virus infection within a population. Recently, we reported that SARS-CoV-2 was significantly inactivated by treatment with black tea, green tea, roasted green tea and oolong tea, as well as their constituents, (-) epigallocatechin gallate (EGCG), theasinensin A (TSA), and galloylated theaflavins. However, it remains unclear to what extent tea inactivates the virus present in saliva, because saliva contains various proteins, nitrogenous products, electrolytes, and so on, which could influence the antivirus effect of tea. Here, we assessed whether tea inactivated the SARS-CoV-2 which was added in human saliva. A virus was added in healthy human saliva in vitro, and after treatment with black tea or green tea, the infectivity of the virus was evaluated by TCID50 assays. The virus titer fell below the detectable level or less than 1/100 after treatment with black tea or green tea for 10 s. The black tea-treated virus less remarkably replicated in cells compared with the untreated virus. These findings suggest the possibility that the ingestion of tea may inactivate SARS-CoV-2 in saliva in infected individuals, although clinical studies are required to determine the intensity and duration of the anti-viral effect of tea in saliva in humans.
Highlights
SARS-CoV-2 is transmitted from a person to another mainly through droplet infection and contact infection [1]
If the SARS-CoV-2 in saliva of infected individuals is effectively inactivated by a beverage, the intake of it could attenuate the spread of virus infection within a population, while causing relatively low negative influence on economic and social activities
We found that theasinensin A (TSA) and TFDG significantly inhibited interaction between recombinant ACE2 and RBD of the Spike protein, which may be, at least partially, involved in the mechanisms underlying the anti-coronavirus effect of tea
Summary
SARS-CoV-2 is transmitted from a person to another mainly through droplet infection and contact infection [1]. If the SARS-CoV-2 in saliva of infected individuals is effectively inactivated by a beverage, the intake of it could attenuate the spread of virus infection within a population, while causing relatively low negative influence on economic and social activities. As for the active constituents, (-) epigallocatechin gallate (EGCG), theaflavin-3,3 -di-gallate (TFDG) and theasinensin A (TSA) strongly inactivated SARS-CoV-2. Potentially, tea could be useful for the inactivation of SARS-CoV-2 in the saliva of infected persons. It remains unclarified as to what extent tea could inactivate the virus present in human saliva that contains various constituents. We performed an in vitro analysis to ask whether tea could inactivate the virus added in healthy human saliva
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