Covid-19: Tannic acid can block viral infection

I want to believe… In December 2020 study from the Chinese Medical University in Taiwan have shown that tannic acid, a polyphenol found in wine (responsible for that tannic side that we treasure so much in red), can prevent the coronavirus from entering our cells and also from multiplying. Enthusiasm among wine drinkers quickly fizzled out before being bombarded with explanations from experts such as the late Axel Kahn in a February 5, 2021 article at Parisian, which denounced the misleading label. But a new study is now pouring water on their mill. This is a Canadian publication dated February 27, 2022 in the newspaper International Journal of Molecular Sciences. She shows that tannic acid can also block the virus and prevent it from sticking to our cells’ ACE2 receptor, thus avoiding infection. But then again, we are talking about tannic acid, not wine!

Tannic acid targets three key processes of the virus

As shown earlier, tannic acid blocks the TMPRSS2 protease (required for the virus to enter our cells) and the viral protease 3-chymotrypsin-like protease (3CLpro), essential for its replication. But this new analysis adds a key point: tannic acid binds to a region of the receptor-binding domain (RBD), a region of a spike protein that recognizes and binds to the human cellular ACE2 receptor. Thus, this polyphenol will prevent this RBD region from attaching to our cells, avoiding infection.

This is at least what we saw with the Alpha variant RBD, which was the majority of the variant during the study.explains Charles Ramasami, an antioxidant expert at the Canadian National Institute for Scientific Research (INRS) and author of the study. Thus, we found that tannic acid can prevent infection as well as suppress it once it has already started by blocking proteases. Thus, this molecule can be used for prophylactic purposes, as well as as an antiviral agent after infection. But all this is yet to be confirmed.” Because this study is only in vitro and didn’t really study the effects of tannic acid on infected cells, let alone animal models.

Very non-toxic molecule

Nevertheless, these results are encouraging and deserve to be verified in further studies. Because if these protective effects are confirmed, tannic acid will become a real competitor to the antivirals currently available against Sars-CoV-2, in particular due to its very low toxicity. “Tannic acid has very few side effects and is very non-toxic compared to the antivirals used against Covid. (how Molnupiravir from Merck, which may pose a risk of mutagenesis, editor’s note), he adds. Thus, even at high concentrations, tannic acid should pose a lower risk.

Bonus: This polyphenol also has antioxidant effects, which could be helpful for coronavirus infections:The observed effect of tannic acid is due directly to its binding to the RBD region, and not a consequence of its antioxidant action. This means that this antioxidant effect will be an additional action of tannic acid, which can help reduce infection-induced inflammation, since the coronavirus is known to cause oxidative stress.

And no, not wine will save us from Covid-19

Tannic acid still has a long way to go before becoming a new weapon against Covid-19, knowing that many of the molecules that appear promising in research in vitro be ineffective live or in people. But even if these positive results were confirmed, this would not mean at all that the wine would protect against Covid: “The amount of tannic acid found in wine is too low to have such a protective effect, you would have to drink ten bottles of red a day to reach the desired concentration!“, – he warns. It should not be forgotten that wine is alcohol and its consequences are not necessarily better than those of a coronavirus infection.

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