Green tea is a popular drink globally and was traditionally used as a medicinal herb to treat many diseases. It is made from the leaves of the Camelia sinensis plant. Research from past decades has shown that green tea and its characteristic polyphenols named catechins can help prevent diabetes, obesity, cancer, and heart diseases.
Green tea polyphenol EGCG, its structure and biological activities
Studies have also shown that tea catechins have anti-viral activities and can be protective against diseases resulting from oxidative stress and inflammation. Some recent studies suggest the potential of green tea to prevent and treat COVID-19 disease caused by the SARS-CoV-2 virus. The most abundant catechin and the major active constituent in green tea is (−)-epigallocatechin-3-gallate (EGCG).
EGCG has a polyphenolic structure and is a strong antioxidant that removes reactive radicals and chelating ions to inhibit the formation of reactive oxygen species (ROS). EGCG has 8 phenolic groups and offers multiple electron donors and acceptors for hydrogen bonding to several molecules such as proteins. This is why EGCG has high affinity to various proteins, binds with them, and inhibits their activities.
Determining the potential of EGCG or tea consumption in COVID-19 prevention and treatment
Researchers recently published an article that reviewed the mechanisms by which EGCG could inhibit SARS-CoV-2 infection and the various syndromes caused by COVID-19. They critically evaluated previously published results in the literature about COVID-19 symptoms and pathology from the perspective of biological differences between humans and rodents, dose-response relationships, and potential side effects. They also analyzed relevant publications evaluating EGCG’s protective activities against COVID-19. Their objective was to determine the utility of EGCG or tea consumption in the prevention, alleviation, and treatment of COVID-19. This study is published in the journal Trends in Food Science & Technology.
Results show EGCG can potentially inactivate SARS-CoV-2 and inhibit viral reproduction
The key findings of their study revealed that EGCG activates Nrf2 and suppresses angiotensin-converting enzyme 2 (ACE2), which is a cellular receptor for SARS-CoV-2, and TMPRSS2, a mediator of virus entry into the host cell. EGCG also inactivates SARS-CoV-2 main protease and inhibits viral reproduction. EGCG’s antioxidant activity may offer protection against SARS-CoV-2-induced mitochondrial ROS, which promotes viral replication and against ROS burst caused by neutrophil extracellular traps. EGCG suppresses ER-resident GRP78 activity and expression and can potentially inhibit the life cycle of SARS-CoV-2.
EGCG may suppress SARS-CoV-2 infection via suppressing the expression of cell surface ACE2 and TMPRSS2 via activating Nrf2. EGCG may also inhibit SARS-CoV-2 Mpro — a protease essential for viral reproduction.”
The researchers also found protective effects of EGCG against (a) thrombosis by suppressing tissue factors and activating platelets; (b) cytokine storm-induced acute lung injury/respiratory distress; (c) sepsis via inactivating redox-sensitive HMGB1; and (d) lung fibrosis by augmenting Nrf2 and suppressing NF-κB.
Findings highlight the need for further studies on the role of EGCG in COVID-19 prevention and treatment
To summarize, EGCG may have the potential to inhibit SARS-CoV-2 infection, suppress SARS-CoV-2 replication, decrease cytokine storm and hence thrombosis and lung fibrosis. According to the authors, no such human studies have not been conducted so far. Other catechins in green tea may exhibit similar protective properties as EGCG, possibly at lower levels. Green tea consumption has been previously shown to decrease the risk for diabetes, obesity, and cardiovascular diseases, all of which increase the risk of severe COVID-19.
However, these observations need to be further substantiated in humans and animals. The possible actions of EGCG against SARS-CoV-2 highlight the relevance of further studies on the role of EGCG in COVID-19 prevention and treatment in humans. These observations also warrant epidemiological studies on the possible preventive effects of green tea consumption on COVID-19.
It is important to conduct epidemiological studies to determine whether regular tea consumption (and the amount required) could decrease risk for SARS-CoV-2 infection and associated syndromes.”