New Study: Green Tea Might Block Viral Growth

Close up of dried green tea leaves on a wooden spoon

Aside from water, green tea is the most widely consumed beverage around the world.

Green tea, which is made from the leaves and buds of the medicinal plant Camellia sinensis, has long been linked with health benefits – everything from reducing the risk of stroke and heart attacks to preventing cancer.

However, despite green tea’s link to positive health outcomes, hard empirical evidence to back up these health claims has been lacking – until recently.

Research at North Carolina State University led by De-Yu Xie, professor of plant and microbial biology, shows how chemical compounds in green tea can block the replication of viral growth in human cells. The research focused particularly on the impact green tea has on blocking a particular enzyme, or protease, in the SARS-COV-2 virus, which is responsible for the COVID-19 disease.

According to Xie, proteases are important to the health and viability of cells and viruses. If proteases are inhibited, cells cannot perform many important functions—like replication, for example.

“One of our lab’s focuses is to find nutraceuticals in food or medicinal plants that inhibit either how a virus attaches to human cells or the propagation of a virus in human cells,” Xie said.

In the study, the NC State researchers performed both computer simulations and lab studies showing how the so-called ‘main protease’ (Mpro) in the SARS-CoV-2 virus reacted when confronted with a number of different plant chemical compounds already known for their potent anti-inflammatory and antioxidant properties.

“Mpro in SARS-CoV-2 is required for the virus to replicate and assemble itself,” Xie said. “If we can inhibit or deactivate this protease, the virus will die.”

Computer simulations showed that the studied chemical compounds from green tea (as well as two varieties of muscadine grapes, cacao powder and dark chocolate) were able to bind to different portions of Mpro.

“Mpro has a portion that is like a ‘pocket’ that was ‘filled’ by the chemical compounds,” Xie said. “When this pocket was filled, the protease lost its important function.”

In vitro lab experiments completed by Yue Zhu, an NC State Ph.D. student in Xie’s lab, showed similar results. The chemical compounds in green tea and muscadine grapes were very successful at inhibiting Mpro’s function; chemical compounds in cacao powder and dark chocolate reduced Mpro activity by about half.

Green tea has five tested chemical compounds that bind to different sites in the pocket on Mpro, essentially overwhelming it to inhibit its function. Muscadine grapes, as well, contain these inhibitory chemicals in their skins and seeds.

According to the researchers, plants use these compounds to protect themselves, so it is not surprising that plant leaves and skins contain these beneficial compounds.

The findings are significant and show that green tea made from the tea plant Camellia sinensis has the potential to stop the COVID-19 virus as well as abnormal cell growth from proliferating.