Some very interesting news came out of North Carolina State University last month regarding a particular variety of grape that grows across much of the East Coast and the Midwest. The mighty muscadine, often used for jams, jellies, juice and wines, contains a chemical compound that can inhibit a SARS-CoV-2 (aka COVID-19) enzyme.

The compound, also found in green tea and dark chocolate, can bind to and block the function of a particular enzyme in the virus, according to plant biologists at NCSU. De-Yu Xie, a professor of plant and microbial biology, explained these enzymes are important to the health and viability of cells. If they’re inhibited, the cells can’t perform necessary functions, like replication.

Xie’s lab focuses on finding nutraceuticals (any product derived from food sources with extra health benefits beyond basic nutritional value) that can inhibit either how a virus attaches to human cells or the propagation of a virus in human cells. In this study, the researchers used both lab studies and computer simulations to see how the main enzyme in COVID-19 (called Mpro) reacted when it was confronted with different plant chemical compounds already known for their anti-inflammatory and antioxidant properties.

Chemical compounds in muscadine grapes effectively inhibit an important SARS-CoV-2 protease.
Photo courtesy of De-Yu Xie, NCSU

“Mpro in SARS-CoV-2 is required for the virus to replicate and assemble itself,” Xie said. If they can inhibit or deactivate it, the virus will die. Their computer simulations showed that the chemical compounds from green tea, two varieties of muscadine grapes, cacao powder and dark chocolate were able to bind to different portions of Mpro.

Mpro’s downfall is having a portion like a pocket that can be filled by the chemical compounds, Xie explained. “When this pocket was filled, the [enzyme] lost its important function.”

Lab experiments completed by Yue Zhu, an NCSU 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.

Xie said muscadine grapes contain the inhibitory chemicals in their skins and seeds. “Plants use these compounds to protect themselves, so it is not surprising that plant leaves and skins contain these beneficial compounds,” he said.

According to North Carolina State Extension, muscadines are native to the Southeastern U.S. and have been cultured by growers for more than four centuries. Native Americans preserved muscadines as dried fruit long before the Europeans inhabited North America. Back in 1997, the USDA-ARS listed the grapes as a “new health food” because they contain significant amounts of resveratrol in their skins, pulp and seeds – resveratrol being the compound that can lower cholesterol and the risk of coronary heart disease. Now it seems growers may be able to tout another healthy function of the fruit.