Quercetin and the active ingredients in green tea, called catechins, are polyphenols known as flavonoids. They have a variety of anti-inflammatory, anti-oxidant and anti-enzymatic activities. Quercetin and its derivatives as well as different catechins found in green tea were found to inhibit the SARS proteases . Specifically, Thi Nguyen et al. Found that both Epigallocatechin Gallate and Quecertin inhibit the SARS main protease, 3CLpro with an IC50 of 73uM in vitro. In addition, Ji Young Park et al. reported that Quercetin inhibits both the SARS Proteases, 3CLpro and PLpro, and the Middle Eastern Respiratory Syndrome virus (MERS) 3CLpro protease with an IC50 of 52.7uM, 8.6uM and 34.8uM respectively, in vitro . Quecertin also modulates the cellular unfolded protein response (UPR). As coronaviruses can utilize the UPR to complete different stages of the viral life cycle during infection, Nabirotchkin et al. suggested that quercetin may have anti-coronavirus effects through its modulation of this pathway .