Mori Cortex Radicis extract inhibits human norovirus surrogate in simulated digestive conditions

Norovirus is a major cause of acute gastroenteritis globally, resulting in enormous health and societal costs. In this study, the antiviral activities of Mori Cortex Radicis (MCR) extract and its bioactive flavonoids, morusin and kuwanon G, were tested against murine norovirus (MNV), a human norovirus surrogate, using plaque assay. The antiviral activity was confirmed in simulated digestive conditions, including simulated saliva fluid (SSF), simulated gastric fluid (SGF), and simulated intestinal fluid (SIF). Pre-treatment of MNV with MCR extract at 1000 µg/mL showed antiviral activity with a 1.1-log reduction. Morusin and kuwanon G also demonstrated a 1.0-log and 0.6-log reductions of MNV titers, respectively, at 100 µM. MCR extract at a concentration of 2 mg/mL in SSF, SGF, and SIF markedly reduced MNV titers by 1.8, 1.9, and 1.5 logs, respectively. Therefore, these data suggest that MCR extract can be used to control norovirus infectivity.