Antiviral Effects of Lindera obtusiloba Leaf Extract on Murine Norovirus-1 (MNV-1), a Human Norovirus Surrogate, and Potential Application to Model Foods

Noroviruses are the leading cause of acute gastroenteritis and food poisoning worldwide. In this study, we investigated the anti-noroviral activity of Lindera obtusiloba leaf extract (LOLE) using murine norovirus (MNV-1), a surrogate of human norovirus. Preincubation of MNV-1 with LOLE at 4, 8, or 12 mg/mL for 1 h at 25 °C significantly reduced viral infectivity, by 51.8%, 64.1%, and 71.2%, respectively. Among LOLE single compounds, β-pinene (49.7%), α-phellandrene (26.2%), and (+)-limonene (17.0%) demonstrated significant inhibitory effects on viral infectivity after pretreatment with MNV-1, suggesting that the anti-noroviral effects of LOLE may be due to the synergetic activity of several compounds, with β-pinene as a key molecule. The inhibitory effect of LOLE was tested on the edible surfaces of lettuce, cabbage, and oysters, as well as on stainless steel. After one hour of incubation at 25°C, LOLE (12 mg/mL) pretreatment significantly reduced MNV-1 plaque formation on lettuce (76.4%), cabbage (60.0%), oyster (38.2%), and stainless-steel (62.8%). These results suggest that LOLE effectively inhibits norovirus on food and metal surfaces. In summary, LOLE, including β-pinene, may inactivate norovirus and could be used as a natural agent promoting food safety and hygiene.