<i>Magnolia officinalis</i> and Its Honokiol and Magnolol Constituents Inhibit Human Norovirus Surrogates

Abstract

Norovirus is a major cause of foodborne disease and nonbacterial gastroenteritis globally. This study evaluated the antiviral effects of <i>Magnolia officinalis</i> extract and its honokiol and magnolol constituents against human norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV) <i>in vitro</i>, and in model food systems. Pretreatment or cotreatment of <i>M</i>. <i>officinalis</i> extract at 1 mg/mL reduced MNV and FCV titers by 0.6-1.8 log. Honokiol and magnolol, which are the major polyphenols in the extract, showed significant antiviral effects against MNV and FCV. The virus-infected cells that were treated with <i>M</i>. <i>officinalis</i> extract exhibited significantly increased glutathione levels (<i>p</i> < 0.05). The extract, honokiol, and magnolol revealed ferric ion-reducing and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activities in a dose-dependent manner. Furthermore, MNV and FCV titers were reduced by >1.6 log or to undetectable levels in apple, orange, and plum juices and by 0.9 and 1.6 log in milk, respectively, when they were treated with the extract at 5 mg/mL. Therefore, the present study suggests that <i>M</i>. <i>officinalis</i> extract can be used as an antiviral food material to control norovirus foodborne diseases.