Antiviral activity of herbal extracts against the hepatitis A virus

Herbal plants have long been used as traditional medicines to treat diseases caused by microbial pathogens. The hepatitis A virus (HAV) causes acute liver infection through the fecal–oral route. Although the antimicrobial activities of herbal extracts against bacterial and some viral pathogens have been extensively studied, their antiviral properties against HAV have not been investigated thus far. This study was designed to investigate the inhibitory effect of 16 herbal extracts against HAV. Significant inhibition of HAV was observed only when HAV was co-treated with extracts. Ten out of the 16 herbal extracts demonstrated significant virucidal activity against HAV. Alnus japonica extract at a concentration of 50 μg/mL reduced HAV titer by 3.43 ± 0.24 logs. Artemisia annua, Allium sativum, Allium fistulosum, and Agrimonia pilosa extracts showed 2.33 ± 0.43, 2.10 ± 0.41, 2.07 ± 0.60, and 2.03 ± 0.26-log reductions, respectively. Pleuropterus multiflorus, Eleutherococcus senticosus, Coriandrum sativum, Ginkgo biloba, and Torilis japonica extracts reduced HAV titer by 1.02 ± 0.21 to 1.90 ± 0.33 logs. Among the 10 herbal extracts, Alnus japonica extract was the most potent in inhibiting HAV without exhibiting cytotoxicity.