Low molecular weight chitooligosaccharide inhibits infection of SARS‐CoV‐2 in vitro

Aims The discovery of antiviral substances to respond to COVID‐19 is a global issue, including the field of drug development based on natural materials. Here, we showed that chitosan‐based substances have natural antiviral properties against SARS‐CoV‐2 in vitro. Methods and Results The molecular weight of chitosan‐based substances was measured by the gel permeation chromatography analysis. In MTT assay, the chitosan‐based substances have low cytotoxicity to Vero cells. The antiviral effect of these substances was confirmed by quantitative viral RNA targeting the RdRp and E genes and plaque assay. Among the substances tested, low molecular weight chitooligosaccharide decreased the fluorescence intensity of SARS‐CoV‐2 nucleocapsid protein of the virus‐infected cells in a dose‐dependent manner. Conclusions In conclusion, the chitooligosaccharide, a candidate for natural treatment, has antiviral effects against the SARS‐CoV‐2 virus in vitro. Significance and Impact of Study In this study, it was suggested for the first time that chitosan‐based substances such as chitooligosaccharide can have an antiviral effect on SARS‐CoV‐2 in vitro.