Lotus (Nelumbo nucifera Gaertn.) leaf water extracts suppress influenza a viral infection via inhibition of neuraminidase and hemagglutinin

Abstract

• Lotus ( Nelumbo nucifera Gaertn.) leaf inhibits influenza virus infection. • Lotus leaf directly blocks IAV binding onto the cells. • Lotus leaf suppresses neuraminidase and hemagglutinin of IAV. • Lotus leaf prevents cytopathic effect by H1N1 and H3N2 IAV. • Isoquercitrin in the lotus leaf is the main active component for an anti-IAV efficacy. Lotus ( Nelumbo nucifera Gaertn.) is a perennial aquatic plant, that has been used in folk to treat various diseases. Here, we first demonstrate the water extract of lotu s leaf (WLL) has a strong inhibitory effect on influenza A virus (IAV) infection by inhibiting neuraminidase (NA) and hemagglutinin (HA). To investigate the effect of WLL on IAV infection, we used green fluorescent protein (GFP)-tagged Influenza A/PR/8/34, fluorescence-activated cell sorting (FACS) analysis, and plaque reduction assay. WLL significantly repressed viral infection, dose-dependently. Immunofluorescence (IF) analysis confirmed that WLL reduces influenza HA, NA, M2, and NP viral proteins expression. WLL strongly inhibited HA and reduced NA activity of IAV. Among six components in WLL, isoquercitrin exerted potent antiviral efficacy. Additionally, WLL potently inhibited the cytopathic effect caused by H1N1 or H3N2 IAV. In conclusion, our results suggest that WLL could be used as a natural viral inhibitor for H1N1 and H3N2 influenza viral infection.