Antiviral effect of flavonol glycosides isolated from the leaf of Zanthoxylum piperitum on influenza virus.

The ethanol extract of Zanthoxylum piperitum (L.) DC. showed in vitro antiviral activity against influenza A virus. Three flavonol glycosides were isolated from the EtOAc fraction of Z. piperitum leaf by means of activity-guided chromatographic separation. Structures of isolated compounds were identified as quercetin 3-O-β-D-galactopyranoside (1), quercetin 3-O-α-L-rhamnopyranoside (2), kaempferol 3-O-α-L-rhamnopyranoside (3) by comparing their spectral data with literature values. The anti-influenza viral activity of isolates was evaluated using a plaque reduction assay against influenza A/NWS/33 (H1N1) virus. The compounds also were subjected to neuraminidase inhibition assay in influenza A/NWS/33 virus. Compounds 1-3 exhibited antiviral activity against an influenza A virus in vitro, and inhibited the neuraminidase activity at relatively high concentrations.