XK and influenza: By a CPE inhibition assay, 2′,4′dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (17) and 3′,5′-dimethylether 3-O-β-D-galactopyranoside (18) (Figure 4) not only had inhibitory activity against the influenza virus H1N1 A/PR/8/34 NA but also showed inhibitory activity against wild-type novel swine influenza (WT) and oseltamivir-resistant (H274Y mutation) viral NA.