An Anti-influenza Component of the Bark of Alnus japonica

This study to identify anti-influenza components of the bark of Alnus japonica resulted in the isolation of four lupane-type triterpenes (1-4) and one steroid (5). Their structures were characterized on the basis of physicochemical properties, NMR evidence, and ESI-MS data compared with reported data in the literature. Betulinic aldehyde (3) exhibited a particularly strong anti-influenza effect against KBNP-0028 relative to a positive control.