Tannins derived from natural plant sources are known to provide many health benefits to humans and animals. Among the various
tannins, those derived from persimmon (Diospyros kaki) have exhibited strong inactivating effects against pathogens that induce diseases in humans. However, few studies have focused on the
antiviral effects of persimmon
tannin against pathogen-induced diseases in animals. In this study, we investigated the
antiviral effects of persimmon
tannin against various
avian influenza viruses revealing that
tannin at a concentration of 1.0 mg ml-1 reduced viral infectivity in >6.0-log scale against all tested
avian influenza viruses. In addition, this persimmon
tannin concentration effectively inhibited the receptor binding and membrane fusion abilities of
viral hemagglutinin (HA), which play important roles in
avian influenza virus infection. These results suggest that persimmon
tannin inactivates the HA of
avian influenza viruses and reduces their infectivity. Persimmon
tannin is a safer natural substance than the currently used chemical compound related to
antiviral substance. When inactivation of the viruses which are present in environmental water such as roosting water of wild birds will be needed, persimmon
tannin is expected to become an
antiviral resource that may prevent the spread of several
avian influenza virus subtypes.