In this paper, we investigated the inhibitory effect of water extract of persimmon leaves and its main contents (kaempferol, quercetin and myricetin) on stimulus-induced superoxide generation in human neutrophils. When the cells were pre-incubated with the water extract of persimmon leaves, the superoxide generation induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP) was significantly suppressed in a concentration-dependent manner. Meanwhile, it also showed a weak inhibitory effect on arachidonic acid (AA) and phorbol 12-myristate 13-acetate (PMA)-induced superoxide generation. Three main flavonoid compounds (kaempferol, quercetin and myricetin) were isolated from water extract; the investigation showed that these three compounds significantly suppressed the superoxide generation induced by fMLP in a concentration-dependent manner. On the other hand, they weakly enhanced the AA-induced superoxide generation in low concentration but suppressed in high concentration. Moreover, they showed weakly inhibitory effect on PMA-induced superoxide generation even at a high concentration. These results indicate the potential value of health protection of persimmon leaf tea.

Persimmon is widely distributed over the world. Persimmon leaves, as an abundant natural resource, has attracted a lot of attention for its exploitation. The persimmon leaf tea is accepted in Asia as health food with anti-oxidantion, anti-aging and immune-enhancement activities. Current work was focused on the superoxide generation inhibitory effect of main flavonoid constituents in persimmon leaf. The results show that the water extract and three flavonoid compounds (kaempferol, quercetin and myricetin) of persimmon leaves suppressed the stimulus-induced superoxide generation in human neutrophils, from which, a protective effect for oxidative stress is expectable from the persimmon leaf tea. This conclusion support the rationality of persimmon leaf tea as health food and may be of help in the research and development of persimmon leaf.