Antioxidant activity in astringent and non-astringent persimmons

Abstract

SummaryCatechins, ascorbic acid and -cryptoxanthin concentrations during fruit development and the antioxidant activity in skin and flesh were investigated in astringent ‘Saijyo’ and non-astringent ‘Fuyu’ persimmons (Diospyros kaki Thunb.). The IC50 values (a midpoint of 50% between zero and full inhibition of diazo dye formation) of superoxide (O2–)-scavenging activity remained low in the skin throughout fruit development.The IC50 values of the activity increased with d after full bloom (DAFB) in the flesh of the non-astringent type, whereas values remained low until harvest in the astringent type. However, IC50 values increased sharply after the removal of astringency with ethanol spray. Catechin concentrations in the flesh also decreased after the removal of astringency, whereas the concentrations in the skin did not decrease. Ascorbic acid concentrations in the skin and flesh were high at the beginning and middle of fruit development, but -cryptoxanthin in the skin and flesh increased toward harvest. However, -cryptoxanthin concentrations in the skin and flesh were lower than catechins and ascorbic acid. In addition, IC50 in the flesh of the non-astringnet type was high despite the increase of -cryptoxanthin at harvest.These results suggest that catechins and ascorbic acid influence O2-scavenging activity at the beginning and middle of fruit development, and catechins are associated with the O2-scavenging activity at ripening. Changes in 1-diphenyl-2-picrylhydrazyl (DPPH)-radicalscavenging activity with fruit developmental stage were similar to that for O2–. That is, IC50 values of DPPH-radical-scavenging activity decreased rapidly after the removal of astringency. -cryptoxanthin did not eliminate the DPPH-radicals. Therefore, the DPPH-radicals in persimmons may be eliminated primarily by catechins and ascorbic acid. The utilization of tannins before the removal of astringency is discussed.