Effects of Shading on the Levels and Activities of Antioxidative Compounds in the Skin of Lemons and Apples

The effects of shading conditions on antioxidative activities of ascorbic acid, β-cryptoxanthin and polyphenols in lemon and apple fruit were studied. The IC50 values of superoxide (O-2)- and 1-diphenyl-2-picrylhydrazyl (DPPH)-radical-scavenging activities in lemon skin from entirely shaded trees (TS) were high compared to the untreated control (UC). Their IC50 values in apple skin were also higher in fruit shaded by paper bags (FS) and in fruit from TS compared to fruit from UC. Ascorbic acid and β-cryptoxanthin concentrations in lemon skin of TS were lower than those of UC. Polyphenolics in apple skins from FS and TS also decreased more than those from UC. These results suggest that shading may regulate the antioxidative components in the fruit, and as a result, may influence antioxidative activity.