Effect of fruit ripening stage on antioxidant components of kiwifruit cultivars

The formation of excessive reactive oxygen species (ROS) can induce oxidative stress, which is related to the development of several diseases including diabetes, dementia, cardiovascular disease, and cancers. However, natural antioxidants can protect cellular components from oxidative processes caused by ROS, so their dietary intake in the form of fruit and vegetables is important. Kiwifruit contains a high level of antioxidants, such as vitamin C, carotenoids, and polyphenolic compounds, but few studies have investigated these because of the short history of cultivation of kiwifruits compared with most other crop plants. Here, I researched the effect of the fruit ripening stage on the antioxidant components of kiwifruit cultivars. Significant differences were observed between cultivars with respect to H-ORAC values ('Sanuki Gold' > 'Rainbow Red' > 'Hayward' > 'Kousui' > 'Kouryoku), as well as polyphenol content and total ascorbate content, which showed similar trends. Total carotenoid levels in three different kiwifruit cultivars were: 'Kousui' > 'Kouryoku' > 'Sanuki Gold'. Interestingly, 'Sanuki Gold' had the lowest carotenoid content despite being the yellowest cultivar. All cultivars contained seven different carotenoids: alpha-carotene, zeaxanthin, lutein-epoxide, beta-carotene, 9'-cis neoxanthin, violaxanthin, and lutein. Kiwifruit was shown to contain more lutein than other fruits such as peaches, apples, and grapes. The carotenoid content was maintained during the ripening process as well as H-ORAC values, polyphenol content, and total ascorbate content. 'Sanuki Gold' appears to be the cultivar with the strongest hydrophilic antioxidative effects, while 'Kousui' had the highest antioxidative effects from carotenoids, so these may therefore be more beneficial for human health.