Chlorophyll Degradation in Mitsuba Leaves during Storage

Article No. IX of the Mechanism of Chlorophyll Degradation in Harvested Leafy Vegetables

Abstract

Changes in levels of chlorophyll (Chl) and its derivative and Chl degrading enzyme activity were examined to elucidate the pathway of Chl degradation in stored mitsuba (Japanese hornwort, Cryptotaenia japonica Hassk. cv Senkaku) leaves. Chl content decreased markedly concurrent with the yellowing of leaves. Chlorophyllide (Chlide) a and 13²-hydroxychlorophyll a eluted as a Chl derivative, but their levels were low and did not increase during storage at 25°C. Chlorophyllase activity increased significantly with the yellowing of leaves. In contrast with its activity, peroxidase activity decreased markedly with the senescence of leaves. Additionally, lipoxygenase activity increased during storage at 1°C and 25°C. The activities of enzymes relating to Chl degradation, such as chlorophyllase, peroxidase, lipoxygenase and Chl oxidase, Were found in the chloroplasts of mitsuba leaves. These results suggest that Chl is degraded by chlorophyllase to Chlide and then the oxidative degradation of Chlide to a colorless compound occurs inside chloroplasts of mitsuba leaves.