Changes in hydrogen peroxide and superoxide anion contents and superoxide dismutase activity during the maturation of sweet pepper (Capsicum annuum L.) fruit

Changes in hydrogen peroxide and superoxide anion contents and superoxide dismutase activity during the maturation of the sweet pepper (Capsicum annuum L.) fruit were investigated. The process of fruit maturity was divided into four stages (Imahori et al., 2000): in the Green stage, the fruit has no yellow pigment. At the Green/Yellow stage, the fruit has 10-20% yellow surface, whereas, in the Yellow/Green stage, the fruit has 50-60% yellow surface. In the Yellow stage, the fruit is completely yellow. The superoxide anion content increased steadily from the Green to the Yellow/Green stage. It then decreased in the Yellow stage, returning to equal that in the Green stage. The hydrogen peroxide content increased during maturation of the sweet pepper fruit. The changes in superoxide dismutase activity during maturation of sweet pepper fruit tended to parallel those of superoxide anion content. Superoxide dismutase activity significantly increased from the Green to the Yellow/Green stage, and then declined from the Yellow/Green to Yellow stage. However, the superoxide dismutase activity was still higher than that in the Green stage. These results indicate that the changes in the content of superoxide anion and the activity of superoxide dismutase may be related to the accumulation of hydrogen peroxide during maturation of sweet pepper fruit.