Comparative Analysis of Oxidative Parameters, Antioxidant Content, and Antioxidant Enzyme Activity during Fruit Ripening in Tomato Pericarp and Pulp

Abstract

L-ascorbate (ASA; a reduced form of vitamin C) and glutathione (GSH) in tomato fruit participate in many diverse biological processes such as fruit ripening. In general, ASA and GSH are regulated by the reactive oxygen species scavenging system (antioxidant system). The tomato is a complex fruit composed of skin, pericarp walls, placenta, locular tissue, and seed tissues, and it is unclear whether the antioxidant contents and systems differ among these tissues. The aim of this study is to clarify tissue-specific changes in oxidative parameters, antioxidant contents, and antioxidant enzymes during fruit ripening in the tomato pericarp (skin, pericarp walls) and pulp (placenta, locular tissue, seeds). Lipid peroxidation and the H2O2 content remained constant during fruit ripening and were lower in the pulp than in the pericarp. In addition, ASA and GSH contents were the same in both these tissues when the fruits were picked at the red stage; however, changes in the superoxide dismutase, catalase, and ASA–GSH cycles, related to enzymes such as ascorbate peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase, showed tissue-specific differences during ripening. These results indicate that ASA and GSH contents in both tissues are the same when fruits are picked at the red stage, but oxidative parameters and antioxidant systems show tissue-specific differences during fruit ripening. Furthermore, our results indicate that oxidative stress in the pulp was lower than that in the pericarp. This work therefore provides a basis for understanding the role of antioxidant systems during tomato fruit ripening.