Preharvest antioxidant activities of tropical fruit and the effect of low temperature storage on antioxidants and jasmonates

Antioxidant activities and antioxidants of the tropical fruit guava (Psidium guajava L.), mango (Mangifera indica L.), banana (Musa spp.), rose apple (Syzygium jambos Alston), and papaya (Carica papaya L.) were investigated. Total phenolics and ascorbic acid (AsA) were analyzed as antioxidants. IC50 values of superoxide (O2−)- and 1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity in fruit are generally linked with total phenolics, but the DPPH IC50 in papaya was associated with AsA concentrations. We also examined the effect of low temperature on antioxidant activity and jasmonates in the skin of bananas and mangoes. The degree of chilling injury was higher at 6 °C compared to 12 °C, but n-propyl dihydrojasmonate (PDJ) treatment decreased chilling injury at 6 °C. Endogenous jasmonates, superoxide dismutase (SOD) activity, total phenolics, and AsA were each linked to the degree of chilling injury. In general, IC50 values of O2−- and DPPH-radical scavenging activity were also associated with the degree of chilling injury, although O2− IC50 in mango showed no significant difference. These results suggest connections among jasmonates, AsA, and polyphenolics when tropical fruit are exposed to low temperatures.