Antioxidant-related activities of ethanol extracts from edible and medicinal plants cultivated in Okinawa, Japan

Antioxidant-related activities was examined in ethanol extracts of 53 parts of 36 species of the plants cultivated and used as edible and medicinal plants in food culture of Okinawa. The activities examined in this study were DPPH radical scavenging, inhibition of AAPH-induced lipid oxidation, and inhibition of H2O2-induced oxidative cell death. Strong DPPH radical scavenging activity was observed in the extracts from the rhizomes of Alpinia speciosa, the leaves of Mallotus japonicus, the branches of Heritiera littoralis, the leaves of Psidium guajava, the leaves of Eucalyptus robusta, and the underground part of Hypericum chinense var. salicifolia. Potent inhibitory activity of lipid peroxidation was observed in the extracts from the leaves of M. japonicus, the leaves of Nandina domestica, the leaves of H. chinense var. salicifolia, the leaves of P. guajava, and the fruits and the rhizomes of A. speciosa. Strong inhibition against oxidative cell death was observed in the extracts from the leaves of P. guajava, the leaves of H. chinense var. salicifolia, the fruits and the rhizomes of A. speciosa, the branches of H. littoralis, the branches of Elaeagnus glabra, the branches of Citrus depressa, and the tuberous roots of Ipomoea batatas. From the results of these three assays, P. quajava, H. chinense var. salicifolia, and A. speciosa were selected as the plants having potent antioxidant ability. Interestingly, the extracts from tuberous roots of two cultivated species of L batatas showed strong protective activity against oxidative cell death, whereas the other activities were very week and their phenol contents were not high.