Evaluation of Antioxidant Activity of Vegetables from Okinawa Prefecture and Determination of Some Antioxidative Compounds

Abstract

We examined the phenolic contents of 45 species of vegetables and their radical scavenging activities for 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·). High contents of phenolic compounds and strong DPPH·scavenging activities were observed in extracts from Nishiyomogi, Ryukyuyomogi, Aojiso, Moroheiya, Hosobawadan, Bajiru, Ensai, Yaeyamakazura, Suizenjina, Botanbouhuu and Uikyou. Eight of these vegetables are traditional foods in Okinawa. These showed strong radical scavenging activities for the superoxide radical (O₂^-·) and tert-butylhydroperoxyl radical (t-BuOO·). We found five antioxidative phenolic compounds, D(+)-chicoric acid, chlorogenic acid, caffeic acid, luteolin 7-O-β-D-glucopyranoside, and luteolin 7-O-β-D-glucuronide, in Hosobawadan (Crepidiastrum lanceolatum Nakai). Their detailed structures were determined using ¹H-NMR, ¹³C-NMR, MS, and UV spectrometry.