Total Polyphenol Content and H-ORAC Values of Traditional Okinawan Vegetables and Change in Antioxidant Activity during Storage

The total polyphenol content and H-ORAC values of 15 traditional Okinawan vegetables were determined and compared with those of spinach. Nishiyomogi, Hosobawadan, Botanboufu, and Suizenjina exhibited higher total polyphenol contents and H-ORAC values than those of spinach. The total polyphenol content and H-ORAC values exhibited a high correlation (r = 0.986, p < 0.01), suggesting that polyphenols are the major contributors to the antioxidant activity of Okinawan traditional vegetables in water systems. The effects of storage temperature on the H-ORAC values and total polyphenol content of six traditional Okinawan vegetables were also investigated. The behavior of the total polyphenol content and H-ORAC values during storage differed among the vegetables. In Nishiyomogi and Suizenjina, the total polyphenol content decreased on the fifth day of storage at 25 ℃. In contrast, for Botanboufu, significant increases in the total polyphenol content and H-ORAC values were observed after the second day of storage at 25 ℃ and on the fifth day of storage at 15 and 25 ℃ compared to the first day of storage. No increase or decrease in the total polyphenol content or H-ORAC values was observed in the other vegetables during storage.