Oxygen Radical Absorbance Capacity and Luteolin Content in Hot Water Infusion of Kawaraketsumei from Noheji, Aomori

Abstract

　Kawaraketsumei is an annual legume whose dried and roasted leaves, stems, and pods are consumed as a healthy tea. Noheji town in Aomori prefecture is promoting the tea as a specialty product of local area. It is known to contain various polyphenols. However, it is unclear whether the kawaraketsumei tea, that is the HWIK (hot water infusion of kawaraketsumei) has antioxidant activity as oxygen radical absorbance capacity (ORAC), and whether it contains polyphenols, especially luteolin. In this study, we investigated hydrophilic-ORAC (H-ORAC) and the total polyphenol, luteolin content in the HWIK (blend of each parts and part-specific). The H-ORAC value was calculated from HWIK, indicating that it has antioxidant activity. Additionally, the HWIK contained polyphenols. It was also found that contained luteolin and luteolin 7-O-glucoside, a glycoside of luteolin. Although all the parameters were not significantly different between the blend ratios, the pod had the highest antioxidant activity and concentrations of polyphenols. These results are expected to lead to the development of processing method and usage utilizing the characteristics of kawaraketsumei.