Phytochemical distribution in hull and cotyledon of adzuki bean (Vigna angularis L.) and mung bean (Vigna radiate L.), and their contribution to antioxidant, anti-inflammatory and anti-diabetic activities

Total saponin content, total phenolics content, total flavonoids content, condensed tannin content in hull, cotyledon and whole grain of both adzuki bean and mung bean were determined by colorimetric methods. Vitexin and isovitexin contents in mung bean were determined by HPLC. Antioxidant effects were evaluated with DPPH scavenging activity and ferric reducing antioxidant power assay. In vitro anti-inflammatory and anti-diabetic effects of beans were evaluated by protease and aldose reductase inhibitory assays, respectively. The results indicated that the bean hulls were the most abundant in phytochemicals and largely contributed antioxidant activities, anti-inflammatory effects and anti-diabetic effects of whole grains. The result showed that mung bean hull was the most abundant with vitexin at 37.43 mg/g and isovitexin at 47.18 mg/g, respectively. Most of the phytochemicals and bioactivities were most predominantly contributed by the bean hulls with exception for condensed tannin of mung bean; which was more abundant in the cotyledon than its hull.