Comparison of the phenolic contents, antioxidant activity and volatile compounds of different sorghum varieties during tea processing.

BACKGROUND: Sorghum grain is rich in phenolic compounds and has the potential to be developed into functional beverages such as sorghum grain tea, in which the health benefits and flavour are the important quality attributes to be considered in tea product development. Therefore, this study investigated the effect of grain tea processing steps on the phenolic contents, antioxidant activity and aroma profile (volatile compounds) of MR-Buster (red-coloured) and Shawaya Short Black 1 (black-coloured) sorghum and the results compared with those for our previously reported Liberty (white-coloured) sorghum. RESULTS: Tea processing had significant impacts on sorghum polyphenols and volatile compounds, but the effect and level varied among sorghum varieties. The phenolic contents and antioxidant activity in these three sorghum varieties were consistent in both raw grain and grain tea samples and in the order Shawaya Short Black 1 > MR-Buster > Liberty. However, the volatile profiles (both individual and grouped volatiles) were significantly different between sorghum varieties, and the abundance and diversity of the volatile compounds of the tea samples were in the order Liberty > MR-Buster > Shawaya Short Black 1. CONCLUSIONS: Black-coloured sorghum with high phenolic content and antioxidant activity is more suitable for making sorghum tea considering the health benefits. In terms of the aroma intensity and diversity, white-coloured sorghum could be the ideal material. However, future study is needed to determine the key volatile compounds that positively contribute to the aroma. This work provides important insights into the selection of grain materials for sorghum grain tea production. © 2019 Society of Chemical Industry.

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.

In vitro antidiabetic effects of selected fruits and vegetables against glycosidase and aldose reductase.

In vitro antidiabetic effect of fruits and vegetables with reports as folk remedies were investigated. The antidiabetic effects were evaluated by comparing the inhibitory properties of α-glycosidase, aldose reductase, and antioxidant activity. The results indicated that lychee extract exhibited the best dose-dependent inhibitory activity against α-glycosidase with IC 50 of 10.4 mg/mL, and lemon peel extract exhibited aldose reductase inhibitory potential with IC 50 value at 3.63 mg/mL. Besides, the result also showed that the inhibitory effects of blueberry and plum against α-glycosidase were strong among the fruits samples. Bitter gourd and eggplant demonstrated significant inhibitory potential against aldose reductase, with IC 50 values at 8.55 mg/mL and 8.06 mg/mL, respectively. The result from correlation analysis part showed that the antioxidant activities of selected fruits and vegetables were found related to their health beneficial effects, as there was positive correlations between total flavonoids content (TFC) and aldose reductase inhibitory activity (r (2) = 0.556).