Study On The Antioxidant Capacity Of Mojiang Purple Rice And Synergistic Antioxidant Effect Of Six Kinds Of Purple Food

Anthocyanins are a group of naturally occurring water-soluble pigments. Multilines of evidence have demonstrated that anthocyanins are rich in significant physiological activities, including radical-scavenging, antichronic, vision-improving, anti-cardiovascular, anti-tumor, and anti-carcinogenic effects. Mojiang purple rice is a special cultivar of rice and widely consumed since ancient times in China. It is of great nutritional and economic values due to high contents of anthocyanin. The objective of this study was to optimize the extraction conditions of anthocynins in Mojiang purple rice using response surface methodology (RSM). The extracts were examined for their in vitro antioxidant activities using the DPPH and ABTS assays. The composition of anthocyanins was also analyzed by HPLC-DAD-MS/MS.The group of antioxidant compents was identified by HPLC-DPPH technique. We investigated the antioxidant activity of Mojiang purple rice, purple wheat, purple corn, purple sweet potato, purple cabbage and purple yam and the potential synergism among them. The main results were as follows:1. Response surface methodology (RSM), based on a Box-Behnken design (BBD), was employed to obtain the best extraction parameters for anthocyanins. The results showed that extraction time, extraction temperature and solid-liquid ratios were the most significant factors that affected the yield of anthocyanins.Design expert software was used to analyze the results. A regression model was established to assess the relationship between the yield of anthocyanins and extraction parameters. The results showed that response surface methodology was efficient and feasible for optimization of preparation of anthocyanins. Results showed that the optimum conditions were as followsLiquid-solid:extraction temperature 50?, extraction time 94 mins, liquid-solid ratio 1:9, and 70% ethanol. Under these conditions, the anthocyanins yield was 169.04 ± 1.4 mg/100g, which was well corresponded with the predictive yield.2. The antioxidant capacity of the anthocyains from Mojiang purple rice was investigated using DPPH and ABTS methods. Results showed that anthocyains of Mojiang purple rice possessed higher antioxidant capability than ascorbic acid and those from black rice. Four anthocyanin components were identified by HPLC-DAD-ESI-MS2, which were cyanidin-3-glucoside, peonidin-3-glucoside, pelargonidin-3-malonyl-glucoside, cyanidin-3-malonyl-glucoside. Moreover, it was found that cyanidin-3-glucoside and peonidin-3-glucoside played the predominant role in scavenging the DPPH free radicals.3. The antioxidant capabilities of different combines were evaluated using the DPPH-radical, ABTS radical, hydroxyl radical, and O2-· scavenging assays and the ferric reducing antioxidant power. The Calcusyn 2.0 software was then used to evaluate the possible synergetic antioxidant effect between different pairs. The combination of pueple cabbage and purple wheat was found to have synergetic antioxidant effect. Finally, nine and six anthocyanin components were identified in purple cabbage extraction and purple wheat by HPLC-DAD-ESI-MS2, respectively.