Optimization of extraction technique and antioxidant activity determination of anthocyanins from black glutinous corncob

The UV absorbance of extracting solution was used to measure the content of anthocyanins from black glutinous corncob.Response surface analysis method was also used to optimize the extraction condition of black glutinous corncob anthocyanins.Based on the single factor experiments, the interaction of the respective variables and their influence on the extraction effect were studied using Box-Benhnken central composite design and response surface analysis.Results showed that the optimum condition was as follows: the ethanol concentration 62%, liquid-solid ratio 24 ∶ 1, temperature 47 ℃, water-bath time 120 min, p H2.Hence, the maximal content of anthocyanins from dry black glutinous corncob was determined, which was57.29 mg/g. In this paper, high performance liquid chromatography with diode array detection combined with electrospray ionization tandem mass spectrometry ( HPLC-DAD-ESI-MS/MS) was used to analyze the extracted anthocyanidin composition. Three mian anthocyanins were identified: cyanidin-3-glucoside, pelargondin-3-glucoside, and petunidin-3-glucoside.The antioxidant activity experiments indicated that anthocyanins from black glutinous corncob possessed certain ability to scavenge DPPH and ABTS free radical, meanwhile the anthocyanins also showed strong reducing power and ferric reducing power.