Optimization of Alkali Extraction of Polysaccharides From Foxtail Millet and Its Antioxidant Activities In Vitro

Abstract

Highlights Extraction of polysaccharides from foxtail millet with alkali solution. Response surface methodology was used. The antioxidant activity of the polysaccharides was investigated in vitro. Model was set up to optimize extraction of polysaccharides. The best extraction conditions were alkali concentration 0.83 mol/L, liquid–solid ratio 20.9:1 mL/g, extraction time 1.1 h and extraction temperature 72.7C. Abstract Response surface methodology was employed to obtain the best possible combination of alkali concentration, liquid–solid ratio, extraction time and extraction temperature for maximum polysaccharide yields in the experiment of alkali extraction of polysaccharides from foxtail millet. The antioxidant activity of the obtained polysaccharides was meanwhile investigated in vitro. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis. The optimum extraction conditions were alkali concentration 0.83 mol/L, liquid–solid ratio 20.9:1 mL/g, extraction time 1.1 h, and extraction temperature 72.7C, the experimental yield was 46.21 mg/g, which was well in close agreement with the model's predicted value (45.60 mg/g). The polysaccharides of foxtail millet have better capacity of radical-scavenging activity on DPPH (1,1-diphenyl-2-picrylhydrazyl) and hydroxyl radical-scavenging activity. The mathematical model had high correlation (P < 0.01) and could be greatly employed to optimize polysaccharide extraction technology. Polysaccharides of foxtail millet can be used as a potential antioxidant agent. Practical Applications This study can be considered as the first report on the extraction of polysaccharides with alkali solution from foxtail millet. Compared with the traditional hot water extraction method, it can improve efficiency, shorten extraction time, reduce extraction temperature and has great potential in large-scale extraction of polysaccharides from foxtail millet.