Optimization of the microwave-assisted enzymatic extraction of Rosa roxburghii Tratt. polysaccharides using response surface methodology and its antioxidant and α-d-glucosidase inhibitory activity

An extraction assay applying microwave-assisted enzymatic treatment for polysaccharides in Rosa roxburghii was developed using response surface methodology. The process parameters were optimized using Plackett-Burman (PB) design and central composite design to enhance the Rosa roxburghii polysaccharide extraction yield. Specific conditions (microwave power, 575   W; microwave time, 18   min; liquid-to-material ratio, 13.5:1   mL/g; and enzyme dose, 6.5   g/mL) generated an experimental yield of 36.21   ±   0.62%, which closely agreed with the predicted value of 35.75%. Purification with a DEAE-52 cellulose column generated two fractions, PR-1 (from 6.2   ×   10 3 to 7.4   KDa) and PR-2 (from 559.8 to 106.6   KDa). Subsequently, the antioxidant activity and α- d -glucosidase inhibitory activity of the two polysaccharide fractions were assessed; PR-1 exhibited stronger antioxidant activity and α- d -glucosidase inhibitory activity than PR-2. Finally, the monosaccharide composition of PR-1 was determined by HPLC using a 1-phenyl-3-methyl-5-pyrazolone precolumn derivatization method. The result showed that PR-1 contained mannose , ribose , rhamnose , glucosamine hydrochloride, glucuronic acid , galacturonic acid, glucose, galactose , arabinose and fucose with molar percentages of 2.1%, 0.54%, 2.1%, 0.26%, 1.5%, 22.7%, 24.0%, 26.4%, 19.6% and 0.89%, respectively.