Purification of total flavonols from mulberry leaves using macroporous absorbent resins

This work focused on purification process of crude alcoholic extract from mulberry leaves using macroporous absorbent resin. Firstly, ten kinds of resins, D4020S-8, XAD-16, AB-8, H103, NKA-9, D101, NKA-II, NKA and X-5, were selected as absorbent materials based on maximization of absorbent and desorbent capability. Through static adsorption and desorption, NKA was chosen as the best purification material. Purification conditions included adsorption (time, pH, ratio of solid to liquid) and desorption (pH, ratio of solid to liquid, ethanol concentration) were optimized using response surface methodology. The results indicated the optimal adsorption conditions were ratio of solid to liquid 1:9.6 (g/mL), pH 3.7, time 27.9 h, and the optimal desorption conditions were ratio of solid to liquid 1:20.95 (g/mL), pH 8.04, 87.8% ethanol. Validation experiments showed that the purity of purified total mulberry flavonols was increased from 7.26% to 23.19%.