Extraction and purification of flavonoids from poplar buds with subcritical water extraction coordinated with macroporous resin adsorption

Subcritical water extraction coupled with macroporous adsorption resin technology was applied to extract and purify flavonoids from poplar buds. Based on the yield of flavonoids, the factors of extraction technology including extraction temperature, liquid-feed ratio was optimized through orthogonal tests. By comparison of four macroporous resins in the adsorption of flavonoids, the optimal macroporous of resin was selected, then adsorption and desorption effects were investigated. The results showed that the optimum process of subcritical water extraction were extraction temperature 180, liquid-feed ratio 30:1, extraction time 10 min. The yield of crude flavonoids was 11.83% and the purity of the product is 13.16%. The HP-20 macroporous adsorption resin was selected to separate and purify flavonoids from poplar buds. The optimal technological conditions were solution concentration 4 g/L, flow rate 60 mL/h, solution pH 2-3, and eluting solvent 90% ethanol. The purity of flavonoids can reach 49.28%.