Abstract: Proanthocyanidins were extracted from buckwheat (Fagopyrum esculentum) hulls by the method of microwave-assisted extraction.The influences of microwave power,microwave time,bath temperature,solid to liquid ratio and ethanol concentration on extraction yield of proanthocyanidins were investigated by single-factor experiments and Plackett-Burman design.By analyzing the statistical regression,microwave time,ethanol concentration and microwave power were found to be the most important factors (P<0.05).On this basis,a quadratic polynomial regression equation of the forecasting model was developed using Box-Behnken design of three factors and three levels.The results indicated that the optimal conditions of microwave extraction were as follows:solid to liquid ratio of 1:30 g/mL,ethanol concentration 35%,bath temperature 70 ℃,microwavepower 280 W,microwave time 28 s.Under these conditions,the yield of proanthocyanidins was 2.21%.

Key words: buckwheat hulls, proanthocyanidins, microwave extraction, response surface analysis