Abstract: In this study,an accurate method for the extraction,qualitative and quantitative analysis of organic acids from purple cabbage was established.On the basis of single factor test,the interaction effects of four crucial parameters were studied by central composite (Box Behnken) and response surface methodology (RSM).The results showed that the optimum process for organ acid extraction was 73% of ethanol concentration,1∶21 of solid to liquid ,11 min and 70 ℃.The organic acids in leaves and petioles of purple cabbage were qualitatively and quantitatively analyzed by UPLC.Five organic acids were detected∶malic acid,citric acid,malonic acid,succinic acid and tartaric acid.Among five organic acids,malic acid content is the highest,15.968 and 5.019 mg/g,and citric acid is the second,9.293 and 1.385 mg/g.The qualitative and quantitative results showed that the leaves and petiole of purple cabbage contained abundant organic acids, and the contents of malic acid, citric acid, malonic acid and tartaric acid in the leaves were higher than those in the petiole, while the contents of succinic acid were lower.

Key words: response surface, ultra performance liquid chromatography, organic acids, purple cabbage