Optimization of extraction technology for total flavonoids from astragali radix by response surface methodology and their preliminary enrichment

Flavonoids in astragali radix exert biological health functions actions such as antioxidant and immune-enhancing effects. They are often added to food and feed as immunopotentiators. The effects of ethanol concentration, the solid/liquid ratio, and extraction time on the extraction content of total flavonoids (TFA) from Astragalus membranaceus were evaluated using single factor experiments. Furthermore, the optimum beneficiation and depuration technology of TFA was investigated with HPD722 macroporous resin-polyamide combination method. The results showed that the extraction content of TFA and relative standard deviation (RSD) were 2.78 mg·g^–1 and 1.41%, respectively, under the conditions of 70% ethanol concentration, solid/liquid ratio of 1∶17, and an extraction time of 70 min. When TFA were enriched and purified using HPD722 macroporous resin-polyamide, the extraction content of TFA was 311 mg·g^–1 and its purity was increased 112 times. As the main component of TFA, the content of calycosin was increased 327 times from 0.13 mg·g^–1 to 42.56 mg·g^–1 and formononetin was increased 132 times from 0.06 mg·g^–1 to 7.89 mg·g^–1.