OBJECTIVE  To study the relationship of isoflavones, saponins and total polysaccharides in root and stem of Astragalus membranaceus.

METHODS  The extraction process of Astragalus polysaccharide by internal boiling under reduced pressure was optimized. Additionally, the total polysaccharide content was determined by ultraviolet-visible spectrophotometry, the isoflavone content was determined by UPLC-DAD, and the saponin content was determined by HPLC-ELSD.

RESULTS  The optimal extraction process of Astragalus polysaccharides was as follows: the concentration of desorption agent was 75%, the solid-liquid ratio of desorption agent was 1∶3, the desorption time was 40 min, the solid-liquid ratio was 1∶12, the extraction time was 45 min, the extraction temperature was 80 ℃, and the extraction times were 2 times. The contents of 4 isoflavones and 3 saponins in the roots and stems of Astragalus membranaceus with green stem were higher than Astragalus membranaceus with purple stem. Among them, the contents of ononin, formononetin and calycosin 7-o-glucoside in stems were very significantly different(P<0.01), the contents of calycosin in stems were significantly different(P<0.05), and the contents of astragaloside Ⅱ in roots were significantly different(P<0.05). There was no significant difference in the total polysaccharide content in the roots or stems of Astragalus membranaceus with different stem colors.

CONCLUSION  The content of isoflavones and saponins in roots and stems of Astragalus membranaceus were related to stem color, which can provide theoretical basis for further breeding and breeding of high-quality Astragalus membranaceus.