Yeast extract improved biosynthesis of astragalosides in hairy root cultures of Astragalus membranaceus

The dried root of Astragalus membranaceus is a well-known herbal medicine, and it is useful in treating chronic diseases and weakness, as well as for improving overall health and vitality. Astragalosides, which are root quality indicators of A. membranaceus, are natural triterpenoid saponins that are used in the treatment of diabetes and cardiovascular diseases. Currently, there is an urgent need to improve their production because of their low quantity in plants and the difficulty of chemical synthesis. In this study, yeast extract was added to facilitate elicitation in Agrobacterium-mediated hairy root cultures, thereby enhancing astragaloside production in A. membranaceus. Results showed that yeast extract could stimulate astragaloside content effectively in the hairy roots of A. membranaceus. Moreover, astragaloside accumulation was positively correlated with the upregulation of mevalonate biosynthetic gene expression in the presence of yeast extract. Our study demonstrated that pretreatment with yeast extract (3.65 mM) for 72 h serves as an effective strategy to enhance astragaloside levels in A. membranaceus hairy root cultures. Thus, these optimal conditions can provide valuable information for the improvement of astragaloside industrial production in A. membranaceus.