Efficient Biotransformation of Astragaloside IV to Cycloastragenol by Bacillus sp. LG-502

Cycloastragenol (CA), an exclusive telomerase activator, was derived from the Astragali Radix which is widely distributed in Turkey. Until now, there is no report to produce CA with effective and environment-friendly methods. Biotransformation is considered to be a promising technology. Thus, the present study was aimed to establish a biotransformation technology that could efficiently produce CA. In this paper, a microorganism, LG-502, was used to successfully transform astragaloside IV (ASI) to CA by analysis of thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The phylogenetic analysis of the 16S rRNA indicated that this strain belongs to Bacillus sp. Three metabolites were separated during the fermentation and characterized to be cyclogaleginoside B, CA, and 20R, 24S-epoxy-6α, 16β, 25-trihydroxy-9, 19-cycloartan-3-one based on NMR and MS spectroscopic analyses. The conversion rate of ASI and yield rate of CA were achieved as high as 89 and 84%, respectively, under optimized conditions. Enzymatic analysis showed that the glycosidases were mainly located inside the bacterial body, and the activities of glucosidases were much higher than the xylosidases under the experimental conditions. This study provides a feasible, effective, and eco-friendly way to prepare CA from ASI, which might greatly contribute to the applications of ASI.