Biotransformation-guided purification of a novel glycoside derived from the extracts of Chinese herb Baizhi

Abstract

Our pursuit of new compounds with enhanced bioavailability and bioactivity prompted us to employ the biotransformation-guided purification (BGP) approach which leverages proficient in vitro biotransformation techniques. Angelica dahurica roots, also called Baizhi in Chinese traditional medicine, are famous for their anti-inflammatory and analgesic properties. Herein, we applied the BGP methodology to Baizhi extracts, employing Deinococcus geothermalis amylosucrase (DgAS), an enzyme demonstrating catalytic competence across diverse substrates, for biotransformation. Initiating with a 70 % methanol extraction, we obtained the crude extract of commercial Baizhi powder, followed by an additional extraction using ethyl acetate. Notably, reactions performed on this extract yielded limited quantities of novel compounds. Subsequently, the extract underwent partitioning into four fractions based on HPLC profiling, leading to the successful isolation of a compound with significant yield from fraction 2 mixtures upon reaction with DgAS. Structural elucidation confirmed the compound as byakangelicin-7″-O-α-glucopyranoside (BG-G), a new alpha glycoside derivative of byakangelicin. Furthermore, validation experiments verified the capacity of DgAS to glycosylate pure byakangelicin, yielding BG-G. Remarkably, the aqueous solubility of BG-G exceeded that of byakangelicin by over 29,000-fold. In conclusion, BGP emerges as a potent strategy combining traditional medicinal insights with robust enzymatic tools for generating new compounds.

Keywords: Amylosucrase; Angelica dahurica; Baizhi; Biotransformation; Byakangelicin; Glycosylation.