Production of New Isoflavone Diglucosides from Glycosylation of 8-Hydroxydaidzein by Deinococcus geothermalis Amylosucrase

Abstract

8-Hydroxydaidzein (8-OHDe) is a non-natural isoflavone polyphenol isolated from fermented soybean foods. 8-OHDe exhibits a wide range of pharmaceutical activities. However, both the poor solubility and instability of 8-OHDe limit its applications. To resolve the limitations of 8-OHDe, Deinococcus geothermalis amylosucrase (DgAS) has previously been used to glycosylate 8-OHDe to produce soluble and stable 8-OHDe-7-O-α-glucopyranoside (8-OHDe-7-G) in a 0.5 h reaction time. In this study, we aimed to use DgAS and an extended reaction time to produce 8-OHDe diglucosides. At least three 8-OHDe derivatives were produced after a 24 h reaction time, and two major products were successfully purified and identified as new compounds: 8-OHDe-7-O-[α-glucopyranosyl-(1→6)-α-glucopyranoside] (8-OHDe-7-G2) and 8-OHDe-7,4′-O-α-diglucopyranoside (8-OHDe-7-G-4′-G). 8-OHDe-7-G-4′-G showed a 4619-fold greater aqueous solubility than 8-OHDe. In addition, over 92% of the 8-OHDe diglucosides were stable after 96 h, while only 10% of the 8-OHDe could be detected after being subjected to the same conditions. The two stable 8-OHDe diglucoside derivatives have the potential for pharmacological usage in the future.