Biosynthesis of natural and non-natural genistein glycosides†
Genistein is the principal isoflavone constituent of soybean. It has attracted more attention than other plant polyphenols because of its significant affinity with medical interests. Herein, we biosynthesized and structurally characterized ten different natural and non-natural analogues of genistein glycopyranosides using versatile glycosyltransferases (GTs) and sugar-O-methyltransferases (SOMTs). Two GTs, AtUGT89C1 from the Arabidopsis thaliana plant and YjiC from Bacillus licheniformis DSM-13 bacteria, catalyzed the glycosylation reaction. Two SOMTs transferred the methyl group to two specific hydroxy positions in the sugar moiety of genistein rhamnopyranoside, thus diversifying the sugar attached to genistein. Among the biosynthesized compounds, four of the 2-deoxy-D-glycopyranosides, 7-O-(2-deoxy-β-D-arabino-hexopyranosyl)genistein, 4′-O-(2-deoxy-β-D-arabino-hexopyranosyl)genistein, 4′,7-bis-O-(2-deoxy-β-D-arabino-hexopyranosyl)genistein, and 4′,5,7-tri-O-(2-deoxy-β-D-arabino-hexopyranosyl)genistein, and two of the O-methyl rhamnopyranosides, 7-O-(3-O-methyl-α-L-rhamnopyranosyl)genistein and 7-O-(4-O-methyl-α-L-rhamnopyranosyl)genistein, are novel compounds that have not been previously reported. The other glycopyranosides are 7-O-(α-L-rhamnopyranosyl)genistein, 7-O-(β-D-glucopyranosyl)genistein, 4′-O-(β-D-glucopyranosyl)genistein, and 4′,7-O-(β-D-glucopyranosyl)genistein. Microbial production of these novel compounds and other glucopyranosides is appreciable in shake flask culture. This study highlights the application of versatile enzymes in the production of diverse glycosides of medicinally important genistein, which can have positive impacts on a variety of molecular targets in future studies, as shown by genistein with remedied drawbacks.