Creating diverse glycosides of 2′-hydroxyflavone through microbial glycosylation

Abstract

Four new 2′-hydroxyflavone glycosides, namely hydroxyflavone-2′-O-β-D-glucuronide (1), hydroxyflavone-2′-O-α-L-rhamnoside (2), hydroxyflavone-2′-O-β-D-glucoside (3), and hydroxyflavone-2′-O-4″-O-methyl-β-D-glucoside (4), were biosynthesized through microbial glycosylation using Streptomyces coeruleorubidus NRRL B-2569, Streptomyces toxytricini NRRL 15443, Escherichia coli BL21(DE3)/pWZ8, and Beauveria bassiana ATCC 7159, respectively. Compounds 1–4 were structurally characterized through extensive analysis of 1D and 2D NMR spectroscopic data. The water solubility of glycosylated products 1–4 were enhanced by 7 to 15 times compared to the substrate 2′-hydroxyflavone. Moreover, antioxidant assays revealed that compounds 1 and 2 exhibited stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity than the substrate, decreasing the logIC50 by 68.7% and 80.7%, respectively. Therefore, this research provides several effective biocatalysts that can be used for structural modification of flavonoids for enhanced water solubility and biological activities.