Enzymatic synthesis of novel quercetin sialyllactoside derivatives

Quercetin and its derivatives are important flavonols that show diverse biological activity, such as antioxidant, anticarcinogenic, anti-inflammatory, and antiviral activities. Adding different substituents to quercetin may change the biochemical activity and bioavailability of molecules, when compared to the aglycone. Here, we have synthesised two novel derivatives of quercetin, quercetin-3-O-β-d-glucopyranosyl, 4′′-O-d-galactopyranosyl 3′′′-O-α-N-acetyl neuraminic acid i.e. 3′-sialyllactosyl quercetin (3′SL-Q) and quercetin-3-O-β-d-glucopyranosyl, 4′′-O-β-d-galactopyranosyl 6′′′-O-α-N-acetyl neuraminic acid i.e. 6′-sialyllactosyl quercetin (6′SL-Q) with the use of glycosyltransferases and sialyltransferases enzymes. These derivatives of quercetin were characterised by high-resolution quadrupole-time-of-flight electrospray ionisation mass spectrometry (HR-QTOF-ESI/MS) and ¹H and ¹³C nuclear magnetic resonance (NMR) analyses.     

Donor substrate flexibility study of AtUGT89C1, a glycosyltransferase from Arabidopsis thaliana

AtUGT89C1, a glycosyltransferase from Arabidopsis thaliana, has shown interesting characteristics such as accepting diverse NDP-D/L-sugars as glycosyl donors. Genistein was used as a substrate to probe in vitro reactions in which different NDP-sugars were used as sugar donors. Among nine different NDP-D/L-sugars tested, AtUGT89C1 accepted five of them, including UDP-α-D-glu-cose, UDP-α-D-galactose, dTDP-β-L-rhamnose, GDP-β-L-fucose, and dTDP-α-2-deoxy-D-glucose and conjugated sugar moieties from the respective donors with the 7-hydroxyl position of genistein. Results showed the promiscuous nature of AtUGT89C1 toward donor and acceptor substrates, thus expanding the biotechnological application of this enzyme in the production of natural and unnatural flavonoid glycosides.     

Phosphonium Ionic Liquid: A Novel Catalyst for Benzyl Halide Oxidation

An environmentally friendly ionic liquid is used for the first time in mild and selective oxidation of aryl halides to corresponding aldehydes using iodoxybenzoic acid as oxidizing agent.