Abstract
α-Flavone glycosides have beneficial properties for applications in the pharmaceutical, cosmetic, and food industries. However, their chemical syntheses are often limited by a low efficiency or scarcity of substrates. In this study, α-flavone glucosides were enzymatically synthesized by amylosucrase from Deinococcus geothermalis (DGAS) using sucrose and various flavones as a donor for glucosyl units and acceptors, respectively. Luteolin was the most effective acceptor in the transglucosylation reaction using DGAS among nine flavone materials (apigenin, chrysin, 6,7-dihydroxyflavone, homoorientin, 7-hydroxyflavone, isorhoifolin, luteolin, luteolin-3′,7-diglucoside, and orientin). The highest production yield of luteolin glucoside was 86%, with a 7:1 molar ratio of donor to acceptor molecules, in 50 mM Tris-HCl buffer (pH 7) at 37°C for 24 h using 2 U of DGAS. The synthesized luteolin glucoside was identified as luteolin-4′-O-α-D-glucopyranoside with a glucose molecule linked to the C-4′ position on the B-ring of luteolin via an α-glucosidic bond, as determined by 1H and 13C nuclear magnetic resonance. This result clearly confirmed that the glucosylated luteolin was successfully synthesized by DGAS and it can be applied as a functional ingredient. Furthermore, this approach using DGAS has the potential to be utilized for the synthesis of various glucosylated products using different types of polyphenols to enhance their functionalities.
Highlights
Flavones are a type of flavonoid with a backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one); they are plant secondary metabolites with anti-inflammatory, anti-tumor, and anti-cancer effects on the human physiology [1,2,3]
Flavone substances are hardly soluble in water, while they dissolve in organic solvents such as ethanol and Dimethyl sulfoxide (DMSO) [26, 27]
To confirm the acceptor specificity of Deinococcus geothermalis (DGAS), the different flavone materials were dissolved in DMSO (2 mg/mL), and DMSO was added to the enzyme reaction solution
Summary
Flavones are a type of flavonoid with a backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one); they are plant secondary metabolites with anti-inflammatory, anti-tumor, and anti-cancer effects on the human physiology [1,2,3]. The poor solubility and stability of flavone compounds limit their applications as functional materials in the pharmaceutical, cosmetic, and food industries [3,4,5,6]. Some flavones are presented in the form of β-linked. Biosynthesis of α-flavone glucoside by Deinococcus geothermalis amylosucrase
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