title: Highly efficient and regioselective synthesis of dihydromyricetin esters by immobilized lipase.
abstract: Dihydromyricetin is the principle component of the Chinese herbal tea Teng-cha and a promising ingredient for functional food and nutraceuticals, but its low solubility limits its application potentials. This study explored enzymatic acylation of dihydromyricetin to improve its solubility in lipid systems. Acylation was achieved with several lipases with the synthesis of a major (>86%) product and a minor product. Isolation and purification of the products by preparative HPLC followed by LC-MS, (13)C NMR, (1)H NMR and 2 D-HSQC NMR analyses showed that the major product was a dihydromyricetin monoester with the acylation site at the 3-OH group of C ring. Quantum chemical calculations revealed that the 3-OH had the lowest antioxidant activity, and therefore acylation at this site was expected to have minimum impact on the antioxidant activity. Several factors, including solvent, acyl donor, enzyme origin, molar ratio of substrates and reaction temperature and time, exhibited significant effects on the initial rate, conversion yield and regioselectivity of the reaction. Acylation occurred only with vinyl acetate as the acyl donor, and highest conversion yields were achieved with immobilized Penicillium expansum lipase and Novozyme 435 with DMSO and acetonitrile being the best solvents. In general, the acylation results were found to be superior to previous reports on acylation of aglycone flavonoids with respects to conversion yield and regioselectivity.
authors.affiliation: Faculty of Light Industries, Hubei University of Technology, Wuhan 430068, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Faculty of Light Industries, Hubei University of Technology, Wuhan 430068, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Wu
authors.affiliation: School of Food Science, Henan Institute of Science and Technology, Xinxiang 453003, China.
authors.forename: Benguo
authors.initials: B
authors.lastname: Liu
authors.affiliation: Lab of Applied Biocatalysis, South China University of Technology, Guangzhou 510640, China; Department of Biotechnology, Guangdong University of Technology, Guangzhou 510006, China.
authors.forename: Xuedan
authors.initials: X
authors.lastname: Hou
authors.affiliation: Faculty of Light Industries, Hubei University of Technology, Wuhan 430068, China.
authors.forename: Duanji
authors.initials: D
authors.lastname: Wan
authors.affiliation: Lab of Applied Biocatalysis, South China University of Technology, Guangzhou 510640, China. Electronic address: wylou@scut.edu.cn.
authors.forename: Wenyong
authors.initials: W
authors.lastname: Lou
authors.affiliation: School of Chemical Engineering, The University of New South Wales, Sydney 2052, NSW, Australia. Electronic address: jian.zhao@unsw.edu.au.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000215:Acylation; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D044948:Flavonols / Q000737:chemistry* / Q000378:metabolism*; D008049:Lipase / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D004800:Enzymes, Immobilized; D044948:Flavonols; D008049:Lipase; C472036:dihydromyricetin
keywords: Acylation; Dihydromyricetin; Flavonoid; Lipase; Regioselectivity