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.
Efficient lipase-mediated research work was successfully exploited for synthesizing potential 6″- O -acyl-polydatin prodrugs in biomass-derived 2-methyltetrahydrofuran (2-MeTHF). The results of the enzyme recognitions of nine acyl donors evidently demonstrated that the position and number of the C C double bond in acyl chains profoundly influenced the behavior of the enzyme, which could be attributable to the resonance effect between the double bond and carbonyl group. Further investigations showed that introducing various acyl groups into the polydatin apparently enhanced its pH stability and 1-octanol-water partition coefficient (log P ). With regard to the human cervical cancer siHa cell apoptosis by a flow cytometry assay, the lipophilic 6″- O -sorboyl-polydatin exhibited improved apoptosis-inducing capability than the parent drug. The presence of the more lipophilic sorboyl chain in the acylated derivative could account for this.
危险品化学品经营许可证（带存储）