Xuan Xin,Mengmeng Zhang,Xiao-Feng Li,Guanglei Zhao
Enzymatic acylation is commonly used to increase the lipophilicity of flavonoids. However, the absence of primary hydroxyl groups makes it challenging to acylate baicalin using traditional acylation methods. In this study, an enzymatic esterification strategy was developed to introduce fatty-acid chains into baicalin at its carboxyl group, hence successfully synthesizing a new series of baicalin ester derivatives in nonaqueous media. Under the optimal reaction conditions, up to 95% conversion of baicalin was achieved. Antimicrobial evaluation of the baicalin ester derivatives indicated a corresponding increase to that of C log P values, with a cutoff effect at C log P = 5.2. Baicalin ester derivatives with C log P values of 4.9–5.2 exhibited the most potent antimicrobial activity. Interestingly, the introduction of medium-length fatty alcohol chains not only increased lipophilicity but also endowed them with membrane-disrupting properties. This study, therefore, provides an understanding of the esterification of flavonoid glycosides and a prospective application of the ester derivatives.
Rice bran oil (RBO) is a great and important vegetable oil resource, but usually contain high content of free fatty acids (FFAs). Phytosterol esters are functional lipids possessing hypocholesterolemic activity. In this study, Candida rugosa lipase (CRL) was immobilized on the octyl-functionalized ordered mesoporous silica (C8-OMMs) to obtain immobilized CRL arrays (CRL@C8-OMMs). The resulting CRL@C8-OMMs arrays showed much better thermal stability and reusability in comparison to free CRL. The deacidification and simultaneous preparation of functional oil rich in phytosterol esters (PEs) was successfully achieved by enzymatic esterification of high-acid RBO with phytosterol. The contents of FFAs and PEs were below 2.3% and above 84.7%, respectively. Repeated reaction tests indicated that CRL@C8-OMSs arrays could be used 11 times with 80.7% of its original catalytic activity still retained. The strategy could not only take advantage of the high-acid oils resources, but also product PEs-enriched functional oils.
The effectiveness of deacidification technologies for high-acid rice bran oil (HRBO) are still one of the main challenges in the industrialization process of rice bran oil (RBO). A novel function of glycerol-based deep eutectic solvents (DESs) as an acyl acceptor in combination with lipases for enzymatic esterification of deacidification of HRBO was described in this study. The maximum deacidification efficiency of 92.38% was obtained under the optimized reaction conditions. Molecular docking simulation indicated that the minimum binding energy of Novozym 435 was lower than those of Lipozyme TL IM and Lipozyme RM IM, which might be one of the underlying mechanisms for its better performance. Additionally, γ-oryzanols, tocopherols and tocotrienols were retained in deacidified RBO. We are convinced that the reusability of biocatalyst and DESs systems provide an alternative strategy to design a facile, environmentally-friendliness DESs towards economic feasibility of applications and processes for oil-refined industries.
危险品化学品经营许可证（带存储）