State Key Laboratory of Materials-Oriented Chemical Engineering, School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 210009, China.
Molecules. 2023 Jan 19;28(3):993. doi: 10.3390/molecules28030993.
Phytosterol esters have attracted widespread academic and industrial interests due to their advantages in lowering cholesterol, as antioxidants, and in preventing or treating cancer. However, the generation of by-products limits the application of phytosterol esters in food fields. In this study, deep eutectic solvents (DESs), a series of green, nontoxic, low-cost and biodegradable solvents, were adopted as the catalyst for the synthesis of pine sterol esters. The results showed that the acidic DES which was prepared with choline chloride (ChCl) and p-toluene sulfonic acid monohydrate (PTSA) with a molar ratio of 1:3 performed best in the prescreening experiments. To further improve the efficiency of the pine sterol ester, the molar ratio of substrates, the amount of catalyst, the reaction temperature and the reaction time were optimized, and its yield was improved to 94.1%. Moreover, the by-products of the dehydration side reactions of the sterol can be efficiently inhibited. To make this strategy more universal, other fatty acids were also used as the substrate for the synthesis of pine sterol esters, and a yield of above 92.0% was obtained. In addition, the reusability of DES was also investigated in this study, and the efficiency of DES was well maintained within five recycled uses. Finally, DFT calculations suggested that the suitable H-bonds between ChCl and PTSA decreased the nucleophilic capacity and increased the steric hindrance of the latter, and further prevented the attack on H and reduced the generation of by-products. This study developed a reliable and eco-friendly strategy for the preparation of high-quality phytosterol esters with low-dosage catalyst usage and high selectivity.
植物甾醇酯因其降低胆固醇、作为抗氧化剂和预防或治疗癌症的优势而引起了广泛的学术和工业关注。然而，副产物的产生限制了植物甾醇酯在食品领域的应用。在这项研究中，深共晶溶剂（DESs），一系列绿色、无毒、低成本和可生物降解的溶剂，被用作合成松树甾醇酯的催化剂。结果表明，在预筛选实验中，由氯化胆碱（ChCl）和一水对甲苯磺酸（PTSA）以摩尔比 1:3 制备的酸性 DES 表现最佳。为了进一步提高松树甾醇酯的效率，优化了底物摩尔比、催化剂用量、反应温度和反应时间，其产率提高到 94.1%。此外，可以有效地抑制甾醇脱水副反应的副产物。为了使这种策略更具普遍性，还将其他脂肪酸用作松树甾醇酯合成的底物，获得了 92.0%以上的产率。此外，还研究了 DES 的可重复使用性，在五次循环使用中，DES 的效率得到了很好的保持。最后，DFT 计算表明，ChCl 和 PTSA 之间合适的氢键降低了后者的亲核能力并增加了空间位阻，进一步阻止了对 H 的攻击并减少了副产物的生成。本研究开发了一种可靠且环保的策略，用于制备高品质的植物甾醇酯，催化剂用量低，选择性高。
