Knowledge Management System Of Institute of process engineering,CAS
|导师||刘会洲 ; 梁向峰|
|关键词||虎杖 白藜芦醇 大黄素 水解 溶剂效应 提取|
虎杖是一种重要的传统中药材，在东南亚地区有着悠久的应用历史。白藜芦醇和 大黄素作为虎杖中的两种主要有效成分，具有多种药理活性。在虎杖中白藜芦醇和大黄素主要以糖苷形式存在，但糖苷的生物利用度和活性均小于其苷元。因此，有必要将糖苷进行水解以提高虎杖中白藜芦醇和大黄素的得率。目前，关于白藜芦醇苷的水解已有许多报道，但其水解的动力学和机制等仍缺乏深入的研究。本学位论文开展了白藜芦醇苷的酸水解动力学研究；并在此基础上，开发了一种高效的同时提取和水解的方法用于获得虎杖中白藜芦醇和大黄素。由于大黄素稳定性好而白藜芦醇苷较难水解，且白藜芦醇对pH值、温度和光照等条件均不稳定，本论文对白藜芦醇苷的酸水解动力学和白藜芦醇得率进行了研究。结果表明：溶剂种类对白藜芦醇苷的水解速率有显著影响。白藜芦醇苷在不同溶剂中的水解速率大小顺序为：乙腈＞丙酮＞四氢呋喃＞甲醇＞乙醇。通过线性溶剂化能关系(LSER)方法分析表明，溶剂的偶极-极化率(π*)和氢键受体能力(β)是影响白藜芦醇苷水解速率的主要因子，且水解速率常数与偶极-极化率呈正相关，与氢键受体能力呈负相关。通过进一步考察HCl浓度和温度对白藜芦醇苷水解速率的影响，发现水解速率随HCl浓度的增加而增大，且50%甲醇水溶液中水解速率增大的幅度较甲醇和丙酮中大；还得到了在甲醇、丙酮和50% (v/v)甲醇水溶液三种溶剂中白藜芦醇苷的水解活化能分别为115.1 kJ/mol、105.8 kJ/mol和123.8 kJ/mol。在甲醇和丙酮中白藜芦醇得率均在95%以上，而在50%甲醇中白藜芦醇的得率小于90%。基于白藜芦醇苷的酸水解动力学研究，本论文开发了一种同时提取和水解的方法用于高效回收虎杖中白藜芦醇和大黄素。本论文以丙酮为萃取剂，考察丙酮浓度、提取温度、提取时间、HCl浓度、固液比和提取次数对白藜芦醇和大黄素得率的影响，获得从虎杖中提取白藜芦醇和大黄素的最佳工艺条件：85%丙酮水溶液作为萃取剂，HCl浓度为1.0 mol/L，固液比为1:50 (w/v)，提取温度70℃，提取时间30 min，提取次数3次。在此条件下，白藜芦醇和大黄素得率分别为10.12 mg/g和13.72 mg/g；与虎杖中含量(游离态)相比分别提高了424%和202%；白藜芦醇和大黄素的回收率分别为79.4%和113.7%。该方法将提取和水解合并为一步，不仅避免了传统提取分离工艺中不同操作单元之间衔接性差、耗时长等不足，还减少了粗提物中成分的种类，提高了目标产物的相对含量，降低了后续分离纯化的难度。综上所述，本论文开展了白藜芦醇苷的水解动力学研究，发现了白藜芦醇苷水解的溶剂效应，探讨了白藜芦醇的水解机理。由此建立了一种快速、高效的同时提取和水解的方法用于提取虎杖中白藜芦醇和大黄素，显著提高了白藜芦醇和大黄素的得率。本论文中相关的研究方法和思路对其它植物糖苷的提取和水解也有良好的借鉴意义。
Polygonum cuspidatum is a well-known traditional Chinese medicinal herb that has been used for the treatment of many diseases in Southeast Asia for a long time. Resveratrol and emodin, as the main bioactive compounds in P. cuspidatum, possess various pharmacological functions. These two compounds exist mainly as glycoside in P. cuspidatum. However, their bioavailability and activity are weaker than those of their aglycones. Therefore, conversion of glycosides into aglycones would greatly improve the yield of resveratrol and emodin. Although the hydrolysis of piceid has been extensively carried out, the hydrolytic kinetics and hydrolysis mechanism of piceid have not been reported. Therefore, this dissertation intents to systematically investigate the hydrolytic kinetics of picied, and based on which a simultaneous extraction/hydrolysis process is developed for the recovery of resveratrol and emodin from P. cuspidatum . Because emodin has good stability, whereas piceid is difficult to be hydrolyzed and its hydrolyzed product i.e. resveratrol is sensitive to pH value, temperature, light and so on, the hydrolytic kinetics of piceid and the recovery of resveratrol via hydrolysis of piceid were investigated in this work. The results showed that solvent species had profound impact on the hydrolysis rate of piceid. The hydrolysis rate of picied in different solvents was in order of: acetonitrile > acetone > THF > methanol > ethanol. The linear solvation energy relationships (LSERS) analysis suggested that the Kamlet-Taft parameters π* (dipolarity/polarizability) and β (hydrogen-bond-accepting basicity) had a close relationship with the hydrolysis rate of piceid. Solvation parameter π* enhanced the acid hydrolysis rate by increasing the extent of charge separation of carbocation intermediate, while β decreased the hydrolysis rate by decreasing the proton activity and the stability of carbocation intermediate. Then, the effects of HCl concentration and temperature on the hydrolysis of piceid were studied. Results demonstrated that hydrolysis rate of piceid enhanced as increasing the concentration of HCl and the rate of increase was lager in 50% aqueous methanol than in methanol or acetone. Moreover, the activation energy of piceid hydrolysis in methanol, acetone and 50% (v/v) aqueous methanol were 115.1 kJ/mol, 105.8 kJ/mol and 123.8 kJ/mol, respectively. Meanwhile, the yield of resveratrol in methanol and acetone were over 95%, while less than 90% in 50% aqueous methanol. Extraction is the first step for the preparation of bioactive ingredients from plants. It not only affects the yield and quality of the products, but also influences the subsequent purification and whole cost. Based on the results above, a simultaneous extraction/hydrolysis process for efficient extraction of resveratrol and emodin from P. cuspidatum was developed in which acetone was selected as the base extractant. The effect of key parameters such as the concentration of extractant, extraction temperature, extraction duration, HCl concentration, solid/liquid ratio and extraction times on the efficiency of simultaneous extraction/hydrolysis process were investigated. The optimal extraction conditions were: 85% aqueous acetone, extraction temperature 70 oC, extraction time 30 min, HCl concentation 1.0 mol/L, solid/liquid ratio of 1:50 (w/v) and extraction times was 3. Under these conditions, the yield of resveratrol and emodin were 10.12 mg/g and 13.72 mg/g, respectively, which were increased by 424% and 202%, respectively, compared to a raw sample without hydrolysis. The recovery of resveratrol and emodin were 79.4% and 113.7%, respectively. The current developed method combining extraction and hydrolysis in one step not only overcomes the drawbacks of conventional extraction and separation methods, but also simplifies the compositions of the crude extract and enhances the relative content of target products, thus facilitating the subsequent purification. In summary, the hydrolytic kinetics of piceid was systematically investigated, and the solvent effect on the hydrolysis of piceid for the first time in this dissertation. The mode of action of piceid hydrolysis was proposed. An efficient simultaneous extraction/hydrolysis process was developed on the basis of the results above for the recovery of resveratrol and emodin from P. cuspidatum. This work would also be helpful to the extraction and hydrolysis of other glycosides such as flavonoid glycosides for producing their more bioactive corresponding aglycones from plants.
|刘芬. 虎杖中白藜芦醇和大黄素的高效提取技术研究[D]. 北京. 中国科学院研究生院,2016.|
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