迷迭香酸在不同溶剂中的热稳定性及其降解产物研究

Study on Thermal Stability of Rosmarinic Acid in Different Solvents and It's Degradation Products

关键词:  迷迭香酸  溶剂  稳定性  高效液相色谱  液质联用  降解产物

Key words:  rosmarinic acid  solvents  stability  HPLC  HPLC-MS  degradation products

摘要:

目的 探讨迷迭香酸对照品在不同溶剂中加热温度和加热时间对其稳定性的影响，并对其在最不稳定的溶剂中的主要降解产物进行定性分析以阐释其降解途径。方法 将迷迭香酸对照品分别溶于水、70%乙醇、甲醇中，分别在不同水浴温度（20~100 ℃）下加热4 h，每隔1 h取样。采用HPLC测定迷迭香酸加热前后色谱峰的峰面积，计算其剩余率，同时采用HPLC-MS对其主要降解产物进行鉴定。结果 当加热温度≤60 ℃时，水溶液、70%乙醇溶液、甲醇溶液中的迷迭香酸剩余率均>95%，且甲醇溶液中的迷迭香酸剩余率高于水溶液和70%乙醇溶液；当迷迭香酸加热时间达到4 h时，水溶液和70%乙醇溶液中的迷迭香酸剩余率显著减小，甲醇溶液中的迷迭香酸剩余率几乎不变。迷迭香酸在水溶液中最不稳定，在水溶液中的降解途径主要有酯键水解、双键加成和氧化反应，降解后产生丹参素、咖啡酸、原儿茶醛、丹参酸C及其异构体等产物。结论 迷迭香酸的稳定性在甲醇中较好，70%乙醇中次之，水中最差；加热温度越高或加热时间越长，迷迭香酸的稳定性越差。因此，在迷迭香酸的研究过程中推荐首选甲醇为溶剂；迷迭香酸及含有该成分的中药在提取分离、加工制备和贮存过程中，温度不宜超过60 ℃，加热时间不宜超过4 h。

Abstract:

OBJECTIVE To investigate the influence of temperature and heating time on the stability of chemical reference of rosmarinic acid in different solvents, and main degradation products of rosmarinic acid in the most unstable media were identified to expound its degradation pathway. METHODS Rosmarinic acid was dissolved in water, 70% ethanol and methanol respectively, heated at different temperatures (20-100 ℃) for 4 h and sampled every hour. The response peak area that before and after heating were determined by HPLC, the remaining percentages of rosmarinic acid were calculated and the main degradation products were identified by HPLC-MS. RESULTS When heating temperature was ≤60 ℃, the remaining percentages of rosmarinic acid in water, 70% ethanol and methanol were all >95%, and the remaining percentage of rosmarinic acid in methanol was higher than the others; when rosmarinic acid was heated for 4 h, the residual rates of rosmarinic acid in water and 70% ethanol were both reduced significantly, while unchanged in methanol. Rosmarinic acid was the most unstable in water among three solvents. Hydrolysis of ester bonds, double-bond addition reaction and oxidation were the main degradation reactions of rosmarinic acid in aqueous solution, and these reactions could produce the major degradation products, such as salvianic acid A, caffeic acid, procatechuic aldehyde, salvianic acid C and its isomer, etc. CONCLUSION Rosmarinic acid is much more stable in methanol than in 70% ethanol, and the most unstable in water. The stability of rosmarinic acid reduces along with temperature rising and heating time increasing. Thus, methanol is suggested to be a suitable solvent for rosmarinic acid in its research. The temperature should not exceed 60 ℃ and heating time should not exceed 4 h in its extraction, separation and preparation process.