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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。
Objective To investigate the influence of heating temperature and heating time on the stability of rosmarinic acid reference substance in different solvents and qualitative analysis of its main degradation products in the most unstable solvents to explain its degradation pathway. Methods The rosmarinic acid reference substance was dissolved in water, 70% ethanol and methanol, respectively, and heated at different water bath temperature (20-100 ℃) for 4 h and sampled every 1 h. The peak area of the chromatographic peaks before and after heating with rosmarinic acid was determined by HPLC, and the residual rate was calculated. The main degradation products were identified by HPLC-MS. Results When the heating temperature was less than or equal to 60 ℃, the residual ratio of rosmarinic acid in aqueous solution, 70% ethanol solution and methanol solution was> 95%, and the residual ratio of rosmarinic acid in methanol solution was higher than that in aqueous solution and 70% ethanol solution When the heating time of rosmarinic acid reached 4 h, the residual ratio of rosmarinic acid in aqueous solution and 70% ethanol solution decreased significantly, while the residual ratio of rosmarinic acid in methanol solution remained almost unchanged. Rosmarinic acid is the most unstable in aqueous solution. The main degradation pathway in aqueous solution is ester bond hydrolysis, double bond addition and oxidation reaction. After degradation, rosmarinic acid, caffeic acid, protocatechuic aldehyde, salvianolic acid C and its Isomers and other products. Conclusion The stability of rosmarinic acid is better in methanol than in 70% ethanol, the water is the worst. The higher the heating temperature or the longer heating time, the worse the rosmarinic acid stability. Therefore, rosmarinic acid is recommended as the solvent of choice in the research process of rosmarinic acid. The rosmarinic acid and the Chinese medicine containing the same are not suitable for extraction, processing, preparation and storage. The temperature should not exceed 60 ℃ and the heating time should not exceed 4 h .