丹参干燥前后游离型和结合型酚酸的比较研究

丹参干燥前后,新鲜和干燥丹参中酚酸成分含量有显著性差异,即在干燥过程中随脱水增加,丹参酚酸含量显著增加。为探究丹参干燥前后游离型和结合型酚酸含量的差异及转化,该实验对丹参酚酸水解方法、水解产物、水解规律等进行研究,采用UPLC测定丹参结合型酚酸4种主要水解产物丹参素、咖啡酸二聚体(SMND-309)、咖啡酸、甘西鼠尾草酸甲(原紫草酸)以及丹参中3种主要游离酚酸成分(迷迭香酸、紫草酸和丹酚酸B)的含量。结果显示,丹参酚酸的碱水解效果显著优于酸水解,优选的碱水解条件为用含有1%抗坏血酸的2 mol·L-1氢氧化钠溶液于70℃水解4 h;游离酚酸和结合酚酸的水解产物相同;新鲜丹参中游离酚酸含量较低,结合酚酸含量较高,而干燥丹参却相反。提示丹参生长过程中已积累储存了大量的结合型酚酸,主要以酯键与细胞壁多糖结合形成了不溶性酚酸,常规方法不易检出,在干燥脱水过程中,结合型酚酸或在相关酶的作用下转化生成大量的游离酚酸。

Comparative study on free and bound phenolic acids before and after drying of Salvia miltiorrhiza

There were significant differences in phenolic acid content between fresh and dried Salvia miltiorrhiza before and after drying.That is to say,the content of phenolic acid in S.miltiorrhiza significantly increased with the increase of dehydration during the drying process.In order to investigate the differences and transformation of free and bound phenolic acids before and after the drying process of S.miltiorrhiza,we studied hydrolysis method,hydrolysates and hydrolysis regularity of phenolic acids in S.miltiorrhiza.UPLC method was used to determine four main hydrolysates of bound phenolic acids,namely danshensu,caffeic acid dimer(SMND-309),caffeic acid,przewalskinic acid A(prolithosperic acid),and three main free phenolic acids in S.miltiorrhiza,namely rosmarinic acid,lithospermic acid,salvianolic acid B.The results of the acid-base hydrolysis experiment of salvianolic acid showed that the alkaline hydrolysis effect was significantly better than acid hydrolysis.The optimal alkaline hydrolysis condition was hydrolysis at 70℃for 4 h with 2 mol·L-1 NaOH solution containing 1%ascorbic acid(Vit C).The hydrolysates of free phenolic acids were the same with the hydrolysates of bound phenolic acids.Fresh S.miltiorrhiza contains a low level of free phenolic acids and a high level of bound phenolic acids,which were exactly opposite to dried S.miltiorrhiza.It was suggested that a large amount of bound phenolic acids was accumulated during the growth of S.miltiorrhiza.These bound phenolic acids were coupled with polysaccharides on the cytoderm through ester bonds to form insoluble phenolic acids,which was not easy to be detected by conventional methods.However,during drying and dehydration processes,the bound phenolic acids were converted to a large amount of free phenolic acids under the action of the relevant enzyme.