白花蛇舌草中环烯醚萜苷类化合物的稳定性研究

Stability of Iridoid Glycosides in Hedyotis Diffusa

利用HPLC法详细考察了不同介质、不同保存容器、温度及光对白花蛇舌草中环烯醚萜苷类化合物的影响,并且用LC/MS对该类化合物变化前后进行了分析。结果发现:白花蛇舌草中环烯醚萜类化合物在酸性介质中部分物质不稳定;在纯水介质中置于塑料容器中易发生变化,且溶液颜色变成蓝色;60℃放置时间不宜超过6h;但其对光并不敏感。根据质谱信息并结合文献报道,推测了几个变化较大的化合物的结构,峰6和8分别为鸡矢藤苷甲酯和去乙酰基车叶草苷酸甲酯,峰1,2,10和12为去乙酰基车叶草苷酸、鸡矢藤苷、车叶草苷酸和车叶草苷,峰5,7为鸡矢藤苷甲酯的同分异构体,并推测环烯醚萜苷类物质在酸性介质中C-4位取代基为COOH的化合物较C-4位取代基为COOCH_3的化合物稳定,在变化过程中COOCH_3会水解为COOH。

The stability of iridoid glycosides extracts from Hedyotis diffusa using HPLC was invesitgated, in the context of storage container, solvent media, temperature, and light irradiation. Variations of iridoid glycosides samples were also determined using LC/MS. The results indicated that the iridoid glycosides in Hedyotis diffusa were more stable in pure water than in and acidic solution and more stable in glass container than in plastic container. However, the iridoids were not found noticeably varied in the context of light irradiation. Iridoid glycosides at an indoor temperature between 40℃ and 60℃ presented a better stability,than at 60℃ for 6 h. Based on the MS data and previous studies,the structures of changed compounds were preliminarily identified, such as peak 1, 2, 6, 8, 10 and 12 （deacetylasperuloside acid, scandoside, scandoside methyl ester, deacetylasperuloside acid methyl ester, asperuloside acid and asperuioside）, and peak 5, 7 （ isomers of scandoside methyl ester）. It was deduced that the iridoid glycosides with a COOH3 group on C - 4 were more stable, compared with the one with a COOCH3 group on C -4. A COOCH3 group on C -4 can be translated into a COOH3 group by hydrolysis in acidic media.