温度和酸度对黄芪皂苷Ⅳ、Ⅲ、Ⅰ稳定性和转化的影响

Stability and transformation of astragaloside Ⅳ,Ⅲ and Ⅰ

目的建立HPLC-ELSD方法测定黄芪皂苷Ⅳ、Ⅲ、Ⅰ含量,并考察酸度和温度对黄芪皂苷Ⅳ、Ⅲ、Ⅰ稳定性和转化的影响。方法分别在p H=2.0和p H=6.8磷酸盐缓冲液中及不同温度(室温、40℃、60℃、80℃)下测定黄芪皂苷Ⅳ、Ⅲ、Ⅰ含量。结果在p H=6.8磷酸盐缓冲液中,黄芪皂苷Ⅳ、Ⅲ随着温度升高和放置时间延长,未出现降解或者转化;而黄芪皂苷Ⅰ含量出现降低,且随温度升高,降低趋势增加。在p H=2.0磷酸盐缓冲溶液中,各考察温度下,黄芪皂苷Ⅳ仍较稳定;黄芪皂苷Ⅲ含量稍有下降;而黄芪皂苷Ⅰ含量有明显下降趋势,且随着温度升高,下降趋势增加。结论酸度和温度对黄芪皂苷Ⅳ、Ⅲ的稳定性影响较小;而对黄芪皂苷Ⅰ有较明显影响,随酸度及温度增加,黄芪皂苷Ⅰ发生酯水解反应转化为黄芪皂苷Ⅳ及其他皂苷。

Objective To establish an HPLC-ELSD method to determine the content of astragaloside Ⅳ, Ⅲand Ⅰ to investigate the influence of acidity and temperature on the stability of 3 astragalosides. Methods The contents of astragaloside Ⅳ, Ⅲ and Ⅰ were determined in p H = 2.0 and p H = 6.8 phosphate buffer solutions（PBS） at room temperature, 40 ℃, 60 ℃ and 80 ℃. Results In p H = 6.8 PBS, astragaloside Ⅳ and Ⅲ were stable without degradation or transformation when the temperature increased and the time expanded. However, with the increase of temperature, the content of astragaloside Ⅰ gradually decreased. In p H = 2.0 PBS, the content of astragaloside Ⅳwas not different and that of astragaloside Ⅲ decreased slightly when the temperature increased. But the content of astragaloside Ⅰ decreased significantly in p H = 2.0 PBS as the temperature increased. Conclusion When the acidity and temperature are changed, there is no obvious influence on the stability of astragaloside Ⅳ and Ⅲ but significant influence on the stability of astragaloside Ⅰ. Astragalosides Ⅰ can be converted into astragaloside Ⅳ, which is relevant with the temperature and the acidity.