Abstract
Dissolution followed by hydrolysis of geraniin during decoction of chopped dried herb of Geranium thunbergii was determined by high-performance liquid chromatography on a column of hydrocarbon polymer. The effects of using vessels of different materials for decoction, on dissolution and hydrolysis of geraniin were also determined. We found that upon slow warming of water, the amount of geraniin in the decoction reaches the maximum in a short time after the water starts to boil, and also that the amount of geraniin then decreases fairly fast. The amount of corilagin which is one of the products of hydrolysis of geraniin, increases at the same time, and continues to increase for some time after most of geraniin disappears. When decoction was carried out in beakers of approximately the same volume and of different materials, no marked difference in the results was noted. However, appreciable differences were observed between an aluminum kettle and an earthen vessel of approximately the same volume and of considerably different weight. Although the traditional way of decoction of crude drugs indicates that use of metalic vessels should be avoided, our results show that the superiority of the earthenware is due to mild warming. The experiments of infusing chopped dried herb of Geranium thunbergii repeatedly in a teapot with hot water showed that this is a good method of extracting geraniin without causing extensive hydrolysis.
