Simultaneous Quantification of Ellagitannins and Related Polyphenols in Geranium thunbergii Using Quantitative NMR

Abstract

Compared to commonly employed liquid chromatography-based methods, quantitative nuclear magnetic resonance (qNMR) is a recently developed method for accurate quantification of natural compounds in extracts. The simultaneous quantification of ellagitannins and the related polyphenols of <i>Geranium thunbergii</i> were studied using qNMR after a short-term and long-term decoction. The qNMR fingerprint for quantifying ellagitannin was presented in this work. Geraniin was observed in the short-term decoction as a major component while corilagin was the major component of the long-term decoction. An aqueous acetone extract of <i>G. thunbergii</i> after long-term decoction was extracted with diethyl ether, ethyl acetate, and <i>n</i>-butanol. Corilagin was found as a major constituent in the ethyl acetate and <i>n</i>-butanol extracts. Furthermore, the contents of these polyphenols in <i>G. thunbergii</i> from six locations in Japan and three locations in China were quantified. The contents of geraniin and corilagin in <i>G. thunbergii</i> from Japan were higher than those from China. Our finding raised the possibility that qNMR can be effectively employed as a simple, accurate, and efficient method for quantification of ellagitannins in medicinal plants.