Quantitative analysis of the polysaccharide and glycoprotein fractions in Echinacea purpurea and Echinacea angustifolia by HPLC-ELSD for quality control of raw material

Abstract

Polysaccharides and glycoproteins are in part responsible for the immunostimulatory effect of Echinacea spp. (Asteraceae). A major problem, however, is finding a suitable analytical method to quantify them in the botanical raw material or in Echinacea extracts. An HPLC method has been developed using an evaporative light scattering detector (ELSD) detector. The fraction containing polysaccharides and glycoproteins (PS/GP) was obtained by precipitation of Echinacea spp. extracts with EtOH. The PS/GP fraction was passed through a 5-kDa molecular weight filter to remove smaller molecules and then analyzed by HPLC-ELSD. The chromatogram shows two peaks, one corresponding to PS/GP with a molecular weight (MW) above 48.6 kDa and one to PS/GP with a MW below 48.6 kDa. The PS/GP fraction is expressed as an arabinogalactan equivalent. This method has been validated and is suitable for quality control of raw material and extracts. The results showed that the composition of polysaccharides differs among species of Echinacea, among organs of the same species, among provenance, and among extracts based on the solvent used. © 2007 Informa Healthcare.