Chemical composition of the water extract of Gnaphalium uliginosum. Part 1

Water and alcohol extracts of Gnaphalium uliginosum are used widely in medical practice. However the chemical composition and structure of components of the extracts are poorly studied. Earlier attempts [1] allowed the separation and elucidation of the structure of only one component, gnaphalosid A (a methoxyflavone), which was attributed by the authors for the medicinal properties of the herb. Nowadays in Russia, Gnaphalium uliginosum herb is used in a form of a dried water extract. Current work is devoted to detailed studies of composition and structure of components of this extract using SPE, analytical and preparative HPLC, UV, LC-MS and high-resolution NMR spectroscopy. We report the presence of gnaphalosid A in the dry herb at less than 0.005%, which is much lower than previously reported [1]. We found no gnaphalosid A in the water extract. Detailed analysis of components of the dried water extract allowed us to separate and to characterize the two groups of compounds for a general class of hydroxycinnamic acids differing in lipophilicity. The more hydrophilic group of compounds contained: caffeic acid, protocatechuic acid, chlorogenic acid and three more substitutional isomers of chlorogenic acid {1,3,4,5-tetra-hydroxycyclohexanecarboxylic acid 1-(3,4-dihydroxycinnamate); 1,3,4,5-tetra-hydroxycyclohexanecarboxylic acid 4-(3,4-dihydroxycinnamate) and 1,3,4,5-tetrahydroxy-cyclohexanecarboxylic acid 5-(3,4-dihydroxycinnamate)}.

References: 1. Konopleva, M., Glyzin, V. et al. (1981) Khim.-Farm.Zh. 15: 72–76.