Qualitative and quantitative analysis of multiple galloyl derivatives of quinic acid from the medicinal plant Galphimia glauca Cav. using HPLC-ESI-MS

Galphimia glauca (Malpighiaceae) is used in Mexican traditional medicine for the treatment of nervous excitement. Pharmacological investigations have reported sedative, anticonvulsant, antiasthmatic, antiallergic properties, hypothermic activity, barbiturate potentiation, protection against strychnine- and leptazol-induced convulsions. The present investigations deal with the identification of Galphimia ingredients with special focus on quinic acid derivatives. Beside evaluation of different extraction techniques, i.e. Aquasolv® extraction [1], microwave assisted extraction (MAE) and traditional extraction, HPLC and mass spectrometric techniques were of central interest for identification and quantification of quinic acid galloyl derivatives. Evaluation of extraction techniques clearly demonstrated that MAE in 50% ethanolic solution afforded highest recovery (concerning dry weight) within shortest time. Mass spectral investigations proved that in addition to the most abundant galloyl derivative of quinic acid, i.e. the tetra-galloyl-quinic acid, several other multiple derivatives were detected differing from each other by 152 mass units. Elution order of these derivatives in reversed phase HPLC system was from lowest mass number to highest one, depending upon increasing hydrophobicity of analytes. Pure quinic acid was also present. Moreover, several different isomers for these multiple galloyl derivatives were identified, e.g. four different isomers both for di- and tri-galloyl-quinic acid, respectively, depending upon the difference in the point of attachment of galloyl moiety to the quinic acid ring structure. Owing to the changing polarity of different target compounds, clear tendencies concerning extraction solvent were observed. Using pure water for MAE delivered highest extraction yields for lower molecular weight derivatives, i.e. mono- to tri-galloyl-quinic acid, while for higher molecular weight galloyl derivatives of quinic acid, 50% EtOH was the right option. Finally the most abundant galloyl derivative found in Galphimia glauca (tetra-galloyl-quinic acid) was quantified at 280 nm, delivering approximately 6.9% (w/w).

References: Bonn, G. et al. (1987) Wood Science and Technology, 21: 179.