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.
