HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ATMOSPHERIC-PRESSURE IONIZATION MASS-SPECTROMETRY OF GYMNEMIC ACIDS

Gymnemic acids (GAs), extracted from the leaves of Gymnema sylvestre, are a mixture of triterpene glucuronides possessing various physiological activities. The molecular masses of GA homologues were determined with high-performance liquid chromatography combined with atmospheric pressure ionization mass spectrometry. A mixture of GAs was chromatographed on an octadecyl silica column eluted with an aqueous methanol solution containing ammonium acetate, and directly introduced into an atmospheric pressure ionization mass spectrometer. Quasimolecular ions of GAs were detected as ammonium adduct ions and/or proton adduct ions. Molecular masses of thirteen different GAs and five compounds not containing glucuronic acid in their molecules were evaluated. Three pairs of geometrical isomers of GAs were found.