CHARACTERIZATION OF PHENOLIC ANTIOXIDANTS FROM MATE (ILEX PARAGUAYENSIS) BY LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY AND LIQUID-CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY

Liquid chromatography/ion trap mass spectrometry with an atmospheric p ressure chemical ionization (APCI) interface in the negative-ion mode, using collision-induced dissociation (CID) of precursor ions in paral lel with UV-diode-array detection (DAD), was applied to the characteri zation in crude extracts of the water-soluble antioxidant phenolics fr om Mad leaves (Ilex paraguayensis), APCI gives unequivocal information about both the molecular mass of these compounds and some indications about their structure, which were confirmed by the UV-DAD fingerprint s and by the diagnostic CID patterns. This allowed the identification of 10 constituents, including the 3 naturally occurring isomers of caf feoylquinic acid (CGA), namely neo-chlorogenic acid, chlorogenic acid and crypto-chlorogenic acid, as well as 3 isomeric dicaffeoyl quinic a cids, rutin (quercetin-3-rutinoside), a diglycosyl derivative of luteo lin, and 2 isomeric caffeoyl-glucosides, The aqueous extract of Mate, quantitatively analyzed for polyphenol and CGA content (HPLC), was tes ted for antioxidant activity in both a cell-free system (quenching of the stable free radical DPPH, 2,2-diphenyl-1-picryl-hydrazyl) and in a model membrane system (phosphatidylcholine liposomes), The results de monstrate that the extract is a strong radical scavenger, considerably more potent than the prototype chlorogenic acid, and this indicates a cooperative antioxidant interaction among its polyphenol components. (C) 1998 John Wiley & Sons, Ltd.