Evaluation of different detection modes for the analysis of procyanidins in leaves and flowers of crataegus spp. Part II. Liquid chromatography-mass spectrometry

Liquid chromatography-mass spectrometry, using electrospray (ESP) as well a s atmospheric pressure chemical ionization (APCI), has been evaluated for t he qualitative analysis of (-)-epicatechin and oligomeric procyanidins in r eference solutions and in extracts of leaves and flowers of Crataegus spp, Applying the APCI interface, considerable fragmentation took place owing to cleavage of the inter-flavanoid bonds and to retro-Diels-Alder fission of the heterocyclic rings, Fragmentations occurred more extensively in the pos itive than in the negative ionization mode. Lowering the corona current or the vaporizer temperature did not increase the abundance of the molecular i ons, but produced lower sensitivities and higher noise levels. The use of t he ESP interface in the negative ionization mode yielded molecular ions as principal signals with all tested compounds. In addition, ions resulting fr om the cleavage of the inter-flavanoid bonds as well as cluster ions, gener ally composed of two analyte molecules, could be detected. The pyran ring s ystems were stable under these mild ionization conditions. The chromatograp hic analysis of extracts from leaves and flowers of Crataegus spp, revealed the presence of procyanidins up to the tetrameric level. Evidence for the occurrence also of pentamers and hexamers could be found in the chromatogra ms, The difficulties in interpreting mass spectra of higher molecular mass compounds as well as different approaches to the quantitative analysis of p rocyanidins using liquid chromatography-mass spectrometry are discussed. Co pyright (C) 2000 John Wiley & Sons, Ltd.