title: Reversed-phase HPLC-ESI/MS analysis of birch leaf proanthocyanidins after their acidic degradation in the presence of nucleophiles.
abstract: Mountain birch leaves contain large amounts of structurally variable polymeric proanthocyanidins. Their isolation procedure was enhanced by the addition of liquid-liquid extractions prior to column chromatography over Sephadex LH-20. Isolated polymeric proanthocyanidins were depolymerised by acid-catalysis in the presence of benzyl mercaptan or phloroglucinol in order to study their composition. The resulting degradation products, flavan-3-ols and flavan-3-ol adducts, were analysed with reversed-phase high-performance liquid chromatography using UV photodiode array detection for quantification and electrospray ionisation mass spectrometry for identification. The results showed that polymeric proanthocyanidins contained (epi)gallocatechins and (epi)catechins as the extension units and, mainly, (+)-catechin as the terminal unit. The mean degree of polymerisation was found to be 26 based on thiolysis and 31 based on phloroglucinol degradation.
authors.affiliation: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20014 Turku, Finland. maarit.karonen@utu.fi
authors.forename: Maarit
authors.initials: M
authors.lastname: Karonen
authors.forename: Anne
authors.initials: A
authors.lastname: Leikas
authors.forename: Jyrki
authors.initials: J
authors.lastname: Loponen
authors.forename: Jari
authors.initials: J
authors.lastname: Sinkkonen
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ossipov
authors.forename: Kalevi
authors.initials: K
authors.lastname: Pihlaja
mesh_terms: D000143:Acids / Q000737:chemistry; D029662:Betula / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D018515:Plant Leaves / Q000737:chemistry*; D011108:Polymers; D044945:Proanthocyanidins / Q000032:analysis* / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000143:Acids; D011108:Polymers; D044945:Proanthocyanidins