Tandem mass spectrometry of the B-type procyanidins in wine and B-type dehydrodicatechins in an autoxidation mixture of (+)-catechin and (-)-epicatechin.
We describe the characterization of the B-type procyanidins in wine and the B-type dehydrodicatechins (dimeric flavan-3-ols) obtained for the autoxidation of (+)-catechin and (-)-epicatechin by tandem mass spectrometry (MS/MS) coupled to reversed-phase high-performance liquid chromatography (HPLC). The MS/MS analysis demonstrates that the interesting major fragments derive from the dissociations of the C-ring on the catechin or epicatechin unit, such as retro-Diels-Alder reactions. The two kinds of dimers give completely different fragmentations because of the striking effect of the C-C interflavan linkage (IFL). For the natural dimers in wine, a catechin or epicatechin unit linking to the C-4 position stabilizes the product ions by forming a large pi-pi hyperconjugated system, whereas a similar pi-pi system is formed within dehydrodicatechin B through the C-C IFL. Thus dissociation in MS/MS experiments was inhibited. Apparently, the fragmentations of the dimers differ from that of the monomer, which is very important in the study of the gas-phase ion behaviour of the polymeric flavan-3-ols. In addition, two specific fragment ions at m/z 451 for native dimers and at m/z 393 for autoxidation species in HPLC/MS/MS were found to be very useful for analysing mixtures of B-type procyanidins and B-type dehydrodicatechins in food and beverages.
Sun
Weixing
W
Chemistry Department, Brock University, St. Catharines, Ontario, Canada, L2S 3A1.
Miller
Jack M
JM
D044946:Biflavonoids; D002392:Catechin / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D019281:Dimerization; D015394:Molecular Structure; D010084:Oxidation-Reduction; D044945:Proanthocyanidins; D021241:Spectrometry, Mass, Electrospray Ionization; D014920:Wine / Q000032:analysis*
D044946:Biflavonoids; D044945:Proanthocyanidins; C017674:procyanidin; D002392:Catechin