Tandem mass spectrometry of the B‐type procyanidins in wine and B‐type dehydrodicatechins in an autoxidation mixture of (+)‐catechin and (−)‐epicatechin

TLDR

Fragmentation of B‑type procyanidin dimers differs from monomers, a key factor in studying gas‑phase ion behavior of polymeric flavan‑3‑ols. The study characterizes B‑type procyanidins in wine and B‑type dehydrodicatechins formed by autoxidation of (+)‑catechin and (−)‑epicatechin using tandem MS/MS coupled to reversed‑phase HPLC. Natural dimers are stabilized by a π–π hyperconjugated system at the C‑4 linkage, while dehydrodicatechins are stabilized by a C‑C interflavan linkage, and both are analyzed by tandem MS/MS with RP‑HPLC. MS/MS reveals that major fragments result from C‑ring retro‑Diels–Alder dissociation, with distinct patterns for natural dimers versus dehydrodicatechins, and diagnostic ions at m/z 451 and m/z 393 enable analysis of mixtures. © 2003 John Wiley & Sons, Ltd.

Abstract

Abstract 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 π–π hyperconjugated system, whereas a similar π–π 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. Copyright © 2003 John Wiley & Sons, Ltd.