- About 60% of extracted litchi pericarp polyphenols corresponded to procyanidins.
- A first molecular structure of the oxidized procyanidins in litchi was achieved.
- Five oxidation markers of procyanidins were clearly identified.
- Thioglycolysis–HPLC–ESI–MS is a useful method to characterize oxidized procyanidins.
Procyanidins (PCs) are polyphenols highly accumulated in litchi fruit (
). Despite their bioactivity, the molecular composition of native and oxidized procyanidins is little understood.
In this paper, polyphenols from litchi pericarp were extracted using two solvents (methanol and acetone).
The mean degree of polymerization (mDP) of native and identification of oxidized PCs were carried out by phloroglucinolysis– and thioglycolysis–HPLC–ESI–MS/MS, respectively. About 60% of extracted polyphenols corresponded to procyanidins from litchi pericarp. Native PCs were mainly oligomeric procyanidins (mDP 4). Only (−)-epicatechin was detected as terminal and extension units in PCs. Thioglycolysis–HPLC–ESI–MS identified five oxidation markers of PCs with [M−H]−
575, 593, 609, 679 and 863. Intra- and intermolecular modifications of A and B-type procyanidins were identified. The method used for the characterization of PCs from litchi pericarp allowed understanding of the structural composition of its native and oxidized tannins.