Identification of A-series oligomeric procyanidins from pericarp of Litchi chinensis by FT-ICR-MS and LC-MS

Abstract

Procyanidin oligomers from litchi pericarp (Litchi chinensis) were isolated and identified by online analysis. Accurate molecular weight (MW) distribution and composition of the procyanidin extracts were recorded on an Apex-Qe–FT–ICR mass spectrometer. The MW range of litchi procyanidins was from 289.07151 to 1439.30529 m/z and composed of A- and B-series oligomeric procyanidins. The variety of the main procyanidins (DP < 5) was identified by HPLC and LC–ESI-MS analysis. There are more than 41.7% of A-series procyanidins in the oligomeric procyanidins, however, B-series procyanidins takes only 24.1% of the litchi pericarp extracts. In this study, we determined the effects of (−)-epicatechin, A-type procyanidin dimer (A2) and trimer, epicatechin-(4β→8, 2β→O→7)-epicatechin-(4β→8)-epicatechin from litchi pericarp on free radical scavenging. The results showed that A-type procyanidin dimer and trimer both had a strong scavenging ability on DPPH and OH, indicating that litchi is a new plant source of A-type procyanidins and natural antioxidant.