A-type proanthocyanidins from pericarp of Litchi chinensis

A tannin extract was isolated from freeze-dried litchi pericarp (Litchi chinensis). HPLC analysis, after thioacidolysis reaction, revealed that this tannin fraction consisted of epicatechin units linked by both and B-type interflavonoid bonds. The calculated average degree of polymerization, considering the presence of A-type linkages, was 6.4. Characterization of oligomeric and polymeric procyanidins was performed using electrospray ionization mass spectrometry. Numerous oligomers containing one or more A-type interflavanoid linkages were detected. A regular repartition of the number of A-type linkages for each polymer length (e.g. from 2 to 7 for DP17 with mostly 4 A-type linkages) was observed. The average number of A-type linkages also increased with the DP, the predominant species containing one A-type linkage (denoted 1A) from DP2 to 5, 2A from DP6 to 10, 3A from DP11 to 15 and 4A from DP16 to 20. The highest DP was estimated at 22, with predominantly 5-6 A-type interflavanoid linkages. (C) 1998 Elsevier Science Ltd. All rights reserved.