A-TYPE PROANTHOCYANIDINS FROM PERICARP OF LITCHI-CHINENSIS

A tannin extract was isolated from freeze-dried litchi pericarp (Litch i chinensis). HPLC analysis, after thioacidolysis reaction, revealed t hat this tannin fraction consisted of epicatechin units linked by both and B-type interflavonoid bonds. The calculated average degree of pol ymerization, considering the presence of A-type linkages, was 6.4. Cha racterization of oligomeric and polymeric procyanidins was performed u sing electrospray ionization mass spectrometry. Numerous oligomers con taining one or more A-type interflavanoid linkages were detected. A re gular repartition of the number of A-type linkages for each polymer le ngth (e.g. from 2 to 7 for DP17 with mostly 4 A-type linkages) was obs erved. The average number of A-type linkages also increased with the D P, 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-ty pe interflavanoid linkages. (C) 1998 Elsevier Science Ltd. All rights reserved.