Structure and Antioxidant Activities of Proanthocyanidins from Elephant Apple (Dillenia indica Linn.)

Proanthocyanidins were isolated and purified from fruits of elephant apple (Dillenia indica Linn.) and their structural and bioactive properties were examined. Bate-Smith alcoholysis, FTIR, and C-13 NMR spectra revealed that elephant apple proanthocyanidins (EAPs) contained a dominant amount of B-type procyanidins (PC) with a minor amount of B-type prodelphinidins (PD) but no A-type interflavan linkage. C-13 NMR spectrum indicated that the cis isomer was dominant in EAPs. The electron spray ionization and matrix-assisted laser desorption ionization time of flight mass spectra of EAPs showed the clear ion peaks corresponding to B-type PC dimer to B-type PD with degree of polymerization of 11. EAPs had strong antioxidant activity, which was evidenced by the high oxygen radical scavenging capacity at 1.06 x 10(4) mu mol TE/g and ferric reducing antioxidant power of 2320 mu mol Fe(II)/g. The results suggest that EAPs could be extracted to be used as promising functional food materials.