Investigation of Ethyl Acetate Soluble Proanthocyanidins in the Inflorescence of Cocos nucifera L.

Abstract

The immature inflorescence of Cocos nucifera L. variety aurantiaca is used in Ayurveda for the treatment of menorrhagia in Sri Lanka. Preliminary phytochemical screening revealed that immature inflorescence predominantly contains proanthocyanidins. The ethyl acetate soluble proanthocyanidin (EASPA) fraction obtained from an acetone/water (7:3) extract of the immature inflorescence was effectively purified and separated from other phenolic compounds by chromatography on sephadex LH-20. EASPA has been fully characterized by chromatographic, spectroscopic and spectrometric methods. Acid catalyzed cleavage followed by TLC indicated that EASPA is composed of (epi)catechin and (epi)afzelechin monomeric units while thiolysis followed by 1H and 13C NMR spectroscopy revealed the monomers to be the epi-isomers. 13C NMR studies of EASPA showed signals characteristic for epicatechin units indicating that EASPA is composed mainly of epicatechin units. Confirming these epicatechin oligomers with degrees of polymerization ranging from 2-5 and mixed oligomers, epicatechin-epiafzelechin dimer and epicatechin-epicatechin-epiafzelechin trimer were observed by ESI-MS.