Radical-scavenging proanthocyanidins from sea buckthorn seed

Water–acetone (3:7) extract of sea buckthorn seeds was separated by Sephadex LH-20 column chromatography into nine fractions. Three of the fractions exhibited strong radical-scavenging activities by DPPH analysis and contained flavan-3-ols. Four monomeric flavan-3-ols, catechin (1), epicatechin (2), gallocatechin (3) and epigallocatechin (4), along with two dimeric procyanidins, catechin(4α-8)catechin (5) and catechin(4α-8)epicatechin (6), were isolated. The dimeric proanthocyanidins were investigated by HPLC, in combination with electrospray ionization mass spectrometric detection. The more abundant polymeric proanthocyanidins were fractionated and their chemical constitutions studied by acid-catalysed degradation in the presence of toluene-α-thiol. The results showed the polymers to be highly heterogeneous, with catechin, epicatechin, gallocatechin and epigallocatechin all being constituent components of both the extension as well as the terminating units. The mean degree of polymerization (mDP) was 12.2. The proportion of prodelphinidins was 81.2%.