Effect of the number of flavanol units on the antioxidant activity of procyanidin fractions isolated from chocolate.

Of three different solvents (acetone, ethanol, and methanol) mixed with water and acetic acid, the acetone/water/acetic acid mixture (70:28:2, v/v) proved to be best for extracting dark-chocolate procyanidins. High-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-MS-ESI) was further used to identify oligomers found in the extract. After HPLC fraction collection, the reduction power of flavanoid fractions was measured in the AAPH [2,2'-azobis(2-amidinopropane)dihydrochloride] assay, where oxidation of linoleic acid is induced in an aqueous dispersion. Even expressed in relative monomeric efficiency units, the oxidation-inhibiting power of polymerized oligomers is much stronger than that of monomers. A comparison with 10 usual antioxidants indicated that oligomers with three or more (epi)catechin units are by far the most efficient.