Fractionation of pine bark extracts: selecting procyanidins

Pine bark is a forest by-product that can be profitable as a source of polyphenols by its content in procyanidins. In this work, barks of two varieties of pine (Pinus pinaster and P. radiata) were extracted with ethanol, and partially purified to obtain a fraction named FOW, that contained mainly flavan-3-ol monomers and procyanidins oligomers. The mean degree of polymerization was 2.1 for pinaster (pOW) and 2.7 for radiata (rOW). FOWs were fractionated on C₁₈ Sep-Pak cartridges into three fractions for each variety by different organic solvents. The phenolic compositions of the fractions were analyzed using HPLC with UV diode array detection and electrospray-ionization mass spectrometry. The compounds identified were: catechin, dihydroquercetin, phenolic acids and their glucosides, procyanidins dimers, trimers and tetramers. FOWs and their fractions were characterized in antioxidant power by DPPH and β-carotene methods. In the former assay, pOW showed major effectiveness, with an antiradical specific activity of 46 units AR/mg procyanidins, whereas for the β-carotene bleaching test rOW (78 ± 0.71%) gave the best inhibition result. Despite this fact the derived fractions, presenting similar values, have advantages because the profile of their constituents is uniform for each one, and, hence, it is easier to investigate their action for potential applications in both medical or food fields