Polymerization Degree Determination And Fractionation Of Procyanidins

Procyanidins are the general term that describe the kind of natural polyphenol compounds existing extensively in the nature,which are polymerized by different amounts of catechin and/or epicatechin monomers and/or their gallates.Procyanidins with lots of phenolic hydroxyl groups show good antioxidant activity and excellent ability to remove free radicals so they are used in medicine,health care,cosmetology,nutrition and other fields widely.The biological activity of procyanidins varies with polymerization degree.The research on procyanidins is focused on the mixtures of polymers with different polymerization degree,which leads to the lack of biological activity data on the specific polymerization degree.To search a convenient,accurate and stable method to determine the polymerization degree of procyanidins is meaningful for the fractionation of procyanidins,enrichment of oligomers and exertion of biological activity.The feasibility to determine the polymerization degree of procyanidins with viscometry was researched in this paper.The proportional constant K and the expansion factor a of the procyanidins were obtained so the Mark-Houwink equation became to[η]=9.582×10-5×M0.870.The polymerization degree with viscometry was consistent with vanillin method.The crude extract of grape seed procyanidins was adsorbed in AB-8 macroporous resin column.Ethanol solution of 10%to 40%(2%interval)and 60%were used to elute the procyanidins in the column.The eluent of 10%ethanol solution contained monomer.The eluents from 12%to 34%contain oligomer mainly and eluent from 22%to 24%contained dimer.The eluents up to 60%contained high polymer.The mass distribution,antioxidant activity,water solubility and color related to the polymerization degree were obtained.The procyanidins polymer obtained from 40%to 60%ethanol solution were hydrolyzed.The degree of hydrolysis varied with pH and temperature when the reaction time was determined.The optimum hydrolysis condition was obtained through experiments consistent with the previous experiment result.