Extraction And Separation Of Proanthocyanidins And Investigation On Their Anti-oxidation And Stability

Proanthocyanidins were obtained from the refluent extraction process with grape seeds and their leaves as main materials. Grape seeds was extracted with a 1/40 proportion of materials to solvents, 50% (v/v) ethanol under reflux at 50℃ for 2h and the ratio of this extraction can reach to 22.01% with a 51.17% pureness; meanwhile grape leaves was extracted with a 1/50 proportion of materials to solvents, 70% (v/v) ethanol under reflux at 80℃ for 3h and the ratio of this extraction can reach to 34.14% with a 13.66% pureness.These extracts were further purified by macroporous adsorbent resin. AB-8 resin made the extracts of grape seeds get to a 94-95% pureness;on the other side, D-101 was more suitable for grape leaves to get to a 25.63% pureness. The optimal dissolvent for grape seeds and leaves extracts are 50% ethanol and 70% ethanol respectively.Experiments for further purification and concentration of oligomeric proanthocyanidins from grape seed extract were carried out by use of sulfonated polyethersulfone ultrafiltration membranes with molecular weight cut-off of 5000 and 1000. The ratio of proanthocyanidins obtained by 5K membrane was 25.18%,and the ratio of monomer catechin obtained was 74.11%;the ratio of proanthocyanidins and catechin obtained by 1K membrane were 34.76% and 48.58% respectively. Catechin contented in the dry extracts obtained by 5K and 1K was 6.6 and 7.7 times to the dry extracts before ultrafiltration. When ultrafiltration was performing, the pressure 20-30 psig and house temperature were recommended. A dimmer of proanthocyanidins was condensed from the separation process by using Sephadex LH20 resin.Proanthocyanidins present more significant antioxidant and free-radical scavenging activities than ascorbic acids, lightly than proanthocyanidins from grape leaves and little than oligmers or polymers after experiments of FRAP and DPPH scavenging.Proanthocyanidins have a desirable stability during 1-2 days with different temperatures, oxygen and light. However, under a long-term (10 days) UV irradiation, proanthocyanidins became unstable and descended to disappear, but their antioxidant and free-radical scavenging activities were not significantly different from the samples without irradiation (p>0.05). Furthermore, the addition of ascorbic acid in the solution of proanthocyanidins prolonged the degradation of proanthocyanidins and protected them from irradiating with UV light, and from...