Study On Supercritical Carbon Dioxide Extraction Technology And Purification Of Resveratrol From Wine Grape Residues

Resveratrol,a polyphenolic compound enriched in Vitis vinifera L.,Polygonum cuspidatum Sieb.et Zucc.and Veratrum nigrum Linn.,has attracted wide attention lately because of its anti-cancer, cardiovascular protection,antioxidation,anti-free radical,estrogen regulation,antimutagenicity, antibacterial,anti-inflammatory and radiation protection properties.Grape is rich in China,and resveratrol is synthesized in the different organs.With the rapidly development of wine industry,a large number of grape residue containing polyphenolic compounds were abandoned,however,if they were utilized comprehensively,not only can the enviromental pollution be reduced,but there will be considerable economic benefits.At present,the domestic super-critical technology in the research of resveratrol has not been reported.Grape residue was used as the material in the experiment,and 90.6%resveratrol was extracted and purificated taking advantages of supercritical liquid extraction technique,multi-pase extraction technique and macroporous resin purification technique.The parameters including cosolvent,extraction temperature,time and pressure for extracting resveratrol with supercritical CO₂ extraction were investigated.Single-factor tests and orthogonal tests of temperature,pressure and time were conducted with 7.5%ethanol cosolvent.The results of significant analysis showed the sequence of these factors effects was pressure＞temperature＞time,and 38℃,13MPa,17min was the optimum condition to extract resveratrol,0.087%average extracting rate of 5 replications,which could be the technical basis for developing grape residues using supercritical fluid extraction techniques.Analyzed from the intercomparision between supercritical CO₂ fluid extraction,organic extraction, enzymatic extraction and ultra-sound method,it was showed their extraction rate from high to low was enzymatic extraction＞ultra-sound method＞organic extraction＞supercritical fluid extraction, 73.18μg·g^-1,51.53μg·g^-1,40.25μg·g^-1,0.075μg·g^-1,respectively.Compared with organic extraction method,not only did ultra-sound extraction enhance resveratrol production,but reduced solvent consumption and energy,shortened the extraction time.Although the extraction rate of organic method was lower than other two methods,its simplicity of operation and low cost made it an effective method.Contrast to the other three methods, supercritical CO₂ extracts has high purity,low impurity,but low extraction rate,so repeated extraction can increase production yield. In the process of purify,resveratrol mainly solved in organic phase,not in aqueous phase;without the organic phase,resveratrol mostly solved in petroleum ether,after removing the solvent, extracting resveratrol with ethyl acetate,the target product can be purified preliminarily,and its purity rate reached 90.6%,0.120%yield. Resveratrol could be detected rapidly by use of coloured solution of 0.6%potassium ferricyanide-0.9%ferric chloride,which had sensitive action,but the two solvents should be mixed before the detection.Besides,this method could be a supplementary mean for HPLC.It was found that extraction solvent had significant effect on HPLC detection,which was always ignored,and suitable solvent was benefit on the result analysis,contrast to acetone,ethyl acetate had a more clear peak.