Study On The Ultrasonic Degradation Of Polymeric Proanthocyanidins

Proanthocyanidins are polyphenols with C3·C6·C3 basic structure,which widely exist in plants.Proanthocyanidins have many biological activities,such as antioxidant activity,prevention and treatment of cardiovascular diseases,cancer prevention and anticancer activity,and the activity of polymers is lower than that of oligomers.Therefore,the degradation of polymers into oligomers is of great significance for the development and utilization of polymeric proanthocyanidin（PP）.In this paper,PP were purified from grape seeds and treated by ultrasound.The structure and activity changes of PP before and after ultrasonic treatment were analyzed and compared,and a method of ultrasonic degradation of PP was established.The main research results are as follows:（1）Macroporous resin was used to purify proanthocyanidins,and then Sephadex LH-20 was used to separate and prepare grape seed PP,and their structure and composition were characterized.Six kinds of macroporous resins were selected,including LSA-10,D101,D301,HPD600,X-5 and AB-8.Static adsorption test showed that HPD600,LSA-10,AB-8 and D101 macroporous resins had better adsorption effect on proanthocyanidins,among which HPD600 had the best adsorption effect,with the highest adsorption rate of86.04%and the adsorption capacity of 57.49 mg/g.Therefore,HPD600 resin was selected for the dynamic adsorption test of macroporous resin.The results showed that the adsorption capacity of HPD600 macroporous resin for crude proanthocyanidins was about55.50 mg/g,which was close to the static adsorption capacity before.According to the results of static adsorption screening of macroporous resin,LSA-10,D101,HPD600 and AB-8 resins were selected for dynamic elution test.The results showed that when LSA-10macroporous resin was used to elute with 50%ethanol as eluent,the elution efficiency was the highest.The content of proanthocyanidins in the crude extract purified by this method can reach 10.2%,which is 44.6%higher than that before purification.PP were separated by Sephadex LH-20 and degraded by acid catalysis.By analyzing the reaction products,it was found that the main extension unit was catechin and the terminal unit was epicatechin,with an average degree of polymerization of 4.36.（2）The effect of ultrasonic treatment conditions on the degradation efficiency of PP was studied by single factor test and response surface test.The degradation conditions were optimized and the method of ultrasonic degradation of PP was established.On this basis,the structure and antioxidant activity of PP before and after ultrasonic treatment were analyzed and compared.The single factor test results showed that the degradation rate was significantly affected by the changes of several ultrasonic parameters（ultrasonic temperature,ultrasonic time,power,duty cycle）except the depth of the amplitude rod immersed in the liquid surface during the ultrasonic process.The optimum ultrasonic degradation parameters obtained by response surface test were ultrasonic temperature35.42℃,power 155.65W,duty cycle 56.59%,ultrasonic time 25 minutes and methanol as ultrasonic solvent.The degradation rate of PP was 27.65%.The results of DPPH free radical scavenging test showed that the EC₅₀ values of PP before and after ultrasonic treatment were 0.0389 mg/mL and 0.0299 mg/mL respective.The results indicated that the antioxidant activity of ultrasound-treated PP was enhanced.The results of RP-HPLC and NP-HPLC showed that PP were degraded obviously after ultrasonic treatment,which again showed that ultrasonic treatment could degrade PP.