Separation And Purification And Antioxidant Activities Of Polysaccharides From Peels And Leaves Of Red Dragen Fruit

In this study,the extraction,purification and characterization of polysaccharides and antioxidant activities of polysaccharides from peels and leaves of Red Dragen Fruit were systematically studied and the results were as follows:1.Ultrasonic extraction?UE?and ultra high pressure extraction?UHPE?were used to extract the polysaccharides from red dragon fruit peels.Response surface methodology?RSM?along with a Box–Behnken design?BBD?based on single-factor experiments was employed to optimize the extraction conditions of polysaccharides.Under these conditions,the the predictive yield of UEPPs were 33.26%and 34.50%,which illustrates that the extraction yield of polysaccharide was higher than that of UE.The UEPPs and UHPPs extracted by the UE and UHPE were obtained by alcohol precipitation,removed protein with the Sevag method,dialyzed against water to remove small molecule ingredients.The UEPPs and UHPPs were separated by ultrafiltration membrane and further purified by Sephadex G-200 molecular sieve gel column chromatography,and ten homogeneous acid heteropolysaccharides were obtained named as UEPP-1,UEPP-2,UEPP-3,UEPP-4,UEPP-5,UHPP-1,UHPP-2,UHPP-3,UHPP-4 and UHPP-5,with average molecular weights of 7191,17518,47210,95280,534438,7951,16461,49979,114409,193709 Da,respectively.They all contain small amounts of proteins?0.06%to 1.29%?and and higher contents of uronic acid?8.12%-33.41%?.The physicochemical properties and structural characteristics of these polysaccharides were characterized and compared using high performance gel permeation chromatography?HPGPC?,high performance liquid chromatography?HPLC?,Fourier Transform infrared?FT-IR?,respectively.UEPP-1,UEPP-2,UEPP-3and UEPP-4 were composed of rhamnose?Rha?,glucuronic acid?GlcA?,galactose?Gal?,glucose?Glc?,galacturonic acid?GalA?,xylose?Ara?and arabinose?Ara?with mole ratio of 11.2:10.8:24.7:11.5:25.7:7.2:5.2,11.5:12.7:27.1:5.5:19.7:10.3:8.9,2.3:3.1:53.8:15.9:4.8:6.6:5.3,4.6:4.9:45.6:18.7:3.1:6.0:5.8,respectively.UEPP-5 was composed of Rha,GlcA,Gal,Glc,GalA and Xyl in a mole ratio of 11.3:23.5:48.5:2.5:3.1:3.5.UHPP-1,UHPP-2 and UHPP-5 were composed of Rha,GlcA,Gal,Glc and GalA with mole ratio of 13.5:10.5:51.3:15.6:3.9,5.5:8.7:71.1:5.9:5.7,3.3:8.6:75.5:4.5:4.1,respectively.UHPP-3 was composed of Rha,GlcA,Gal,Ara with mole ratio of65.3:9.4:7.8:14.9.UHPP-4 was composed of GlcA,Gal and GalA in a mole ratio of7.8:80.2:5.1.FT-IR showed that these samples all had characteristic absorption peaks of polysaccharides,containing uronic acid and protein,with?-and?-glycosidic bond configuration and pyranose rings.The antioxidant activities of samples were determined by?DPPH,?OH and?O₂^-test,and the results showed that the ten polysaccharides all had significant antioxidant activities,and their antioxidant activities were positively correlated with the concentrations of polysaccharides.Moreover,the research found that the?DPPH activity of UEPP-1 was significantly higher than that of UEPP-5;the?DPPH activity of UHPP-1 was significantly higher than that of UHPP-5,indicating that polysaccharides with relatively lower molecular weight has relatively higher antioxidant activity.These results indicate that the polysaccharides by UE from pitaya peel has higher antioxidant activity,and that the low-molecular-weight polysaccharide fraction can be used as a potential natural antioxidant.2.UE and UHPE were used to extract the polysaccharides from the Red Dragon fruit leaves.Then ten homogeneous polysaccharides fractions?UELP-1,UELP-2,UELP-3,UELP-4,UELP-5,UHLP-1,UHLP-2,UHLP-3,UHLP-4 and UHLP-5?were obtained by removed protein with the Sevag method,dialyzed against water to remove small molecule ingredients,separated using ultrafiltration membrane,and purified by Sephadex G-200 gel filtration chromatography,respectively.They all contain small amounts of proteins?0.16%to 6.62%?and higher amounts of uronic acid?7.63%-43.85%?.The structural characteristics of polysaccharides were performed by HPGPC,HPLC and FT-IR,with average molecular weights of 9048,12650,24375,81833,114409,5937,14745,32175,74361 and 120019 Da,which they were all acidic heteropolysaccharides.UELP-1 and UHLP-1 were composed of GlcA,Gal,Glc,GalA,and Xyl with the molar ratio of 6.2:10.8:27.5:8.5:40.6 and 11.5:16.8:15.8:32.1:17.6.UELP-2 and UHLP-2 wre composed of Rha,GlcA,Gal,Glc,GlcA,Xyl and Ara with the molar ratio of 1.6:3.7:38.5:30.0:5.1:6.9:4.8,7.2:34.1:3.3:16.2:17.4:7.8:8.6.UHLP-3was composed of Rha,GlcA,Gal,Glc,GalA,Xyl with the molar ratio of 5.4:13.9:48.0:8.2:9.8:9.0.UHLP-4 was composed of GlcA,Gal,Glc,GalA,Xyl and Ara in a molar ratio of 3.2:34.1:24.3:6.4:11.4:10.2.UELP-3,UELP-4 and UELP-5 were composed of Rha,Gal,Glc,GalA and Xyl in a molar ratio of 1.6:69.8:2.0:11.1:5.6,1.4:65.5:2.3:12.6:6.9,1.2:46.5:2.1:29.6:7.2.UHLP-5 was composed of Rha,GlcA,Gal,Glc,GalA in a molar ratio 40.0:21.6:8.9:13.9:7.5.FT-IR spectra showed that all the polysaccharides had multiple characteristic absorption peaks of polysaccharide and uronic acid,contained pyranose and protein,and had C-H variable angle vibration and C-O-C stretching vibration in the sugar ring.The antioxidant capacities of these polysaccharides were analyzed by free radical??DPPH,?OH and?O₂^-?scavenging test.The results showed that the polysaccharides of dragon fruit leaves have significant antioxidant activity,of which UELP-1 and UHLP-1 have the highest DPPH scavenging ability,indicating that their Low molecular weight,high content of uronic acid,UHLP-3has the strongest ability to scavenge?O₂^-,probably because of its lower molecular weight and higher content of Gal.The results show that the antioxidant activity was related to the relative molecular weight and the content of uronic acid and Gal.Different extraction methods were used to extract the polysaccharides from the peels and leaves of Red Dragon Fruit,concluding that the UE and UHPE processes were good.Under the optimal conditions,the UHPE had a higher yield of polysaccharides than that of the UE,and the peel polysaccharide was easier to extract than that of the stems and leaves.According to the antioxidant activity experiments of fruit stems and leaves,it could be seen that the polysaccharides extracted from the peel and the stem and leaf polysaccharides extracted from the two methods had strong antioxidant activity and could be used as a potential antioxidant in medicine or functional foods.