Extraction And Bioactivity Of Polysaccharide From Passion Fruit Peel

Passiflora edulis,also known as passion fruit,is a grassy vine of the genus Passionflower.The skin and edible parts of passion fruit contain rich bioactive substances.In this paper,the extraction of polysaccharide from passion fruit peel can not only enrich the basic research and development of natural active ingredients in passion fruit,but also improve the comprehensive utilization of passion fruit peel resources.The response surface method（RSM）was used to optimize the extraction conditions of polysaccharides from passion fruit peel by hot reflux extraction（HRE）,microwave complex enzymatic hydrolysis（MEE）and ultra-high pressure complex enzymatic hydrolysis（UPEE）.The components,physical and chemical properties,monosaccharide composition and biological activities of the polysaccharides from passion fruit peel prepared under the optimal processing conditions were studied.The main research contents and results are as follows:The optimal extraction conditions of HRE were as follows:liquid-solid ratio of 50m L/g,reflux time of 150 min and reflux temperature of 60℃.Under these conditions,the yield of polysaccharide was 3.57%.The optimum process parameters of MEE were as follows:liquid-solid ratio 50.13 m L/g,microwave power 501.38 W,extraction time 40min,microwave temperature 52.10℃,and compound enzyme dosage 1%（w/w）.Under these conditions,the yield of polysaccharide（ME-PPs）was 6.19%.The optimum process parameters of UPEE were as follows:pressure 256.66 MPa,extraction time 14.99 min,compound enzyme dosage 0.91%（w/w）,liquid-solid ratio 60 m L/g.Under these conditions,the yield of polysaccharide（UPE-PPs）was 11.58%.ME-PPs and UPE-PPs were separated by DEAE Sepharose CL-6B and further purified by Sephadex-G-100 to obtain seven homogeneous polysaccharide components:ME-PP-1,ME-PP-2,ME-PP-3,UPE-PP-1,UPE-PP-2,UPE-PP-3,and UPE-PP-4.The results of polysaccharide composition analysis showed that total sugar content was 28.46%-86.84%,uronic acid content was 9.54%-17.2%,protein content was 0.67%-2.24%,flavonoid content was 2.32%-2.89%and polyphenol content was 0.9%-2.45%.The water solubility result indicated that all homogeneous polysaccharides had good water solubility.The molecular weight（Mw）and monosaccharide composition of polysaccharide were determined by high performance gel chromatography（HPGPC）.The results showed that the molecular weights of H-PPs,ME-PPs,UPE-PPs,ME-PP-1,ME-PP-2,ME-PP-3,UPE-PP-1,UPE-PP-2,UPE-PP-3 and UPE-PP-4 were 234.42,58.88,55.80,9.55,14.45,55.58,8.51,20.89,53.70,5.52 k Da,respectively.ME-PP-1,ME-PP-2 and ME-PP-3 were all composed of mannose（Man）,rhamnose-rha（Rha）,galacturonic acid（Gal A）,glucose（Glc）,xylose（Xyl）,galactose（Gal）and arabinose（Ara）with molar ratios of 6.78:7.51:20.78:19.57:13.55:13.96:8.27;9.37:10.08:18.48:16.4:9.07:18.82:8.28;9.06:9.53:16.42:16.72:17.41:9.82:10.28 respectively.UPE-PP-1,UPE-PP-3 and UPE-PP-4 were all composed of Man,Rha,Gal A,Glc,Xyl,Gal and Ara,and their molar ratios were 9.57:10.16:11.34:20.4:13.85:11.85:9.35;0.44:2.87:44.56:39.21:1.14:2.97:0.99;13.3:12.97:30.01:24.68:1.6:14.71:1.26 respectively.UPE-PP-2 was composed of Man,Rha,Gal A,Glc,Xyl and Gal with a molar ratio of 2.87:30.85:28.36:27.97:3.04:1.08.Fourier infrared spectroscopy（FT-IR）analysis showed that the strong and wide characteristic absorption peak of polysaccharide was O─H stretching vibration near3438-3423 cm^-1.The absorption peak near 2934-2917 cm^-1 is the stretching vibration of polysaccharide C─H.The characteristic absorption peak of uronic acid was near1637-1617 cm^-1.The absorption peak near 1383-1420 cm^-1 indicated that there were proteins in all seven homogeneous polysaccharides.The absorption peak near 1000-1200cm^-1 indicates the presence of pyranose.The absorption peaks near 867-945 cm^-1 showed thatβ-glucoside bond existed in all seven homogeneous polysaccharides.The absorption peaks near 816-831 cm^-1 showed thatα-glycosidic bond existed in all seven homogeneous polysaccharides.The results showed that different extraction methods had no significant effect on the characteristic absorption peaks of polysaccharides.The results of thermal stability analysis of polysaccharides showed that all polysaccharides were composed of complex polymers with different structuresand had high thermal stability.The difference of their stability was related to the composition and molecular weight of polysaccharides.X-ray diffraction（XRD）results show that all purified components are in the coexistence of crystal and non-crystal state,and different extraction technology will affect the purity of polysaccharide,so that its crystallinity is also different.The maximum absorption wavelength of ME-PP-2,ME-PP-3 and UPE-PP-1 shows a red shift,which indicates that ME-PP-2,ME-PP-3 and UPE-PP-1 have a triple-helix structure.The maximum absorption wavelength of ME-PP-1,UPE-PP-2,UPE-PP-3 and UPE-PP-4showed no redshift at all the concentrations of Na OH,indicating that they did not have the triple helix structure.The trihelix structure test showed that the extraction technology had certain influence on the trihelix structure of polysaccharide.Ultraviolet-visible spectra showed very small amounts of protein in each purified component.The results of circular dichroic chromatography showed that there were molecular asymmetrical structures in ME-PP-1,ME-PP-3,UPE-PP-1,UPE-PP-2 and UPE-PP-3.In vitro antioxidant experiments of polysaccharides showed that,all the polysaccharides of passion fruit peel had certain DPPH?,?O₂^-,?OH and ABTS⁺?scavenging ability within the tested range,and a significant positive correlation was observed with the polysaccharides concentration.The results showed that the antioxidant activity of polysaccharides was positively correlated with the contents of uronic acid,total phenol and total flavonoids,and negatively correlated with the Mw of polysaccharides.In vitro hypoglycemic activity experiment showed that the polysaccharide from passion fruit peel had good hypoglycemic activity,and the activity was positively correlated with the concentration of polysaccharide.In general,the polysaccharide from passion fruit peel extracted by UPEE method had better hypoglycemic activity.Escherichia coli,staphylococcus aureus and candida albicans were used to perform in vitro bacteriostatic experiments on the polysaccharides from the fruit peel.The results showed that ME-PPs and UPE-PPs had good inhibitory effects on Escherichia coli,staphylococcus aureus and candida albicans,while ME-PP-3 had no obvious inhibitory effects on these three bacteria.In conclusion,the polysaccharide from passion fruit peel has good physicochemical properties and biological activities,and can be used as a natural active substance to provide a new idea for high value-added utilization of passion fruit peel polysaccharide.