| Chaenomeles sinensis(CS)resource is abundant in China.The fruit of CS is not only the traditional Chinese medicine,but also a kind of food after proccessed,such as canned fruit,juice,which is popular by consumers.For a long time,researches about the composition confined to polyphenols and flavonoids.However,there were few focus on polysaccharides in CS.In this paper,the structure and application value of water-soluble polysaccharides and xylan in CS were studied,with the pre-treated CS as the raw material.We ami to provide a theoretical guidance for the comprehensive utilization of CS.The main results of this study are summarized as follows:(1)We used hot-compressed water method(HCW)to fractionate the polysacchaeides from CS.The effects of HCW conditions on the yield of polysaccharides were investigated.We further tudied the effect of temperature on the structure of polysaccharides.Results showed that appropriate high temperature,appropriate extension of the extraction time and a lower solid to water ratio contributed to the obtain of PA.PA extracted at different temperatures were similar structure.In the range of 120-150 ?,high temperature was conducive to hemicellulose dissolution,but not to lignin and xylan.(2)Using the polysaccharide(135 °C,1:10,45 min)as material,a neutral fragment CSP-1 and two acidic polysaccharides(CSP-2 and CSP-3)were obtained after further purification.The primary structure,morphology and thermal stability of the three polysaccharides were analyzed.The main monosaccharide composition of CSP-1was Ara,the mole percentage was 45.4%.CSP-2 and CSP-3 were rich in GlaA,which were 53.23% and 73.62%,respectively.FT-IR results showed that the three polysaccharides contained both pyranose and furanose,linked mainly by ?-glycosidic bonds.CSP-1 was heterogeneous,but CSP-2 and CSP-3 were homogeneous(59.1 kDa and 57.9 kDa).From pictures taked by SEM,CSP-1 was loose,with holes and microspheres connected to the filament.Meanwhile,CSP-2 and CSP-3 deposited into a lamellar,owing to the presence of a large number of uronic acid.The three polysaccharide chains were entangled with each other and curled into a spherical shape in the 2D and 3D images by AFM.(3)For further study,the methylation and NMR techniques were used.It could be speculated that the skeleton of CSP-2 consisted of HG and RG-I.In the region of HG,a linner 1,4-?-D-GalpA were partically methyl esterification or acetylation at the C-2 / C-3 position,and all of the Rha in the hairy region were subsititted at O-4.Side chains were mainly composed of galactans,arabinose and arabinogalactan,with small amounts of glucan and mannose interrupted.(4)Alkali-soluble xylans were treated by gradient ethanol(30%,50%,70%,90%)before or after treatment with HCW(120 ?,1:10,45 min).The low concentration of ethanol can precipitate xylan with high linearity and high molecular weight(Mw).After pretreatment by HCW,the Mw of xylan was larger and the content of xylose was higher Low concentration of ethanol precipitation were a linear high degree of polymerization.The xylose content and molecular weight of the xylan obtained after HCW was higher.The main chain of UPX30(Mw: 120.8 kDa)and PX30(Mw: 207.7 k Da)were 1,4-?-D-Xylp,and was partically substituted by 4-O-methyl-D-GluAp at O-2 position,with some Ara and Gal existing in side chains.(5)The antioxidant activity of polysaccharides of CS showed a concentrationdependent,and the presence of uronic acid could improve the hydroxyl free radical scavenging ability of polysaccharides.The total reducing ability became weaker after purification.CSP and CSP-1 were stronger than acidic polysaccharide in DPPH scaving.The antioxidant activity of polysaccharides was stronger than that of Vc.The xylanbased hydrogel was prepared by chemical cross-linking acrylic monomers.When the pH is netural or the solution contained fewer ion,they showed a higher Swelling degrees,but had a maximum of 59.5 g/g in distilled water. |
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