【作者】 吴敏；

【导师】 秦广雍；

【作者基本信息】 郑州大学 ， 生物物理， 2017， 硕士

【摘要】 我国光皮木瓜资源丰富,其果实不仅是传统的中药,经过加工后制成的罐头、果汁、果酒等深受消费者喜爱。但是长期以来,人们对光皮木瓜成分的研究局限于多酚、黄酮类物质上,鲜有对其中的多糖类物质的报道。本论文以预处理过的光皮木瓜为原料,以对高压水热法初步分离产物的研究为起点,对光皮木瓜中水溶性多糖和木聚糖的结构及其应用价值进行研究,旨在为光皮木瓜的综合利用提供理论指导和数据支持,主要结论如下:(1)采用高压水热法(HCW)提取光皮木瓜多糖,研究温度、时间、料液比对得率的影响,并进一步研究温度对各部分结构的影响。结果表明,适当的高温、适当延长提取时间和减少料液比有利于醇沉多糖PA的获取;在120-150℃范围内,固体残渣(SR)和醇沉多糖(PA)具有相似的结构;高温有利于半纤维素的溶解,但并不能使半纤维素和木聚糖成分有效的降解。(2)利用经过在135℃,料液比为1:10条件下,提取45 min后醇沉制得的PA为原料,进一步经过DEAE-52纯化后得到一个中性糖片段CSP-1和两个酸性多糖片段CSP-2、CSP-3,并利用FT-IR、NMR、GC-MS、AFM、SEM、TGA等技术对三种多糖的初级结构、形貌和热稳定性分析。由结果可知,CSP-1的主要单糖成分为阿拉伯糖(Ara),摩尔百分含量占45.4%,CSP-2和CSP-3主要为GlaA,摩尔百分含量分别为53.23%和73.62%;红外结果显示三种多糖同时存在吡喃糖和呋喃糖形式,主要为α-糖苷键;CSP-1为分子量不均一多糖,CSP-2和CSP-3分子量均一,其分子量分别为59.1 kDa和57.9 kDa;扫描电子显微镜(SEM)观察到CSP-1结构疏松,带有孔洞和连接微球的细丝,CSP-2和CSP-2由于大量糖醛酸的存在紧密堆积成片层状;在原子力显微镜(AFM)下观察,三种多糖链相互缠绕、卷曲成球形。(3)利用甲基化及核磁共振(NMR)技术进一步研究CSP-2中的糖苷键连接,发现CSP-2骨架由光滑区(Homogalacturon,HG)和须状区-I(rhamnogalaturonan-I,RG-I)构成。HG区域的GalpA部分甲酯化或在C-2/C-3位置发生乙酰化取代,在须状区域中的Rha全部发生O-4取代;侧链主要由半乳聚糖、阿拉伯糖和阿拉伯半乳聚糖构成,同时含有少量的葡萄聚糖和甘露糖。(4)利用梯度乙醇法(30%、50%、70%和90%)对光皮木瓜中木聚糖进行了分级纯化,依次得到UPX30、UPX50、UPX70和UPX90;以经过HCW处理的SR为原料,用同样的方法依次得到PX30、PX50、PX70和PX90。研究结果表明:较低浓度乙醇能够沉淀出线性聚合度高且分子量较大的木聚糖,经过高压水热处理后得到的木聚糖整体分子量偏大,并且木糖(Xyl)含量较高;利用化学法和红外、二维核磁波谱对UPX30和PX30的一级结构进行解析,推测两种木聚糖均以1,4-β-D-Xylp为主链,部分Xyl在O-2位置被4-O-甲基-D-GluAp取代,同时还含有Ara和Gal的侧链。(5)光皮木瓜多糖的抗氧化活性表现出浓度依赖性,糖醛酸的存在能够提高多糖的羟自由基清除能力;经过DEAE-52纯化过的多糖的总还原能力明显弱于纯化前;CSP和CSP-1能够清除DPPH能力强于酸性多糖。通过化学交联丙烯酸单体制备的木聚糖水凝胶,在偏中性以及较低的离子浓度中,吸水率较高,其在蒸馏水中吸水率最高可达59.5倍。更多还原

【Abstract】 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 α-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-α-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-β-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.更多还原