摘要
【目的】对籽用西瓜果实瓜瓤多糖进行单糖组成及其一级结构进行鉴定,分析其与生物活性的关系,以评价籽用西瓜多糖的利用价值。【方法】通过水提醇沉法提取籽用西瓜瓜瓤粗多糖,使用Sephadex-G75(葡聚糖凝胶柱层析-G75)和DEAE-Sepharose(DEAE-纤维素柱层析)色谱分离纯化粗多糖得到纯化多糖(SⅠ),利用高效液相色谱法(HPLC)测定其相对分子质量和单糖组成,再通过红外光谱和核磁共振进一步鉴定其一级结构,最后采用体外抗氧化试验和体外抑菌试验分析其生物活性。【结果】纯化多糖SⅠ的HPLC分析结果表明该多糖相对分子质量为1 747 Da,由甘露糖、鼠李糖、半乳糖醛酸、葡萄糖、半乳糖、木糖、阿拉伯糖7种单糖组成,摩尔比为2.4∶2.2∶6.6∶36.8∶32.1∶7.2∶12.7;红外光谱分析和核磁共振分析显示SⅠ含有糖类化合物、糖醛酸基团和吡喃糖环的特征吸收峰,多糖中葡萄糖和半乳糖为α-D构型,甘露糖为β-D构型,鼠李糖为β-L构型。SⅠ对羟自由基和DPPH自由基均有清除作用,对Fe^(3+)具有一定还原力。SⅠ对酵母菌有较好的体外抑制效果。【结论】籽用西瓜瓜瓤多糖由多种单糖组成,单糖构型多样,具有较好的抗氧化活性和抑菌活性,在食品和医疗保健等行业中具有很大的开发利用价值。
【Objective】Seed watermelon(Citrullus lanatus var.megulasnemus Lin et Chao)is rich in the phytochemical compounds such as polysaccharides,pectin,vitamins,trace elements,amino acids and so on,and thus has high nutritional value and benefit to human health.But,at present,seed watermelon is mainly used to get seeds as a snack,while the peel and pulp are discarded creating huge waste of resources.It is well known that polysaccharides have many biological functions,and their biological activity is closely related to their chemical structures.However,to date there have been few studies on the monosaccharide components and antioxidant activity of polysaccharides in seed watermelon.The purpose of this study was to identify the monosaccharide components in seed watermelon and their primary structures and biological activities.The results will be helpful for utilization of seed watermelon polysaccharides as a potential natural antioxidant in the food and pharmaceutical industry.【Methods】’Neimeng Heizhongpian’seed watermelon pulp was used as the material to extract crude polysaccharides using water extraction and alcohol precipitation method.Effects of extraction time,extraction temperature and material-liquid ratio on the yield of crude polysaccharide were studied through an orthogonal experiment of L9(33)to optimize the extraction protocol to improve polysaccharide extraction yield.Proteins and pigments were removed from the crude polysaccharides by Sevag and by activated carbon,respectively,and polysaccharides were purified by Sephadex-G75 chromatography.The purified polysaccharides SⅠ,SⅡand SⅢwere obtained through DEAE-Sepharose chromatography.The polysaccharide fraction defined as SⅠwith the highest contents of polysaccharides and uronic acids was used for qualitative analysis of monosaccharide component,and the relative molecular weight was measured by HPLC.The structures of SⅠwere studied by IR and NMR.Finally,antioxidant activity and antibacterial activity of SⅠwere measured in vitro.The antioxidant activity was quantified by hydroxyl radical scavenging capacity,2,2-diphenyl-1-picrylhydrazyl(DPPH)radical scavenging capacity,and ferric ion reducing antioxidant power(FRAP).Antimicrobial activities of SⅠwere studied through determining bacteriostatic diameter.Staphylococcus aureus,Bcillus subtilis,Escherichia coli,Rhizopus nigricus,Aspergillus niger and yeast were selected as the test strains.【Results】SⅠ,which accounted for 70.26%of polysaccharide and 7.09%of uronic acid,was chosen for subsequent research.The results showed the relative molecular weight of SⅠwas 1747 Da.It was composed of mannose,rhamnose,galacturonic acid,glucose,galactose,xylose and arabinose with a molar ratio of 2.4∶2.2∶6.6∶36.8∶32.1∶7.2∶12.7.SⅠhad some characteristic absorption peaks in the range of 400-4000 cm^-1.The three absorption peaks within 950-1250 cm^-1 indicated that SⅠcontains pyran ring and furan ring.There were several vibration absorption peaks within 750-920 cm^-1,suggesting that SⅠprobably contains xylose,rhamnose,arabinose and mannose and other monosaccharides.The hydrogen signal peak of the 1H-NMR spectra in 4.971 mg·L^-1 and 5.124 mg·L^-1 and the carbon signal peak of the 13C-NMR spectra in 98.11 mg·L^-1 and 101.55 mg·L^-1 showed that the SⅠcontainsɑ-D-glucose andɑ-D-galactose.Similarly,the hydrogen signal peak of the 1H-NMR spectra in 4.887 mg·L^-1 and 4.686 mg·L^-1 and the carbon signal peak of the 13C-NMR spectra in 94.6 mg·L^-1 indicated that the SⅠcontainsβ-D-mannose andβ-L-rhamnose.In vitro antioxidant experimental results showed that SⅠpossesses high activities of scavenging hydroxyl free radical and DPPH radical as well as high FRAP,and the antioxidant capacity of SⅠhad dose-dependent manner within certain concentration range,but its antioxidant activity was lower than VC.In vitro antimicrobial test results showed that SⅠpossessed some antimicrobial activity and had certain specificity,as it had had no inhibitory effect on black Rhizopus nigricans and Aspergillus niger,a weak inhibitory effect against Staphylococcus aureus,Bacillus subtilis and Escherichia coli,and a strong inhibitory effect on yeast,and the inhibition ability increased with the increase in SⅠconcentration.【Conclusion】The result showed that polysaccharides of seed watermelon pulp possess antioxidant and antimicrobial activity in vitro,which is closely related to their chemical structure.They can be potentially used as natural antioxidant for food and pharmaceuticals industries.
作者
代彩玲
王萍
李书颉
杨永升
于晓婧
DAI Cailing;WANG Ping;LI Shujie;YANG Yongsheng;YU Xiaojing(Inner Mongolia Agricultural University,Hohhot 010018,Inner Mongolia,China)
出处
《果树学报》
CAS
CSCD
北大核心
2020年第8期1196-1206,共11页
Journal of Fruit Science
基金
内蒙古科技计划项目(20090707、20100704、20110711、20120212)
内蒙古自然科学基金项目(2016MS0356)。
关键词
籽用西瓜
多糖
分离纯化
结构鉴定
体外生物活性
Seed watermelon
Polysaccharides
Separation and purification
Structure identification
Bioactivity
