本文从山苦茶中提取得到两个多糖组分水溶性多糖(MOWP)和碱溶性多糖(MOAP),得率分别为6.00%和3.07%。采用高效凝胶渗透色谱法(GPC)分别测定了MOWP和MOAP的分子量分布;采用PMP柱前衍生-高效液相色谱法(HPLC)分别测定了MOWP和MOAP的单糖组...本文从山苦茶中提取得到两个多糖组分水溶性多糖(MOWP)和碱溶性多糖(MOAP),得率分别为6.00%和3.07%。采用高效凝胶渗透色谱法(GPC)分别测定了MOWP和MOAP的分子量分布;采用PMP柱前衍生-高效液相色谱法(HPLC)分别测定了MOWP和MOAP的单糖组成;采用甲基化-气相色谱质谱法(GC/MS)研究了MOWP和MOAP的糖苷键连接方式。此外,采用DPPH·清除法、还原力法以及氧自由基吸收(ORAC)法,评价了MOWP和MOAP的体外抗氧化活性。结果表明:MOWP分子量分别为906 k Da和49 k Da,MOAP的分子量为95 k Da。木糖、半乳糖及葡萄糖构成了酸性多糖MOWP的骨架结构,而酸性多糖MOAP由甘露糖、木糖及半乳糖构成骨架。MOWP和MOAP中→3)-Xylf-(1→、→3)-Galp-(1→以及→3)-Glcp-(1→残基含量均较高。MOWP和MOAP均有一定的抗氧化能力,MOWP清除DPPH·的能力较强,MOAP具有较强的还原能力和氧自由基吸收能力。展开更多
The traditional degradation of organic pollutants is based on the sacrifice of chemical or biological reagents. In this study, a purely physical technique was developed to break the chemical bonds and consequently dec...The traditional degradation of organic pollutants is based on the sacrifice of chemical or biological reagents. In this study, a purely physical technique was developed to break the chemical bonds and consequently decompose macromolecules in aqueous solution. Assisted with a high-speed mechanical blade, refined quartz sand grains with particularly sharp nanoscale edges can act as ‘nano-knives', which are able to cut the long chain of carboxymethyl cellulose(CMC, as a model molecule). High performance size exclusion chromatography measurements evidenced that the original CMC molecules(41,000 Da) were decomposed into a series of smaller molecules(460, 1000, 2200, 21,000, 27,000 and 31,000 Da). Consequently, the initial viscosity of the CMC solution(2 g/L) rapidly decreased by approximately 50% after 3 min treatment by the nano-knife materials along with the mechanical blade. Fourier transform infrared(FTIR) spectra indicated that the original functional groups were still present and new functional groups were not produced after shearing. The intensity of the main functional groupβ-1-4-glycosidic bond(wavenumber 1062 cm-1) was observed to markedly decrease after shearing. These results indicated that the long-chain CMC was cleaved into short-chain CMC. A degradation mechanism was proposed whereby the cutting force generated by the rapid motion of the nano-knives may be responsible for the breakage of β-1-4-glycosidic bonds in the macromolecular cellulose backbone. These results provide support for a potentially more affordable and environment-friendly strategy for physical-based decomposition of recalcitrant organic pollutants from aqueous solution without the need of chemical or biological reagents.展开更多
Sulfonamide residue in honey existed in a form bonded to sugar via the N-glycosidic bond.It would result in the possible underestimation of concentration of sulfonamide if it is not decomposed by chemical methods.Howe...Sulfonamide residue in honey existed in a form bonded to sugar via the N-glycosidic bond.It would result in the possible underestimation of concentration of sulfonamide if it is not decomposed by chemical methods.However,in China's Mainland and Taiwan（P.R.China）,the regulation for sulfonamide residue analysis does not include hydrolysis and has been applied to a very broad range of samples,for example,egg,milk,meat,seafood as well as honey.This paper demonstrates the necessity of hydrolysis of it prior to extracting honey.The breaking efficiencies of N-glycosidic bond were investigated by 2 mol/L hydrochloric acid,pure methanol and 0.5 mol/L hydrochloric acid in methanol,respectively.It was found that acid plays the key role in breaking the N-glycosidic bond,and it was also noticed that the dissolution of liberated sulfonamide in methanol could carry the reaction forward in favor of breaking the N-glycosidic bond.展开更多
文摘本文从山苦茶中提取得到两个多糖组分水溶性多糖(MOWP)和碱溶性多糖(MOAP),得率分别为6.00%和3.07%。采用高效凝胶渗透色谱法(GPC)分别测定了MOWP和MOAP的分子量分布;采用PMP柱前衍生-高效液相色谱法(HPLC)分别测定了MOWP和MOAP的单糖组成;采用甲基化-气相色谱质谱法(GC/MS)研究了MOWP和MOAP的糖苷键连接方式。此外,采用DPPH·清除法、还原力法以及氧自由基吸收(ORAC)法,评价了MOWP和MOAP的体外抗氧化活性。结果表明:MOWP分子量分别为906 k Da和49 k Da,MOAP的分子量为95 k Da。木糖、半乳糖及葡萄糖构成了酸性多糖MOWP的骨架结构,而酸性多糖MOAP由甘露糖、木糖及半乳糖构成骨架。MOWP和MOAP中→3)-Xylf-(1→、→3)-Galp-(1→以及→3)-Glcp-(1→残基含量均较高。MOWP和MOAP均有一定的抗氧化能力,MOWP清除DPPH·的能力较强,MOAP具有较强的还原能力和氧自由基吸收能力。
基金supported by the National Natural Science Foundation of China (Nos. 21277161, 41573114)the National Key Research and Development Program of China (No. 2017YFA0207204)
文摘The traditional degradation of organic pollutants is based on the sacrifice of chemical or biological reagents. In this study, a purely physical technique was developed to break the chemical bonds and consequently decompose macromolecules in aqueous solution. Assisted with a high-speed mechanical blade, refined quartz sand grains with particularly sharp nanoscale edges can act as ‘nano-knives', which are able to cut the long chain of carboxymethyl cellulose(CMC, as a model molecule). High performance size exclusion chromatography measurements evidenced that the original CMC molecules(41,000 Da) were decomposed into a series of smaller molecules(460, 1000, 2200, 21,000, 27,000 and 31,000 Da). Consequently, the initial viscosity of the CMC solution(2 g/L) rapidly decreased by approximately 50% after 3 min treatment by the nano-knife materials along with the mechanical blade. Fourier transform infrared(FTIR) spectra indicated that the original functional groups were still present and new functional groups were not produced after shearing. The intensity of the main functional groupβ-1-4-glycosidic bond(wavenumber 1062 cm-1) was observed to markedly decrease after shearing. These results indicated that the long-chain CMC was cleaved into short-chain CMC. A degradation mechanism was proposed whereby the cutting force generated by the rapid motion of the nano-knives may be responsible for the breakage of β-1-4-glycosidic bonds in the macromolecular cellulose backbone. These results provide support for a potentially more affordable and environment-friendly strategy for physical-based decomposition of recalcitrant organic pollutants from aqueous solution without the need of chemical or biological reagents.
基金Supported by the National Natural Science Foundation of China(No.20907046)the Natural Science Foundation of Zhejiang Province of China(No.Y4100623)
文摘Sulfonamide residue in honey existed in a form bonded to sugar via the N-glycosidic bond.It would result in the possible underestimation of concentration of sulfonamide if it is not decomposed by chemical methods.However,in China's Mainland and Taiwan（P.R.China）,the regulation for sulfonamide residue analysis does not include hydrolysis and has been applied to a very broad range of samples,for example,egg,milk,meat,seafood as well as honey.This paper demonstrates the necessity of hydrolysis of it prior to extracting honey.The breaking efficiencies of N-glycosidic bond were investigated by 2 mol/L hydrochloric acid,pure methanol and 0.5 mol/L hydrochloric acid in methanol,respectively.It was found that acid plays the key role in breaking the N-glycosidic bond,and it was also noticed that the dissolution of liberated sulfonamide in methanol could carry the reaction forward in favor of breaking the N-glycosidic bond.
