The Separation And Analysis Of Carbohydrates Assisted By Ionic Liquids

The carbohydrate is a kind of organic compounds abundant in natural world.In organisms,the carbohydrate serves as the resources of energy,such as the starch and glycogen;as the structural compounds of cells,such as cellulose in plant and chitin in insect;as functional compounds,such as glycans,playing significant roles in many biological processes,including signal transduction,fertilization,infection,immune system recognition and many other crucial intercellular recognition events.Ionic Liquids(ILs)exhibit a number of beneficial characteristics,such as high thermal stability,negligible vapor pressure,and excellent solvation ability and also have been recognized as tunable designer solvents.ILs could be used as task-specific fluids in fields of natural product.However,the application of ILs for carbohydrates,including the analysis and separation,has not been reported enough yet.Thus,different ILs have been designed and synthesized in the present study to use for carbohydrates further.The details,including three parts,are as follows:The selective precipitation of polysaccharides assisted by ILs:The ILs were synthesized through two steps with high yield.D100K was used as model compound in IL precipitation system.The recovery efficiency ratio was affected by content of ionic liquid,water and anti-solvent in system,as well as temperature.Dextrans with a higher molecular weight were easier to be precipitated.The precipitation ability of ILs decreases in the order:[PEG3mim][PF6]>[PEG2mim][PF6]>[PEG1mim][PF6].Treated by this ILs system,the polysaccharides precipitate,while water soluble small molecules are still dissolved in ILs solution.The selective precipitation of polysaccharides assisted by[PEG1-3 mim][PF6]was probably due to the interaction between ILs and polysaccharides.The structural analysis of BTpl(a polysaccharide from Botrychium ternatum)assisted by ILs:3AQ-CHCA was synthesized using a-cyano-4-hydroxycinnamic acid as organic acid and 3-aminoquinoline as organic base.Compared with traditional organic matrices,3AQ-CHCA had higher ion generation efficiency.Based on the 3AQ-CHCA,the molecular weight of BTp1 was determined to be 11644 Da directly.Combining enzymatic hydrolysis and subsequent MALDI-MS analysis,a linear backbone of BTp1,consisted of(1?5)-linked a-L-Araf,was inferred quickly.Then according to IR and NMR experiments,the whole structure of BTpl was established.The repeating unit of BTp1 was deduced as a linear backbone with branches at O-2,O-3 and its neighboring O-2 positions terminated with(1?)-linked a-L-Araf,respectively.In addition,BTp1 could significantly promote the release of NO in RAW 264.7 cells.The qualitative and quantitative detection of carbohydrates assisted by ILMs:The non-derivative ILMs have been designed and synthesized using DHB as organic acid and secondary amines as organic base.DHB/N-MA and DHB/N-EA,performing best for carbohydrate detection,have been screened out.The limit of detection for oligosaccharide provided by DHB/N-MA and DHB/N-EA were as low as 10 fmol.DHB/N-MA and DHB/N-EA showed significantly higher ion generation efficiency than DHB.Using these two ILMs,D2000 and D4000 could be detected at 10 pmol level.Their outstanding performance were probably due to the stronger UV absorption at ?=355 nm and the lower proton affinities of their conjugate base.What is more,taking DHB/N-MA as an example,quantitative analysis of fructo-oligosaccharide mixtures extracted and identified from rice noodles has been accomplished sensitively using an internal standard method.