The Analysis Of Cell Wall Structural Phenolic And Molecular Weight Of Phenylpropanoid Compounds Of Cotton Fiber

Cotton fiber is the important raw material used for yarn and textile manufacturing. The formation of fiber quality directly affects the quality of cotton fiber products. The cotton fiber has a cell wall cross-linking structure formed by the phenylpropanoid compounds. phenylpropanoid compounds is one of the main components of plant secondary cell wall which influences and determines the morphological structure, physical and chemical properties, and biological characteristics of plant cell wall. The study of the modle of phenolic acids, and the distribution of molecular weight of phenylpropanoid compounds in the formation of cross-linked structure of cotton fiber cell wall, has an important significance to further reveal the mechanism of cell wall cross linking structure to the formation of fiber quality.In this study, to lay a foundation for a better study of the structure of phenylpropanoid compoundsand and type of cross-linked structure formed in the cell wall of cotton fiber, At first, the structure of phenolic acids in the fiber cell wall of different cotton varieties were analyzed in different fiber development stage.The acetyl bromide method was carry out to detect the content of phenylpropanoid compounds. Second,dioxane/water was used to treated the complete cotton fibers To find out the suitable method for cotton fiber lignin extraction without destruction of its phenylpropanoid compoundsand structure, and lay the foundation for the study of the monomer of phenylpropanoid compounds and effects of the treatment on the morphology and lignin of cotton fiber were investigated. Then the distribution of molecular weight of phenylpropanoid compounds in cotton fiber were analyzed. The results are as follows:1. Types of phenolic acids in cotton fibers were tested by HPLC(high performance liquid chromatography), Vanillic acid, p-Coumaric acid, Sinapic acid, Isoferulic acid, Ferulic acid, Cinnamic acid,4-Methoxycinnamic acid and L-phenylalanine were be detected in fiber at different developmental stages.L-phenylalanine was found in all the developmental stages of cotton fiber, Proved phenylpropanoid pathway were dynamic exist in the secondary wall development stage of cotton fiber, in view of Lphenylalanine is the initial product in this pathway. Besides, type of of phenolic acids were differently exist in each cotton fiber development stage and mature fibers, and also in different cotton varieties.2. Acetyl Bromide Method were used to detected the content changes of phenylpropanoid compounds during the process of fiber development in different upland cotton cultivars which suitable for planting in northern or southern Xinjiang. The result show that the content of phenylpropanoid compoundsand were different among each cultivars, and low content were found in early maturing variety. With the timeprolongation of fiber development, decline trend of the content of phenylpropanoid compounds were showed in per unit of cotton fiber, and increase trend were showed in per unit of cotton ball.3. Complete fiber were treated by different ratios of dioxane/water, UV spectrophotometer and scanning electron microscopy(SEM) were used combinatively to selecting and verifying the relative optimum treatment. The result showed that, in the 12 treatments, the conditions with the hydrochloric acid catalysis had higher lignin absorbance. When the volume ratio of dioxane/water was 85/15 and the heat-treatment temperature was 86?, the UV scanning curve of the extracted fiber lignin was similar to that of standard sample lignin. SEM observation results show that the cotton fiber cell wall structure, in the crosslinking structure of cellulose, hemicellulose and lignin, was destroyed and made the secondary wall exposed sufficiently, which benefit the release of structural material of cotton fiber. the method would provide a new approach to study the lignin monomer in cotton fiber.4. Molecular weight distribution of phenylpropanoid compounds in cotton fiber were obtained by different methods of dioxane treatment and enzymatic hydrolysis-mild acidolysis, the analysis results fundamentally show that: weight average molecular weight of fiber lignin extracted by dioxane treatment were 2924 g/mol, average molecular weight of that were 2403 g/mol, Slightly higher than weight average molecular weight(2169 g/mol) and average molecular weight(1970 g/mol) of fiber lignin extracted by enzymatic hydrolysis-mild acidolysis. Furthermore, molecular weight distribution of extraction of lignin in dioxane were more wide, the structure of it were tend to be more complex and polydispersity coefficient were slightly lower than in enzymatic hydrolysis-mild acidolysis, and homogeneity of lignin in enzymatic hydrolysis-mild acidolysis were higher than in dioxane. So lignin in enzymatic hydrolysis-mild acidolysis were selected. Molecular weight of lignin extracted by 2 different methods were analyzed, result showed that the distribution of molecular weight of fiber lignin extracted from different fibers of cotton varieties were range from 938-2169 g/mol, polydispersity coefficient were less than 2.