| Natural colored cotton is a kind of textile fibers with environmental friendly feature. whose products are welcomed by market because of their wearing comfort. However, there are also factors restricting their further development, such as color limitation and their color not bright enough,. The color of grown cotton applied in the textile is more stable than that of green cotton,and the pigment in green cotton is more complex, therefor ,the study of its composition and structure is very difficult. It is important to master pigment's properties and types which could benefit to the processing and breeding of natural colored cotton. In this paper, the extraction, separation and structure of the natural green cotton pigment is investigated.In this paper, the extraction of the natural green cotton pigment is firstly studied. The solubility of the naturally green cotton pigment is found to have good solubility in moderate polarity solvent and alkaline solvent. According to the results, ethanol is selected as the solvent for pigment extraction. In order to investigate the extraction conditions for the green cotton pigment, a method for the relative quantitative test of pigment in naturalyl green cotton using ultraviolet spectrophotometer is firstly confirmed, and then the analytical results showed that the absorption around 360nm is linearly correlated with pigment concentration with a R2=0.9992. The results indicated that the pigment structure extracted by ultrasonic -assisted extraction is as same as that extracted by normal extraction while the extraction efficiency is significantly increased. The pigment amount extracted by ultrasonic -assisted extraction in 20min can reach the same amount with that extracted by normal extraction in 5 hours. This paper also studied the influence of extracting temperature, time, liquid to material ratio on the yield of extraction. By orthogonal experiment, the analysis results showed that the optimum extraction condition used by ultrasonic -assisted extraction is : temperature of 70℃, time of 100min, solvent to material ratio of 1:125 , when the ultrosonic conditions are frequency of 40KHz and power of 100W .By GC-MS research the results showed that the main volatile substances in natural green cotton and white cotton extracted by ethanol is 2-Methyl allylamine, 2-Cyclohexen-1-ol,2-methyl-5-(1-methylethenyl)-,1-propanoate,Diaminomaleonitrile,2-(Acryloyloxy)Ethyl acetoacetat, and 2,4-Di-tert-butylphenol. Naturally green cotton contains a substance that does not exist in white cotton, which is called methacrylic acid isobutyl ester. The thermal stability and light irradiation stability of naturally green cotton which is extracted treatment wit petroleum ether is also studied, finding that the thermal stability of natural green cotton increased significantly, so is the light irratiation stability. The methacrylic acid isobutyl ester may be the factor causing color change of natural green cotton under high-temperature, but specific mechanism needs a further research.A kind of relatively pure pigment is got by separating and purifying the natural green cotton pigment with C18 reversed-phase silica gel column. It is found from the HPLC picture that naturally green cotton pigments contain four main substances at least. Then the physical and chemical property of this composition were studied and compared with crude extracted pigments, Both of them are of the similar properties, therefore, it is speculated that this composition is the main ingredient of the green cotton's pigment. This naturalyl green cotton pigment has the property of alkali soluble and acid precipitation, and can form Osylates with the acid. There are two absorption bands between 200-400nm in the UV spectrum of carbinol which can form precipitation with irontrichloride .This composition is guessed to be flavonoids with o-hydroxybenzoic acid. The UV, IR, MS and NMR analysis of this pigment is studied, indiciating that this pigment's molecular weight is 592 and this pigment is probable of the member of flavonols, the results also indicated that this green cotton pigment has 6, 7-OH, 5-OCH3 8-C-glu in ring A and 3',4'-OH in ring B, in addition, 3-OH is possibly substituted flavonoids. |
