| Green wheat is an unique species bred in China. Compared to ordinary wheat species, green wheat is rich more than 20 types of trace elements, like selenium, zinc, iron, and calcium. In this thesis, the natural green pigments was extracted by percolation method from green wheat bran and fractionated by neutral ethanol, acidic ethanol solution successively. The resulting rough extract was separated by macro-porous resin and thin-layer chromatography (TLC). The stability of the final extract was subsequently analyzed by ultraviolet and visible spectrometry (UV) and infrared spectrometry. The results are as follows:1. Rough pigment extract was obtained. An optimized extraction parameters achieved by means of single-factor and orthogonal experiments were pH 1.0,70% ethanol solution, dried bran/solvent (1/10),60℃,1 hr, for two times. Extraction yield was 83%.2. Brown precipitate was obtained from ethonal extract. The precipitate was soluble in alkaline water or acidic ethanol solution, but was insoluble in acidic water. Its Rf value was 0.39 determined by normal phase silica gel TLC, with chloroform:methane acid:ethyl acetate (16:3:1) as mobile phase. It was visualized by ferric chloride. This result was speculated that the brown precipitate were likely to contain phenol compounds.3. Green solution that was not absorbed by AB-8 macro-porous resin was condensed and filtered, placed in a 4℃refrigerator while a white precipitate appeared. The white precipitate was dissolved using acidic ethanol, and subjected to reversed-phase silica gel thin layer chromatography with 15% acetonitrile and 2 drops of glacial acetic acid as mobile phase. Rfwas determined to be 0.3, though trailing phenomenon was severe and speckles are not strictly round. Absorption was observed under 254nm UV light. The reaction of Molish reagent indicated that it may not contain carbohydrate.4. Other characteristics of white precipitate were as follows:The hue of the green pigment which exists in the acidic extraction part changed with different pH values. The pigment was green in the acidic pH, nearly colorless in the neutral pH; brown-red with precipitate in the alkaline pH. The ratio of the absorbance of the maximum and secondary absorption peak of the pigment changed with different pH values, which showed that the molecular structure of the pigment was changed with different pH values. The infrared spectrogram of the pigment and color reaction of alkaloid reagent indicated that it may contain amides structure. As a result, green pigment of green wheat was not anthocyanidin but alkaloids. 5. Optimum purification condition for rough pigment extract by AB-8 macro-porous resin was:ambient temperature, pH 1.0, absorption:0.612×100. Absorption period 24 hours, absorption rate 1.5 mL/min. Desorption was conducted using ethanol solvent in concentration order of 10%,30%,40%.6. Study on stability of green pigment showed that:(1)more stable in in-door natural lighted or dark conditions; (2)susceptible to high temperature, more stable at 20-80℃; at 100℃, dramatic increase in absorption was observed; (3)stable at high acidic condition (pH 1.0-4.0); (4)stable to reducing agents; (5)stable to oxidizing agents; (6)some degree of sugar resistant; (7)more stable when salinity was below 10%, unstable when above 15%; (8)citric acid had negligible effect on its stability; (9)K+,Ca2+,Zn2+,Mg2+ had slight effect on its stability, Cu2+,Fe3+,Fe2+ had destructive effect on its stability.
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