Rusting of Foods : Red Pigments Formed by Prostaglandin-Like Structure Substances

研究了类藜芦素共轭羰基化合物与氨基酸反应生成的红色色素的性质和结构。在40 ° C黑暗中氧化多不饱和脂质后，依次通过Sephadex LH-20凝胶色谱、硅胶60柱色谱和mu-Porasil高效色谱（HPLC）制备羰基化合物，最大产量为所用脂质的0.05- 0.1%。在预实验中，在自氧化γ-亚麻酸酯中发现了一个新的羰基5-[2-（2-甲酰乙烯基）-3-羟基-5-氧代环戊基]戊酸甲酯及其前体。以纯化的3-（2-乙基-5-羟基-3-氧代环戊基）-2-丙烯醛和甘氨酸为原料，研究了pH值和反应温度对红色素生成的影响：pH值为7时红色素生成量最大，酸性条件下反应速率最小，碱性条件下或高温条件下红色素不稳定，变为荧光物质。使用具有UV、维斯和荧光检测器的HPLC设备，分析通过与各种氨基酸反应获得的每种颜料混合物。观察到一个或多个所用氨基酸特有的色素峰（A_）<515nm>，但没有荧光。结果表明，该方法不经席夫碱缩合，氨基酸分子均以完整的形式被引入到红色颜料中。红色素的结构分析正在通过质谱和NMR光谱进行。

Properties and structures of the red pigments formed by the reaction of prostaglandin-like conjugated carbonyls with amino acids were studied. After oxidation of polyunsaturated lipids in the dark at 40^ﾟC, the carbonyls, 0.05-0.1 % maximum production of applied lipids, were prepared successively by gel chromatography on Sephadex LH-20, column chromatography on Silica gel 60 and High Performance Chromatography (HPLC) on mu-Porasil. In the preparatory experiment, a new carbonyl of methyl 5-[2-(2-formylvinyl)-3-hydroxy-5-oxocyclopentyl] pentanoate and it's precursor were found in autooxidized gamma-linolenate. Using purified 3-(2-ethyl-5-hydroxy-3-oxo-cyclopentyl)-2-propenal and Gly, effects of pH and reaction temperature on the formation of red pigments were investigated : at pH 7 the maximum production was obtained ; at acidic pH the least reaction rate was observed ; at alkaline pH or in high temperature the pigments were unstable and changed into fluorescent substances. Using a HPLC-equipment with UV, VIS, and fluorescence detectors, each of the pigment mixtures obtained by the reaction with various amino acids was analyzed. One or more of pigment peaks (A_<515nm> peculiar to the applied amino acids were observed without fluorescence. The results suggested that the whole molecules of amino acids were incorporated without Schiff base condensation into red pigments. Structure analyses of red pigments are in progress by mass spectrometry and NMR-spectrometry.