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从成熟的植物栀子果实中提取分离得到藏花素(1),采用半合成法制得藏红花酸二乙酯(2).利用紫外光谱研究了醇水混合体系中藏花素在紫外光照和自然光照下褪色的动力学反应,利用电子自旋共振技术研究了藏花素褪色过程中的自由基种类,利用气相色谱/质谱联用对藏红花酸二乙酯的褪色产物进行了结构推断.结果表明:藏花素的褪色反应遵循动力学一级反应,反应速率常数随醇/水混合体系中乙醇含量的增加而减少,且紫外光照下比自然光照下减小的更快;单线态氧和超氧阴离子参与了藏花素的褪色反应.其褪色原因主要是共轭双键被氧化加成和酯键水解光催化重排所致.最后,提出了藏花素褪色反应的可能途径.
The crocetin (1) was isolated from the mature plant gardenia fruit and the diethyl saffron (2) was obtained by the semisynthetic method. The UV-Vis spectra of crocin in the mixture of water and alcohol were studied. The kinetic reaction of fading under light irradiation was studied. The free radical species in the process of fading of crocin was studied by electron spin resonance (NMR) technique, and the fading products of crocetin diethyl ester were identified by gas chromatography / mass spectrometry : The fading reaction of crocin followed the kinetic first order reaction, the reaction rate constant decreased with the increase of ethanol content in the alcohol / water mixed system, and decreased faster under UV light than under natural light. The singlet oxygen and super Oxygen anion is involved in the fading reaction of crocin, which is mainly caused by the oxidative addition of conjugated double bonds and the hydrolysis of the ester bond by photocatalysis rearrangement.Finally, the possible ways of the fading reaction of crocin were proposed.