Kubec Roman, Velísek Jan
Department of Chemistry, University of South Bohemia, BranisovskA 31, 370 05 Ceské Budejovice, Czech Republic.
J Agric Food Chem. 2007 May 2;55(9):3491-7. doi: 10.1021/jf070040n. Epub 2007 Apr 10.
Structural requirements for compounds involved in Allium discoloration have been investigated in detail. The abilities of all 20 protein amino acids and six naturally occurring 1-propenyl-containing thiosulfinates to form the pigments have been studied. Furthermore, several analogues of these thiosulfinates were prepared by synthesis, and their color-forming abilities were evaluated, together with those of various amino compounds. It has been found that an unsubstituted primary amino group and a free carboxyl group are essential structural features required for amino compounds to be able to generate the pigments. Out of the thiosulfinate analogues tested, only those containing at least a three-carbon chain with the beta-carbon bearing a hydrogen atom yielded the pigments after reacting with glycine. Thiosulfonates, sulfoxides, sulfides, and disulfides did not form any colored products when mixed with glycine. The pH optimum for pigment formation has been found to be between 5.0 and 6.0 for all thiosulfinates tested.
已对与葱属植物变色相关化合物的结构要求进行了详细研究。研究了所有20种蛋白质氨基酸和六种天然存在的含1-丙烯基硫代亚磺酸盐形成色素的能力。此外，通过合成制备了这些硫代亚磺酸盐的几种类似物，并评估了它们与各种氨基化合物一起的成色能力。已发现未取代的伯氨基和游离羧基是氨基化合物能够产生色素所需的基本结构特征。在所测试的硫代亚磺酸盐类似物中，只有那些含有至少一个三碳链且β-碳上带有氢原子的类似物在与甘氨酸反应后产生色素。硫代磺酸盐、亚砜、硫化物和二硫化物与甘氨酸混合时不会形成任何有色产物。已发现所有测试的硫代亚磺酸盐形成色素的最适pH值在5.0至6.0之间。
