Gandul-Rojas Beatriz, Gallardo-Guerrero Lourdes, Mínguez-Mosquera M Isabel
Department of Food Biotechnology, Instituto de la Grasa, CSIC, Sevilla, Spain.
J Agric Food Chem. 2009 Jun 24;57(12):5306-14. doi: 10.1021/jf900426h.
Chlorophyll a, chlorophyll b, and the Mg-free chlorophyll derivatives pheophytin a, pheophytin b, pyropheophytin a, pheophorbide a, and pyropheophorbide a, dissolved in an oily matrix, were subjected to a simulated in vitro digestion procedure coupled with uptake by human intestinal Caco-2 cells. The native chlorophylls showed greater instability to the digestive process than the Mg-free chlorophyll derivatives. In addition to pheophytinization reactions, allomerization and oxidation to uncolored compounds were found to greater extents for the former. After digestion, the pigment dispersion degree in the colloid system (aqueous-"micellar" phase) showed significant differences (p < 0.05) among series a and series b derivatives. However, when a mixture of pheophytin a and pheophytin b was digested, there was a positive effect for pheophytin b. Both the dispersion degree and the accumulation rate by the Caco-2 intestinal epithelial cells were significantly higher (p < 0.05) for dephytylated chlorophyll derivatives. Differences in the transport route were also found. Whereas phytylated chlorophyll derivatives showed passive absorption by simple diffusion, the dephytylated ones showed passive absorption by facilitated diffusion in the lower range of concentrations tested. These results showed that the structural modifications of the chlorophyll pigments, mainly the de-esterification of phytol, significantly increased--by an estimated 65-fold--its transfer from the food matrix to the intestinal epithelial cells during digestion, making it more bioaccessible. The possible relationship between the phototoxicity associated with pheophorbide and the high bioaccessibility demonstrated in this work is discussed.
将溶解于油性基质中的叶绿素a、叶绿素b以及不含镁的叶绿素衍生物脱镁叶绿素a、脱镁叶绿素b、焦脱镁叶绿素a、脱镁叶绿酸a和焦脱镁叶绿酸a进行体外模拟消化，并让人肠道Caco-2细胞摄取。天然叶绿素在消化过程中比不含镁的叶绿素衍生物表现出更大的不稳定性。除了脱镁叶绿酸化反应外，前者还更易发生异构化和氧化为无色化合物的反应。消化后，a系列和b系列衍生物在胶体系统（水相 - “胶束”相）中的色素分散度存在显著差异（p < 0.05）。然而，当脱镁叶绿素a和脱镁叶绿素b的混合物被消化时，脱镁叶绿素b有积极作用。脱植基叶绿素衍生物的分散度和Caco-2肠上皮细胞的积累率均显著更高（p < 0.05）。还发现了转运途径的差异。植基化叶绿素衍生物通过简单扩散进行被动吸收，而脱植基化叶绿素衍生物在测试的较低浓度范围内通过易化扩散进行被动吸收。这些结果表明，叶绿素色素的结构修饰，主要是叶绿醇的去酯化，在消化过程中显著增加了（估计增加了65倍）其从食物基质向肠上皮细胞的转移，使其生物可及性更高。本文还讨论了脱镁叶绿酸相关的光毒性与本研究中证明的高生物可及性之间的可能关系。
