Karg Cornelia A, Parráková Lucia, Fuchs Dietmar, Schennach Harald, Kräutler Bernhard, Moser Simone, Gostner Johanna M
Department of Pharmaceutical Biology, Ludwig-Maximilian University of Munich, Butenandtstr. 5-13, 81977 Munich, Germany.
Institute of Medical Biochemistry, Medical University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria.
Antioxidants (Basel). 2022 Oct 19;11(10):2056. doi: 10.3390/antiox11102056.
Phyllobilins are natural products derived from the degradation of chlorophyll, which proceeds via a common and strictly controlled pathway in higher plants. The resulting tetrapyrrolic catabolites-the phyllobilins-are ubiquitous in nature; despite their high abundance, there is still a lack of knowledge about their physiological properties. Phyllobilins are part of human nutrition and were shown to be potent antioxidants accounting with interesting physiological properties. Three different naturally occurring types of phyllobilins-a phylloleucobilin, a dioxobilin-type phylloleucobilin and a phylloxanthobilin (PxB)-were compared regarding potential antioxidative properties in a cell-free and in a cell-based antioxidant activity test system, demonstrating the strongest effect for the PxB. Moreover, the PxB was investigated for its capacity to interfere with immunoregulatory metabolic pathways of tryptophan breakdown in human blood peripheral mononuclear cells. A dose-dependent inhibition of tryptophan catabolism to kynurenine was observed, suggesting a suppressive effect on pathways of cellular immune activation. Although the exact mechanisms of immunomodulatory effects are yet unknown, these prominent bioactivities point towards health-relevant effects, which warrant further mechanistic investigations and the assessment of the in vivo extrapolatability of results. Thus, phyllobilins are a still surprisingly unexplored family of natural products that merit further investigation.
叶胆色素是叶绿素降解产生的天然产物，在高等植物中，叶绿素的降解通过一条常见且严格受控的途径进行。由此产生的四吡咯分解代谢产物——叶胆色素——在自然界中普遍存在；尽管它们含量丰富，但人们对其生理特性仍缺乏了解。叶胆色素是人类营养的一部分，并且已被证明是具有有趣生理特性的强效抗氧化剂。在无细胞和基于细胞的抗氧化活性测试系统中，比较了三种不同的天然存在的叶胆色素——一种叶白胆色素、一种二氧胆色素型叶白胆色素和一种叶黄胆色素（PxB）——的潜在抗氧化特性，结果表明PxB的效果最强。此外，还研究了PxB干扰人外周血单核细胞中色氨酸分解免疫调节代谢途径的能力。观察到色氨酸分解代谢为犬尿氨酸受到剂量依赖性抑制，这表明对细胞免疫激活途径有抑制作用。尽管免疫调节作用的确切机制尚不清楚，但这些显著的生物活性表明其与健康相关的作用，值得进一步进行机制研究以及评估结果的体内外推性。因此，叶胆色素是一类仍令人惊讶地未被充分探索的天然产物，值得进一步研究。
