Phospholipids as antioxidants - preparation and characterization of phosphatidylethanolamine complexes with selected sugar-reductons

在食品中使用α-生育酚作为天然抗氧化剂一直是首选。在卵磷脂、L-抗坏血酸和α-生育酚的混合物中，磷脂酰乙醇胺作为卵磷脂的组成部分，与L-抗坏血酸形成共价键合的缩合物，这是三元混合物具有极高抗氧化效果的原因。这种稳定作用是基于一种协同机制，即依赖于磷脂酰基-抗坏血酸(第一应用阶段)对氧化降解的α-生育酚的再生。然而，缩合物的确切化学结构尚未确定，因为它也可以以二聚体的形式存在，这扰乱了制备分离和结构解析。后续应用的目的是首先阐明磷脂酰抗坏血酸络合物的化学结构(S)。类似于L-抗坏血酸的反应及其抗氧化活性，从美拉德反应中产生的还原内酯(D-葡萄糖酮、呋喃醇、去甲呋喃和还原酸)与磷脂酰乙醇胺和α-生育酚结合起来，研究它们的抗氧化活性。磷脂酰乙醇胺结合α-生育酚再生(协同效应)激活D-葡萄糖醇的抗氧化性能已经被证明。它也发生在D-葡萄糖中，但令人惊讶的是，它在D-葡萄糖醛酸-γ-内酯中更严重。由于协同作用只发生在与磷脂酰乙醇胺(在某些情况下甚至没有α-生育酚)的混合物中，其背后的反应和涉及的产品有待阐明。我们认为磷脂酰乙醇胺的Amadori化合物是关键的中间体，与磷脂酰抗坏血酸相比具有更高的稳定性。

The use of α-tocopherol as natural antioxidant in food is always the first choice. In a mixture of lecithin, L-ascorbic acid and α-tocopherol, phosphatidylethanolamine as component of lecithin thermally forms with L-ascorbic acid a covalently linked condensate, which is responsible for the extremely high antioxidat effect of the ternary mixture. The stabilizing effect is based on a synergistic mechanism, that depends on the regeneration of oxidatively degraded α-tocopherol by the phosphatidyl-ascorbic acid (1st application phase). However, the exact chemical structure of the condensate has not yet been determined since it can also be present as a dimer, which deranges preparative separation and structural elucidation.The aim of the follow-up application is firstly to elucidate of the chemical structure(s) of the phosphatidyl-ascorbic acid complexe. In analogy to the reaction of L-ascorbic acid and its antioxidant activity, reductones from the Maillard reaction (D-glucosone, furaneol, norfuranol and reductic acid) in combination with phosphatidylethanolamine and α-tocopherol are to be investigated for their antioxidant activity. The activation of the antioxidant properties by phosphatidylethanolamine combined with an α-tocopherol regeneration (synergistic effect) has already been shown for D-glucosone. It occurs with D-glucose as well, but surprisingly it is much greater with D-glucuronic acid-γ-lactone. Since the synergistic effect only occurs in a mixture together with phosphatidylethanolamine (in some cases even without α-tocopherol), the reactions behind, and the involved products are to be elucidated. We assume that the Amadori compounds of the phosphatidylethanolamine to be the key intermediats, characterized by higher stability compared to phosphatidyl-ascorbic acid.