BIO-ANTIOXIDATION MECHANISM AND PHSIOLOGICAL FUNCTION OF L-ASCORBIC ACID

l -抗坏血酸（ASA），又称维生素C，是一种必需的水溶性营养素，广泛参与胶原蛋白的合成、芳香氨基酸的代谢、脂质代谢、免疫系统的激活和细胞增殖。然而，ASA生物学功能的具体机制尚不清楚。此外，由于ASA具有很强的还原性，在食品储存和加工中被广泛用作抗氧化剂。近年来，关于抗氧化功能与生物功能之间关系的报道较多，但其具体关系尚不清楚。为了阐明ASA的生物学功能与抗氧化功能之间的详细关系，我们采用实验和计算化学的方法来阐明这些尚未解决的问题。首先，计算了ASA及其相关化合物的优化结构，并通过半经验分子轨道计算获得了电子密度、偶极矩、生成热等理化参数。阐明了ASA分子与三态氧分子的自氧化反应机理。通过对苏酸、草酸等多种自氧化产物的鉴定，确定了ASA在自氧化过程中产生超氧阴离子，并在此基础上提出了ASA新的自氧化机理。

L-Ascorbic Acid(ASA), which is also called Vitamin C, is an essential water soluble nutrient, and is widely known to be involved in the blo-synthesis of collagen, metabolism of aromatic amino acids, lipid metabolism, activation of immune system and cell multiplication. However, the detailed mechanism of the biological function of ASA is still unknown. Furthermore, ASA is widely used as antioxidant in food storage and processing making use of its very strong reducing property. Recently, there have been many reports which describe the relationship between the antioxidant function and biological function, however the details of their relationship is still unclear. In order to clarify the detailed correlation between the biological function and antioxidant function of ASA, both experimental and computational chemical methods were applied to elucidate these unresolved problems. First, the optimized structures of ASA and its related compounds were calculated, and other various physico-chemical parameters, such as electron densities, dipole moment, heat of formation etc., were obtained by semi-empirical molecular orbital calculations. The auto-oxidation reaction mechanism of ASA molecule with triplet oxygen molecule was also clarified. Identification of various auto-oxidation products including threonic acid and oxalic acid were made and confirmation of the production of super-oxide anion during the auto-oxidation of ASA was also made, Based on the results obtained in this study, a new auto-oxidation mechanism of ASA was proposed.