水杨酸的光电离和光激发机理

Photoionization and Photoexcitation Mechanisms of Salicylic Acid

水杨酸(SA)是阿司匹林的主要有效成分,具有多种医疗疗效如美容和抗癌作用.本研究运用激光闪光光解瞬态吸收技术,考察了在266 nm激光的激励条件下水杨酸的光物理和光化学行为.实验结果表明,在266 nm的激光作用下SA可发生单光子电离,量子产率为0.21,光致电离效率较高.在细胞含氧体系中,由SA光电离生成的水合电子易与O2结合生成超氧阴离子自由基,可杀灭癌细胞.SA光电离产生的阳离子自由基可以脱质子生成中性自由基,测得其pKa是2.95.用SO-4誗0自由基氧化SA,获得了具有390 nm特征吸收的SA+誗,测得SO-4誗0氧化SA的反应速率常数为2.28×109 L.mol-1.s-1,进一步验证了SA光电离反应机理.同时发现SA可能受266nm激光激发生成激发三线态(3SA*),转而有可能生成单线态氧(1O2*).这些结果为水杨酸作为一种潜在的抗肿瘤药物提供了依据.

Salicylic acid（SA）,the active ingredient of aspirin,is effective in various medical treatments such as cosmetology and anticancer therapy.We investigated the photophysical and photochemical behavior of SA using 266 nm laser flash photolysis.Results demonstrate that SA can be photoionized and photoexcited by 266 nm photons to give SA＋ and 3SA＊.SA is highly photosensitive and can be photoionized via a monophotonic process with a quantum yield of 0.21.Under the aerobic conditions we find that in cells,hydrated electrons easily combine with oxygen to generate O-20,which can kill cancer cells.SA＋ can be converted into neutral radicals by deprotonation and its pKa value is 2.95.SA also can be oxidized by SO-40 and the rate constant is 2.28×109 L.mol-1.s-1,which further confirms the photoionization ability of SA.In addition,SA can be excited to 3SA＊,which then generates 1O2＊.This research provides introductory theory for the potential of SA to be used as an anticancer drug.