| The evidence is accumulating that oxygen free radicals are closely linked to human health and responsible for several pathological conditions, such as brain ischemia, cardiovascular disease and carcinogenesis when they are generated in excess or the cellar antioxidant defense is impaired. Antioxidants can prevent or control the above diseases by blocking the chain reaction of oxygen free radical. Searching for effective antioxidants with low toxicity has attracted increasing interests. Thus, the development of a sensitive, rapid and simple method to detect antioxidant ability is of great importance in screening and developing the new antioxidants.In this study, an FAB-MS method to predict and detect the antioxidant ability of phenolic compounds was investigated based on the similarity of M+· ion formation under FAB conditions and free radical scavenging mechanism of phenolic compounds. In addition, an LC-MS/MS method was developed to detect hydroxyl radical and evaluate the antioxidant ability of compounds.1. The formation and influential factors of M+· and [M＋H]+ ion in FAB-MS spectraThe optimum conditions were determined by comparing the relative peak intensity ratio of M+· ion to [M＋H]+ ion, i.e. I(M+·)/I([M＋H]+) value (the isotopic contribution from M+· peak has been corrected for) of different compounds under different experiment conditions including matrix, scan time, sample concentration and solvent. The results showed that the I(M+·)/I([M＋H]+) value was mainly dependant on competitive formantion of M+· and [M＋H]+ ion of the compound though it was affected by different experiment parameters. 2. Development of an FAB-MS method to predict and dectect the antioxidant ability of phenolic compounds5 kinds of compouds with different structral sckeletons including vitamin E related compounds, flavonoids, phenolic acids, lignanoids and diphenyl ethylene compounds were selected and detected by FAB-MS method using optimal experiment conditions. The I(M+·)/I([M＋H]+) values were obtained from their FAB-MS spectra. A simple, sensitive and rapid FAB-MS method to predict and detect the antioxidation of phenolic compounds was developed by investigating the correlation of I(M+·)/I([M＋H]+) value and antioxidant ability of above compounds. This method was applied to detect the antioxidation of some phenolic compounds and it was proved to be reliable by contrasting the I(M+·)/I([M＋H]+) values with the results assayed by conventional screening technique for antioxidant.3. Development of an LC-MS/MS method for the determination of hydroxyl radical and evaluating the antioxidant ability of compoundsA rapid and simple LC-MS/MS method was established for determination of hydroxyl radical in MRM mode by investigating the mass spectrometric behavior of spin adduct of spin trap with hydroxyl radical and the influential factors of its yield such as pH value, reaction time and the reagent concentrations. The reproducibility and effectiveness of the method had been investigated. The present method was successfully employed to evaluate the antioxidant ability of several phenolic acids by detecting hydroxyl radical scavenging capacity.
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