Study On The Biological Activities Of Salicylic Acid And Methyl Salicylate

Salicylic acid (SA) and Methyl Salicylate (MeSA) are important phenolic spices applied in the area of food and cosmetic products. SA and MeSA in plants may serve to strengthen the plants'resistance to adverse condition as signal molecules in plants to response to stress. So far, investigation reports with regard to the biological activity and mechanisms of SA and MeSA have been conducted mainly in cellular and physiological levels, but rarely in molecular level.In this paper we use steady-state pyrogallol autoxidation method, microbiological method, UV method and agarose gel electrophoresis to study the biological activities and main affecting factors of SA and MeSA to remove toxicants such as superoxidate radicals(·O2-), singlet oxygen (1O2) and nitrosamines in water and O/W microemulsion. Based on this, we investigated the antagonistic activities of SA and MeSA in water or O/W microemulsion system to DNA damages by UV radiation and compared that with traditional antioxidant. With the assistance of time-resolved pulse radiolysis technology, through the observation of the feature transient absorption spectra and kinetics of interactions between SA, MeSA and DNA, the original evidence that SA and MeSA may quickly repair the damaged product of DNA was obtained and the rate constant of reaction were measured. The molecular mechanism of the reaction was also discussed.This paper is divided into six chapters:Chapter 1: Introduction. The structure and nature of SA and MeSA are introduced in details. The comprehensive review on SA and MeSA applications in agriculture, food and medicine and research progress of the biological activities of SA and MeSA is also involved in this chapter, based on which the assumption of this paper is put forward.Chapter 2: The performance of SA and MeSA in clearing·O2- in water or O/W microemulsion system and the main affecting factors are assessed by pyrogallol autoxidation method. The result showed that both SA and MeSA have a good clearance ability towards·O2-. In optimal conditions (water bath for 20 min, 25℃, pH8.20), the clearance of 1.60 mmol/L SA and MeSA in aqueous solution to·O2- are 41.53%, 46.60%, and 27.49% and 37.74% in O/W microemulsion system.Chapter 3: The inhibitory effect of SA and MeSA on 1O2 in water or O/W microemulsion system is assessed through microbiological method. The results showed that: SA and MeSA had a favorable inhibition ability to 1O2 , Especially in O/W microemulsion system, the highest inhibition rate of 8 mmol/L SA and MeSA could reach 74.70%,95.31%, which is better than Vc (63.17%) with the same concentration.while MeSA on 1O2 in water system could reach 94.37%,Chapter 4: The Blocking effect and its main affecting factors for SA and MeSA on nitrosamines in water and O/W microemulsion system are investigated using UV treatment. The results show that under optimal reaction conditions, 1.28 mmol/L SA and MeSA in O/W microemulsion solution have a high nitrosamine-blocking rate up to 72.27% and 73.34%, respectively, compared with that in aqueous system.Chapter 5: We investigated the interactions between DNA and SA or MeSA in water and O/W microemulsion system induced by strong light and electron beam with agarose gel electrophoresis and pulse radiolysis respectively. The antagonistic and synergistic effect of SA and MeSA on DNA damage due to UV radiation and the corresponding concentrations are determined by gel electrophoresis in two different systems. Compared with that in aqueous solution, 0.1～0.8 mmol/L SA and MeSA in microemulsion system have not shown synergistic but significant antagonistic effect to DNA damage caused by UV radiation. The findings obtained from pulse radiolysis confirmed that 0.1mmol/L SA, MeSA could repair the damage products of DNA(DNA-OH) by transferring electrons quickly and produce corresponding phenoxy radicals (PhSAO·,PhMeSAO·). The rate constants of transient reaction are 9.07×109 dm3·mol-1·s-1and 5.23×109 dm3·mol-1·s-1, respectively.Chapter 6: Conclusions and recommendations. Make a summary for the results of this study and propose recommendations for further related research in the future.