Abstract
This article describes the synthesis and antioxidative properties of melatonin derivatives. Tryptamines and cysteinyl or mercaptopropionyl derivatives were deliberately condensed with coupling reagents to give melatonin derivatives 4a-d and 5a, b. The preliminary evaluation indicated that compound 4c showed improved scavenging activity compared with vitamin C (IC50 43 microM vs 65 microM, where IC50 is the concentration of the test compound that induced a change of 50% in absorbance during the 30 min observation) on diphenyl-p-picrylhydrazyl (DPPH) tests. Derivative 5b, which possesses the thiolactyl moiety, showed moderate potency compared with melatonin (IC50 235 microM vs 690 microM) in the H(2)O(2) scavenging test. Intriguingly, 4c displayed 2-fold more potency than melatonin (IC50 51 microM vs 125 microM) in scavenging NO in the macrophage model. These results suggested that the cysteinyl-conjugated derivative 4c may be a suitable lead to further optimize potent antioxidants for certain oxidative stress conditions.
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