Reactivity and Radical Scavenging Activity Potential of Melatonin and Its Derivatives

Melatonin (5-methoxy-N-acetyltryptamine) is hormone produced by human organism with a general function to regulate the processes of sleep and wakefulness, but it has also well proved antioxidant potential. In this study, the dissociation enthalpies of the most easily cleaved N-H and C-H bonds in melatonin and its three selected derivatives, formed during reactions with HO• and H2O2, were calculated. B3LYP/DFT quantum chemical calculations with a 6-311++G orbital basis set, accounting for the solvent effect of water using the SCRF/PCM approach, were performed. The results revealed that, after the transformation of melatonin, the resulting compounds exhibited radical-scavenging properties similar to those of the parent compound. This behavior is atypical for most radical scavengers, as they usually undergo conversion into reactive and more toxic derivatives when reacting with oxygen-containing species. Finally, these findings provide valuable insight into the critical role of melatonin in living organisms.