NORHARMANE, A NATURALLY OCCURRING PHOTOSENSITIZER: PHOTOOXIDATION OF 2´-DESOXYADENOSINE-5´-MONOPHOSPHAT

M. MICAELA GONZALEZ; FEDERICO A. RASSE SURIANI; MATÍAS A. ALÉS-GANDOLFO; MARIANO FARACE; SANTIAGO ROLDAN ; ROSA ERRA-BALSELLS; FRANCO M. CABRERIZO

Mendoza

Conferencia; XXI Inter American Photochemical Society (I-APS) Conference; 2011

Inter-American Photochemical Society

UV-A radiation (320?400 nm) induces damages to the DNA molecule and itscomponents through photosensitized reactions. Norharmane is an alkaloid widespread inbiological systems showing photosensitizing properties. Upon UV-A radiation, norharmane isable to induce chromosome damage in mammalian cells,1 and/or to photoinduce DNArelaxation.2 Although these, the mechanisms involved in those processes are, to date,nevertheless still poorly understood.In the present work, we have studied the capability of norharmane to induce 2´-desoxyadenosine-5´-monophosphate (dAMP) photooxidation, in aqueous solution, upon UVAexcitation. The effect of pH was evaluated and the participation of reactive oxygen species(ROS), such as hydroxyl radical (HO?), superoxide anion (O2?-) and singlet oxygen (1O2) wasinvestigated. A strong dependence of the dAMP photosensitization on the pH was observed.The extent of the reaction was shown to be higher in the experiments performed at pH 4.7than those performed at pH 10.2. Kinetic studies using ROS scavengers revealed that thechemical reactions between ROS and dAMP are not the main pathways responsible for dAMPphotooxidation. Further analysis suggest that the predominant mechanism takes place, mostprobably, via electron transfer reactions (i.e., type I mechanism) from the single excited stateof the protonated form of norharmane.In addition, the chemical nature of the photoproducts formed upon photosensitizationwas characterized by mass spectrometry (ESI-MS and UV-MALDI-TOF-MS).