INHIBITORY EFFECTS OF ESSENTIAL AMINO ACIDS ON THE PEAK CHEMILUMINESCENCE OF THE CELL-FREE SYSTEMS

The inhibitory effect of essential amino acids in aqueous solutions, on the peak chemiluminescence of hydrogen peroxide (H2O2), hypochlorous (HOCI) (derived from NaOCl) or peroxynitrite (ONOO-) was evaluated by using flow injection analysis (FlA)-luminol chemiluminescence (CL) method. The chemiluminescence was measured as the luminometer output in mV and the effects of amino acids were considered by the depression of the signal from its uninhibited level and expressed as the percentage attenuation of the peak chemiluminescence due to the oxidant. The luminol-H2O2 HOCl or ONOO--induced CL signal was inhibited by either amino acids or ascorbate (well characterized, chain-breaking antioxidant) in a concentration-dependent manner. The log IC50 values of the inhibitor effect of amino acids were calculated and found that histidine and tryptophan displayed the most potent inhibitory activity against H202 or HOCl induced peak chemiluminescence, respectively. Results were concluded that the inhibitory effect of the essential aminoacids on the peak chemiluminescence might represent their free radical scavenger activit