ABSTRACT

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 activity.