Melatonin and its precursors scavenge nitric oxide


Address reprint requests to Dr. Yasuko Noda, 251 Life Sciences Addition, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley CA 94720-3200.


Abstract: Nitric oxide (NO) scavenging activity of melatonin, N-acetyl-5-hydroxytryptamine, serotonin, 5-hydroxytryptophan and L-tryptophan was examined by the Griess reaction using flow injection analysis. l-Hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1 - triazene (NOC-7) was used as NO generator. The Griess reagent stoichiometrically reacts with NO2, which was converted by a cadmium-copper reduction column from the stable end products of NO oxidation. Except for tryptophan, all the compounds examined scavenged NO in a dose-dependent manner. Melatonin, which has a methoxy group in the 5-position and an acetyl side chain, exhibited the most potent scavenging activity among the compounds tested. Serotonin. N-acetyl-5 hydroxytryptamine, and 5-hydroxytryptophan, respectively, showed moderate scavenging activity compared to melatonin. Tryptophan, which has neither a methoxy nor a hydroxyl group in the 5-position, exhibited the least NO scavenging activity.