5-hydroxytryptophan is a more potent in vitro hydroxyl radical scavenger than melatonin or vitamin C.
Hydroxyl radicals are involved in direct damage of important biomolecules. Potent radical scavengers such as vitamin C and indoles of the tryptophan family can avert the potential damage. Melatonin and its precursor 5-hydroxytryptophan (5-HTP) were compared with water-soluble vitamin C. Different scavenger concentrations were measured in a steady-state luminol chemiluminescence system (SLCL-system) with combined Fe(II) chloride (0.1 mm) and hydrogen peroxide (1.0 mm) as hydroxyl radical generators. 5-HTP showed highest hydroxyl radical scavenging effects with a 50% inhibition concentration (IC50) of 1.8 microm. For vitamin C an IC50 of 12.7 microm was measured, whereas melatonin in pure demineralized water was much less efficient (IC50=724 microm). A comparison between melatonin in aqueous solution and melatonin in ethanol solution revealed that melatonin was significantly more effective in pure demineralized water.
Keithahn
Christian
C
School of Engineering and Science, International University Bremen, Bremen, Germany.
Lerchl
Alexander
A
D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000494:pharmacology*; D049449:Luminescence; D008550:Melatonin / Q000494:pharmacology*
D016166:Free Radical Scavengers; D006916:5-Hydroxytryptophan; D008550:Melatonin; D001205:Ascorbic Acid