Research: KEITHAHN and LERCHL,

Listed in Issue 120


KEITHAHN and LERCHL, School of Engineering and Science, International University Bremen, Bremen, Germany, have found that 5-hydroxytryptophan is potentially a more potent antioxidant than melatonin or vitamin C.


Hydroxyl radicals cause oxidative damage of biological tissues. Potent radical scavengers such as the antioxidants vitamin C and derivatives of the amino acid, tryptophan, can avert the damage. In this study, the pineal hormone melatonin and its precursor 5-hydroxytryptophane were compared with vitamin C.


Biochemical in vitro study.


5-hydroxytryptophan showed the highest hydroxyl radical scavenging effect with a 50% inhibition concentration (IC50) of 1.8 micromolar. For vitamin C, an IC50 of 12.7 micromolar was measured, and for melatonin 724 micromolar.


This study was conducted in a test tube in water. The experiments need to be repeated in biological tissues in order to verify that this metabolite of tryptophan is a potent antioxidant.


Keithahn C, Lerchl A. 5-hydroxytryptophan is a more potent in vitro hydroxyl radical scavenger than melatonin or vitamin C. Journal of Pineal Research 38 (1): 62-66, Jan 2005.

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