Application of the oral administration of the amino acid L-tryptophan as a possible antioxidant precursor

Cubero, J. and Valero, V. and Narciso, D. and Sánchez, J. and Rodríguez, A. and Barriga, C. (2007) Application of the oral administration of the amino acid L-tryptophan as a possible antioxidant precursor. Acta Alimentaria, 36 (4). pp. 419-424. ISSN 0139-3006

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Abstract

The use of melatonin as antioxidant has been extensively established. But what would the antioxidant function be if one were to go one step back in the anabolism of that amine, and orally administer its precursor — the amino acid tryptophan? Diurnal animals (Streptopelia roseogrisea) were administered orally capsules containing 125 or 300 mg L-tryptophan/kg b.w. for 7 days at the end of the light period (20h). A control group received capsules with methylcellulose. The antioxidant function was studied through the reduction of nitroblue tetrazolium (NBT) by superoxide anion, and through the levels of malonaldehyde (MDA) produced in the lipoperoxidation that occurs from the respiratory burst in response to the presence of a foreign particle in phagocytic cells (heterophils), which were extracted at 2h — at the acrophase of melatonin in the blood stream. In the heterophils extracted from the group that received 125 mg kg−1 b.w. tryptophan, there was less oxidative stress as determined by the NBT reduction than in those from the 300 mg kg−1 b.w. group. In the study of the lipoperoxidation of the membranes as determined by the levels of MDA, however, no significant variations were observed between the different groups. The lower concentration (125 mg L-tryptophan/kg b.w.), administered orally, succeeded in diminishing the free radicals produced in the heterophils for the destruction of the ingested foreign agent, but not fully or maximally. The possible solution to this prooxidant/antioxidant imbalance would be to administer a lower concentration of tryptophan to attain the perfect balance for application in nutritional treatments.

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