Effect of melatonin and structural analogs on lipid peroxidation of triglycerides rich in w-3 PUFAs

FAGALI, N. S.; CATALÁ, A.

Rosario

Congreso; XLII Reunion Anual de la Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular.; 2006

SAIB

The lipid peroxidation of triglycerides rich in C20:5 ù3 and C22:6 ù3 was investigated by photoemission techniques and the malondialdehyde (MDA) assay. We have compared melatonin [MLT] antioxidant activity with that of several structural analogs: 5-OH tryptophan [5-OHTRY], n-acetyl serotonin [NAS] and 5- methoxytryptamine [5-MTA]. Butylated hydroxytoluene [BHT], a classical antioxidant, 5-OHTRY and NAS, intermediaries in the synthesis of MLT, inhibited light emission and MDA formation in a concentration dependent manner. The total relative luminic units was found to be lower in those systems incubated in the presence of either BHT, NAS or 5-OHTRY; this decreased proportionally to the concentration of the compound tested. The order of inhibition was 5-OHTRY > NAS > BHT. The free radical scavenger activity of the indoles was also analyzed by the 2, 2- Diphenyl-1-picrylhydrazyl (DPPH) method. The results indicate that 5-OHTRY and NAS exhibited a dose-dependent free-radical scavenging ability of 73.5 % and 84.71 % at the 10 µM level, compared to 51 % activity of BHT. MLT and 5-MTA showed only 1.85 % and 5 % activity. MLT and 5-MTA have very low scavenging activity, enhance photoemission and are unable to inhibit the lipid peroxidation of triglycerides in solution. Melatonin’s o-methyl and n-acetyl residues appears to be decisive for its properties in this system.