| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1252050 | Chemistry and Physics of Lipids | 2011 | 8 Pages |
Melatonin and its structural analogues display antioxidant activity in vivo but their activity in model membranes is not very well known. In this study, we have investigated the antioxidant capacity of melatonin and structural analogues on Fe2+-initiated peroxidation of sonicated liposomes made of retinal lipids. The indoleamines were evaluated against butylated hydroxitoluene (BHT) which was chosen as a reference standard because of its high antioxidant capacity. After the addition of Fe2+ as initiator of lipid peroxidation, quick production of conjugated dienes was observed. With addition of increasing concentrations of BHT the start of the reaction was delayed and initial reaction rates were lower. However, this reduction was not proportional to the increase in concentration. The start of the reaction and initial reaction rates were not modified in the presence of melatonin and its structural analogues. The formation of TBARS started immediately after the addition of Fe2+. The increase in the concentration of BHT avoided the emergence of TBARS. Changes were not observed in the presence of melatonin or structural analogues. Retinal lipids showed a high content of docosahexaenoic (22: 6 Δ4,7,10,13,16,19) acid, characteristic of this tissue. A little bit of that fatty acid was lost when sonicated liposomes were prepared with these retinal lipids. The polyunsaturated fatty acids (PUFAs) diminished significantly after incubation of liposomes with Fe2+ during 1 h. BHT preserved PUFAs whereas melatonin and its related indoleamines did not. These data reinforce the hypothesis that melatonin and structural analogues do not possess antioxidant properties per se in this liposomal model system.
► This study analyze the behavior of MLT and related indoleamines during progress of lipid peroxidation of liposomes made of retinal lipids using Fe2+ as initiator. ► PUFAs in liposomes were affected by peroxidation diminishing significantly to almost disappear. ► BHT preserved PUFAs. ► Melatonin and its structural analogues do not possess antioxidant properties per se in this liposomal model system. ► 5HOTRP not only did not show antioxidant activity but also it is possible that it has prooxidant effect.
