| Abstract text: |
β-carotene (BC) and canthaxanthin (CTX) were incorporated into mitochondrial membranes, being transferred from EYPC liposomes doped with 0.6 M of each carotenoid (experiment 1), and we found different incorporation yields, up to 98% for BC and 48% for CTX. In order to evaluate the antioxidant potential of these carotenoids in membranes, we used three systems: ascorbate/ADP/FeCl3 system, and transition metal ions (Cu+2, Zn+2, Fe+3) (experiments 2a and 2b, respectively) and a free radical promoter (tBOOH), at two different concentrations (0.5 and 5 mM) (experiment 2c). We evaluated by spectrometry the malonedialdehyde as a marker for lipid peroxide formation and noticed that CTX showed a stronger antioxidant activity than BC, especially in experiments 2a and 2b. This difference may be explained considering the location of CTX, closer to the water/lipid membrane interface, where water soluble promoters are present (as ascorbate/ADP/FeCl3and metal ions Cu+2, Zn+2, Fe+3), while BC, located mainly in the hydrophobic membrane region, had lower availability to pro-oxidants. In non-polar environments, using tBOOH as free radical promoter (experiment 2c), BC showed its antioxidant capacity, acting as a free radical quencher, particularly at lower concentrations. According to these data we conclude that, generally, CTX, in spite of its lower yield of incorporation into mitochondrial membranes, compared to BC, can act as a more effective antioxidant in mitochondrial membranes, especially in pro-oxidant watery environments. Therefore, canthaxanthin may support better the mitochondrial defense system against lipid peroxidation, data in mitochondria, a site of many redox processes which need proton-donors and efficient antioxidant protection. |
