Ubiquinol-3 and ubiquinol-7 exhibit similar antioxidant activity in model membranes.

This study was undertaken to compare, on a kinetic basis, the antioxidant efficiency of an ubiquinol homologue having a short isoprenoid side-chain length, such as ubiquinol-3, with that of the long chain ubiquinol-7, by determining their rate constants of inhibition with respect to alpha-tocopherol. To this purpose we incorporated ubiquinol-3, or ubiquinol-7, or alpha-tocopherol into liposomes of egg yolk lecithin, and triggered lipid peroxidation with the thermal decomposition of a lipophilic azocompound. The results show that: i) the rate constants of inhibition for the two quinols are similar and slightly lower than that of alpha-tocopherol; ii) the length of the radical chain obtained in the presence of the two quinols is almost the same. From these data we concluded that the two homologues tested behave as chain-breaking antioxidants with quite similar effectiveness.