In vitro Antioxidant Activity of Ubiquinone and Ubiquinol, Compared to Vitamin E

Abstract Coenzyme Q10 (CoQ10) is the prevalent ubiquinone in human organism, largely present in its reduced form, ubiquinol (QH2), to which the antioxidant, free radical scavenger activity is ascribed by many authors. However, some studies indicate that also the oxidized form presents some effect in preventing the cellular oxidative stress. In this article four in vitro chemical test methods (TEAC, FRAP, DPPH, and BR) were used to assess the free radical scavenging power of CoQ10, QH2, and vitamin E. The results showed that CoQ10 is almost ineffective, while in three of the tests QH2 presents a higher antioxidant activity than vitamin E. From these results, it can be concluded that the interconversion CoQ10⇌QH2 leading to the prevalence of QH2 in biological tissues is responsible for the antioxidant action of coenzyme Q10 in living organisms.