Abstract
In vivo and in vitro experimental data from our laboratory have provided evidence showing that coenzyme Q homolog (CoQ_n), especially its reduced form (CoQ_nH_2), acts as an antioxidant which protects cells from oxidative damage. The mechanism of antioxidant function of CoQ_nH_2, especially in relation to that of α-tocopherol (α-Toc), has been also studied with isolated hepatocytes exposed to a water-soluble radical initiator, 2, 2'-azobis (2-amidinopropane) dihydrochloride (AAPH). Evidence obtained supports the following views. 1. CoQ_nH_2, but not oxidized CoQ_n, has a potent antioxidant activity by scavenging lipid-peroxyl radicals in a variety of in vivo and ex vivo experiments. 2. The antioxidant activity of endogenous CoQ_9H_2 is different from that of endogenous CoQ_<10>H_2 : the former act as a better antioxidant than the latter in isolated hepatocytes exposed to AAPH. 3. The antioxidant function of endogenous CoQ_nH_2 is independent of that of endogenous α-Toc and both act as strong antioxidants against cellular damage induced by AAPH.
