Ubiquinones, Plastoquinones and Vitamins K

Herbicidal activity and redox properties of 3-aryl-6-(perfluoroalkyl)-1,2,4,5-tetrazines and 1,2-dihydro derivatives

“…Recent experiments (Dawson, 1972) with naphtho-and heterocyclic quinone herbicides Devlin, 1971,1972); have shown that redox potentials for these quiñones are significantly more positive (+70 to -225 mV) than those for the dipyridylium herbicides, which have a similar mode of action. Substituted 1,4-benzo-and naphthoquinones play a vital role in the respiratory and photosynthetic elements of biological systems (Morton, 1971). These quiñones, acting as electron acceptors, are reversibly reduced to hydroquinones (Morton, 1971;Schmidt-Mende and Rumberg, 1968) or possibly semiquinones (Cox et al, 1970;Stiehl and Witt, 1969) when functioning in vivo.…”

“…Substituted 1,4-benzo-and naphthoquinones play a vital role in the respiratory and photosynthetic elements of biological systems (Morton, 1971). These quiñones, acting as electron acceptors, are reversibly reduced to hydroquinones (Morton, 1971;Schmidt-Mende and Rumberg, 1968) or possibly semiquinones (Cox et al, 1970;Stiehl and Witt, 1969) when functioning in vivo. The chloroplast reduction process of a quinone, denoted Q in eq 2, therefore ¿so involves transfer of protons as well as electrons.…”

Effect of coenzyme Q10 on the disposition of doxorubicin in rats

“…The endogenous CoQ IO is generally recognized to be an important component in mitochondrial electron transport processes (34), as well as a proton carrier as part of the mechanism for creating a chemiosmotic proton gradient required for ATP synthesis (35). Besides, in mitochondria, high levels of COQIO were also present in the microsomal fraction from cells, especially in Golgi apparatus membranes as well as plasma membranes that are relative to endoplasmic reticulum (36,37).Since CoQ IO in the plasma membrane also acts as an agent for proton transfer as in mitochondria (38), it may improve the NAD(P)H-dependent cytochrome P450 enzyme reactions in the endoplasmic reticulum by increasing the efficiency of electron transport and improving energy metabolism.…”

Dietary supplements in patients with cancer: Risks and key concepts, part 1

“…Because coenzyme Q 10 (ubiquinone) is structurally similar to vitamin K 2 , it may have antagonistic effects on warfarin. 70 There are at least four case reports of patients taking warfarin with stable INRs that became subtherapeutic with the use of coenzyme Q 10 . [71][72][73] As an inducer of the cytochrome P-450 (CYP) enzyme system, St. John's wort (Hypericum perforatum) can increase the metabolism and decrease the efficacy of warfarin.…”