What's the difference between hydroquinone and quinhydrone?
Hydroquinone
Definition:
(n.) A white crystalline substance, C6H4(OH)2, obtained by the reduction of quinone. It is a diacid phenol, resembling, and metameric with, pyrocatechin and resorcin. Called also dihydroxy benzene.
Example Sentences:
(1) These series were prepared by oxidation of the new hydroquinone precursors.
(2) In the liver, the major site of benzene metabolism, benzene is converted by a cytochrome P-450-mediated pathway to phenol, the major metabolite, and the secondary metabolites, hydroquinone and catechol.
(3) Here we report that phenol hydroxylation to hydroquinone is also catalyzed by human myeloperoxidase in the presence of a superoxide anion radical generating system, hypoxanthine and xanthine oxidase.
(4) We tested nine (cadmium chloride, chloral hydrate, colchicine, diazepam, econazole nitrate, hydroquinone, pyrimethamine, thiabendazole, thimerosal) of the 10 known or suspected spindle poisons of the coordinated programme to study aneuploidy induction sponsored by the Commission of the European Communities using Saccharomyces cerevisiae D61.M (mitotic chromosomal malsegregation system).
(5) Comparison of these two activities for both the quinone and hydroquinone showed that the hydroquinone form had superior activities.
(6) 2-Chloro-1,4-dimethoxybenzene (IV) is oxidized by lignin peroxidase to generate 2,5-dimethoxy-1,4-benzoquinone (V), which is reduced to 2,5-dimethoxy-1,4-hydroquinone (VI).
(7) Bis(alkylthio)quinones 4a-d and 5a-d, and corresponding hydroquinones 9b-d exhibited high activities both in vitro and in vivo.
(8) Glutathione (GSH) conjugates of 2-bromohydroquinone are more difficult to oxidize than the parent hydroquinone.
(9) The activity of cytochrome P-450 reductase, which reduces quinones to hydroquinones in the estrogen redox cycle, was 6-fold higher in liver than in kidney of both control and estrogen-treated animals.
(10) The hydrolytic products of lignins, humic acids and industrial waste including hydroquinone, catechol, resorcinol, pyrogallol and 1,2,4-benzenetriol are widely distributed in water sources.
(11) Treatment with hydroquinone and 1,2,4,-benzenetriol produced DNA adducts not detected after treatment with either metabolite alone.
(12) The changes were also prevented by 0.02% hydroquinone.
(13) Compounds such as butylated hydroxytoluene, catechol, chlorobenzene, hydroquinone, potassium chloride, phenol, cis-stilbene, trans-stilbene, and toluene did not elicit positive responses in either strain.
(14) Catechol given alone was not inhibitory but when phenol was added to catechol, erythropoiesis was suppressed, as observed for the phenol and hydroquinone combination.
(15) Ethoxyquin, propyl gallate and butylated hydroquinone only partially inhibited rTNF-alpha-induced cytotoxicity, while the antioxidants butylated hydroxytoluene (BHT), alpha-tocopherol, ascorbic acid and thiodipropionic acid had minimal effects.
(16) Hydroquinone is estimated to be nonmutagenic by the Ames test but induces chromosome aberrations or karyotypic effects in eucaryotic cells.
(17) This observation prompted us to study in a well-defined in vitro system the possible allosteric interaction between the propeptide binding site and the vitamin K hydroquinone binding site on carboxylase.
(18) The present data indicate that hydroquinone and 1,2,4-benzenetriol in the presence of copper ions can lead to the formation of reactive hydroxyl radicals which can release TBAR from glutamate or DNA.
(19) In Tris-washed spinach chloroplasts (incapable of O2 evolution), the chlorophyll a fluorescence transient in the presence of various artificial electron donors (hydroquinone, diphenylcarbazide, MnCl2 and NH2OH) and in the absence of bicarbonate ions shows a rapid initial rise; the addition of 10 mM NaHCO3 restores the transient to one characteristic of normal chloroplast.
(20) The relative toxic potencies of the hydroquinone and quinone metabolites of AMAP were comparable to that of NAPQI, and do not readily explain the marked difference between the cytotoxic effects of AMAP and APAP.
Quinhydrone
Definition:
(n.) A green crystalline substance formed by the union of quinone with hydroquinone, or as an intermediate product in the oxidation of hydroquinone or the reduction of quinone.
Example Sentences:
(1) The quinole oxidizes then to the quinhydrone and finally to primin itself.
(2) Its spectral characteristics, as well as the kinetic effects induced by substitution of the benzenoid part of the flavine, can hardly be taken into account by a quinhydrone-like structure for the intermediate dimers at any pH value.
(3) The redox electrodes are typified by the Quinhydrone electrode.
(4) Absorption and retention of all of these actinides was increased substantially by fasting and by the addition of mild oxidizing agents, ferric iron and quinhydrone.
(5) In contrast, fasting increased 210Pb absorption fivefold, and the oxidizing agents ferric iron and quinhydrone blocked the effect of fasting.
(6) Absorption of 233U, 238Pu, 241Am, and 244Cm from the gastrointestinal (GI) tract was measured in rats, fed ad libitum or fasted, that were gavaged with solutions containing ferric iron, ferrous iron, iron powder, quinhydrone or ascorbic acid.
(7) Both cutaneous melanin and adrenochrome appear to exist in a quinhydrone status.