Since the higher redox potential of quinone molecules has been correlated with enhanced cellular deleterious effects, we studied the ability of the association of ascorbate with several quinones derivatives (having different redox potentials) to cause cell death in K562 human leukaemia cell line. The rationale is that the reduction of quinone by ascorbate should be dependent of the quinone half...

Water soluble quinones are a group of cytotoxic anti-bacterial compounds that are secreted by many species of plants, invertebrates, fungi and bacteria. Studies in a number of species have shown the importance of quinones in response to pathogenic bacteria of the genus Pseudomonas. Two electron reduction is an important mechanism of quinone detoxification as it generates the less toxic quinol. ...

BACKGROUND Better understanding of the transannular influence of a substituent on the redox-potentials of bicyclo[2.2.2]octane-derived quinones will help in the design of new compounds with controlled biological activity. However, attempts to directly relate the reduction potentials of substituted triptycene-quinones to the electronic effects of substituents are often unsuccessful. RESULTS Fi...

Steffen Runge, M athias O. Senge* Institut für Organische Chemie (WE02), Fachbereich Chemie, Freie Universität Berlin, Takustraße 3, D-14195 Berlin, Germany Z. Naturforsch. 53b, 1021-1030 (1998); received June 15, 1998 Porphyrins, Quinones, Electron Transfer Compounds, Crystal Structure, Conformation A series of 5-(benzoquinone)-10,15,20-trialkylporphyrins was synthesized via cross conden­ sati...

The chemical defence of the millipede Pachyiulus hungaricus is reported in the present paper, in which a chemical characterization is given and antimicrobial activity is determined. In total, independently of sex, 44 compounds were identified. All compounds belong to two groups: quinones and pentyl and hexyl esters of long-chain fatty acids. The relative abundances of quinones and non-quinones ...

Enterobacter cloacae NAD(P)H:nitroreductase (NR; EC 1.6.99.7) catalyzes two-electron reduction of a series of quinoidal compounds according to a "ping-pong" scheme, with marked substrate inhibition by quinones. The steady-state catalytic constants (k(cat)) range from 0.1 to 1600s(-1), and bimolecular rate constants (k(cat)/K(m)) range from 10(3) to 10(8)M(-1)s(-1). Quinones, nitroaromatic compo...

The role of quinones in electron transport has attracted considerable recent interest (27). Coenzyme Q1O, which is present in plant mitochondria, is closely related to the respiratory chain (6), and the very similar benzoquinone, plastoquinone, appears to be involved in photosynthesis (7) Vitanmin K-type naphthoquinones have been imlplicated in respiratory electron transfer (30), oxidative phos...

The relationship between the NADH:lipoamide reductase and NADH:quinone reductase reactions of pig heart lipoamide dehydrogenase (EC 1.6.4.3) was investigated. At pH 7.0 the catalytic constant of the quinone reductase reaction (kcat.) is 70 s-1 and the rate constant of the active-centre reduction by NADH (kcat./Km) is 9.2 x 10(5) M-1.s-1. These constants are almost an order lower than those for ...