ESTIMATION OF REDOX PROPERTIES OF CHEMICAL-COMPOUNDS BY THEIR REACTIONS WITH FREE-RADICALS

The electron-donor and electron-acceptor properties of biologically active compounds were estimated on the basis of their reactions with free radical intermediates of the excited dye eosin. After dye excitation by a short flash of light, the kinetics of dye anion radicals in the pure dye solution were compared with those in the presence of the natural reducing agent NADH or a number of substances which are known as local anesthetics (LA). LA individually slowed the decay of dye anion radicals and enhanced their concentration to a lesser extent than NADH, thus acting as electron donors toward dye radicals. The electron-donor properties of LA studied correlate with their ability to block. sodium channels. In contrast, the sodium channel agonist veratridine decreased the concentration of dye anion radicals, thus showing electron-acceptor properties. The opposite redox features of the channel antagonist and the agonist were revealed also by a modified method suitable for steady-light spectroscopy. Promoted by NADH, eosin photobleaching was slowed by the electron acceptor ferricyanide as well as by veratridine and some phenols. The electron-acceptor properties of the latter compounds correlated with their ability to inhibit ATP synthesis by submitochondrial particles. Thus, these methods may be used to evaluate the redox properties of compounds not characterized by electrochemical methods and to predict their biological activity. (c) 1994 Academic Press,Inc.