Charge transfer mechanism for benzodiazepine (BZ) action

Mechanism of Anesthetic Toxicity: Metabolism, Reactive Oxygen Species, Oxidative Stress, and Electron Transfer

There is much literature on the toxic effects of anesthetics. This paper deals with both the volatiles and locals. Adverse effects appear to be multifaceted, with the focus on radicals, oxidative stress (OS), and electron transfer (ET). ET functionalities involved are quinone, iminoquinone, conjugated iminium, and nitrone. The non-ET routes involving radicals and OS apparently pertain to haloalkanes and ethers. Beneficial effects of antioxidants, evidently countering OS, are reported. Knowledge at the molecular level should aid in devising strategies to combat the adverse effects.

Bioelectronome. Integrated Approach to Receptor Chemistry, Radicals, Electrochemistry, Cell Signaling, and Physiological Effects Based on Electron Transfer

Bioelectronome refers to the host of electron transfer (ET) reactions that occur in living systems. This review presents an integrated approach to receptor chemistry based on electron transfer, radicals, electrochemistry, cell signaling, and end result. First, receptor activity is addressed from the unifying standpoint of redox transformations in which various receptors are discussed. After a listing of receptor-binding modes, receptor chemistry is treated with focus on generation of reactive oxygen species (ROS), activation by ROS, and subsequent cell signaling involving ROS. A general electrostatic mechanism is proposed for receptor-ligand action with supporting evidence. Cell-signaling processes appear to entail electron transfer, ROS, redox chains, and relays. The widespread involvement of phosphate from phosphorylation may be rationalized electrostatically by analogy with DNA phosphate. Extensive evidence supports important participation of ET functionalities in the mechanism of drugs and toxins. The integrated approach is applied to the main ET classes, namely, quinones, metal complexes, iminium species, and aromatic nitro compounds.

Ototoxicity and noise trauma: electron transfer, reactive oxygen species, cell signaling, electrical effects, and protection by antioxidants: practical medical aspects

Ototoxins are substances of various structures and classes. This review provides extensive evidence for involvement of electron transfer (ET), reactive oxygen species (ROS) and oxidative stress (OS) as a unifying theme. Successful application is made to the large majority of ototoxins, as well as noise trauma. We believe it is not coincidental that these toxins generally incorporate ET functionalities (quinone, metal complex, ArNO(2), or conjugated iminium) either per se or in metabolites, potentially giving rise to ROS by redox cycling. Some categories, e.g., peroxides and noise, appear to operate via non-ET routes in generating OS. These highly reactive entities can then inflict injury via OS upon various constituents of the ear apparatus. The theoretical framework is supported by the extensive literature on beneficial effects of antioxidants, both for toxins and noise. Involvement of cell signaling and electrical effects are discussed. This review is the first comprehensive one based on a unified mechanistic approach. Various practical medical aspects are also addressed. There is extensive documentation for beneficial effects of antioxidants whose use might be recommended clinically for prevention of ototoxicity and noise trauma. Recent research indicates that catalytic antioxidants may be more effective. In addition to ototoxicity, a widespread problem consists of ear infections by bacteria which are demonstrating increasing resistance to conventional therapies. A recent, novel approach to improved drugs involves use of agents which inhibit quorum sensors that play important roles in bacterial functioning. Prevention of ear injury by noise trauma is also discussed, along with ear therapeutics.

Mechanism of teratogenesis: Electron transfer, reactive oxygen species, and antioxidants

Teratogenesis has been a topic of increasing interest and concern in recent years, generating controversy in association with danger to humans and other living things. A veritable host of chemicals is known to be involved, encompassing a wide variety of classes, both organic and inorganic. Contact with these chemicals is virtually unavoidable due to contamination of air, water, ground, food, beverages, and household items, as well as exposure to medicinals. The resulting adverse effects on reproduction are numerous. There is uncertainty regarding the mode of action of these chemicals, although various theories have been advanced, e.g., disruption of the central nervous system (CNS), DNA attack, enzyme inhibition, interference with hormonal action, and insult to membranes, proteins, and mitochondria. This review provides extensive evidence for involvement of oxidative stress (OS) and electron transfer (ET) as a unifying theme. Successful application of the mechanistic approach is made to all of the main classes of toxins, in addition to large numbers of miscellaneous types. We believe it is not coincidental that the vast majority of these substances incorporate ET functionalities (quinone, metal complex, ArNO2, or conjugated iminium) either per se or in metabolites, potentially giving rise to reactive oxygen species (ROS) by redox cycling. Some categories, e.g., peroxides and radiation, appear to generate ROS by non-ET routes. Other mechanisms are briefly addressed; a multifaceted approach to mode of action appears to be the most logical. Our framework should increase understanding and contribute to preventative measures, such as use of antioxidants.

Electrochemistry of anticonvulsants: electron transfer as a possible mode of action

Reduction potentials were determined for various anticonvulsants, including progabide, SL 75.102, CGS 9896, pyridazines, zonisamide, 1,2,3-triazoles, and copper complexes. The values generally were in the range of about -0.1 to -0.6 V for the protonated drugs and the metal complexes. Reduction potentials provide information on the feasibility of electron transfer (ET) in vivo. If the value is relatively positive (greater than about -0.6 V), the agent can act catalytically as an electron acceptor from an appropriate cellular donor. A concomitant favorable influence on abnormal neuronal processes associated with epilepsy could occur. We describe ET as a possible mode of action of anticonvulsants as well as some antiepileptic agents with no electrochemical data based on this hypothetical ET approach.

Theoretical calculations on calcium channel drugs: is electron transfer involved mechanistically?

Theoretical studies were done on calcium channel drugs in order to gain insight into the mode of action. Empirical force field calculations with nifedipine, a calcium channel antagonist, indicate that the E-conformation at the ring juncture is lower in energy than the Z-conformation. This energy difference is only 0.2 kcal/mol when the esters in the 3- and 5-positions of the dihydropyridine (DHP) ring are both synperiplanar (sp, sp). Molecular orbital calculations on the ground and excited states in the Z-conformation with the esters in the (ap, sp) conformation show a low lying excited state with substantial intramolecular electron transfer (ET) character. This excited state is only 1.8 eV higher in energy than the ground state and corresponds to a transfer of approximately 0.3 electron from the DHP ring to the nitrobenzene moiety. We suggest that ET may play an important role in the mechanism of action, either intramolecular or, as previously proposed, intermolecular, along with lipophilicity and steric effects.

Electrochemistry of cyclic alpha-imino carboxylates and their metal complexes: correlation with physiological activity

Cyclic voltammetry data were obtained for delta 1-pyrroline-2-carboxylate, delta 3-thiazoline-4-carboxylate, delta 2-thiazoline-2-carboxylate and their complexes with Cu(II), Fe(III), and Fe(II). The free ligands were reduced at about -0.35 V and were oxidized in the range of 0.42-0.52 V. Complexing the imine carboxylates with metal ions produces reduction and oxidation in the ranges of 0.05-0.37 V and 0.52-0.74 V, respectively. Prior reports show that these ligands take part in various biological functions. We propose that electron transfer may be involved in some aspects of the physiological activity. The captodative effect can be applied.

Mode of action of antiprotozoan agents. Electron transfer and oxy radicals

Cyclic voltammetry data were obtained for most of the main classes of antiprotozoan agents, specifically, nitroheterocycles, quinones, metal complexes and derivatives, iminium-type ions, and azo compounds. The reductions were generally reversible in the range of -0.3 to -0.9 V. Catalytic production of oxidative pressure from redox cycling involving oxygen is believed to be an important mode of action by the medicinal agents. Literature data contribute support.

Cyclic voltammetry of quinolinium salts and related compounds: correlation with structure and anticancer activity

Cyclic voltammetry data were obtained for 12 salts of quinolines, one pyridine, and one open-chain imine which possess varying degrees of anticancer activity. The structural features include sidechain bis(2-methylthio)vinyl, 2-methylthio-2-aminovinyl, dithioacetic acid, 2-quinolylvinyl, 2-styrylvinyl, and guanidine sulfide functionalities. Reduction potentials ranged from -0.43 to -1.08 V. The electrochemical results are correlated with structure. A possible mechanism of anticancer action is addressed.

An integrated concept of amebicidal action: electron transfer and oxy radicals

Cyclic voltammetry data were obtained for most of the main categories of antiamebic agents, specifically, quinones, heterocyclic nitro compounds, metal derivatives and chelators, and iminium-type ions. The reductions (our data and literature values) were for the most part reversible, with potentials usually in the favorable range of +0.10 to -0.56 V. The drug effect is believed to result generally from the catalytic production of oxidative stress usually arising from the formation of superoxide via electron transfer. In addition, relevant literature data are provided.

Cyclic voltammetry of phenazines and quinoxalines including mono- and di-N-oxides. Relation to structure and antimicrobial activity

Cyclic voltammetry data were obtained for eight phenazines and phenazine-N-oxides, and eleven quinoxalines and quinoxaline-N-oxides: 1,6-phenazine-diol-5,10-dioxide (iodinin), iodinin copper complex, 6-methoxy-1-phenazinol-5,10-dioxide 1,6-dimethoxyphenazine-5-oxide, 1,6-phenazinediol, 1,6-dimethoxyphenazine, quinoxaline-1,4-dioxide, 2-methylquinoxaline-1,4-dioxide, 2,3-diphenylquinoxaline-1,4-dioxide, 2-carboxyquinoxaline-1,4-dioxide, 5-hydroxyquinoxaline-1,4-dioxide, 5-hydroxy-8-methoxyquinoxaline-1,4-dioxide, 2-methylquinoxaline, 2,3-diphenylquinoxaline, 5-hydroxyquinoxaline, 5-hydroxy-8-methoxyquinoxaline and 2-(2-quinoxalinylmethylene)hydrazine carboxylic acid methyl ester-1,4-dioxide (Carbadox). The di-N-oxides exhibit the most positive E1/2 values within each class. Reversible first wave reductions were observed for iodinin, iodinin copper complex, 1,6-dimethoxyphenazine-5-oxide, 1,6-dimethoxyphenazine, quinoxaline-1,4-dioxide, 2-methylquinoxaline-1,4-oxide and 2,3-diphenylquinoxaline-1,4-dioxide. The results are correlated with structure. Some relationships exist between reduction potential and reported antimicrobial activity. A possible mechanism of drug action is addressed.

Mechanism of antibacterial action: electron transfer and oxy radicals

Most of the main categories of bactericidal agents, namely, aliphatic and heterocyclic nitro compounds, metal derivatives and chelators, quinones, azo dyes, and iminium-type ions, are proposed to exert their action by a unified mechanism. The toxic effect is believed to result generally from the catalytic production of reactive oxygen radicals that usually arise via electron transfer. Cyclic voltammetry was performed on a number of these agents. Reductions were for the most part reversible, with potentials in the favorable range of -0.20 to -0.58 V.