Assessing the effect of N-oxidation on the mutagenicity of 1-pyrazolines using the Ames assay.

-Nitrosamines are well known as environmental carcinogens. We have reported that -nitroso--methylbutylamine was oxidized by Fe-Cu-HO to 5-methyl-5-nitro-1-pyrazoline, a direct-acting -oxide. 1-Pyrazolines have not been reported to exhibit genotoxicity.

Antimutagenic components in Dunn against -methyl--nitrosourea.

Background: An extract from () Dunn has been reported to show potent antimutagenic effects against -alkyl--nitrosoureas in screening. The aim of this study was to identify the antimutagenic components from extracts of against -methyl--nitrosourea (MNU) in the Ames assay with strain TA1535 and to elucidate the antimutagenic mechanism of the flavonoids.

Results: From the ethyl acetate fraction obtained from fractionation of the methanol extract of Dunn, medicarpin, formononetin and isoliquiritigenin were successfully isolated through a combination of normal- and reversed-phase chromatography.

The mutagenic mechanism of oxygenated alkylhydrazones occurs through alkyl radicals and alkyldiazonium ions.

Acetone alkylhydrazones have been reported to be mutagenic in TA1535 after exposure to oxygen, and the corresponding 2-alkylazo-2-propyl hydroperoxides are formed by autoxidation as a result. The aims of this study were to investigate the mutagenic mechanisms of a methyl analogue, 2-methylazo-2-propyl hydroperoxide (MAPH), by comparing the mutagenic potency of specific strains, detecting the DNA adducts that cause mutagenicity, and observing the hydroxyl radical and methyl radical with the electron spin resonance (ESR) spin-trapping method. MAPH showed stronger mutagenicity in both YG3001, a strain sensitive to hydroxyl radicals, and YG7108, a strain sensitive to alkylating agents, than the original TA1535 strain.

Isolation and characterization of antimutagenic components of against -methyl--nitrosourea.

Background: A powdered ethanolic extract of root exhibits antimutagenic activity against -methyl--nitrosourea (MNU) based on the Ames assay with TA1535. The aim of this study was to identify the antimutagenic components of the powdered ethanolic extract of root.

Results: The powdered ethanolic extract of root was sequentially suspended in -hexane, carbon tetrachloride, dichloromethane, ethyl acetate, and ethanol, and each solvent soluble fraction and the residue were assayed for antimutagenic activity against MNU in TA1535.

Antimutagenic components in Glycyrrhiza against N-methyl-N-nitrosourea in the Ames assay.

Antimutagenesis against N-nitroso compounds contribute to prevention of human cancer. We have found that Glycyrrhiza aspera ethanolic extract exhibits antimutagenic activity against N-methyl-N-nitrosourea (MNU) using the Ames assay with Salmonella typhimurium TA1535. In the present study, eight purified components from Glycyrrhiza, namely glabridin, glycyrrhetinic acid, glycyrrhizin, licochalcone A, licoricesaponin H2, licoricesaponin G2, liquiritigenin and liquiritin were evaluated for their antimutagenicity against MNU in the Ames assay with S.

Effect of alkyl group on transnitrosation of N-nitrosothiazolidine thiocarboxamides.

S-Nitrosoglutathione (GSNO) relaxes vascular smooth muscles, prevents platelet aggregation, and acts as a potential in vivo nitric oxide donor. 3-Nitroso-1,3-thiazolidine-4-thiocarboxamide (1), a N-nitrosothio-proline analogue, exhibited a high GSNO formation activity. In this study, two compounds (2 and 3) based on compound 1 were newly synthesized by introducing either one or two methyl groups onto a nitrogen atom on the thioamide substituent in 1.

Transnitrosation of non-mutagenic N-nitrosoproline forms mutagenic N-nitroso-N-methylurea.

N-Nitroso-N-methylurea (NMU) is a potent carcinogen and suspected as a cause of human cancer. In this study, mutagenic NMU was detected by HPLC after the transnitrosation of non-mutagenic N-nitrosoproline (NP) to N-methylurea in the presence of thiourea (TU) under acidic conditions. The structure of NMU was confirmed by comparing (1)H NMR and IR spectra with that of authentic NMU after fractionation by column chromatography.

The role of PKD in cell polarity, biosynthetic pathways, and organelle/F-actin distribution.

Protein Kinase D (PKD) 1, 2, and 3 are members of the PKD family. PKDs influence many cellular processes, including cell polarity, structure of the Golgi, polarized transport from the Golgi to the basolateral plasma membrane, and actin polymerization. However, the role of the PKD family in cell polarity has not yet been elucidated in vivo.

Transnitrosation of alicyclic N-nitrosamines containing a sulfur atom.

Aromatic and aliphatic nitrosamines are known to transfer a nitrosonium ion to another amine. The transnitrosation of alicyclic N-nitroso compounds generates S-nitrosothiols, which are potential nitric oxide donors in vivo. In this study, certain alicyclic N-nitroso compounds based on non-mutagenic N-nitrosoproline or N-nitrosothioproline were synthesised, and the formation of S-nitrosoglutathione (GSNO) was quantified under acidic conditions.

Chlorine atom substitution influences radical scavenging activity of 6-chromanol.

Synthetic 6-chromanol derivatives were prepared with several chlorine substitutions, which conferred both electron-withdrawing inductive effects and electron-donating resonance effects. A trichlorinated compound (2), a dichlorinated compound (3), and three monochlorinated compounds (4, 5, and 6) were synthesized; compounds 2, 3, and 6 were novel. The antioxidant activities of the compounds, evaluated in terms of their capacities to scavenge galvinoxyl radical, were associated with the number and positioning of chlorine atoms in the aromatic ring of 6-chromanol.

Isolation and structural identification of a direct-acting mutagen derived from N-nitroso-N-methylpentylamine and Fenton's reagent with copper ion.

N-Nitrosodialkylamines show their mutagenicity by forming α-hydroxynitrosamines in the presence of rat S9 mix in the Ames assay. The hydroxyl radical derived from Fe(2+)-H(2)O(2) (Fenton's reagent) with Cu(2+) activates N-nitrosamines, with an alkyl chain longer than a propyl constituent, to a direct-acting mutagen. The reactivity of Fe(2+)-Cu(2+)-H(2)O(2) on nitrosamines in relation to their metabolic activation is not fully characterized.

Activation mechanism for N-nitroso-N-methylbutylamine mutagenicity by radical species.

N-Nitrosodialkylamines are known to be potent indirect-acting mutagens/carcinogens, which are activated by cytochrome P450. The reaction product of N-nitroso-N-methylbutylamine (NMB) with modified Fenton's reagent supplemented with copper salt (Fe²(+)-Cu²(+)-H₂O₂) was reported to be mutagenic in Salmonella typhimurium TA1535 without S9 mix. In this study, the NMB activation mechanism was investigated by ESR spectroscopy with radical trapping agents to detect radical species and also by observing changes in mutagenic potency with a Salmonella strain in the Ames assay in the presence of radical trapping agents.

Mutagenicity of aromatic amines and amides with chemical models for cytochrome P450 in Ames assay.

Chemical models for cytochrome P450, consisting of water-insoluble or water-soluble iron porphyrin plus an oxidant, have been used to detect the mutagenicity of promutagens in genotoxicity assays. The procedure for using chemical models for cytochrome P450 as substitutes for the S9 mix in the Ames assay have been already established. Aromatic amines and amides require metabolic activation by cytochrome P450 when they exert their mutagenicity in Salmonella typhimurium strains.

Unique behavior of 2,6-bis(bromomethyl)naphthalene as a highly active organic DNA crosslinking molecule.

Among 14 bis-halomethylated naphthalenes and quinolines, 2,6-bis(bromomethyl)naphthalene was found to have highly active crosslinking activity on DNA. The unique behavior of high microbial mutagenicity, even though it had a low propensity to form double-strands in linearized plasmid DNA, suggested that it would offer a new seed, capable of forming intrastrand crosslinks similar to cisplatin. The electron withdrawal extent of the halogen atoms, the substitution patterns of two halomethyl groups, and the introduction of a nitrogen atom into the aromatic nucleus had remarkable effects on the activity of the molecule.

Oxidative transformation of 2-acetylaminofluorene by a chemical model for cytochrome P450: A water-insoluble porphyrin and tert-butyl hydroperoxide.

Oxidation of 2-acetylaminofluorene (AAF), a carcinogen, by a chemical model for cytochrome P450 was investigated to identify an active mutagen and elucidate the oxidation pathway. The oxidation system consisted of a water-insoluble tetrakis(pentafluorophenyl)porphyrinatoiron(III) chloride and tert-butyl hydroperoxide. The mutagen derived from AAF by the chemical model was 2-nitro-9-fluorenone (NO(2)=FO), which was mutagenic in Salmonella typhimurium TA1538.

Metabolism of a liver-selective nitric oxide-releasing agent, V-PYRRO/NO, by human microsomal cytochromes P450.

Endogenously generated nitric oxide (NO) mediates a host of important physiological functions, playing roles in the vascular, immunological, and neurological systems. As a result, exogenous agents that release NO have become important therapeutic interventions and research tools. O(2)-Vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (V-PYRRO/NO) is a prodrug designed with the hypothesis that it might release nitric oxide via epoxidation of the vinyl group by cytochrome P450, followed by enzymatic and/or spontaneous epoxide hydration to release the ultimate NO-donating moiety, 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (PYRRO/NO) ion.

PABA/NO as an anticancer lead: analogue synthesis, structure revision, solution chemistry, reactivity toward glutathione, and in vitro activity.

PABA/NO is a diazeniumdiolate of structure Me(2)NN(O)=NOAr (where Ar is a 5-substituted-2,4-dinitrophenyl ring whose 5-substituent is N-methyl-p-aminobenzoic acid). It has shown activity against human ovarian cancer xenografts in mice rivaling that of cisplatin, but it is poorly soluble and relatively unstable in water. Here we report structure-based optimization efforts resulting in three analogues with improved solubility and stability in aqueous solution.

Electron-transfer mechanism in radical-scavenging reactions by a vitamin E model in a protic medium.

The scavenging reaction of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH.) or galvinoxyl radical (GO.) by a vitamin E model, 2,2,5,7,8-pentamethylchroman-6-ol (1H), was significantly accelerated by the presence of Mg(ClO4)2 in de-aerated methanol (MeOH).

Kinetic study of the electron-transfer oxidation of the phenolate anion of a vitamin E model by molecular oxygen generating superoxide anion in an aprotic medium.

Electron-transfer reduction of molecular oxygen (O2) by the phenolate anion (1-) of a vitamin E model, 2,2,5,7,8-pentamethylchroman-6-ol (1H), occurred to produce superoxide anion, which could be directly detected by a low-temperature EPR measurement. The rate of electron transfer from 1- to O2 was relatively slow, since this process is energetically unfavourable. The one-electron oxidation potential of 1- determined by cyclic voltammetric measurements is sufficiently negative to reduce 2,2-bis(4-tert-octylphenyl)-1-picrylhydrazyl radical (DOPPH*) to the corresponding one-electron reduced anion, DOPPH-, suggesting that 1- can also act as an efficient radical scavenger.

Chemical models for cytochrome P450 as a biomimetic metabolic activation system in mutation assays.

DNA damage is a critical factor in carcinogenesis. The Ames assay is a short-term test that screens for DNA-damaging agents. To be detected in the assay, most carcinogens require oxidation by cytochrome P450, a component of the liver homogenate preparation (S9 mix) that is traditionally used to metabolize promutagens to an active form in vitro.