Search results for "Styrene oxide"
showing 10 items of 22 documents
Effect of dietary antioxidants on benzo[a]pyrene metabolism in rat liver microsomes
1983
Feeding of rats with 1% ethoxyquin (EQ) and butylated hydroxytoluene (BHT) but not butylated hydroxyanisole (BHA) increases the formation rate of benzo[a]pyrene (BP)-4,5-dihydrodiol from BP in hepatic microsomes. The production of other BP-dihydrodiols and of BP phenols is decreased after treatment with EQ, BHT and BHA. EQ and BHT are more effective than BHA in inducing epoxide hydrolase (EH) activity towards styrene oxide as the substrate.
Purification and characterization of rat-liver cytosolic epoxide hydrolase.
1988
Rat liver cytosolic epoxide hydrolase has been purified and characterized. The enzyme was purified from tiadenol-induced rat liver 540-fold with respect to trans-stilbene oxide as a substrate. Similar purification was obtained with the substrates trans-beta-ethyl styrene oxide and styrene 7,8-oxide, the specific activities decreasing in the order trans-beta-ethyl styrene oxide greater than styrene 7,8-oxide greater than trans-stilbene oxide. The enzyme exerts highest activity at pH 7.4 Km and Vmax of the pure enzyme for trans-stilbene oxide were 1.7 microM and 205 nmol x min-1 x mg protein-1 respectively. With trans-stilbene oxide as a substrate, the inhibition by organic solvents (2.5% by …
Endogenous role of epoxide-hydratase. Development of a steroid epoxide-hydratase assay and properties of the enzyme.
1979
A highly sensitive and rapid radiometric assay for the determination of specific epoxide hydratase activity with a steroid epoxide (16α, 17α-epoxy-1,3,5(10)-estratrien-3-ol, ‘estroxide’) has been developed. The unreacted substrate was separated from the product 1,3,5(10)-estratrien-3,16β,17α-triol by extraction into light petroleum. The product was then extracted into ethyl acetate and measured by scintillation spectrometry. Radiochromatography established that after subtraction of the blank the entire radioactivity measured in the ethyl acetate phase resulted from the product 1,3,5(10)-estratrien-3,16,17-triol, whilst high performance liquid chromatography with the four possible isomers of…
Some substrates and inhibitors of cytosolic epoxide hydrolase induce sister-chromatid exchanges in mammalian cells, but do not induce gene mutations …
1993
Abstract Trans -stilbene oxide, trans -β-methylstyrene, 7,8-oxide, trans -β-ethylstyrene, 7,8-oxide, trans -β-propylstyrene 7,8-oxide and 4-fluorochalcone oxide were investigated for genotoxic activity in bacterial and mammalian cells, in the absence of external xenobiotic-metabolising systems. All compounds strongly enhanced the frequency of sister-chromatid exchanges (SCE) in cultured human lymphocytes. None of them was mutagenic in Salmonella typhimurium (reversion of the his − strains TA98, TA100 and TA104). The limit of detection was 1 20,000 to 1 10 6 of the activity of the positive control, benzo[ a ]pyrene 4,5-oxide, depending on the compound and the bacterial strain. Trans -β-methy…
Epoxide Hydratase: Purification to Apparent Homogeneity as a Specific Probe for the Relative Importance of Epoxides among Other Reactive Metabolites
1977
Aromatic and olefinic compounds can be metabolized by microsomal monooxygenases to epoxides which chemically represent electrophilic species (for reviews, see refs. 1–5). Spontaneous binding of such epoxides to DNA, RNA, and protein has been observed (6–10). Accordingly, such metabolites have been suggested and, in some instances, shown to disturb the normal functions of cells, leading to such effects as mutagenesis (11–14), malignant transformation (15–19), or cell necrosis (20). However, aromatic and olefinic compounds are biotransformed to a vast array of metabolites (cf. refs. 21–27), possibly including a considerable number of reactive metabolites other than epoxides. The relative impo…
Radioactively labelled epoxides. Part IV. Tritium labelled α- and β-methyl styrene oxides
1983
Tritium labelled α-methyl styrene oxide (2-methyl-2-phenyloxirane) and cis- and trans-β-methyl styrene oxides (Z- and E-2-methyl-3-phenyl oxirane) have been prepared using tritiated water as the inexpensive source of tritium. The two geometrical isomers of β-methyl styrene oxide were synthesized by a sequence of reactions which led to stereochemically pure products, and obviated any need to separate the isomers.
Epoxidation of Olefins with a Silica-Supported Peracid
2012
Anhydrous [2-percarboxyethyl] functionalized silica (2a) is an advantageous oxidant for performing the epoxidation of olefins 1. Epoxides 3 do not undergo the ring-opening reactions catalyzed by the acidic silica surface, except for particularly activated cases such as styrene oxide. The hydrophilic and acidic character of the silica surface does not interfere with the directing effects exerted by allylic H-bond acceptor substituents. The alkenes 1 carrying hydroxyl groups react with silica-supported peracid 2a faster than unsubstituted alkenes, thus reversing the trend known for reactions with soluble peracids. These results are attributed to the H-bond interactions of substrate 1 with the…
ISOLATION OF RAT LIVER EPOXIDE HYDRATASE: PROPERTIES AND SUBSTRATE SPECIFICITY OF THE PURE ENZYME
1977
ABSTRACT The microsomal enzyme epoxide hydratase has been purified to homogeneity as judged by electrophoretical, ultracentrifugal and immunological criteria and by C- and N-terminal analysis. The preparation procedure consisted of solubilisation using the non-ionic detergent cutscum, (NH4)2SO4 precipitation, ion-exchange chromatography on DEAE-cellulose and cellulose phosphate and hydrophobic chromatography on butyl-sepharose. The product was detergent-free, had a relatively high content of hydrophobic amino acids and tended to aggregate in aqueous solutions. The protein had a minimum molecular weight of 49,000 ± 500 with a sedimentation coefficient of S20w≃ 3. Antibodies raised against th…
ChemInform Abstract: Epoxidation of Olefins with a Silica-Supported Peracid.
2012
Anhydrous [2-percarboxyethyl] functionalized silica (2a) is an advantageous oxidant for performing the epoxidation of olefins 1. Epoxides 3 do not undergo the ring-opening reactions catalyzed by the acidic silica surface, except for particularly activated cases such as styrene oxide. The hydrophilic and acidic character of the silica surface does not interfere with the directing effects exerted by allylic H-bond acceptor substituents. The alkenes 1 carrying hydroxyl groups react with silica-supported peracid 2a faster than unsubstituted alkenes, thus reversing the trend known for reactions with soluble peracids. These results are attributed to the H-bond interactions of substrate 1 with the…
Endogenous Role of Microsomal Epoxide Hydrolase
2005
The specific activities of microsomal epoxide hydrolase with 16α,17α-epoxyandrosten-3-one (androstene oxide) as substrate were measured in various metabolically important and in various steroidogenic organs of the male and female rat and compared with the activities of 16α,17α-epoxyestratrienol (estroxide) and benzo[a]pyrene 4,5-oxide. Androstene oxide was an exceptionally good substrate. The specific activities differed widely between organs but the ratio of the activities towards these substrates was constant in all organs investigated. The ratios compared to benzo[a]pyrene 4,5-oxide were 2.5 for estroxide, and 8.6 for androstene oxide. The ontogenetic development of specific epoxide hydr…