Metabolism of 2-methylnaphthalene in rats (in vivo and in vitro) ... was investigated. Conversion of 2-methylnaphthalene to both monohydroxylated compound and dihydrodiols was decreased by incubation with carbon monoxide, omission of NADPH or use of denatured microsomes, implying involvement of cytochrome(s) p450-linked mixed function oxidase activity. Pretreatment ... with phenobarbital and beta-naphthoflavone selectively altered the rate of formation of specific dihydrodiols by rat liver microsomes. Although phenobarbital had no significant effect on rate of dihydrodiol formation, beta-naphthoflavone was strong inducer.
The NADPH-dependent metabolism of naphthalene and 2-methylnaphthalene to covalently bound metabolites in lung or liver microsomal incubations occurred at easily measurable rates. Renal microsomal NADPH-dependent metabolism of either substrate was not detected. The formation of covalently bound naphthalene or 2-methylnaphthalene metabolites was dependent upon NADPH and was inhibited by the addition of reduced glutathione, piperonyl butoxide, and SKF 525A. Covalent binding of radioactivity from (14)C2-methylnaphthalene also was strongly inhibited by incubation in a nitrogen atmosphere or at 2 degree. The arachidonic acid-dependent formation of reactive metabolites from naphthalene or 2-methylnaphthalene was undetectable in microsomal incubations from lung, liver or kidney. Indomethacin, 1 hr before and 6 hr after the administration of 300 mg/kg naphthalene or 2-methylnaphthalene, failed to block the pulmonary bronchiolar injury induced by these aromatic hydrocarbons. These studies suggest that the major enzymes involved in the metabolic activation of naphthalene or 2-methylnaphthalene in vitro are the cytochrome P-450 monooxygenases and that cooxidative metabolism by the prostaglandin synthetases appears to play little role in the formation of reactive metabolites in vitro.
PAH metabolism occurs in all tissues, usually by cytochrome P-450 and its associated enzymes. PAHs are metabolized into reactive intermediates, which include epoxide intermediates, dihydrodiols, phenols, quinones, and their various combinations. The phenols, quinones, and dihydrodiols can all be conjugated to glucuronides and sulfate esters; the quinones also form glutathione conjugates. (L10)
IDENTIFICATION AND USE: 2-Methylnaphthalene is a solid. It is used in organic synthesis; insecticides, pesticide adjuvant. It is also used as dye carrier. Pure 2-methylnaphthalene is used primarily as a raw material for the production of vitamin K preparations. HUMAN EXPOSURE AND TOXICITY: In contrast to naphthalene, the only reported effects of methylated naphthalene in man are skin irritation and skin photosensitization. It is not a human carcinogen. Chromosome analyses were carried out in human lymphocytes treated in vitro with 2-methylnaphthalene in the presence and absence of the mammalian metabolic activation system. Without metabolic activation there was no indication of induction of any significant cytogenetic effect by either compound. With metabolic activation a weak clastogenic effect was apparent at 4 mM 2-methylnaphthalene and sister-chromatid exchange frequencies were significantly increased at each dose of 2-methylnaphthale, yet always less than twice the control level. The present observations do not indicate that 2-methylnaphthalene must be classified as potential genotoxic substance. ANIMAL STUDIES: 2-Methylnaphthalene is an eye and skin irritant in rabbits. Single doses of 0 or 300 mg/kg 2-methylnaphthalene were administered to male mice by intraperitoneal injection, with sacrifice 24 hours later. Histological examinations identified bronchiolar necrosis in all treated animals, and no lesions among controls. 2-methylnaphthalene produced depression of the respiratory rate in rats under acute inhalation exposure. In mice treated by i.p. injection naphthalene and 2-methylnaphthalene were about equally toxic. In all cases the first evidence of cytotoxic effects was seen in the Clara cells of the bronchiolar epithelium, and, at the highest doses, toxic effects were found in the adjacent ciliated cells. Changes could be detected at the ultrastructural level at all doses, and within 6 hours after treatment. Only slight effects were seen in other cell types. Other studies demonstrated that a pulmonary toxic dose of 2-methylnaphtalene (400 mg/kg, i.p.) administered to mice significantly depleted reduced GSH in the liver and lung and to a lesser extent, in the kidney. Carcinogenicity studies in mice indicated that 2-methylnaphthalene induces pulmonary alveolar proteinosis but does not possess unequivocal carcinogenic potential in mice. 2-Methylnaphthalene was tested quantitatively using S. typhimurium TA98 and TA100 with and without metabolic activation, the concentration used was 3 umol/plate. 2-Methylnaphthalene was not mutagenic. ECOTOXICITY STUDIES: 2-Methylnaphthalene was toxic to Dungeness crab (C magister) larvae LC50 5 mg/L at 48 hr, LC50 1.3 mg/L at 96 hr.
The ability of PAH's to bind to blood proteins such as albumin allows them to be transported throughout the body. Many PAH's induce the expression of cytochrome P450 enzymes, especially CYP1A1, CYP1A2, and CYP1B1, by binding to the aryl hydrocarbon receptor or glycine N-methyltransferase protein. These enzymes metabolize PAH's into their toxic intermediates. The reactive metabolites of PAHs (epoxide intermediates, dihydrodiols, phenols, quinones, and their various combinations) covalently bind to DNA and other cellular macromolecules, initiating mutagenesis and carcinogenesis. (L10, L23, A27, A32)
Not directly listed by IARC. 2-Methylnaphthalene is found in coal tar mixtures, and occupational exposures during coal-tar distillation and during paving and roofing with coal-tar pitch are classified as carcinogenic to humans (Group 1). (L135)
PAHs are carcinogens and have been associated with the increased risk of skin, respiratory tract, bladder, stomach, and kidney cancers. They may also cause reproductive effects and depress the immune system. Exposure to large amounts of 2-methylnapthalene may damage or destroy the red blood cells, resulting in hemolytic anemia. (L10, L12)
English sole were exposed to oiled (Alaskan north slope crude oil) sediments over 4 months to assess bioavailability and tissue hydrocarbon distribution kinetics in flatfish. Crude oil was mixed with aromatic hydrocarbon free sediments to a concentration of 700 ug/g dry weight at the beginning of the experiment. During the first month, this concentration decreased to 400 ug/g dry weight, and remained relatively stable during the remainder of the 4 month period. Flatfish accumulated alkane and aromatic hydrocarbons in skin, muscle and liver. 1- and 2-methylnaphthalene was accumulated to greater extent than other aromatic hydrocarbons. Tissue levels decreased with time, after 27 day continuous exposure only liver contained detectable levels.
来源:Hazardous Substances Data Bank (HSDB)
吸收、分配和排泄
在短期和长期接触水溶性(14)C标记的2-甲基萘后,研究了虹鳟鱼组织中(14)C的积累和消除情况。
The accumulation and elimination of (14)C in rainbow trout tissues following short and long term exposures to aqueous (14)C-labeled 2-methylnaphthalene was studied.
... Single intraperitoneal injections of 400 mg/kg (14)C-2-methylnaphthalene /were administered/ to male C57BL/6J mice. Groups of 4 mice were sacrificed at 0.5, 1, 3, 6, 12, or 24 hours after injection for measurement of radioactivity in fat, kidney, liver, and lung. Blood 2-methylnaphthalene concentrations decreased with a reported elimination half-life of 3 hours, indicative of rapid distribution to other tissues or elimination from the body. Peak tissue concentrations of 2-methylnaphthalene equivalents (nmol/mg wet weight) were attained about 1 hour after injection in the liver, 2 hours after injection in the fat, and 4 hours after injection in the kidney and the lung. Peak concentrations were highest in fat (13 nmol/mg), followed by lower concentrations in liver (3.5 nmol/mg), kidney (2.9 nmol/mg), and lung (0.7 nmol/mg). The results demonstrate that 2-methylnaphthalene did not preferentially accumulate in the lung although the lung was the only site of toxicity. Histological examination found that the single 400 mg/kg dose induced bronchiolar necrosis (minimal to prominent sloughing of lining cells in the bronchiolar lumen as revealed by light microscopy) in all exposed mice. No lesions were found in the liver or kidney of exposed mice at any time point. Consistent with the attainment of peak lung tissue concentration at 4 hours after injection, no lesions were evident until 8 hours after injection. The authors also evaluated distribution by measurement of irreversible binding of label from (14)C-2-methylnaphthalene to various tissues over a dose (0, 50, 100, 300, and 500 mg/kg; intraperitoneal injection) and time course (1, 2, 4, 8, 12, and 24 hrs). Maximum irreversible binding of 2-methylnaphthalene metabolites was observed in lung, liver, and kidney tissues at 8 hours post administration. The binding was dose- dependent in all tissues between 50-500 mg/kg and concentrations of bound radioactivity were higher in the liver and kidney than in the lung (the only tissue where lesions were found).
The available animal data indicate that 2-methylnaphthalene is absorbed rapidly following ingestion (approximately 80% within 24 hours). Once absorbed, it is widely distributed among tissues, reaching peak concentrations in less than 6 hours. It is quickly metabolized by the liver, lungs, and other tissues. 2-Methylnaphthalene is rapidly excreted (approximately 70-80% within 48 hours in guinea pigs and 55% in rats), primarily as urinary metabolites.
Iron-catalyzed thioesterification of methylarenes with thiols in water
作者:Liang Wang、Jing Cao、Qun Chen、Ming-yang He
DOI:10.1016/j.tetlet.2014.10.155
日期:2014.12
An iron-catalyzed coupling reaction of methylarenes with thiols leading to thioesters has been developed. The reactions were carried out in water with tert-butyl hydroperoxide (TBHP) as the oxidant and polyoxyethanyl α-tocopheryl sebacate (PTS) as the surfactant. The reaction medium is compatible with a series of functional groups and can be reused.
Synthesis and spectroscopic properties of 1,4-diarylbutenynes
作者:Alois H. A. Tinnemans、Wim H. Laarhoven
DOI:10.1039/p29760001104
日期:——
Several new diarylbutenynes have been synthesized and analyses of the n.m.r. and u.v. spectra are described. For planar trans-isomers a conformational preference was found for 1-(α-naphthyl)- but not for 1-(β-naphthyl)-4-arylbutenynes. This difference is also found between compounds with C-1 attached to the α- or β-position of a larger aryl group.
Nanolayered cobalt–molybdenum sulphides (Co–Mo–S) catalyse borrowing hydrogen C–S bond formation reactions of thiols or H<sub>2</sub>S with alcohols
作者:Iván Sorribes、Avelino Corma
DOI:10.1039/c8sc05782f
日期:——
Nanolayered cobalt–molybdenum sulphide (Co–Mo–S) materials have been established as excellent catalysts for C–S bond construction. These catalysts allow for the preparation of a broad range of thioethers in good to excellent yields from structurally diverse thiols and readily available primary as well as secondary alcohols. Chemoselectivity in the presence of sensitive groups such as double bonds,
Low-Valent Titanium-Mediated Radical Conjugate Addition Using Benzyl Alcohols as Benzyl Radical Sources
作者:Takuya Suga、Shoma Shimazu、Yutaka Ukaji
DOI:10.1021/acs.orglett.8b02305
日期:2018.9.7
A concise method to directly generate benzyl radicals from benzyl alcohol derivatives has been developed. The simple and inexpensive combination of TiCl4(collidine) (collidine = 2,4,6-collidine) and manganese powder afforded a low-valent titanium reagent, which facilitated homolytic cleavage of benzylic C–OH bonds. The application to radicalconjugate addition reactions demonstrated the broad scope
Hypoglycemic 5-phenyl and 5-naphthyl oxazolidine-2,4-diones and the pharmaceutically-acceptable salts thereof; certain 3-acylated derivatives thereof; a method of treating hyperglycemic animals therewith; and intermediates useful in the preparation of said compounds.