Earlier studies ... demonstrated that benz[a]anthracene (BA), 7-methylbenz[a]anthracene (7-MBA) and 12-methylbenz[a]anthracene (12-MBA) undergo a bio-alkylation substitution reaction in the meso-anthracenic position(s) or L-region leading to the biosynthesis of the potent carcinogen 7,12-dimethylbenz[a]anthracene (7,12-DMBA). These results support the hypothesis that for most, if not all, unsubstituted polycyclic aromatic hydrocarbon carcinogens, the chemical or biochemical introduction of an alkyl group in the meso-anthracenic position(s) or L-region is a structural requirement for strong carcinogenic activity. Here we report that the L-region methyl derivatives 7-MBA, 12-MBA and 7,12-DMBA are oxidized to hydroxymethyl derivatives by a rat liver cytosol preparation without any apparent oxidation of the ring positions.
The homogeneous 3 alpha-hydroxysteroid-dihydrodiol dehydrogenase of rat liver cytosol catalyzes the NADP-dependent oxidation of a wide variety of polycyclic aromatic trans-dihydrodiols and has been implicated in their detoxification. This study examined the influence of methyl groups on the velocity and stereochemical course of enzymatic benz(a)anthracene (BA) trans-dihydrodiol oxidation. The racemic trans-3,4-dihydrodiols of BA and 7-methylbenz(a)anthracene (7-MBA) were completely consumed by the purified dehydrogenase, indicating that both stereoisomers are substrates. However, 50% of the ( +/- )-trans-3,4-dihydrodiols of 12-methylbenz(a)anthracene (12-MBA) and 7,12-dimethylbenz(a)-anthracene (DMBA) were oxidized, suggesting that only one stereoisomer is utilized in each case. At low substrate concentrations, enzymatic oxidation of the trans-3,4-dihydrodiols of BA, 12-MBA, and DMBA followed simple first-order kinetics. By contrast, oxidation of the 3,4-dihydrodiol of 7-MBA was of higher order, due to differences in the rate of oxidation of each stereoisomer. Rate constants estimated for each reaction indicate that the non-bay-region methyl group at position 7 has a greater enhancing effect on the rate of oxidation than the bay-region methyl group at position 12 (10- versus 4-fold, respectively). The 3,4-dihydrodiol of DMBA, which possesses both non-bay- and bay-region methyl groups, is oxidized more than 30 times faster than the unmethylated parent hydrocarbon. The absolute stereochemistry of the preferentially oxidized dihydrodiols was assigned by circular dichroism spectrometry. For the 3,4-dihydrodiols of DMBA and 12-MBA, the stereoisomer oxidized has the 3S,4S configuration. A large negative Cotton effect was observed in the circular dichroism spectrum of the 7-MBA 3,4-dihydrodiol which remained at the end of the rapid phase of oxidation of this racemic substrate, indicating that the dehydrogenase displays partial stereochemical preference for the 3S,4S enantiomer. These results suggest that methylation of BA at C-7 greatly enhances the oxidation of the 3S,4S-dihydrodiol, while the presence of a bay-region methyl group at C-12 completely blocks the oxidation of the 3R,4R-stereoisomer. Rapid, stereoselective oxidation of methylated polycyclic aromatic trans-dihydrodiols by this route in vivo may significantly influence their carcinogenicity.
Yields trans-5,6-dihydro-5,6-dihydroxy-12-methylbenzanthracene in rat; yields trans-8,9-dihydro-8,9-dihydroxy-12-methylbenzanthracene, S-(5,6-dihydro-6-hydroxy-12-methylbenzanthr-5-yl)glutathione, and 3-hydroxy-12-methylbenzanthracene probably in rat. /From table/
IDENTIFICATION AND USE: 12-Methylbenz(a)anthracene (12-MBA) is a solid. It can be formed from incomplete combustion of organic materials. It is used mostly for biochemical research. HUMAN EXPOSURE AND TOXICITY: There are no data available. ANIMAL STUDIES: Mice received sc administration of 12-MBA, 100 ug three times a week for 12 months. 17% of mice developed mammary tumors. In the classical two-stage initiation-promotion experiment, 12-MBA was causing 1.0 papillomas/mouse. Dihydrodiol dehydrogenase decreased the mutagenicity of the 12-MBA tested in Salmonella typhimurium TA 100 with metabolic activation. There appeared to be little quantitative correspondence between carcinogenic and mutagenic potency for this group of chemicals.
Immediate First Aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand-valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR if necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Aromatic hydrocarbons and related compounds/
Basic treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary. ... For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 mL/kg up to 200 L of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool. Administer activated charcoal ... . /Aromatic hydrocarbons and related compounds/
Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag-valve-mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Consider administering a beta agonist such as albuterol for severe bronchospasm ... . Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start IV administration of D5W TKO /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's (LR) if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... . Treat seizures with diazepam (Valium) or lorazepam (Ativan) ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Aromatics hydrocarbons and related compounds/
/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ /Mice received sc administration of 12-methylbenz(a)anthracene, 100 ug three times a week for 12 months. 17% of mice developed mammary tumors./ /From table/
Substituent Effects in Benz[<i>a</i>]anthracene Carbocations: A Stable Ion, Electrophilic Substitution (Nitration, Bromination), and DFT Study
作者:Kenneth K. Laali、Maria A. Arrica、Takao Okazaki、Ronald G. Harvey
DOI:10.1021/jo070936r
日期:2007.8.31
computed relative energies by DFT. Charge delocalization paths in the resulting carbocations were deduced based on the magnitude of Δδ13C values. For the thermodynamically more stable C-12 protonated carbocations, the charge delocalization path is analogous to those derived based on computed NPA charges for the benzylic carbocations formed by 1,2-epoxide (bay-region) and 5,6-epoxide (K-region) ring opening
在FSO 3 H / SO 2 ClF中通过低温质子化作用,由异构的单烷基化和二烷基化的苯并[ a ]蒽(BAs)生成了一系列新型的碳正离子化反应。C-7具有单烷基衍生物(5-甲基,6-甲基,7-甲基和7-乙基)以及D环甲基化类似物(9-甲基,10-甲基和11-甲基),或在所有情况下均观察到C-12质子化的碳正离子(作为唯一或主要的碳正离子)。12-甲基衍生物的质子化(9)得到C-7质子化的碳正离子(9H +)作为动能种类和本位-protonated碳阳离子(9AH +)作为热力学阳离子。与12-乙基衍生物(10),在箱式区域空间张力的浮雕大大有利于本位-protonation(10AH +)。具有3,9-二甲基(14),C-7质子化(14H +)(C-12质子化<10%)受到强烈青睐,在1,12-二甲基(15)的情况下,观察到的唯一物质是C-7质子化的碳正离子化(15H +)。对于7-甲
Influence of diet on development and oviposition of <i>Forficula auricularia</i> (Dermaptera: Forficulidae)
In North America, the life cycle of the European earwig (Forficula auricularia L.) can be divided into a nesting phase (hypogean phase) and a free-foraging phase (epigean phase) (Crumb et al. 1941; Behura 1956; Lamb and Wellington 1975). Adults spend the nesting phase in the soil; females burrow into the ground at the onset of the cold weather, lay eggs, and then care for the eggs. Hatching occurs in spring; first- or second-instar nymphs move to the soil surface for the free-foraging period. The earwig, a nocturnal insect, spends the entire daylight period of hiding under trash or in dark crevices. Where two broods occur, females reenter the ground a second time (Lamb and Wellington 1975). Stomach content analyses (Crumb et al. 1941; Sunderland and Vickerman 1980) and food preference tests (McLeod and Chant 1952; Buxton and Madge 1976) revealed that the European earwig is omnivorous. Under laboratory conditions, nymphs fed freshly frozen aphids, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), survive better than those fed green algae or carrots, develop faster, and produce heavier females (Phillips 1981; Carrillo 1985).
Synthesis of Phenol and Quinone Metabolites of Benzo[<i>a</i>]pyrene, a Carcinogenic Component of Tobacco Smoke Implicated in Lung Cancer
作者:Daiwang Xu、Trevor M. Penning、Ian A. Blair、Ronald G. Harvey
DOI:10.1021/jo801864m
日期:2009.1.16
12-BP phenols and the BP 1,6-, 3,6-, 6,12-, and 9,10-quinones are now reported. The syntheses of the BP phenols (except 6-HO-BP) involve the key steps of Pd-catalyzed Suzuki−Miyaura cross-coupling of a naphthalene boronate ester with a substituted aryl bromide or triflate ester. The BP quinones were synthesized from the corresponding BP phenols by direct oxidation with the hypervalentiodine reagents
多环芳烃(PAH)是有机物燃烧时产生的广泛环境污染物。 PAHs存在于汽车尾气和烟草烟雾中,最近被指定为人类致癌物。目前的证据表明,PAH 被酶促激活,产生与 DNA 相互作用的诱变代谢物。有证据表明存在三种激活途径:二醇环氧化物途径、自由基-阳离子途径和醌途径。这些途径对人类肺癌的相对重要性尚未确定。我们现在报道了原型 PAH 致癌物苯并[ a ]芘 (BP) 的主要苯酚和醌异构体的合成,已知或怀疑这些异构体是人支气管肺泡细胞中 BP 的代谢产物。合成方法被设计为适用于BP代谢物的13 C标记类似物的制备。这些化合物需要作为敏感 LC−MS/MS 方法的标准品,用于分析肺细胞中形成的 BP 代谢物。目前已报道了 1-、3-、6-、9- 和 12-BP 苯酚以及 BP 1,6-、3,6-、6,12- 和 9,10-醌的高效新型合成方法。 BP 苯酚(6-HO-BP 除外)的合成涉及萘硼酸酯与取代的芳基溴或三氟甲磺酸酯的
Synthesis of 9,10-Dimethyl-1,2-benzanthracene and of a Thiophene Isolog
作者:Reuben B. Sandin、Louis F. Fieser
DOI:10.1021/ja01868a055
日期:1940.11
Coördination of Polycyclic Aromatic Hydrocarbons with Silver Ion; Correlation of Equilibrium Constants with Relative Carcinogenic Potencies<sup>1</sup>