Trihalomethanes (haloforms) were metabolized to carbon monoxide by a rat liver microsomal fraction requiring both NADPH and molecular oxygen for maximal activity. GSH alone did not serve as a cofactor; however, GSH in the presence of NADPH and oxygen produced an 8-fold increase in the metabolism of bromoform to CO. Similar results were obtained with other sulfhydryl compounds. The biotransformation of bromoform to CO was characterized with respect to time course, microsomal protein concentration, pH and temperature. The metabolism of haloforms to CO followed the halide order; thus, iodoform yielded the greatest amount of CO, whereas chloroform yielded the smallest amount. A KM of 6.78 +/- 2.71 mM was established for bromoform and the Vmax was 1.09 +/- 0.19 nmol of CO per mg of microsomal protein per min. The energy of activation for this reaction was 6.5 +/- 0.18 kcal/mol. Cytochrome P-450 was found to bind bromoform to produce a type I binding spectrum. Treatment of rats with phenobarbital or 3-methylcholanthrene increased the rate of conversion of bromoform to CO. Cobaltous chloride treatment of rats or storage of microsomal preparations at 4 degrees C reduced the rate of formation of CO from bromoform. SKF 525-A inhibited the conversion of bromoform to CO. These results suggest that haloforms are metabolized to CO via a cytochrome P-450-dependent mixed-function oxidase system.
Admin to rats of (13)C-bromoform led to formation of enriched (13)C monoxide a dose-dependent relationship between bromoform dose and carbon monoxide production was observed.
Bromine is mainly absorbed via inhalation, but may also enter the body through dermal contact. Bromine salts can be ingested. Due to its reactivity, bromine quickly forms bromide and may be deposited in the tissues, displacing other halogens. (L626)
IDENTIFICATION AND USE: Bromoform is a colorless heavy liquid. It is used as intermediate in organic synthesis, geological assaying, solvent for waxes, greases, and oils. It is also used in hair treatment formulations. Bromoform was formerly used as an antiseptic and sedative. HUMAN STUDIES: Accidental ingestion of the liquid has produced central nervous system depression with coma and loss of reflexes; smaller doses have led to listlessness, headache, and vertigo. Exposure to bromoform vapor caused irritation of the respiratory tract, pharynx, and larynx, as well as lacrimation and salivation. Several cases of poisoning have occurred in children; some have had maximally constricted pupils, but others have had mydriasis, probably related to depth of depression of CNS. Bromoform induced sister chromatid exchanges and cell-cycle delays in human lymphocytes in vitro. ANIMAL STUDIES: Undiluted bromoform was moderately irritating to rabbit eyes, and healing was complete in 1 to 2 days. Repeated skin contact caused moderate irritation to rabbit skin. Inhalation of very high concentrations (56,000 or 84,000 ppm) of bromoform vapor for 1 hour has been reported to cause death in dogs. The chief symptoms noted were initial excitation followed by deep sedation. This indicates that central nervous system depression is probably the chief cause of death in such acute exposures. A single ip dose of 3 mmol/kg bw given to rats has also been shown to produce renal dysfunction, characterized by a reduction in glomerular filtration rate, reduced renal concentrating ability and elevated blood urea nitrogen levels. Following administration of bromoform by gavage to mice, changes included fatty infiltration of liver and signs of hemorrhage in kidneys, adrenals, lung, and brain. Males were more sensitive than females. In mice, bromoform has been observed to produce tubular hyperplasia and glomerular degeneration after an oral dose of 289 mg/kg bw daily for 14 days. No significant alterations in the number of resorption sites, fetuses per litter, fetal body weights, fetal malformations or visceral anomalies were observed in the offspring of rats administered up to 200 mg/kg/day bromoform in corn oil by oral gavage on gestational days 6-15. NTP studies demonstrated carcinogenic activity of bromoform in male and female rats but not in male or female mice. Bromoform exhibited mutagenicity in Salmonella typhimurium strain TA100 in the absence of metabolic activation and in strains TA97 and TA98 when exposure occurred in the presence of metabolic activation. Bromoform produced no increases in revertant colonies in TA1535 or TA1537 with or without metabolic activation. When tested in cultured Chinese hamster ovary cells for cytogenetic effects, bromoform produced an increase in both sister chromatid exchanges and chromosomal aberrations in the absence, but not in the presence of metabolic activation. ECOTOXICITY STUDIES: Bromoform, chloroform, and tetrachloroethylene act synergistically to alter a key regulator of neuronal development in surf clam embryo.
Bromine is a powerful oxidizing agent and is able to release oxygen free radicals from the water in mucous membranes. These free radicals are also potent oxidizers and produce tissue damage. In additon, the formation of hydrobromic and bromic acids will result in secondary irritation. The bromide ion is also known to affect the central nervous system, causing bromism. This is believed to be a result of bromide ions substituting for chloride ions in the in actions of neurotransmitters and transport systems, thus affecting numerous synaptic processes. (L626, L627, A543)
Evaluation: No epidemiological data relevant to the carcinogenicity of bromoform were available. There is limited evidence in experimental animals for the carcinogenicity of bromoform. Overall evaluation: Bromoform is not classifiable as to its carcinogenicity to humans (Group 3).
CLASSIFICATION: B2; probable human carcinogen. BASIS FOR CLASSIFICATION: Based on inadequate human carcinogen data and sufficient evidence of carcinogenicity in animals, namely an increased incidence of tumors after oral administration of bromoform in rats and intraperitoneal administration in mice. Bromoform is genotoxic in several assay systems. Also bromoform is structurally related to other trihalomethanes (e.g., chloroform, bromodichloromethane, dibromochloromethane) which have been verified as either probable or possible carcinogens. HUMAN CARCINOGENICITY DATA: Inadequate. ANIMAL CARCINOGENICITY DATA: Sufficient. /Based on former classification system/
来源:Hazardous Substances Data Bank (HSDB)
毒理性
致癌性证据
A3; 对人类相关性未知的动物致癌物。
A3; Animal carcinogen with unknown relevance to humans.
Bromoform may be absorbed through the lungs, from the gastrointestinal tract, and, to a certain extent, through the skin. The brain contains higher concentrations of bromoform than blood and liver following inhalation.
... Bromoform ... labeled with (14)C was administered by intragastric intubation to male Sprague-Dawley rats and male B6C3F1 mice. After 36 or 48 hr, necropsies were performed. Blood, bladder, brain, kidneys, liver, lung, skeletal muscle, pancreas, stomach, and thymus were studied. The total radioactivity for sampled organs ranged from 3 to 6% of the total dose in the rats versus 5 to 14% for the mice. In both species, the urine contained less than 5% of total radiolabel at 8 hr post intubation and less than 10% of the total radiolabel at 36 to 48 hr. ... (14)C activity was found in the blood following bromoform dosing. Mice metabolize /bromoform/ to a greater extent than rats.
Trihalomethanes (THMs; chloroform, bromoform, bromodichloromethane, dibromochloromethane), formed as by-products of chlorine disinfection, are found to occur in combination in drinking water supplies. THMs are metabolized by cytochromes P-450 and are likely substrates of CYP2E1. Therefore, it is possible that mixed exposure results in toxicokinetic interactions among THMs. The toxicokinetics of THMs during mixed exposures has not been investigated previously. The purpose of this study was to characterize the blood kinetics of the four THMs administered singly or in combination in the rat. A single dose of 0.25 mmol/kg or 0.5 mmol/kg bw, of each THM alone, or of a quaternary mixture containing 0.25 mmol/kg of each THM (total dose of 1.0 mmol/kg) was administered by gavage. The venous blood concentrations of the THMs were measured by headspace gas chromatography (GC) at 20, 40, 60, 120, 180, 270 and 360 min post-administration. Results showed a nonlinear relationship between the area under the blood concentration versus time curves (AUCs) and administered doses of THMs, suggesting that metabolism is saturated in this dose range. The venous blood concentrations of THMs following administration of the quaternary mixture were significantly higher compared to single exposures. The altered kinetics of THMs during combined exposures is consistent with the occurrence of mutual inhibition of their hepatic metabolism...
来源:Hazardous Substances Data Bank (HSDB)
吸收、分配和排泄
在氯化的饮用水中沐浴会导致人们接触到潜在的有毒消毒副产物(DBPs)...当前的研究...测量了三种重要类别的DBPs——三卤甲烷(THMs)、卤代酮(HKs)和卤代乙酸(HAAs)——在体外扩散室中通过人类皮肤的渗透系数(K(p))。使用线性混合效应模型来计算稳态渗透系数。当供体溶液温度为25摄氏度时,THMs的渗透系数范围从0.16到0.21厘米/小时。溴仿具有最高的K(p)值,而氯仿通过皮肤的渗透性最低。THMs的渗透性大约是HKs的10倍,而HAAs通过皮肤的渗透性非常低(1到3 x 10^-3厘米/小时,pH 7)。当温度从室温(20摄氏度)升高到沐浴温度(40摄氏度)时,HKs的渗透性增加了三倍。发现了THMs的渗透性与它们的辛醇/水分配系数之间存在直接关系,但HKs和HAAs则没有。使用美国环保局推荐的方法估算了一个平均成人每天沐浴活动的皮肤剂量,发现对于THMs来说,这一剂量是每日摄入剂量的40-70%,对于HKs来说是摄入剂量的10%,而对于HAAs来说则是摄入剂量的一个微不足道的百分比。除了摄入之外,皮肤吸收也是接触THMs和HKs的一个重要途径...。
Bathing in chlorinated drinking water causes significant exposure to potentially toxic disinfection by-products (DBPs). ...The present studies ... measured the permeation coefficients (K(p)) of three important classes of DBPs, trihalomethanes (THMs), haloketones (HKs), and haloacetic acids (HAAs), in aqueous solution across human skin using in vitro diffusion chambers. Linear mixed-effects model was utilized to calculate the steady-state permeability coefficients. The permeability coefficients of THMs ranged from 0.16 to 0.21 cm/hr when the donor solution was at 25 degrees C. Bromoform had the highest K(p) value, while chloroform was the least permeable through the skin. THMs were approximately 10 times more permeable than HKs, while the permeability of HAAs through the skin was very low (1 to 3 x 10-3 cm/hr, pH 7). The permeability of HKs tripled as the temperature was increased from room temperature (20 degrees C) to bathing temperature (40 degrees C). A direct relationship was found between the permeability of THMs, but not HKs and HAAs, and their octanol/water partition coefficients. The dermal dose from daily bathing activities was approximated for an average adult using U.S. EPA recommended methods and found to be 40-70% of the daily ingestion dose for the THMs, 10% of the ingestion dose for HKs, and an insignificant percentage of the ingestion dose for the HAAs. In addition to ingestion, dermal absorption is an important route of exposure to THMs and HKs ... .
Electrocchemicai oxidatiob of ketones in methanol in the presence of alkali metal bromides
摘要:
Electrochemical oxidation of methyl ketones in methanol in the presence of alkali metal bromides affords methyl carboxylates. Benzyl alkyl ketones are transformed under similar conditions into methyl 3-phenylalkanoates, while ketones lacking alpha-benzyl or alpha-methyl group are oxidized into alpha-hydroxyketals.
An enantioselective alkoxycarbonylation-amination cascade process of terminalallenes with CO, methanol, and arylamines has been developed. It proceeds under mild conditions (room temperature, ambient pressure CO) via oxidative Pd(II) catalysis using an aromatic spiroketal-based diphosphine (SKP) as a chiral ligand and a Cu(II) salt as an oxidant and affords a wide range of α-methylene-β-arylamino
Palladium-Catalyzed Oxidative Carbonylative Coupling of Arylallenes, Arylboronic Acids, and Nitroarenes
作者:Hui-Qing Geng、Jin-Bao Peng、Xiao-Feng Wu
DOI:10.1021/acs.orglett.9b02925
日期:2019.10.18
In this Letter, a palladium-catalyzed multicomponent procedure for the selective synthesis of α-substituted α,β-unsaturated ketones has been developed. With readily available allenes, arylboronicacids, and nitroarenes as the substrates, the reaction proceeds selectively to the desired α-substituted enones. Notably, no manipulation of carbon monoxide gas is needed here, and Mo(CO)6 has been applied
Diboration of 3-substituted propargylic alcohols using a bimetallic catalyst system: access to (<i>Z</i>)-allyl, vinyldiboronates
作者:Cheryl L. Peck、Jan Nekvinda、Webster L. Santos
DOI:10.1039/d0cc03563g
日期:——
A Pd/Cu catalyst system facilitates the diboration of unactivated propargylic alcohols with pentafluoroboronic acid and diboron to generate (Z)-allyl, vinyldiboronates.
A RhIII‐catalyzed intramolecularoxidative cross‐coupling between double bonds for the synthesis of macrolides is described. Under the optimized reaction conditions, macrocycles containing a diene moiety can be formed in reasonable yields and with excellent chemo‐ and stereoselectivity. This method provides an efficient approach to synthesize macrocyclic compounds containing a 1,3‐conjugated diene
Copper-Catalyzed Difunctionalization of Allenes with Sulfonyl Iodides Leading to (<i>E</i>)-α-Iodomethyl Vinylsulfones
作者:Ning Lu、Zhiguo Zhang、Nana Ma、Conghui Wu、Guisheng Zhang、Qingfeng Liu、Tongxin Liu
DOI:10.1021/acs.orglett.8b01765
日期:2018.7.20
A highly regioselective iodosulfonylation of allenes in the presence of CuI and 1,10-phenanthroline has been developed for the synthesis of various useful (E)-α-iodomethyl vinylsulfones in moderate to excellent yields. This practical reaction is fast, operationally simple, and in particular, proceeds under very mild conditions to afford the target products with high regio- and stereoselectivity. The