Chemistry of Essential Oils
K. Hüsnü Can Başer, Gerhard Buchbauer in Handbook of Essential Oils, 2020
Production of shikimates from petrochemicals for commercial use mostly involves straightforward chemistry (Arctander, 1969; Däniker, 1987; Bauer and Panten, 2006; Sell, 2006). Nowadays, the major starting materials are benzene (180) and toluene (181), which are both available in bulk from petroleum fractions. Alkylation of benzene with propylene gives cumene (182), the hydroperoxide of which fragments to give phenol (183) and acetone. Phenol itself is an important molecular building block and further oxidation gives catechol (184). Syntheses using these last two materials will be discussed in the succeeding text. Alkylation of benzene with ethylene gives ethylbenzene, which is converted to styrene (185) via autoxidation, reduction, and elimination in a process known as styrene monomer/propylene oxide (SMPO) process. The epoxide (186) of styrene serves as an intermediate for 2-phenylethanol (47) and phenylacetaldehyde (187), both of which occur widely in essential oils. 2-Phenylethanol is also available directly from benzene by Lewis acid–catalyzed addition of ethylene oxide and as a by-product of the SMPO process. Currently, the volume available from the SMPO process provides most of the requirement. All of these processes are illustrated in Figure 6.31.
Properties, Occurrences, and Emissions
Muzaffer Aksoy in Benzene Carcinogenicity, 2017
Although benzene had been commercially recovered from both coal and petroleum sources in former days (benzene is a natural constituent of crude oil5), the current production of benzene is almost exclusively based on petroleum. For example, about 91% of benzene production in Japan in 19846 and 92% of that in the U.S. in 19787 were from petroleum. It is primarily used as a raw material for production of various chemicals including cyclohexane, cumene, ethylbenzene, styrene, nitrobenzene, maleic anhydride, chlorinated benzenes, etc.8 Its application as an organic solvent is very limited. For instance, as early as 1967 in Japan, the amount of benzene used as solvent was already less than 1% of the produced amount.9 A nationwide survey in Japan on solvent-containing products such as paints, thinners, inks, and adhesives disclosed that benzene was seldomly detected among over 1000 samples collected from factories.10,11
Cross Talk Between Heat Shock and Oxidative Stress Inducible Genes During Myocardial Adaptation to Ischemia
John J. Lemasters, Constance Oliver in Cell Biology of Trauma, 2020
Superoxide dismutase activity was assayed by its inhibitory action on the superoxide-dependent reduction of ferricytochrome by xanthine-xanthine oxidase.35 The final concentrations in the assay medium (total volume 1 ml) were these: 100 μM cytochrome c, 100 μM hypoxanthine, 10 mM Tris-HCl, and 50 to 80 μg of enzyme protein. The reaction was initiated by addition of 8 mU of xanthine oxidase. Catalase was estimated by measuring the decreases in the absorbance of H2O2 at 240 nm. The final concentrations in the assay medium (total volume 1 ml) were these: 35 mM phosphate buffer, pH 7.2,0.02% Triton X-100, and 30-50 μg of enzyme protein. The reaction was started by the addition of 30 μl of 1 % H2O2 and monitored by the decrease in absorbance of H2O2 at 240 nm. Glutathione peroxidase was estimated by measuring the decrease in absorbance of NADPH at 340 nm. The final concentrations in the assay medium (total volume 1 ml) were these: 62 mM Tris-HCl, pH 7.6, 0.2 mM NADPH, 0.1 mM EDTA, 0.5 mM GSH, and 1 U/ml GSSG-reductase. The reaction was initiated by adding 100 μl 2 mM cumene hydroperoxide. Glutathione reductase activity was estimated by measuring the decrease in absorbance of NADPH at 340 nm. The final concentrations in the assay buffer (1 ml total volume) were these: 90 mM Tris-HCl, pH 7.8, 0.8 mM EDTA, 0.2 mM NADPH, and the decrease in OD was followed at 340 nm for 10 min.
Tandem repeated irritation test (TRIT) studies and clinical relevance: Post 2006
Published in Cutaneous and Ocular Toxicology, 2019
Schliemann et al. investigated the tandem effects of two undiluted organic solvents (octane and cumene) and SLS, a common amphiphilic detergent irritant.12 They used the classical TRIT and measured outcomes of visual scoring, skin color reflectance (chromameter), skin hydration, and TEWL. Individually, n-octane was the more powerful irritant compared to cumene. However, the combined exposure to both organic solvents resulted in increased irritation and erythema more than octane, cumene, and SLS did alone.12 The tandem effect did not exceed the skin changes and skin barrier impairment induced by repeated application of SLS. These findings contrast with studies others to 2006 that show that tandem application of SLS and another organic solvent, toluene, induces skin barrier impairment and increased skin irritation than repeated application of SLS alone.
Whole-body inhalation exposure to 2-ethyltoluene for two weeks produced nasal lesions in rats and mice
Published in Inhalation Toxicology, 2021
Madelyn C. Huang, Cynthia J. Willson, Sridhar Jaligama, Gregory L. Baker, Alan W. Singer, Yu Cao, Jessica Pierfelice, Esra Mutlu, Brian Burback, Guanhua Xie, David E. Malarkey, Barney Sparrow, Kristen Ryan, Matthew Stout, Georgia K. Roberts
The toxicity of some C9 alkylbenzenes and related isomers is understudied. While inhalation of some C9 alkylbenzenes has been reported to be carcinogenic in rodent studies (cumene and ethylbenzene: NTP 2009, 2013; IARC 2000; NTP 1999) or have reproductive and neurobehavioral effects (trimethyl benzenes: Gralewicz and Wiaderna 2001; Korsak and Rydzyński 1996; EPA 2016b, xylenes: ATSDR 2007), there is little safety data on ethyltoluene (ET) isomers which make up 25–35% of the C9 aromatic fraction of Naphtha (ICCA 2012). The available literature on ethyltoluene isomers is limited to studies of 4-ET. Oral gavage studies of animals with 4-ET show developmental toxicity at doses ≤200 mg/kg and significant changes in liver weight, leukocyte differentials, and clinical pathology at doses ≥100 mg/kg (IRDC 1980, 1981; Borriston 1983; Hazleton 1983). 4-ET was found to cause mild skin and eye irritancy and changes in leukocyte number in bronchiolar lavage with inhalation exposure (Swiercz et al. 2000).
The neuroprotective effects of an ethanolic turmeric (Curcuma longa L.) extract against trimethyltin-induced oxidative stress in rats
Published in Nutritional Neuroscience, 2019
Sapto Yuliani, Ginus Partadiredja
The GPx activity was determined using an assay kit (Cat. K762-100, BioVision) according to the manufacturer’s instructions. Approximately 0.1 g of the brain tissue homogenates dissolved in 0.2 ml cold assay buffer was centrifuged at 10 000 rpm for 15 minutes at 4°C. The supernatant of this mixture was collected and used for the assay. Ten microliters of the supernatants were transferred into 96-well plates. Forty microliters of reaction mix (containing 33 µl of assay buffer, 3 μl of a 40 mM NADPH solution, 2 μl of GR solution and 2 μl of GSH solution) were added to the plates to deplete the GSSG in the samples and this mixture was incubated for 15 minutes. Ten microliters of a cumene hydroperoxide solution were added to the mixture to start the GPx reaction. The GPx activity was measured at a wavelength of 340 nm at 5 and 140 minutes. The NADPH levels were calculated based on a standard curve. The GPx activity was expressed as mU/mg protein.
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