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At least 757 records · Page 42Linked to original sources
PubMed1994

In vitro esterification of fatty acids by various alcohols in rats and rabbits.

The ability of six alcohols--1-propanol, 2-propanol, 1-butanol, 1-amyl alcohol, isoamyl alcohol and 1-octanol--to esterify fatty acids in vitro was determined in liver, lung and pancreas from rats and rabbits by incubating tissue homogenates with [14C]oleic acid and isolating and quantifying the esterified fatty acid. There was considerable variation in the amount of esterified fatty acid formed depending upon the alcohol. The relative rates of formation among the tissues were pancreas >> liver > lung. In view of the deleterious effects associated with the esters formed by ethanol, consideration must also be given to these other alcohols as well.

1-Butanol↗
PubMed2005

Influence of esterification and modification of A-ring in a group of lupane acids on their cytotoxicity.

The aim of this work was to find an optimal ester group for preparation of lupane derivatives connecting high cytotoxicity with good chemical and pharmacological properties. Activities of methyl-, pivaloyloxymethyl- (Pom-), and acetoxymethyl- (Acm-) esters were compared with the activity of free acids. Although the methyl- and Pom-esters were generally less active than free acids, some Acm-esters had cytotoxicity similar to or even better than the starting compounds. Cytotoxic activity was measured in five cancer cell lines.

Carboxylic Acids↗
PubMed2005

Surface esterification of cellulose fibers: characterization by DRIFT and contact angle measurements.

The surface chemical modification of microcrystalline cellulose and cellulose fibers obtained from different sugar cane bagasse pulping processes, viz. Kraft, organosolv ethanol/water and organosolv/supercritical carbon dioxide, were studied in heterogeneous conditions using modest amounts of octadecanoyl and dodecanoyl chloride. The ensuing surfaces acquired a non-polar character, suitable for incorporating these fibers as reinforcing agents in composite materials based on polymeric matrices. The success of these chemical modifications was assessed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, elemental analysis, scanning electron microscopy (SEM) and contact angle measurements. In particular, the dynamic and equilibrium contact angle measurements, before and after the treatments, revealed that the value of the polar component (gamma(s)p) of the surface energy had decreased very considerably following the modification.

Cellulose↗
PubMed2003

Preparation of sulfoacetate derivatives of cellulose by direct esterification.

A new and efficient method for the preparation in one step of water-soluble cellulose acetate sulfate derivatives (CAS) is reported. Acetylation and sulfation were carried out simultaneously, using a mixture of acetic anhydride and sulfuric acid in glacial acetic acid. The reaction time and the amount of acetic anhydride were optimized and the method provided water-soluble esters, with a degree of acetylation in the range 1.6 and 2.4 and a degree of sulfation of 0.3. This method has been successfully applied to pure cellulose and to cellulose-enriched materials obtained from agricultural by-products. The product exhibited a high viscosity in aqueous solution suggesting interesting rheological properties.

Acetates↗
PubMed2000

Determination of chlorophenoxy acid herbicides in water by in situ esterification followed by in-vial liquid-liquid extraction combined with large-volume on-column injection and gas chromatography-mass spectrometry.

A new approach for rapidly analysing chlorophenoxy acid herbicides in water is presented. The chlorinated acids are derivatised with dimethyl sulphate in the water sample itself (800 microl) and, next, the methyl esters are extracted with 800 microl of n-hexane. A 200-microl volume of the extract is injected into the GC-MS system. The miniaturisation of both the methylation and extraction steps could be implemented because of the use of large-volume on-column injection and mass spectrometric detection. The optimisation of the methylation reaction for the simultaneous determination of (3,6-dichloro-2-methoxy)benzoic acid, (2-methyl-4-chlorophenoxy)- and (2,4-dichlorophenoxy)acetic acids, (+/-)-2-(4-chloro-2-methylphenoxy)- and 2-(2,4-dichlorophenoxy)propanoic acids and 4-(4-chloro-2-methylphenoxy)- and 4-(2,4-dichlorophenoxy)butyric acids showed that tetrabutylammonium salts act as catalysts. Addition of sodium hydroxide was required to obtain quantitative reaction yields for 4-(4-chloro-2-methylphenoxy)- and 4-(2,4-dichlorophenoxy)butyric acids. The methylation-cum-extraction procedure takes only 3 min per sample for a batch of seven samples. Linear calibration plots were obtained for the complete procedure and the limits of detection were of 10-60 ng/l with a signal-to-noise ratio (S/N) of 6. Relative standard deviations ranged from 8 to 15% (n=7) for analyte concentrations of 0.5 microg/l in surface water.

Esterification↗
PubMed1977

Esterification of trifluoroacetic acid with phenyldiazomethane for quantitative gas chromatographic analysis. Methods involving separation from biological materials.

Trifluoroacetic acid in biological materials has been quantitatively determined by gas chromatography. Benzyl trifluoroacetate has been prepared by the reaction of the acid with phenyldiazomethane, and has been successfully analyzed by gas chromatography without any interference from other peaks. The procedure has been used to determine trifluoroacetic acid in microsomal suspension incubated with halothane, a gaseous anaesthetic.

Animals↗
PubMed1999

Esterification of decanoic acid during supercritical fluid extraction employing either methanol-modified carbon dioxide or a methanol trap.

The methylation of decanoic acid during the supercritical fluid extraction process was investigated. It was found that the majority of the methylation occurred not during the extraction, but during the collection step, in the presence of methanol. Increasing dynamic extraction time (and hence collection time) from 0 to 60 min increased acid to ester conversions from 2% to 4%. The addition of HCl as a catalyst to the reaction increased the reaction rate 10-fold, and resulted in 88% conversion to the methyl ester within 30 min, without any detrimental effects on the chromatographic system. Higher collection temperatures appeared to increase conversion, but decreased methyl ester collection efficiency.

Carbon Dioxide↗
PubMed2000

Comparative methodology in the determination of alpha-oxocarboxylates in aqueous solution ion chromatography versus gas chromatography after oximation, extraction and esterification.

The alpha-oxocarboxylates (alpha-ketocarboxylates) and the corresponding alpha-oxoacids (alpha-ketoacids) have been reported as byproducts of ozonation of potable water supplies. Some of these species also occur in biophysiological systems. Five analytes were investigated in this study: oxoethanoate (glyoxylate), 2-oxopropanoate (pyruvate), 2-oxobutanoate (2-ketobutyrate), 2-oxopentanoate (2-ketovalerate) and oxopropanedioate (ketomalonate, mesoxalate). Ion chromatography (IC) and gas chromatography (GC) were evaluated for the quantitation of these analytes at concentrations < or =200 ng ml(-1). For the IC method, the samples are run directly with minimal to no pre-treatment. For the GC method, the analytes must be derivatized with O-(2,3,4,5,6-pentafluorobenzyl)oxylamine to form oximes. The oximes are extracted into tert-butyl methyl ether and the carboxylic acid is esterified (methylated) with diazomethane. It was concluded that the ion chromatographic determination is significantly superior to the gas chromatographic method for these analytes.

Carboxylic Acids↗
PubMed2003

Differences in positional esterification of 14,15-epoxyeicosatrienoic acid in phosphatidylcholine of porcine coronary artery endothelial and smooth muscle cells.

Epoxyeicosatrienoic acids (EETs) are readily incorporated into phospholipids of smooth muscle cells (SMC) and endothelial cells (EC). Incorporation of EETs into intact porcine coronary arteries potentiates EC-dependent relaxation, but not vasorelaxation induced by agents that act solely on SMC. To explore the potential mechanisms responsible for this difference, porcine coronary artery SMC and EC preloaded with [3H]14,15-EET were treated with calcium ionophore A23187. Although the amount of EET incorporated into EC and SMC was similar, A23187 stimulated a five-fold increase in release of radioactivity from EC, but only a 21% increase in release from SMC. Thin layer chromatography (TLC) examination of cell lipids demonstrated that > 70% of the incorporated radioactivity was present in phosphatidylcholine (PC) in both SMC and BC. After treatment of EC PC with PLA2, TLC analysis indicated that approximately equal to 75% of radioactivity was present as free EET, and 25% of radioactivity was present as lyso-PC. Therefore, most of the 14,15-EET was esterified into the sn-2 position of PC in EC. However, in SMC, approximately equal to 70% of radioactivity was present as lyso-PC after PLA2 treatment, indicating that the EET was predominately esterified into the sn-1 position. In contrast, all of the 14,15-EET was esterified into the sn-2 position of PI in both EC and SMC. These results suggest that the preferential incorporation of 14,15-EET into the sn-1 position of PC in SMC may help to explain the greater retention of the compound in SMC, while incorporation into the sn-2 position of PC in EC may facilitate agonist-induced 14,15-EET release and potentiation of EC-dependent porcine coronary artery relaxation.

8,11,14-Eicosatrienoic Acid↗
PubMed2003

Esterification of cidofovir with alkoxyalkanols increases oral bioavailability and diminishes drug accumulation in kidney.

Smallpox was eradicated by vaccination in the 1970s. However, concerns have arisen about the potential use of variola virus as a biological weapon. Most of the world's population has little residual immunity because systematic vaccination against smallpox ceased in the early 1970s. Vaccination of key elements of the population against smallpox is again being considered. However, there are now large numbers of persons who cannot be safely vaccinated with the current vaccine because of AIDS, immunosuppressive drugs, and certain common skin disorders. It would be useful to have a potent orally active drug as an alternative for these persons in case of an outbreak of smallpox. Alkoxyalkyl esters of cidofovir (CDV) have been shown to be highly active and selective against poxviruses in vitro with activities several logs greater than the activity of unmodified CDV. This is due in large part to increased cellular penetration and conversion to CDV-diphosphate, the active antiviral. In this paper, the oral pharmacokinetics of 14C-labeled hexadecyloxypropyl-cidofir (HDP-CDV), octadecyloxyethyl-cidofir (ODP-CDV), and oleyloxypropyl-cidofir (OLP-CDV) are examined and oral bioavailability and tissue distribution assessed and compared with parenteral CDV. The alkoxyalkyl CDVs are highly orally bioavailable and do not concentrate in kidney, the site of the dose-limiting toxicity of CDV. Plasma and tissue drug levels are many times greater than the in vitro EC(50s) for variola, cowpox, and vaccinia viruses. Thus, the compounds are good candidates for further development for prevention and treatment of smallpox infection and the complications of vaccination.

Administration, Oral↗