Acid metabolites

In man, the metabolic pathways of mepirizole were distinct from those in experimental animals, since hydroxylation on each of the aromatic rings did not occur in man. Compound (752) was obtained by oxidation of the 3-methyl group to the carboxylic acid (a similar process occurs with 5-methylpyrazole-3-carboxylic acid, an active metabolite of 3,5-dimethylpyrazole). However, the carboxylic acid metabolite of mepirizole had no analgesic activity and did not decrease blood glucose. 

The anticonvulsant progabide 24) is useful in a wide variety of seizure disorders. It was synthesiied as a y-aniinobutync acid (GABA) prodrug but its activity appears to reside in the parent drug and its acid metabolite, as well as the GABA liberated [21],... 

Type I allergic reactions are inappropriate immune responses to an allergen with preferential synthesis of immunoglobulin E (IgE), a special antibody class, which binds to mast cells and basophilic granulocytes via Fee receptors. Binding of the allergen to the cell-bound IgE initiates the rapid release of allergic mediators, most prominently histamine, and the de novo synthesis of arachidonic acid metabolites and cytokines, which are responsible for the clinical symptoms. 

Tomita Y, Maeda K, Tagami H (1992) Melanocyte-stimulation properties of arachidonic acid metabolites, possible role of post-inflammatory. Cell Res 5 357-361... 

Palytoxin is hemolytic (4) and is an extremely potent toxin (7). We have shown that in rat liver cells palytoxin stimulates de-esterification of cellular lipids to liberate arachidonic acid (5). These rat liver cells metabolize this increased arachidonic acid via the cyclooxygenase pathway to produce prostaglandin (PG) I2 and lesser amounts of PGE2 and PGp2. Palytoxin acts on many cells in culture to stimulate the production of cyclooxygenase metabolites (Table I). Clearly, the myriad pharmacological effects of the arachidonic acid metabolites must be considered in any explanation of the many clinical manifestations of palytoxin s toxicity. 

Schlondorff, D. and Ardaillon, R. (1986). Prostaglandins and other arachidonic acid metabolites in the kidney. Kidney Int. 29, 108-119. 

Thus, organic solvent extraction methods for the extraction of pesticides from water samples can be replaced by the SPE method using Ci8 and PS-2. Ethobenzanid, clomeprop, naproanilide and their acidic metabolites are determined by a multi-residue analytical method using Cig or PS-2 cartridge extraction after acidification of the water samples with hydrochloric acid or other acidic media, followed by HPLC or LC/MS detection. 

Acetic acid, [(ethoxymethyl)(2-ethyl-6-methylphenyl)amino]oxo-, sodium salt, should be >95% pure (EMA-producing oxanilic acid metabolite, referred to from this point as Metabolite I)... 

The analytical method for carfentrazone-ethyl and its major metabolites in/on corn grain, grits, meal, flour, and starch (nonoil matrices) consists of extractions with acetone and deionized water, followed by a partition with hexane, which allowed the separation of the parent carfentrazone-ethyl from the acid metabolites. The hexane... 

Vigorously mix the aqueous and hexane fraction to partition carfentrazone-ethyl into the hexane fraction. Centrifugation may be necessary to break any emulsion that occurs. Remove and collect the hexane fraction for analysis of carfentrazone-ethyl. Partition the aqueous fraction with an additional 10 mL of hexane and add the hexane to the hexane from the first partition step. The aqueous fraction will be used for the analysis of the acid metabolites (see below). 

Transfer the aqueous fraction from the hexane-aqueous partition (25-30 mL) into a 50-mL round-bottom flask. Add 3-3.5 mL of concentrated HCl (such that the final acid concentration is > 1N and several boiling chips to the round-bottom flask and reflux the sample for 1 h under a water-cooled condenser. This acid reflux step will cleave any conjugated acid metabolites in the crop matrices. 

Crop refined oils should be dissolved in hexane and partitioned with deionized water in a separatory funnel. The hexane fraction containing the carfentrazone-ethyl should be further partitioned with acetonitrile, and the rest of the analytical procedures for the parent compound should be followed. Concentrated HCl is added to the aqueous fraction to make the solution 1N and the samples are boiled under reflux for 1 h the rest of the analytical procedures for the acid metabolites should be followed. 

The analytical method to determine carfentrazone-ethyl and the major animal metabolites (C-Cl-PAc and C-Pac) in bovine matrices is similar to the method for crop matrices. The hexane-aqueous partition to separate carfentrazone-ethyl from the acid metabolites can be replaced by a Cig SPE cartridge. After the SPE, use 12 mL of water-acetonitrile (7 3, v/v) to elute the metabolites and then use 12 mL of hexane-ethyl acetate (4 1, v/v) to elute carfentrazone-ethyl after drying the cartridge. Follow the rest of the respective analytical procedures for carfentrazone-ethyl and the acid metabolites described in Sections 6.3 and 6.4. However, no reflux under boiling is necessary for the analysis of acid metabolites based on a goat metabolism study, because no conjugated acid metabolites were detected. Also, since HM-C-Cl-Pac is not analyzed for in the bovine matrices, no acylation is needed in the method. Analyze the metabolites by GC/MS, and monitor the ions at m/z 362 for C-Cl-Pac and 303 for C-PAc. 

A calibration curve was generated for each analyte at the initiation of the analytical phase of the smdy. Standard solutions for injection contained carfentrazone-ethyl or derivatized acid metabolites. Standard solutions were injected at the beginning of each set of assays and after every two or three samples to gage the instrument response. 

Carfentrazone-ethyl, C-Cl-PAc, C-PAc, DM-C-Cl-PAc and HM-C-Cl-PAc stock solutions of 1000 xg mL were prepared by dissolving the appropriate amounts of the analytical standards in acetonitrile. Working solutions were prepared in volumetric flasks by appropriate dilutions of the stock solutions for each analyte or combination of analytes. Working solutions containing the parent were prepared only in acetonitrile and working solutions containing acid metabolites were prepared in acetonitrile (underivatized) or hexane (derivatized). Underivatized solutions (containing the parent and/or metabolites in acetonitrile) were used for fortification. Solutions of derivatized esters were prepared simultaneously with the samples. Standard solutions... 

During the initial partition with hexane and water, the aqueous pH must not exceed 8. Carfentrazone-ethyl is extremely unstable under alkaline conditions and will rapidly degrade to C-Cl-PAc. At times, the workup of the crop samples, including the fortification step, should be completely separated for carfentrazone-ethyl and the acid metabolites, to avoid any possible interference from the parent compound. 

More recently, liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) have been evaluated as possible alternative methods for carfentrazone-ethyl compounds in crop matrices. The LC/MS methods allow the chemical derivatization step for the acid metabolites to be avoided, reducing the analysis time. These new methods provide excellent sensitivity and method recovery for carfentrazone-ethyl. However, the final sample extracts, after being cleaned up extensively using three SPE cartridges, still exhibited ionization suppression due to the matrix background for the acid metabolites. Acceptable method recoveries (70-120%) of carfentrazone-ethyl metabolites have not yet been obtained. 

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