Characterization of artefacts produced by treatment of organic acids with diazomethane

Novel Pyrene Excimer and Fluorogenic Probe for the Detection of Alkylating Agents

A pyrene-containing salicylic acid derivative (4) was found to be low in fluorescence, but its derivative pyrene-containing methyl salicylate (3) was found to be highly fluorescent in aqueous solution. This derivative has been tested in solution and found to be superior in the fluorogenic assay of pharmaceutical compounds, detection of chemical warfare agents, a preliminary toxicology test, mutagenicity of medicinal compounds, and other chemical analyses, including trimethylsilyl diazomethane; alkyl bromides and iodides; a sulfur mustard mimic 2-chloroethyl ethyl sulfide; and anticancer drugs, busulfan and pipobroman. The salicylic acid derivative (4) was applied as a fluorogenic probe for the detection of alkylating agents by esterification and generating fluorescence at 475 nm in solutions at low concentrations.

Linoleic acid peroxidation--the dominant lipid peroxidation process in low density lipoprotein--and its relationship to chronic diseases

Modern separation and identification methods enable detailed insight in lipid peroxidation (LPO) processes. The following deductions can be made: (1) Cell injury activates enzymes: lipoxygenases generate lipid hydroperoxides (LOOHs), proteases liberate Fe ions--these two processes are prerequisites to produce radicals. (2) Radicals attack any activated CH2-group of polyunsaturated fatty acids (PUFAs) with about a similar probability. Since linoleic acid (LA) is the most abundant PUFA in mammals, its LPO products dominate. (3) LOOHs are easily reduced in biological surroundings to corresponding hydroxy acids (LOHs). LOHs derived from LA, hydroxyoctadecadienoic acids (HODEs), surmount other markers of LPO. HODEs are of high physiological relevance. (4) In some diseases characterized by inflammation or cell injury HODEs are present in low density lipoproteins (LDL) at 10-100 higher concentration, compared to LDL from healthy individuals.

Artifacts and contaminants in the analysis of food flavor

The qualitative and quantitative complexity of food flavor makes its complete analysis rather difficult, involving a series of necessary successive steps, from the transport of the samples to the laboratory to the final quantification of the volatiles in the extract. However, because of the minute amounts of most odorous substances in food, these numerous manipulations of the sample are often the cause of alterations of the flavor, and complementary techniques are generally recommended to get a clear idea of its original composition. Arguments and clues, from 95 publications dealing with the analysis of various types of food, demonstrating that some of the volatile substances finally identified could have been in fact contaminants or artifacts arising from the analysis itself are presented. For practical reasons, the logical sequence of treatments successively applied to the sample throughout the flavor analysis is adopted.

Reactions of diazomethane with glycerolipids in the presence of serum or inorganic salts

Diazomethane is widely used for the selective methylation of nonesterified fatty acids in the presence of other lipids. However, when the reaction is carried out directly with plasma or serum, substantial methanolysis of phospholipid acyl groups occurs. Because of the importance of rigorous selectivity in the assay of unesterified fatty acids which are present only in trace amounts in cells and body fluids, we have investigated the diazomethane procedure in detail and reached the following conclusions: (i) When diazomethane reacts with lipid extracts in organic solvent, no ester hydrolysis occurs. (ii) In the presence of serum or plasma, diazomethane reacts with water and inorganic salts, causing the solution to become basic (CH2N2 + NaCl + HOH-->Ch3Cl + Na+ + OH- + N2); methoxide ions are formed from methanol (CH3OH + OH(-)-->CH3O- + HOH) causing extensive methanolysis (CH3O- + RO-CO-R'-->CH3O-CO-R' + RO-). An analogous reaction takes place with ethanol. All esters of glycerol are transesterified in aqueous salt solution by this mechanism. It is therefore essential to prepare a lipid extract prior to the assay of unesterified fatty acids when using the diazomethane procedure.

Intra-injector methylation of free fatty acids from aerobically and anaerobically cultured Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus

Free fatty acids from the type strains of anaerobically and aerobically broth-cultured Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus cells were Soxhlet-extracted with hexane. The fatty acids were identified and quantified by gas chromatography and gas chromatography-mass spectrometry after intra-injector derivation with trimethylanilinium hydroxide. This derivatization method, which we propose as suitable for routine use in clinical microbiology, is fast, accurate and sensitive, with low toxicity. Whereas the fatty acid content of A. actinomycetemcomitans was affected by the cultivation atmosphere, i.e. C16:1, decreased under aerobic growth and C16:0 increased, that of the closely related H. aphrophilus was more stable.

Basic profiles of organic acids in urine

Altogether 143 of the organic acids regularly occurring in urine of healthy individuals are identified as methyl esters by gas chromatography-mass spectrometry with respect to their complete chemical structures. They are classified as dicarboxylic acids, oxocarboxylic acids, hydroxycarboxylic acids, aromatic acids, furancarboxylic acids, nitrogen-containing acids and acid conjugates. By pre-fractionating the complex mixture of the total organic acids, peak overlap is minimized, and substances in low concentrations can also be detected and identified. The qualitative patterns of the urinary organic acids in the fractions are constant and reproducible, and in many cases a reliable identification of organic acids is possible by gas chromatography alone, using methylene units and separation on OV-1701 capillary columns.

Routine gas chromatographic/mass spectrometric analysis of urinary organic acids. Results over a three-year period

Organic acidaemias are an important part of inborn errors of metabolism. The biochemical diagnosis is based on gas chromatographic/mass spectrometric identification of urinary organic acids. Since 1973 we have used gas chromatographic analysis of the methyl esters of urinary organic acids. Mass spectral identification was performed only when an abnormal gas chromatographic profile was suspected. In 1983 we introduced routine gas chromatographic/mass spectrometric analysis organic acids. More than 1500 urine samples from 1000 children have been analysed and we encountered more than 40 abnormal profiles: 18 classical organic acidaemias (propionic, methylmalonic, isovaleric, glutaric type I and 3-hydroxy-3-methyl glutaric acidaemias); 6 aminoacidopathies with excretion of branched chain keto acids (leucinosis) or succinylacetone (tyrosinosis type I); 14 massive dicarboxylic acidurias with excretion of suberyl and hexanoyl glycine and deficiency of the medium chain acyl CoA dehydrogenase in four patients. The use of gas chromatography/mass spectrometry routinely allows the identification of abnormal metabolites excreted in small amounts: beta-methyl-crotonyl glycine indicative of biotin deficiency: gamma-hydroxybutyric acid; and 3-methyl-glutaconic + 3-methy-glutaric acid is in a 3-methyl-glutaconic aciduria type II. Abnormal profiles due to metabolites of drugs as valproate, salicylate and barbiturate can be recognized immediately. This simple gas chromatographic/mas spectrometric system can lead to diagnosis, in one day, of rare but severe diseases needing a specific and early treatment.

Gas chromatographic profiling of ketone bodies and organic acids in diabetes

Diabetes mellitus is a defect not only in glucose metabolism, but also in the metabolism of lipids and amino acids. Gas chromatographic and gas chromatographic--mass spectrometric profile analyses have contributed much to the understanding of the metabolic changes connected with this defect. Ketones are isolated by a gas-phase extraction and adsorption technique and profiled after thermal desorption. Organic acids are isolated by solvent extraction or anion exchange, derivatized and separated either as total acid profiles or subprofiles after pre-fractionation of the acid derivatives. The main results are as follows. (a) Increased total 4-heptanone is inherently connected with diabetes mellitus. Its urinary levels are elevated in therapeutically well controlled patients. (b) A general ketogenesis pathway leads to higher molecular weight ketone bodies in addition to the conventional ketone bodies. (c) During diabetic ketoacidosis, in addition to the fatty acids the following acids are elevated in serum and in urine: dicarboxylic acids resulting from omega- and beta-oxidation of monocarboxylic acids; oxomonocarboxylic acids as metabolites of the amino acids valine, leucine and isoleucine and as products of ketogenesis; and hydroxymonocarboxylic acids, also originating from amino acids and from ketogenesis.