The bioavailability of iron picolinate is comparable to iron sulfate when fortified into a complementary fruit yogurt: a stable iron isotope study in young women.

Purpose: A technological gap exists for the iron (Fe) fortification of difficult-to-fortify products, such as wet and acid food products containing polyphenols, with stable and bioavailable Fe. Fe picolinate, a novel food ingredient, was found to be stable over time in this type of matrix. The objective of this study was to measure the Fe bioavailability of Fe picolinate in a complementary fruit yogurt.

Improvement of AOAC Official Method 984.27 for the determination of nine nutritional elements in food products by Inductively coupled plasma-atomic emission spectroscopy after microwave digestion: single-laboratory validation and ring trial.

A single-laboratory validation (SLV) and a ring trial (RT) were undertaken to determine nine nutritional elements in food products by inductively coupled plasma-atomic emission spectroscopy in order to improve and update AOAC Official Method 984.27. The improvements involved optimized microwave digestion, selected analytical lines, internal standardization, and ion buffering.

Analysis of advanced glycation endproducts in dairy products by isotope dilution liquid chromatography-electrospray tandem mass spectrometry. The particular case of carboxymethyllysine.

A fully validated multiple-transition recording isotope dilution liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantitative determination of N(epsilon)-carboxymethyllysine (CML) and lysine in dairy products is described. Internal standards were [N-1',2'-(13)C(2)]CML and [1,2,3,4,5,6-(13)C(6)-2,6-(15)N(2)]lysine, and the method was validated by evaluating the selectivity, linearity, precision (repeatability and reproducibility) and trueness, using both powder and liquid products. For liquid dairy products, the repeatability and reproducibility was 2.

Evaluating the extent of protein damage in dairy products: simultaneous determination of early and advanced glycation-induced lysine modifications.

An isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to determine lysine (Lys), N(epsilon)-fructosyllysine (FL), N epsilon-carboxymethyllysine (CML), and pyrraline (Pyr) in dairy products. The presented approach entails protein cleavage via enzymatic digestion to liberate the aforementioned compounds, which were then quantified using a stable isotope dilution assay. LC-MS/MS analysis was performed by positive electrospray ionization recording two transition reactions per analyte in selected reaction monitoring mode.

Absence of 2'-deoxyguanosine-carbon 8-bound ochratoxin A adduct in rat kidney DNA monitored by isotope dilution LC-MS/MS.

The contribution of DNA adduct formation in the carcinogenic action of the mycotoxin ochratoxin A (OTA) has been subject to much debate. Recently, a carbon-bonded ochratoxin A-2'-deoxyguanosine adduct (dGuoOTA) formed by photochemical reaction in vitro has been shown by 32P-postlabeling/TLC to comigrate with a spot detected in DNA isolated from rat and pig kidney following exposure to OTA. Considering the large body of evidence arguing against covalent DNA binding of OTA and the poor resolution and specificity of postlabeling analysis, we developed a stable isotope dilution LC-MS/MS method to analyze dGuoOTA in kidney DNA isolated from rats treated with OTA.

N(epsilon)-carboxymethyllysine-modified proteins are unable to bind to RAGE and activate an inflammatory response.

Advanced glycation endproducts (AGEs) containing carboxymethyllysine (CML) modifications are generally thought to be ligands of the receptor for AGEs, RAGEs. It has been argued that this results in the activation of pro-inflammatory pathways and diseases. However, it has not been shown conclusively that a CML-modified protein can interact directly with RAGE.

A comparative study of proteolysis methods for the measurement of 3-nitrotyrosine residues: enzymatic digestion versus hydrochloric acid-mediated hydrolysis.

A common approach for the quantification of 3-nitrotyrosine (NY) in routine analyses relies on the cleavage of peptide bonds in order to release the free amino acids from proteins in tissues or fluids. NY is usually monitored by either GC-MS(/MS) or LC-MS/MS techniques. Various proteolysis methods have been employed to combine digestion efficiency with prevention of artifactual nitration of tyrosine.

Quantitative determination of four nitrofuran metabolites in meat by isotope dilution liquid chromatography-electrospray ionisation-tandem mass spectrometry.

A confirmatory method based on isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the low-level determination of residues of four nitrofuran veterinary drugs in meat, e.g., furazolidone, furaltadone, nitrofurantoin, and nitrofurazone.

Analysis of matrix-bound nitrofuran residues in worldwide-originated honeys by isotope dilution high-performance liquid chromatography-tandem mass spectrometry.

A sensitive and selective isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) method is presented for the simultaneous analysis of the metabolites of four nitrofuran veterinary drugs, that is, furazolidone, furaltadone, nitrofurantoin, and nitrofurazone, in honey samples. The method entails a combined hydrolysis of protein-bound drug metabolites and derivatization of the resulting metabolites with 2-nitrobenzaldehyde (NBA) during an overnight incubation, followed by a liquid-liquid extraction and a cleanup on a polymeric solid-phase extraction cartridge. Mass spectral acquisition is carried out in the positive ion mode by applying multiple reaction monitoring (MRM) of three diagnostic transition reactions for each analyte under survey.

Preparation of stable isotope-labeled 2-nitrobenzaldehyde derivatives of four metabolites of nitrofuran antibiotics and their comprehensive characterization by UV, MS, and NMR techniques.

A convenient method is presented for the preparation of the carbon-13-labeled 2-nitrobenzaldehyde derivatives of the nitrofuran metabolites 3-amino-2-oxazolidinone (AOZ), semicarbazide (SC), 1-aminohydantoin (AH), and 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), with the purpose of using them as internal standards for the quantification of trace levels of nitrofuran residues by liquid chromatography-tandem mass spectrometry in foods of animal origin. The synthesis encompasses the nitration of [1,2,3,4,5,6-(13)C(6)]toluene prior to chromyl compound-mediated oxidation of the methyl group into the corresponding aldehyde. The four metabolites of nitrofuran antibiotics were derivatized independently with the resulting ring-labeled 2-nitrobenzaldehyde (NBA) to obtain the target compounds.

The effects of coffee on enzymes involved in metabolism of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in rats.

The effects of coffee on the metabolism and genotoxicity of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were investigated. Coffee diminished the bacterial mutagenicity of PhIP in the Ames reversion assay through inhibition of cytochrome P450 1A2 (CYP1A2), a key enzyme involved in the metabolic activation of PhIP. When given as part of the diet (0, 1 or 5% w/w) to male Fischer-344 rats for 2 weeks, coffee affected the expression of hepatic enzymes involved in PhIP metabolism.

Artifactual nitration controlled measurement of protein-bound 3-nitro-L-tyrosine in biological fluids and tissues by isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry.

A sensitive and selective method is presented to accurately determine the level of protein-bound 3-nitro-L-tyrosine (NTyr) in rat plasma and kidney samples. This assay is based on isotope dilution liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The sample preparation entails protein precipitation, acid hydrolysis with 6 N HCl, and solid-phase extraction (using reverse and aminopropyl phase cartridges) prior to the determinative step.

Simultaneous determination of 3-nitrotyrosine and tyrosine in plasma proteins of rats and assessment of artifactual tyrosine nitration.

A sensitive and specific isotope dilution liquid chromatography-electrospray tandem mass spectrometry method was developed for the determination of the 3-nitrotyrosine residue levels in rat plasma proteins. The assay is based on the cleavage of proteins with concentrated hydrochloric acid to release both 3-nitrotyrosine and tyrosine. To control the potential artifactual nitration of tyrosine residues during the proteolysis, samples are spiked with (13)C(9)-labeled tyrosine and the level of (13)C(9)-labeled 3-nitrotyrosine is measured.

Analysis and quantification of DNA adducts of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in liver of rats by liquid chromatography/electrospray tandem mass spectrometry.

Liquid chromatography with electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) was used to measure DNA adducts of the carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) with a microbore C-18 reversed-phase column. Quantification of the isomeric adducts N-(deoxyguanosin-8-yl)-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (dG-C8-MeIQx) and 5-(deoxyguanosin-N(2)-yl)-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (dG-N(2)-MeIQx) was achieved using synthetic, isotopically labeled internal standards. The reaction of the N-acetoxy ester of 2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline (HONH-MeIQx) with calf thymus DNA (ct DNA) resulted in formation of these adducts in a ratio of 5:1 (dG-C8-MeIQx:dG-N(2)-MeIQx).