Mass spectrometric evidence for the formation of pigmented polymers in red wine

The polymeric materials (wine tannin) were isolated from a three-year-old Pinot Noir using Toyopearl TSK HW 40-F size exclusion chromatography. The wine tannin was analysed by reversed-phase and gel permeation high performance liquid chromatography, UV-Vis spectrophotometry and mass spectrometry. Analysis by gel permeation chromatography indicated that the isolate was in large part polymeric, and also indicated the presence of pigmented material monitored at a wavelength of 520 nm. Acid-catalysis in the presence of phloroglucinol indicated that the wine tannin contained 45% w/w known proanthocyanidin material. The wine tannins gave a complicated mass spectrum featuring a large number of intense signals derived from proanthocyanidins and, to a much lesser extent, a series of ions corresponding to masses consistent with direct condensation products of an anthocyanin with proanthocyanidins. The degree of polymerisation by mass spectrometry was detected to be as high as an octamer composed of an anthocyanin combined with a proanthocyanidin heptamer. Based upon current evidence, the anthocyanin was proposed to be bound from the C-6/8 or C-4 positions of the anthocyanin to the respective electrophilic or nucleophilic centre of the proanthocyanidins. Only the species with the C-6/8 position of the anthocyanin linked with the proanthocyanidins seemed to be pigmented. Under acid-catalysed conditions, an increase in malvidin-3-glucoside was observed, suggesting that the non-pigmented form is possibly converted to the pigmented flavylium form. This is the first mass spectrometric evidence confirming the existence of pigmented polymers with an extension to octamers in wine.     

A sensitive and selective method for the quantitative determination of fatty acid tryptamides as shell indicators in cocoa products

 Tetracosanoyl-2-(3-indolyl)ethane amide (lignocerinic acid tryptamide; LAT) and docosanoyl-2-(3-indolyl)ethane amide (behenic acid tryptamide; BAT) were identified as the most prominent tryptamides in cocoa shells based on electrospray ionisation mass spectrometry and ¹H NMR measurements. The structure of LAT, which is reported for the first time in cocoa shells, and also that of BAT were confirmed by synthesis. By using synthesised heptadecanoyl-2-(3-indolyl)ethane amide as the internal standard, a sensitive and reproducible method was developed for the quantification of LAT and BAT in the picogram range by means of HPLC/fluorescence detection. The detection limit was determined to be 30 pg/run. In authentic shell samples, 50-fold higher concentrations of both tryptamides were determined compared to the cocoa cotyledons. In 15 commercial chocolate samples, concentrations of 23.1–63.0 μg of the tryptamides (sum of both) per gram of fat were found. A first experiment attempted to correlate the tryptamide content with the amounts of shells in a model chocolate showed that the method is a promising tool to determine the shell content in the quality assessment of cocoa products. Received: 8 May 1998     

Development of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of glucocorticoid residues in edible tissues of swine,cattle, sheep,and chicken

A confirmatory and quantitative method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine the presence of eight glucocorticoids (prednisone, prednisolone, hydrocortisone, methylprednisolone, dexamethasone, betamethasone, beclomethasone, and fludrocortisone) in the muscles and livers of swine, cattle, and sheep and the muscle of chicken is described. After deconjugation in alkali media, samples were extracted with ethyl acetate for glucocorticoids followed by solid-phase extraction clean-up and reconstitution in the LC mobile phase. The hydrolysis procedure with sodium hydroxide was used to reduce handling time. A single-step solid-phase extraction method was optimized which is suitable for the clean-up of the compounds of interest in many diverse tissue matrices. LC separations were performed on a C₁₈ column with gradient elution using acetonitrile and water (containing 0.2% formic acid) and the two epimers betamethasone and dexamethasone were successfully separated. LC-electrospray ionization (ESI)-MS/MS in negative mode with selected reaction monitoring (SRM) mode was performed to improve method sensitivity and reduce matrix interference. Two SRM transitions were used for each compound. The recovery of glucocorticoids spiked at levels of 0.5–16 µg kg^?1 ranged from 55% to 107%; the between-day relative standard deviations were no more than 15%. The limits of quantification were 0.5–2.0 µg kg^?1 in muscle and 1–4 µg kg^?1 in liver. The optimized procedure was successfully applied to monitor the food at the 2008 Summer Olympics Games in Beijing, China, demonstrating the method to be simple, fast, robust, and suitable for identification and quantification of glucocorticoids residues in foods of animal origin.