A simple and fast method for metabolomic analysis by gas liquid chromatography-mass spectrometry.

INTRODUCTION: The metabolomic profile is an essential tool for understanding the physiological processes of biological samples and their changes. In addition, it makes it possible to find new substances with industrial applications or use as drugs. As GC-MS is a very common tool for obtaining the metabolomic profile, a simple and fast method for sample preparation is required. OBJECTIVES: The aim of this research was to develop a direct derivatization method for GC-MS to simplify the sample preparation process and apply it to a wide range of samples for non-targeted metabolomic analysis purposes. METHODS: One pot combined esterification of carboxylic acids with methanol and silylation of the hydroxyl groups was achieved using a molar excess of chlorotrimethylsilane with respect to methanol in the presence of pyridine. RESULTS: The metabolome profile obtained from different samples, such as bilberry and cherry cuticles, olive leaves, P. aeruginosa and E. coli bacteria, A. niger fungi and human sebum from the ceruminous gland, shows that the procedure allows the identification of a wide variety of metabolites. Aliphatic fatty acids, hydroxyfatty acids, phenolic and other aromatic compounds, fatty alcohols, fatty aldehydes dimethylacetals, hydrocarbons, terpenoids, sterols and carbohydrates were identified at different MSI levels using their mass spectra. CONCLUSION: The metabolomic profile of different biological samples can be easily obtained by GC-MS using an efficient simultaneous esterification-silylation reaction. The derivatization method can be carried out in a short time in the same injection vial with a small amount of reagents.

Characterization of cuticle composition after cold storage of "Celeste" and "Somerset" sweet cherry fruit.

Cuticle composition and structure may be relevant factors affecting the storage potential of fruits, but very few studies have analyzed fruit cuticle composition from a postharvest perspective. In this work, the chemical composition of waxes and cutin (major cuticular components) was analyzed in cuticle samples isolated from "Celeste" and "Somerset" cherries (Prunus avium L.) after cold storage at 0 °C. Total cuticle amounts per surface unit (µg cm(-2)) increased along with cold storage. The triterpene ursolic acid, the alkane nonacosane, linoleic acid, and ß-sitosterol were the most abundant components of cuticular waxes, whereas cutin composition was dominated by C18-type monomers. In spite of being comprised of similar chemical families, cultivar-related differences were found regarding the abundance and the evolution of some compound families during cold storage. To the best of our knowledge, this is the first report on changes in cuticle composition of sweet cherry during postharvest storage.

Fruit cuticle composition of a melting and a nonmelting peach cultivar.

Although postharvest quality of fruit is greatly affected by cuticle composition, structure, and properties, very few published studies have analyzed fruit cuticle composition from a postharvest perspective. In this work, the chemical composition of waxes and cutin, major cuticular components, was analyzed in fruit cuticle samples isolated from a melting ('October Sun') and a nonmelting ('Jesca') peach (Prunus persica L. Batsch.) cultivar at harvest and after a simulated shelf-life period of 5 days at 20 °C. Cutin composition was dominated by 18-hydroxyoleic acid, whereas the triterpenoid ursolic and oleanoic acids and the alkanes n-tricosane and n-pentacosane were quantitatively prominent among the wax compounds identified. Some quantitative differences were found between both cultivars for particular compound families and in their postharvest modifications. To the best of the authors' knowledge, this is the first study characterizing the composition of the cuticle of peach fruit and describing the changes therein after harvest.

Parallel synthesis: a new approach for developing analytical internal standards. Application to the analysis of patulin by gas chromatography-mass spectrometry.

The polymer-assisted reaction of 4-(hydroxymethyl)furan-2(5H)-one (4HM2F) with 21 carboxylic acids using polystyrene-carbodiimide (PS-carbodiimide) yielded an ester library. Four of the esters, (5-oxo-2,5-dihydrofuran-3-yl)methyl acetate (IS-1), (5-oxo-2,5-dihydrofuran-3-yl)methyl butyrate (IS-2), (5-oxo-2,5-dihydrofuran-3-yl)methyl 2-methylpropanoate (IS-3), and (5-oxo-2,5-dihydrofuran-3-yl)methyl chloroacetate (IS-4), were tested as internal standards for the quantification of patulin in apple juice by gas chromatography-mass spectrometry in the selected ion monitoring mode (GC-MS-SIM). The developed method combines an AOAC official extractive step and a GC-MS-SIM analysis. Using a chromatographic column containing trifluoropropylmethylpolysiloxane as the stationary phase and IS-1 as the internal standard, it was possible to perform an accurate and precise quantification of underivatizated patulin in apple juice at concentrations down to 6 microg/L. A detection limit of 1 microg/L was established.