A fast and selective method for anthocyanin profiling of red wines by direct-infusion pneumatic spray mass spectrometry.

RATIONALE: Anthocyanins confer the color to red wines. During wine aging, new anthocyanin derivatives with peculiar chromatic characteristics are formed. A fast and selective method for screening the anthocyanin composition of wine has been developed. METHODS: Direct-infusion electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of wine extracts has been performed by operating in positive ion mode with a low spray capillary voltage (0.5 kV) to detect only the species already present in ionic form. The method has been called direct-infusion pneumatic spray (DIPS) mass spectrometry. The anthocyanin profiles of thirteen red wines at different aging stages were studied. Using malvidin-3,5-diglucoside as internal standard, the indices of wine color and of wine color evolution were estimated. RESULTS: By decreasing the spray capillary voltage a dramatic increase in selectivity toward anthocyanins has been observed and the related peaks are the most abundant in the spectra. Several anthocyanins and anthocyanin derivatives (pyranoanthocyanins and derivatives formed by reaction with flavan-3-ols) have been identified in the wines. The younger wines showed higher total anthocyanin index. The aged wines showed color evolution index higher than 20% while it was lower in the younger samples. CONCLUSIONS: The anthocyanin fingerprint is effective for estimating the aging state of wine. The color evolution index can be correlated to barrel conditions during wine aging and used to distinguish between aged and younger wines. The study of pyranoanthocyanins and anthocyanin-flavanol derivatives can be useful to predict wine color stability.

The protein profile of Theobroma cacao L. seeds as obtained by matrix-assisted laser desorption/ionization mass spectrometry.

The water-soluble protein profile of the seeds of green, red, and yellow Theobroma cacao L. fruits has been determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS). The seeds were powdered under liquid nitrogen and defatted. The residues were dialyzed and lyophilized. The obtained samples were suspended in the matrix solution of sinapinic acid. The obtained MALDI mass spectra showed the presence of a wide number of proteins with molecular weight ranging from 8000 to 13,000 Da and a cluster of peaks centered at 21,000 Da that were attributed to albumin. The abundance of this peak was found to depend on the different portion of the seed (husk, apical and cortical parts); however, the MALDI mass spectra obtained from the different varieties of cocoa were practically superimposable. Changes in the protein profiles were also observed after the cocoa seeds were treated by fermentation and roasting, which are processes usually employed for the commercial production of cocoa.

On the mechanisms of the reactions between some perfluorinated compounds and CH(5) (+) --experimental and theoretical approaches.

Five perfluorocompounds [perfluoropentane, 4-(perfluoroethoxy)-perfluorobutane, 5-(perfluoroethyl)-perfluorotetrahydrofuran, 2-(trifluoromethyl)-perfluorotetrahydropyran, and 4-(trifluoromethyl)-perfluorotetrahydropyran] were analyzed by electron ionization (EI) and chemical ionization (CI), using methane and isobutane as reagent gases. Under CI conditions, isobutane does not lead to significative results whereas methane leads to high ionic yields [with respect to both CI (isobutane) and EI]. Under EI conditions, practically only fragment ions are observed, with the complete loss of molecular weight. In contrast under CI(CH(4) ) conditions, [M-F](+) ions are produced. Under these conditions, the behavior of oxygen-containing molecules is strongly different from that of perfluoropentane. This is because oxygen can greatly stabilize the formation of the [M-F](+) carbocation by a π-electron donor effect, especially in the case of cyclic structures. Moreover, π-stabilization can be considered a useful tool to rationalize the position of tertiary carbon atom in trifluoromethyl-perfluoro-pyrane isomeric ions. The experimental data formed the starting point for the theoretical calculation, which allowed us to explore the mechanisms of the reactions of CH(5) (+) ions with selected perfluorocompounds. The computational methods used show that a direct protonation of the perfluoroethers (PFEs) by CH(5) (+) as well as iBu(+) is very unlikely. In the theoretical calculations, the PFE molecule served rather as the F(-) donor, and the elimination of HF molecule occurred when the PFE molecule was placed close to H(+) or CH(5) (+) ions. The fact that the latter is very unstable and decomposes to a proton and methane molecule explains why the use of methane in CI is so successful in the generation of [M-F](+) ion. In contrast, the isobutonium cation rearranges to an isopropyl cation/methane complex rather than that it abstracts F(-) from the PFE molecule. Similar results can be expected for other PFEs and perfluoroalkanes (PFAs) because both CH(5) (+) and H(+) were able to abstract the HF molecule also by attacking along the perfluoroalkyl chain of the PFE.

Parental relationships among three grape varieties studied by MALDI of grape seed protein profiles.

Two Raboso cultivars, i.e. Raboso Veronese and Raboso Piave, are two black Vitis vinifera varieties. A genetic study suggested that Raboso Veronese is the progeny of a spontaneous cross between Raboso Piave and Marzemina Bianca cultivars. Parental relationships are usually investigated by genetic studies, which are effective to establish genetic links among different cultivars. Considering that proteome is the genome expression, in this article we evaluated the power of seed protein profiles obtained by matrix-assisted laser desorption/ionization (MALDI)/MS for parentage investigation. The three cultivars lead to very similar spectra with differences in the relative intensity of the most abundant species and the presence of very weak specific ions. In order to evaluate the analytical significance of these aspects, the variability due to instrumental factors and due to different harvesting areas and years of the same cultivars have been considered and measured by the calculation of discrepancy factor values. On one hand, the results obtained can be considered a valid confirmation of the genomic findings, whereas on the other hand, the results provide evidence for the ability of MALDI/MS to individuate minor differences in protein profiles of complex protein mixtures.