Cambios en la composición proximal y en las características de los aceites durante el desarrollo de semillas de linaza

Atmospheric Pressure Photoionization-Mass Spectrometry (APPI-MS) and High Performance Liquid Chromatography (HPLC) are the two analytical methods that were used to characterize Triacylglycerols (TAGs) during flaxseed development. The HPLC method of the oils showed the presence of 15 TAG species. In contrast to the HPLC chromatograms, the APPI-MS showed 17 peaks of TAG. APPI-MS is more rapid than the HPLC method (11 min). The iodine value of the oils showed a gradual increase, while the oil stability continuously decreased. Proximate composition during flaxseed development revealed that flaxseed is potentially a good source of dietary energy and protein. At full maturity, flaxseed contained 37% oil and 24% protein on a dry-weight basis; albumin was the major storage protein (53% of total storage proteins) followed by globulin (33%) and glutelin fractions (11%). Prolamins had the lowest percentage with 3%. α-amylase activity was higher in the mature seeds than the young ones.Fotoionización a presión atmosférica-Espectrometría de masas (APPI-MS) y cromatografía líquida de alta resolución (HPLC) son dos métodos de análisis que se utilizaron para caracterizar triglicéridos (TAGs) durante el desarrollo de semillas de linaza. El método HPLC mostró la presencia de 15 especies de TAG, en contraste, los cromatogramas de APPI-MS mostraron 17 picos de TAG siendo el método APPI-MS más rápido que el de HPLC (11 min). El índice de yodo de los aceites mostró un aumento gradual, mientras que la estabilidad disminuyó continuamente. El estudio de la composición proximal de la linaza durante su desarrollo, mostró que esta semilla es una fuente potencialmente buena de energía y de proteína para la dieta. Al final de la maduración, la linaza contenía 37 % de aceite y 24 % de proteína sobre peso seco; albúmina fue la principal proteína de almacenamiento (53% sobre el total de las proteínas de almacenamiento) seguido de la globulina (33 %) y glutelina (11 %). Las prolaminas presentaron el porcentaje más bajo con 3 %. La actividad α-amilasa fue mayor en las semillas maduras que en las más jóvenes

Theoretical and experimental study of tropylium formation from substituted benzylpyridinium species

Fragmentation pathways of unsubstituted and substituted benzylpyridinium compounds were investigated using mass-analysed kinetic energy (MIKE) technique in combination with high level of quantum chemical calculations in the gas phase. Fast atom bombardment (FAB) source was used for ionisation of the studied compounds. The formation of both benzylium and tropylium species were investigated. Hybrid Hartree-Fock/Density Functional Theory calculations have been performed to assess the geometries and the energies of the transition states and intermediates. For each cases, different reaction pathways were investigated, and particularly in the case of the formation of tropylium species, the formation of the seven-membered ring before or after the loss of pyridine were studied. The effect of para-methyl and para-methoxy substituents on the activation energy of the rearrangement process to form thermodynamically stable tropylium compounds has been studied. Theoretical calculations showed competition between direct bond cleavage and rearrangement reactions to form benzylium and tropylium compounds, respectively. Experimental results also suggested that the rearrangement process takes place to yield stable tropylium under “soft ionisation techniques”, such as FAB

Stereochemical Effects During [M - H]- Dissociations of Epimeric 11-OH-17β-Estradiols and Distant Electronic Effects of Substituents at C(11) Position on Gas Phase Acidity

The affinity of estradiol derivatives for the estrogen receptor (ER) depends strongly on nature and stereochemistry of substituents in C(11) position of the 17β-estradiol (I). In this work, the stereochemistry effects of the 11α-OH-17β-estradiol (IIIα) and 11β-OH-17β-estradiol (IIIβ) were investigated using CID experiments and gas-phase acidity (ΔH°acid) determination. The CID experiments showed that the steroids decompose via different pathways involving competitive dissociations with rate constants depending upon the α/β C(11) stereochemistry. It was shown that the fragmentations of both deprotonated [IIIα-H]- and [IIIβ-H]- epimers were initiated by the deprotonation of the most acidic site, i.e. the phenolic hydroxyl at C(3). This view was confirmed by H/D exchange and double resonance experiments. Furthermore, the ΔH°acid of both epimers (IIIα and IIIβ), 17β-estradiol (I), and 17-desoxyestradiol (II) was determined using the extended Cooks' kinetic method. The resulting values allowed us to classify steroids as a function of their gas-phase acidity as follows: (IIIβ) ≫ (II) > (I) > (IIIα). Interestingly, the α/β C(11) stereochemistry appeared to influence strongly the gas-phase acidity. This phenomenon could be explained through stereospecific proton interaction with π-orbital cloud of A ring, which was confirmed by theoretical calculation. © 2009.SCOPUS: ar.jinfo:eu-repo/semantics/publishe