Efecto de extractos de hojas y frutos de Schinus molle sobre la estabilidad oxidativa de aceites mediante oxidación acelerada

The most highly recommended oils for the diet are those which are rich in unsaturated fatty acids. However, the presence of these components in the oils is related to oxidation, which can be determined by the induction period. Further safety and the prolongation of the storage period for such oils can be achieved by the addition of efficient antioxidants, which today are preferably from natural sources. In order to contribute to the related research, the main objective of this study was to evaluate the efficacy of Schinus molle extracts compared to synthetic antioxidants (BHT) in delaying the oxidation of some vegetable oils. The results of the present study showed that the fruit and leaf extracts of Schinus molle presented activities and potential for being used as antioxidants in vegetable oils based on the tested methods (DPPH and ABTS). The extracts were also characterized as containing phenolic compounds by the Folin Ciocalteau method and by high performance liquid chromatography (HPLC). The action of the extracts as natural antioxidants was proven in the vegetal oils of chia (Salvia hispanica) and peanut (Arachis hypogaea) by the Rancimat method. It was observed that the oils increased their resistance to oxidation when incorporated with the extracts of Schinus molle, and the extract from the leaves increased the induction period of peanut oil by more than three hours (from 19.5 to 22.9 hours) with an extract concentration of 2.5%. The fruit extract was more efficient in delaying the oxidation of chia oil, prolonging its induction period by more than one hour with a concentration of 2.5% (from 3.1 to 4.3 hours). According to the results, the extracts of Schinus molle have favorable properties for possible use as an additive which inhibits the oxidation process of the tested vegetables oils.Los aceites más recomendados para la dieta son los ricos en ácidos grasos insa­turados. Sin embargo, la presencia de estos componentes está relacionada con la oxidación del aceite, que puede determinarse por el período de inducción. La seguridad adicional de tales aceites y la prolongación del almacenamiento se pueden lograr mediante la adición de antioxidantes eficientes, que hoy en día se prefieren los provenientes de fuentes naturales. Para contribuir con estas investigaciones, el objetivo principal de este estudio fue evaluar la eficacia de los extractos de Schinus molle en comparación con el antioxidante sintético BHT, para retrasar la oxidación de algunos aceites vegetales. Los resultados del presente estudio mostraron que los extractos de frutas y hojas de Schinus molle presentan potencial para ser utilizados como antioxidan­tes en aceites vegetales, presentando actividades basadas en métodos probados, DPPH y ABTS. Los extrac­tos también se caracterizaron por la presencia de compuestos fenólicos determinados mediante el método de Folin Ciocalteau y por cromatografía líquida de alta resolución (HPLC). La acción de los extractos como antioxidantes naturales se evidenció en aceites vegetales de chía (Salvia hispanica) y maní (Arachis hypogaea) por el método Rancimat. Se observó que los aceites aumentan la resistencia a la oxidación cuando se le incor­poran extractos de Schinus molle, aumentando el periodo de inducción en más de tres horas (de 19,5 a 22,9 horas) del aceite de cacahuete con una concentración de extracto del 2,5%. El extracto de fruta fue más efi­ciente en retrasar la oxidación del aceite de chia, prolongando el período de inducción de este aceite en más de una hora con una concentración del 2,5% (de 3,1 a 4,3 horas). De acuerdo con los resultados, los extractos de Schinus molle tienen propiedades favorables para un posible uso como un aditivo inhibidor del proceso de oxidación de los aceites vegetales ensayados

Estabilidad oxidativa de aceites de soja y maíz enriquecidos con extracto hidroalcohólico de Pluchea quitoc

Soybean and corn oils are among the most popular vegetable oils, and are ingredients which are widely used in cooking and in the food industry. These oils contain many unsaturated fatty acids such as oleic, linoleic and linolenic acids, which makes them easily oxidized by oxygen. Extensive efforts are being made to prevent or minimize vegetable oil oxidation through the development of antioxidants. Phenolic antioxidants which are present in some extracts can be used as food additives to prevent lipid oxidation. In this study chromatographic analyses (HPLC and GC) of the Pluchea quitoc hydroalcoholic extract were performed. The content of phenolic compounds by the Folin-Ciocalteau method and the antioxidant properties against radicals 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) were also evaluated. The effect of samples prepared with soybean and corn oils enriched with Pluchea quitoc hydroalcoholic extract was determined and compared with samples of these oils which were free of antioxidants and with samples containing the synthetic antioxidant BHT. The results showed potential for application of the extract. A high content of phenolic compounds (314 milligrams of gallic acid equivalents (GAE)/g of extract) and good IC50 values were detected for the inhibition of the radicals DPPH and ABTS (13.2 µg·mL-1 and 5.6 µg·mL-1). In the evaluation of the oxidative stability of the oils enriched with this extract, it was found that at 1% concentration it was possible to obtain values of induction period (IP) close to the samples with added BHT.Los aceites de soja y maíz se encuentran entre los aceites vegetales más populares, ingredientes ampliamente utilizados en la cocina y también en la industria alimentaria. Estos aceites contienen muchos ácidos grasos insaturados como los ácidos oleico, linoleico y linolénico que se oxidan fácilmente con el oxígeno. Se están realizando grandes esfuerzos para prevenir o minimizar la oxidación de los aceites vegetales mediante el desarrollo de antioxidantes. Los antioxidantes fenólicos presentes en algunos extractos se pueden utilizar como aditivos alimentarios para prevenir la oxidación de lípidos. En este estudio se realizó la obtención y análisis cromatográficos (HPLC y GC) del extracto hidroalcohólico de Pluchea quitoc. El contenido de compuestos fenólicos se evaluó por el método de Folin-Ciocalteau y las propiedades antioxidantes frente a radicales DPPH y ABTS. Se determinó el efecto de muestras preparadas con aceites de soja y maíz enriquecidas con extracto hidroalcohólico de Pluchea quitoc y se comparó con muestras de estos aceites libres de antioxidantes y con el antioxidante sintético BHT. Los resultados mostraron potencial para la aplicación del extracto. Se detectó un alto contenido de compuestos fenólicos (314 mg GAE) y buenos valores de IC50 para la inhibición de los radicales DPPH y ABTS (13.2 µg·mL-1 y 5.6 µg·mL-1). En la evaluación de la estabilidad oxidativa de los aceites enriquecidos con este extracto, se encontró que para la concentración del 1% es posible obtener valores de período de inducción (IP) cercanos a las muestras adicionadas con BHT

CHIRAL ANALYSIS OF MONOTERPENES IN VOLATILE OILS FROM PROPOLIS

ABSTRACT The essential oils obtained by hydrodistillation from samples of propolis manufactured in three regions of Rio Grande do Sul State at Brazil, were analyzed through CG, CG-MS and chiral phase gas chromatography (CPGC). These analyses display the presence of samples with elevated essential oil purport, when compared with plants. The yields obtained were until 3.8%. The samples exhibited similar composition, with predominance of the monoterpenes a-pinene (57-63%), b-pinene (12.5-30.8%) and limonene (1.5-11.2%). In chiral analysis of these constituents were observed modifications in the enantiomeric excess of isomers of a-pinene and limonene in relation with source location of the sample, already in the chiral analysis of b-pinene were detected only elevated excess of the enantiomer with the (-) configuration. The antimicrobial activity of the crude essential oil was assayed against five bacteria. The best result was obtained against Staphylococcus aureus

Measurement of the Polarized Structure Function σLT′\sigma_{LT^\prime} for p(e⃗,e′π+)np(\vec{e},e'\pi^+)n in the Δ(1232)\Delta(1232) Resonance Region

The polarized longitudinal-transverse structure function $\sigma_{LT^\prime}$ has been measured using the $p(\vec e,e'\pi^+)n$ reaction in the $\Delta(1232)$ resonance region at $Q^2=0.40$ and 0.65 GeV$^2$. No previous $\sigma_{LT^\prime}$ data exist for this reaction channel. The kinematically complete experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at an energy of 1.515 GeV. A partial wave analysis of the data shows generally better agreement with recent phenomenological models of pion electroproduction compared to the previously measured $\pi^0 p$ channel. A fit to both $\pi^0 p$ and $\pi^+ n$ channels using a unitary isobar model suggests the unitarized Born terms provide a consistent description of the non-resonant background. The $t$-channel pion pole term is important in the $\pi^0 p$ channel through a rescattering correction, which could be model-dependent.Comment: 6 pages, LaTex, 5 eps figures: Submitted to PRC/Brief Reports v2: Updated referenc

Deeply virtual and exclusive electroproduction of omega mesons

The exclusive omega electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q2) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross sections were measured up to large values of the four-momentum transfer (-t < 2.7 GeV2) to the proton. The contributions of the interference terms sigma_TT and sigma_TL to the cross sections, as well as an analysis of the omega spin density matrix, indicate that helicity is not conserved in this process. The t-channel pi0 exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction gamma* p -> omega p, even for Q2 as large as 5 GeV2. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross sections is nearly Q2-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit.Comment: 15 pages,19 figure

Q^2 Dependence of the S_{11}(1535) Photocoupling and Evidence for a P-wave resonance in eta electroproduction

New cross sections for the reaction $ep \to e'\eta p$ are reported for total center of mass energy $W$=1.5--2.3 GeV and invariant squared momentum transfer $Q^2$=0.13--3.3 GeV$^2$. This large kinematic range allows extraction of new information about response functions, photocouplings, and $\eta N$ coupling strengths of baryon resonances. A sharp structure is seen at $W\sim$ 1.7 GeV. The shape of the differential cross section is indicative of the presence of a $P$-wave resonance that persists to high $Q^2$. Improved values are derived for the photon coupling amplitude for the $S_{11}$(1535) resonance. The new data greatly expands the $Q^2$ range covered and an interpretation of all data with a consistent parameterization is provided.Comment: 31 pages, 9 figure

Measurement of Inclusive Spin Structure Functions of the Deuteron

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer ($Q^2$ = 0.27 -- 1.3 (GeV/c)$^2$) and final hadronic state mass in the nucleon resonance region ($W$ = 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ($^{15}$ND$_3$) and detected the scattered electrons with the CEBAF Large Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal double spin asymmetry $A_{||}$ and the spin structure function $g_1^d$. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function $g_1^d$ and study its approach to both the deep inelastic limit at large $Q^2$ and to the Gerasimov-Drell-Hearn sum rule at the real photon limit ($Q^2 \to 0$). We find that the first moment varies rapidly in the $Q^2$ range of our experiment and crosses zero at $Q^2$ between 0.5 and 0.8 (GeV/c)$^2$, indicating the importance of the $\Delta$ resonance at these momentum transfers.Comment: 13 pages, 8 figures, ReVTeX 4, final version as accepted by Phys. Rev.

A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments

We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.Comment: revtex4 18 pp., 12 figure