Study of the local field distribution on a single-molecule magnet-by a single paramagnetic crystal; a DPPH crystal on the surface of an Mn12-acetate crystal

The local magnetic field distribution on the subsurface of a single-molecule magnet crystal, SMM, above blocking temperature (T >> Tb) detected for a very short time interval (~ 10-10 s), has been investigated. Electron Paramagnetic Resonance (EPR) spectroscopy using a local paramagnetic probe was employed as a simple alternative detection method. An SMM crystal of [Mn12O12(CH3COO)16(H2O)4].2CH3COOH.4H2O (Mn12-acetate) and a crystal of 2,2- diphenyl-1-picrylhydrazyl (DPPH) as the paramagnetic probe were chosen for this study. The EPR spectra of DPPH deposited on Mn12-acetate show additional broadening and shifting in the magnetic field in comparison to the spectra of the DPPH in the absence of the SMM crystal. The additional broadening of the DPPH linewidth was considered in terms of the two dominant electron spin interactions (dipolar and exchange) and the local magnetic field distribution on the crystal surface. The temperature dependence of the linewidth of the Gaussian distribution of local fields at the SMM surface was extrapolated for the low temperature interval (70-5 K)

Single crystals of DPPH grown from diethyl ether and carbon disulfide solutions - Crystal structures, IR, EPR and magnetization studies

Single crystals of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) obtained from diethyl ether (ether) and carbon disulfide (CS2) were characterized by the X-ray diffraction, IR, EPR and SQUID magnetization techniques. The X-ray structural analysis and IR spectra showed that the DPPH form crystallized from ether (DPPH1) is solvent free, whereas that one obtained from CS2 (DPPH2) is a solvate of the composition 4DPPH.CS2. Principal values of the g-tensor were estimated by the X-band EPR spectroscopy at room and low (10 K) temperatures. Magnetization studies revealed the presence of antiferromagnetically coupled dimers in both types of crystals. However, the way of dimerization as well as the strength of exchange couplings are different in the two DPPH samples, which is in accord with their crystal structures. The obtained results improved parameters accuracy and enabled better understanding of properties of DPPH as a standard sample in the EPR spectrometry

Assessment of the Scavenging Activity of Crude Methanolic Stem Bark Extract of Newbouldia Laevis on Selected Free Radicals

From ancient times, the therapeutic application of medicinal plants, also known as alternative medicine has been popular. Today, biological research has shown that this practice of phytotherapy will remain with man for sometime. Some medicinal applications of parts of Newbouldia laevis are known. Air dried leaves of N. laevis (Bignoniaceae) were powdered and extracted with 95%v/v methanol by maceration, and the extract concentrated at 40oC using Rotary evaporator. The weight of the extracted plant material was noted for the purpose of calculating yield. In vitro assessment of the ability of the extract to scavenge the Reactive Oxygen Species (ROS), hydrogen peroxide, superoxide anion and the synthetic radical 1, 1-Diphenyl-2-picrylhydrazyl (DPPH) was determined. Buthylated hydroxyanisole (BHA), a synthetic antioxidant was used as a positive control. Plant extract showed concentration- dependent scavenging activity on all reactive species used. Scavenging activity of plant extract on hydrogen peroxide and superoxide was more than that of BHA on same. However, BHA was more effective at scavenging DPPH radical than plant extract

In vitro Assessment of the Free Radical Scavenging Activity of Psidium Guajava

Observable significant revisit of ancient approach to prophylaxis and anaphylaxis (herbaltherapy), though with modern dimensions of study envelopes our world of research today. Reports on the medicinal use of parts of Psidium guajava (Myrtaceae), including leaves and stem barks have been reported in, and beyond Africa. Air dried leaves of P. guajava were powdered and extracted with 95%v/v methanol by maceration, and the extract concentrated at 40oC using Rotary evaporator. The weight of the extracted plant material was recorded for yield calculations. In vitro assessment of the ability of the extract to scavenge the Reactive Oxygen Species (ROS), hydrogen peroxide, superoxide and the synthetic radical 1,1-Diphenyl-2-picrylhydrazyl (DPPH) was determined with reference to the synthetic antioxidant Buthylated hydroxyanisole (BHA). Plant extract showed concentration- dependent scavenging activity on all reactive species used. Scavenging activity of plant extract on hydrogen peroxide and superoxide was more than that of BHA on same. However, BHA showed greater DPPH scavenging activity than plant extract

Comparative Antioxidant Activity on the Ficus Benjamina and Annona Reticulata Leaves

Antioxidants can prevent free radical formation. Natural antioxidants found in many plants, such as Ficus benjamina and Annona reticulata. The study aimed to compare the antioxidant activity of extracts and fractions of Ficus benjamina and Annona reticulata leaves against 1,1-diphenyl-2-picrilhydrazyl. The steps of this study consist of extraction, fractionation with n-hexane, ethyl acetate and water, phytochemical screening, antioxidant activity determination, and comparing the IC50 values. Percentage scavenging activity of the extracts and fractions against DPPH was calculated to determine the antioxidant activity. The IC50 value of Ficus benjamina was 127.86 ppm for ethanolic extract, 94.01 ppm for water fraction, 115.48 ppm for ethyl acetate fraction, and 335.50 ppm for n-hexane fraction. The IC50 value of Annona reticulata was 274.31 ppm for ethanolic extract, 211.42 ppm for water fraction, 367.91 ppm for ethyl acetate fraction, and 741.08 ppm for n-hexane fraction. The results showed that the Ficus benjamina water fraction was the best antioxidant compared to other extract and fraction

Larix decidua Bark as a Source of Phytoconstituents: An LC-MS Study

Larix decidua bark is a waste of the timber industry and is widely diffused in Northern Italy. This material can be considered a good source of antioxidants and phytoconstituents with possible use in cosmetic or nutraceutical products. In this study, simple extraction of larch bark was performed using mixtures of ethanol/water. Furthermore, the phytochemical composition of larch bark extract was studied using LC-MS(n) methods and the main constituents were identified as flavonoids, spiro-polyphenols, and procyanidins. To confirm the identification by LC-MS semi-preparative HPLC was performed in order to isolate the main constituents and verify the structures by \ub9H-NMR. Antioxidant properties were studied using an in vitro approach combining DPPH assay and LC-MS in order to establish different roles of the various classes of phytochemicasl of the extract. DPPH activity of some of the isolated compounds was also assessed. The overall results indicate this waste material as a good source of antioxidant compounds, mainly procyanidins, whichresulted the most active constituents in the DPPH assay

Escobajos de la vid como fuente de compuestos fenólicos con propiedades antioxidantes

Winemaking industry generates considerable amounts of bunch stems that are usually wasted despite their potential value as source of bioactive compounds. Phenolic profiles and antioxidant capacity (AC) of bunch stem extracts from eight grape varieties of Vitis vinifera L. were determined. Sixteen phenolic compounds (PC) were quantified by high performance-liquid chromatography-diode array detection (HPLC-DAD). The maximum concentrations corresponded to the flavanols (+)-catechin (6462 μg g-1 DW) and procyanidin B1 (1987 μg g-1 DW), followed by the hydroxycinnamic acid caftaric acid (2967 μg g-1 DW). Naringin, myricetin and OH-tyrosol were identified for the first time in grape bunch stems. Total phenolic content (TPC) of extracts, assessed as gallic acid equivalents (GAE), ranged between 47 and 125 mg GAE g-1 DW. The AC of extracts was appraised by ORAC, ABTS and DPPH assays, with a good correlation between TPC and AC when measured by ABTS and DPPH (r ≥ 0.92), while for ORAC the correlation was lower (r ≤ 0.41). Samples of cv. Malbec, the most representative variety of Argentina, presented the highest contents in PC, particularly flavanols. The results showed that grape bunch stems may be an inexpensive, sustainable and high value source of bioactive compounds as functional ingredients.La industria vitivinícola genera cantidades considerables de escobajo que generalmente se desperdician a pesar de su valor potencial como fuente de compuestos bioactivos. En este trabajo se determinaron los perfiles fenólicos y capacidad antioxidantes (CA) de extractos de escobajo de ocho variedades diferentes de Vitis vinífera L. Se cuantificaron 16 compuestos fenólicos (PC) utilizando cromatografía líquida de alta resolución acoplada a detector de arreglo de diodos (HPLC-DAD). Las concentraciones más elevadas obtenidas correspondieron a los flavanoles (+)-catequina (6462 μg g-1 peso seco) y procianidina B1 (1987 μg g-1 peso seco), seguido del ácido caftárico (2967 μg g-1 peso seco). La naringenina, miricetina y OH-tirosol fueron identificados por primera vez en escobajos. El contenido total de compuestos fenólicos (TPC) de los extractos determinado con equivalentes de ácido gálico (GAE) presentó valores entre 47 y 125 mg GAE g-1 peso seco. La CA de los extractos fue determinada mediante las técnicas ORAC, ABTS y DPPH, evidenciando una buena correlación entre TPC y la CA medida mediante ABTS y DPPH (r ≥ 0,92), mientras que para ORAC la correlación fue más baja (r ≤ 0,41). La muestra de variedad más representativa de Argentina, cv. Malbec, presentó los mayores niveles de PC, particularmente flavanoles. Los resultados evidencian que los escobajos pueden ser una fuente económica, sostenible y de alto valor de compuestos bioactivos para su utilización como ingredientes funcionales.Fil: Ferreyra, Susana Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; ArgentinaFil: Bottini, Ambrosio Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina. Universidad "Juan Agustín Maza"; ArgentinaFil: Fontana, Ariel Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentin

Seasonal Variation in Leaf Growth and Antioxidant Content of Moringa oleifera Cultivated at Buenos Aires, Argentina

The properties and applications of Moringa oleifera are so vast that it is called the "miracle tree". The objective of this work is to study the seasonal variations in the leaf antioxidant content and the scavenging activity on DPPH radicals in concordance with its growth on M. oleifera plants of two seed origin, Commercial (C, seeds that were obtained from a market) and Bolivia (B, seeds that were obtained from a commercial forest of Santa Cruz de la Sierra, Bolivia); the experiment was conducted at Buenos Aires, Argentina. Significant differences were found on leaf growth, antioxidant content and DPPH activity along the growing season. The lower leaf dry weight as percentage of fresh weight, higher specific leaf area, higher relative growth rate and lower phenol content on B leaves than C leaves could indicate that B plants are geared for a higher productivity rate of resource acquisition than C plants. Specific leaf area, leaf dry weight as percentage of fresh weight, phenol content and activity of DPPH radicals on leaf extracts were significantly correlated, which could be used on productivity estimation and nutraceutical valuation. The phenol content and activity of DPPH radicals of leaf extracts of B and C origins indicate that the leaves of the plants growing in the described conditions are of noteworthy value. These are the first antecedents for M. oleifera growing at Buenos Aires, Argentina, allowing to preliminary consider this area as one of the southernmost zone.Fil: Arena, Miriam Elisabet. Universidad de Morón. Facultad de Agronomía y Ciencias Agroalimentarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Radice, Silvia. Universidad de Morón. Facultad de Agronomía y Ciencias Agroalimentarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Potential of Lignins as Antioxidant Additive in Active Biodegradable Packaging Materials

Lien vers la version éditeur: http://link.springer.com/article/10.1007/s10924-013-0570-6Due to their polyphenolic structure lignins bear a number of interesting functional properties, such as antioxidant activity. Natural antioxidants are very much looked for in the aim of protection of light or oxygen sensitive goods and are being used in active packaging. Poly(lactide) (PLA)-lignin films were prepared by twin screw extrusion followed by thermo-compression using two different commercial sources of alkali lignins obtained from gramineous plants. A good dispersion of lignin in the matrix was observed. Mechanical properties of the compounded material were merely diminished and oxygen barrier properties slightly enhanced. The chromatographic study of the lignins revealed that the low molecular weight fraction of both lignins increased during the polymer processing. The migration of low molecular weight compounds in an ethanol/water solution simulating fatty foodstuff was performed and the antioxidant activity of the extract was analysed. It was found that the activity increases with increasing severity of the heat treatment because of the generation of free phenolic monomers during processing. These results open an interesting way for application of lignins as an active compound in packaging materials. Lignins do not impair the mechanical and barrier performance of the polymer and the plastics processing even allows for the generation of active substances