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The conjugation of biomolecules to magnetic nanoparticles has emerged as promising approach in biomedicine as the treatment of several diseases, such as cancer. In this study, conjugation of bioactive peptide fractions from germinated soybeans to magnetite nanoparticles was achieved. Different fractions of germinated soybean peptides (>10 kDa and 5-10 kDa) were for the first time conjugated to previously coated magnetite nanoparticles (with 3-aminopropyltriethoxysilane (APTES) and sodium citrate) by the Ugi four-component reaction. The crystallinity of the nanoparticles was corroborated by X-ray diffraction, while the particle size was determined by scanning transmission electron microscopy. The analyses were carried out using infrared and ultraviolet-visible spectroscopy, dynamic light scattering, and thermogravimetry, which confirmed the coating and functionalization of the magnetite nanoparticles and conjugation of different peptide fractions on their surfaces. The antioxidant activity of the conjugates was determined by the reducing power and hydroxyl radical scavenging activity. The nanoparticles synthesized represent promising materials, as they have found applications in bionanotechnology for enhanced treatment of diseases, such as cancer, due to a higher antioxidant capacity than that of fractions without conjugation. The highest antioxidant capacity was observed for a >10 kDa peptide fraction conjugated to the magnetite nanoparticles coated with APTES.

The anodic oxidation of mercury in the presence of hydrogen peroxide in differential pulse voltammetry (DPV) was used to determine the antioxidant (AO) character of radical scavengers. Hydroperoxide radical is formed at the potentials of the oxidation peak on mercury electrodes, such radical reacting with the antioxidants in different extension. The parameter C10 (antioxidant concentration at which the peak area decreases by 10%) is used to measure the scavenging activity of the individual antioxidants. To establish the scavenging activity of antioxidant mixtures as a whole, the parameter, μ10 as the reverse of V10, V10 being the volume necessary to decrease the peak area in DPV by 10%, was selected. Higher μ10 values correspond to higher scavenging activity. The studies have been extended to aqueous extracts of some species. The results may be useful in explaining the effect of spices in vitro and in vivo studies.

Antioxidant activity of a number of small (low molecular weight) natural compounds found in spices, condiments or drugs (gallic acid, sesamol, eugenol, thymol, carvacrol, vanillin, salicylaldehyde, limonene, geraniol, 4-hexylresorcinol, etc.) has been evaluated using electrochemical and DPPH• radical scavenging measurements. Structural analysis of the tested compound suggest a remarkable activity for phenol derivatives and the importance of the -R groups located on the phenolic ring in the molecule's ability to act as free radical scavenging as well as their influence in the electrochemical behavior. The voltammetric method can be used for the determination of the antioxidant capability in the same manner as the DPPH• radical scavenging because of the correlation found between oxidation potentials and anti-radical power (ARP = 1/EC₅₀). Such electrochemical determination is fast and cheap and allows making measurements under a variety of experimental conditions. The accuracy of the electrochemical measurements is the same for all the compounds, irrespective of their scavenging activity, the opposite of what occurs in the DPPH• test.

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The oxidation process occurring on mercury electrodes in the presence of hydrogen peroxide has been analized in basic solutions by polarography and voltammetry in their linear scan and differential pulse modes. The process involves Hg(I) ion - in addition to Hg(II) ion - and hydroperoxide radicals, these last formed at trace levels. To demonstrate this radical generation radical scavengers (antioxidants), characterized with the DPPH* radical scavenging assay, were employed. The interaction of the radicals with the antioxidant originate the decrease in signal, but the antioxidant itself does not react with the hydrogen peroxide in the absence of Hg. In the absence of antioxidant, the process is two-electron, being the rate-determining step the second electron transfer; at high concentrations of antioxidant, the oxidation corresponds to a reversible one-electron transfer followed by a chemical reaction between the hydroperoxide radicals and the antioxidant. A reaction scheme is proposed for intermediate antioxidant concentrations. [ABSTRACT FROM AUTHOR]

Objective. Evaluate the effect on tegument pigmentation, survival, growth and antioxidant capacity in diets supplemented with tomato extract and lycopene as additives in experimental feed for Carassius auratus and Xiphophorus maculatus. Materials and methods. The additives were added in different concentrations to a basic diet. We performed beginning and an ending biometrics for 100% of the population in each bioassay. The growth and survival of organisms were evaluated. The antioxidant capacity was analyzed by ABTS assay, both in the tomato extract sample as well as in foods used in different bioassays. The concentration of lycopene was determined in food and liver and muscle samples offish fed with it. Acquired pigmentation offish was assessed through photographs analyzed with Adobe Photoshop®. The results were evaluated by analysis of variance, and when differences were found (p<0.05) the means were compared by the Tukey test. Results. No significant effect (p>0.05) on pigmentation and growth of the organisms under the established experimental conditions was obtained. Significant differences in antioxidant capacity (p<0.05) were obtained in foods with added lycopene. Conclusions. The inclusion of lycopene or tomato extract in food for the organisms used is not recommended to improve pigmentation, but further studies are needed to demonstrate antioxidant effect. [ABSTRACT FROM AUTHOR]

The polarographic (direct current, dc, and differential pulse, DP) and voltammetric oxidation of hydrogen peroxide on mercury electrodes has been examined. The electrooxidation of H2O2 involves hydroperoxide radical and superoxide anion radical able to interact with radical scavengers (antioxidants), namely 3-hydroxycoumarin, carvacrol, vanillin and gallic acid. For such interaction, theoretical equations are derived using the convective diffusion approximation and the steady-state conditions, as well as solving the differential equations of the Nernst diffusion-layer approximation by the method of dimensionless variables. The experimental results agree with the theoretical predictions and a kinetic parameter is proposed to evaluate the scavenging activity of antioxidants. [ABSTRACT FROM AUTHOR]

Objective. Evaluate the effect on tegument pigmentation, survival, growth and antioxidant capacity in diets supplemented with tomato extract and lycopene as additives in experimental feed for Carassius auratus and Xiphophorus maculatus. Materials and methods. The additives were added in different concentrations to a basic diet. We performed beginning and an ending biometrics for 100% of the population in each bioassay. The growth and survival of organisms were evaluated. The antioxidant capacity was analyzed by ABTS assay, both in the tomato extract sample as well as in foods used in different bioassays. The concentration of lycopene was determined in food and liver and muscle samples of fish fed with it. Acquired pigmentation of fish was assessed through photographs analyzed with Adobe Photoshop®. The results were evaluated by analysis of variance, and when differences were found (p0.05) on pigmentation and growth of the organisms under the established experimental conditions was obtained. Significant differences in antioxidant capacity (p