EVALUATION OF THE ANTIOXIDANT ACTIVITY OF THE FLAVONOIDS ISOLATED FROM HELIOTROPIUM SINUATUM RESIN USING ORACFL, DPPH AND ESR METHODOLOGIES

Indexación: Web of Science; Scielo.The antioxidant capacity has been determined for a number of flavonoid compounds from Heliotropium sinuatum, a plant that grows in arid areas in the north of Chile. The methodologies used were: ORAC(FL) (oxygen radical absorbance capacity - fluorescein), DPPH (2,2-diphenyl-2-picrylhydrazyl) bleaching and electron spin resonance (ESR). These compounds were studied in homogeneous and heterogeneous media. The results showed that the 7-o-methyleriodictiol and 3-o-methylisorhamnetin are those with the highest antioxidant capacity.http://ref.scielo.org/m82cz

Cyrhetrenylaniline and new organometallic phenylimines derived from 4- and 5-nitrothiophene: Synthesis, characterization, X-Ray structures, electrochemistry and in vitro anti-T. brucei activity

A novel series of cyrhetrenyl (3a-4a) and ferrocenyl (3b-4b) Schiff bases were synthesized through a condensation reaction, between the known 4-ferrocenylaniline (2b) or the unreported 4-cyhretrenylaniline (2a) with 4- or 5-nitrothiophenecarboxaldehyde. The structure of 2a and the new Schiff bases have been elucidated using conventional spectroscopic techniques (FT-IR, 1H and 13C NMR), mass spectrometry, and single-crystal X-ray diffraction analysis of compounds 2a, 4a and 3b. Cyclic voltammetry of organometallic phenylimines derived from 5-nitrothiophene showed NO2 group reduction potentials (E1/2z 0.575 V) that were more anodic than those registered for their 4-nitro analogues (E1/2z 0.981 V). All organometallic imines were tested against the bloodstream form of Trypanosoma brucei. Evaluation indicated that the most active complexes are the 5-nitrothiophene derivatives, 4a, which were remarkably more active than nifurtimox. In addition, complex 4b resulted in less toxicity to host L6 cells than nifurtimox. The results revealed that the electronic effects of cyrhetrene and ferrocene are not an influential factor in E1/2 and anti-Trypanosoma brucei activity for these new imines, which is probably due to the non-coplanarity of the [(h5-C5H4)-C6H4-N=CH-(C4H2S)] system

NMR as a tool for simultaneous study of diasteroisomeric inclusion complexes, part 2: Complexes formed by racemic mixture of 4′- hydroxyflavanone and two cyclodextrins

Complexes formed by (±)-4′-hydroxyflavanone (OHFL) and the cyclodextrins β-cyclodextrin and (2-hydroxypropyl)-β-CD were obtained using the racemic mixture of the OHFL. These complexes were able to be studied due to their enantiodifferentiation by 1H-NMR spectroscopy. Stoichiometry, association constants and thermodynamic parameters were obtained from these NMR data, and inclusion geometries were proposed from ROESY spectra. The results show a 1:1 stoichiometry, K a values decrease with increasing temperature, a spontaneous and exothermic complexes formation, and that ROESY spectra cannot differentiate between enantiomers, and therefore the estimated inclusion geometries were proposed for the mixture of diasteroisomeric complexes. © 2011 Springer Science+Business Media B.V

NMR as a tool for simultaneous study of diastereoisomeric inclusion complexes formed by racemic mixture of 4′-hydroxyflavanone and heptakis-(2,6-O-dimethyl)-β-cyclodextrin

The complexes formed by (±)-4′-hydroxyflavanone (OHFL) and heptakis-(2,6-O-dimethyl)-β-cyclodextrin (DM-β-CD) were obtained using the racemic mixture of OHFL. These complexes were able to be studied due to their enantiodifferentiation by 1H-NMR spectroscopy. Stoichiometry, association constants and thermodynamic parameters were obtained from these NMR data, and inclusion geometries were proposed from ROESY and docking experiments. The results show that diastereoisomeric complexes can be studied even when they are formed by enantiomeric mixtures. © 2010 Springer Science+Business Media B.V

ESR, electrochemical and ORAC studies of nitro compounds with potential antiprotozoal activity

Cyclic Voltammetry (CV) and electron spin resonance (ESR) techniques were used in the investigation of several potentially antiprotozoal nitro derivatives of dihydroquinoxaline and indazole. A self-protonation process involving protonation of the nitro group due to the presence of an acidic proton in the structure of the nitro compound was observed in the first step of an ECErev reduction mechanism. ESR spectra of the free radicals obtained by electrochemical reduction in situ were characterized and analyzed. The ESR spectra showed three different hyperfine patterns for both families of compounds. In order to evaluate the free radical scavenger properties of these nitrocompounds we carried out ORAC-Fl (Oxygen Radical Antioxidant Capacity) assay. These derivatives showed a low antioxidant capacity

Contribution of metals, sulfur-dioxide and phenolic compounds to the antioxidant capacity, of Carmenere wines

Univ Talca, Fac Ciencias Agr, Talca, Chile. Laurie, VF (Felipe Laurie, V.)In this research, we determined the chemical composition of 37 Vitis vinifera cv. Carmenere wines and established their antioxidant capacity (AC). A set of 26 measurements of chemical species potentially related to AC, including phenolic compounds, free and combined sulfites and iron, copper and manganese were obtained for each wine. The AC was estimated by DPPH center dot and ORAC-FL methods. Statistical analyses showed good correlations between chemical profiles and AC values (DPPH rho(2) = 0.90 and ORAC-FL rho(2) = 0.87). The main chemical markers contributing to AC were the fraction of color given by free and copigmented anthocyanins (39.1%) for DPPH and gallic acid (30.7%) for ORAC-FL. These are a good indication of the complexity of the wine matrix, and the wide variety of substances possibly contributing to AC. (C) 2014 Elsevier Inc. All rights reserved

New insights into the antioxidant activity of hydroxycinnamic and hydroxybenzoic systems: Spectroscopic, electrochemistry, and cellular studies

© 2014 Informa UK, Ltd. A series hydroxycinnamic and gallic acids and their derivatives were studied with the aim of evaluating their in vitro antioxidant properties both in homogeneous and in cellular systems. It was concluded from the oxygen radical absorbance capacity-fluorescein (ORAC-FL), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and cyclic voltammetry data that some compounds exhibit remarkable antioxidant properties. In general, in homogeneous media (DPPH assay), galloyl-based cinnamic and benzoic systems (compounds 7-11) were the most active, exhibiting the lowest oxidation potentials in both dimethyl sulfoxide (DMSO) and phosphate buffer. Yet, p-coumaric acid and its derivatives (compounds 1-3) disclosed the highest scavenging activity toward peroxyl radicals (ORAC-FL assay). Interesting structure-property- activity relationships between ORAC-FL, or DPPH radical, and redox potentials have been attained, showing that the latter parameter can be a valuable antioxidant measure. It w