Role of Superoxide Anions in the Redox Changes Affecting the Physiologically Occurring Cu(I)-Glutathione Complex

The physiologically occurring copper-glutathione complex, [Cu(I)-[GSH]2], has the ability to react continually with oxygen, generating superoxide anions (O2∙−). We addressed here the effects that superoxide removal has on the redox state of Cu(I) and GSH present in such complex and assessed the formation of Cu(II)-GSSG as a final oxidation product. In addition, we investigated the potential of a source of O2∙− external to the Cu(I)-[GSH]2 complex to prevent its oxidation. Removal of O2∙− from a Cu(I)-[GSH]2-containing solution, whether spontaneous or Tempol-induced, led to time-dependent losses in GSH that were greater than those affecting the metal. The losses in GSH were not accompanied by increments in GSSG but were largely accounted for by the cumulative formation of Cu(II)-GSSG molecules. Notably, the redox changes in Cu(I) and GSH were totally prevented when Cu(I)-[GSH]2 was coincubated with hypoxanthine/xanthine oxidase. Data suggest that the generation of O2∙− by Cu(I)-[GSH]2 implies the obliged formation of an intermediate whose subsequent oxidation into Cu(II)-GSSG or back reduction into Cu(I)-[GSH]2 is favoured by either the removal or the addition of O2∙−, respectively

Antioxidant effect of 5-amino salicylic acid on copper-mediated LDL oxidation

The antioxidant effect of 5-Aminosalicylic acid (5-ASA) on copper-mediated LDL oxidation was followed either by the emitted chemiluminiscence (CL) or by UV-vis spectroscopy. 5-ASA addition extends the lag phase in a concentration-dependent manner without changes in the rate of the process in the autoaccelerated phase. The antioxidant behavior of 5-ASA was very similar to that of Trolox, a very efficient water soluble antioxidant. The copper-binding capacity of 5-ASA was evaluated by UV-visible spectroscopy. The addition of copper to a 5-ASA solution increases the absorbance at 332 nm and generates a new band at 298 nm. These changes in the UV-vis spectra indicate formation of a complex between 5-ASA and copper. However, LDL protection by 5-ASA is unrelated to its copper chelating capacit

Identification of the transition state for fast reactions: The trapping of hydroxyl and methyl radicals by DMPO - A DFT approach

Up to date, attempts to locate the transition state (TS) for the trapping reaction between ̇OH and ̇DMPO have been unsuccessful, and the lack of molecular mechanisms by which ̇OH binds to the spin-trap constitutes a question still unsolved. Herein, we have taken a step forward on this task by describing the theoretical TS for the trapping of ̇OH and ̇CH 3 by DMPO and the intrinsic reaction coordinates. This work aims to provide new understandings on the molecular orbital (MO) interactions that rule these reaction paths. Besides we assessed the degree of involvement of weak interactions and the charge transfer (CT) phenomenon involved in such interactions. Regarding the trapping of ̇OH, the beginning of the reaction would be ruled by weak interactions to then give way to stronger MO interactions conducive to the formation of the TS. For ̇CH3, the reaction is, instead, early ruled by significant MO interactions, and a relatively small contribution in the weak interactions range. At the

An in vitro study of the antioxidant and antihemolytic properties of buddleja globosa (Matico)

The antioxidant and antihemolytic properties contained in the leaves of Buddleja globosa (B. globosa), also known as "Matico," were determined. Aqueous extracts of leaves were assayed in human erythrocytes and molecular models of its membrane. The latter were bilayers built-up of lipids located in the outer and inner leaflets of the erythrocyte membrane. Observations by scanning electron microscopy showed that the extract altered the morphology of erythrocytes inducing the formation of crenated echinocytes. This result implied that the extract components were inserted into the outer leaflet of the cell membrane. This conclusion was confirmed by experiments carried out by fluorescence spectroscopy of red cell membranes and vesicles (LUV) of dimyristoylphosphatidylcholine (DMPC) and by X-ray diffraction of DMPC and dimyristoylphosphatidylethanolamine bilayers. Human erythrocytes were in vitro exposed to HClO, which is a natural powerful oxidant. Results demonstrated that low concentrations of B. globosa aqueous extract neutralized the harmful capacity of HClO. Hemolysis experiments also showed that the extract in very low concentrations reduced hemolysis induced by HClO.FONDECYT Grant, 109004

Apple peel polyphenol extract protects against indomethacin-induced damage in Caco-2 cells by preventing mitochondrial Complex i inhibition

The aim of this work was to investigate the role of mitochondrial dysfunction in the development of oxidative stress and cytotoxicity induced by indomethacin and to evaluate the potential of an apple peel polyphenol extract (APPE) in protecting against these events Indomethacin induced, time-dependently, mitochondria] and oxidative perturbations which led to cell losses An inhibition of complex I activity, shown for first time here, which resulted in a concomitant drop in cellular ATP and an increment in mitochondrial superoxide production, was observed after 10 mm of exposure These early cytotoxicity-triggering events were followed by an increase in the intracellular production of superoxide (20 min), an elevation in the activity of xanthine oxidase which led to an increased lipid peroxidation (30 mm), and a decline in cell viability which manifested after 40 nun These events were selectively prevented using allopurinol, tempol and APPE (a standardized apple peel polyphenol extract) While the oxidative and cell lytic effects of indomethacin were equally prevented by the three agents, only APPE protected against complex I inhibition and its downstream oxidative consequences Since tempol (a SOD mimetic)prevented the elevation xanthine oxidase activity, and allopurinol (a xanthine oxidase inhibitor) totally abolished the increment in lipid peroxidation and loss of cell viability, it appears that a superoxide-dependent increase in xanthine oxidase activity is critical to trigger cytotoxicity Thus, preventing the early increment in superoxide formation that, as a result of inhibiting complex I, takes place within mitochondria would be key toward protecting the cells against the oxidative and cytolytic effects of indomethacin The ability of APPE in preventing the inhibition of complex land the subsequent superoxide-dependent increase in XO activity warrants further studies to evaluate the mechanism involves in the protecting effect of APPE against the indomethacin-associated adverse effects in viv

Oxidation of Quercetin and Kaempferol Markedly Amplifies Their Antioxidant, Cytoprotective, and Anti-Inflammatory Properties

The contention that flavonoids’ oxidation would necessarily lead to a loss of their antioxidant properties was recently challenged by the demonstration that quercetin oxidation leads to the formation of 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (Que-BZF), a metabolite whose antioxidant potency was notably higher than that of its precursor. Here, we compared and expanded the former observation to that of the quercetin analogue kaempferol. Oxidation of kaempferol led to the formation of a mixture of metabolites that included the 2-(4-hydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (Kae-BZF). Following the chromatographic isolation of Kae-BZF from such a mixture, its antioxidant, mitochondria- and cell-protecting, and NF-kB-inhibiting effects were assessed, and compared with those of Que-BZF, in Caco-2 cells exposed to indomethacin as a source of ROS. The concentrations of Que-BZF (100 nm) and Kae-BZF (1 nm) needed to attain their maximal protection effects were 50- and 5000-fold lower than those of their respective precursors. The former differences in concentrations were also seen when the abilities of Que-BZF and Kae-BZF to inhibit the indomethacin-induced activation of NF-kB were compared. These data not only reveal that the oxidative conversion of quercetin and kaempferol into their respective 2-benzoyl-2-hydroxy-3(2H)-benzofuranones (BZF) results in a considerable amplification of their original antioxidant properties, but also that the in the case of kaempferol, such amplification is 100-fold greater than that of quercetin

Pharmacokinetic implications associated to the use of drugs as racemates or pure enantiomers Implicancias farmacocinéticas asociadas al uso de fármacos como racematos o enantiómeros puros.

This article critically reviews the recent specialized literature concerning the influence of the stereochemical nature of quiral drugs on the pharmacokinetic processes and its pharmacological implications. Evidence is presented indicating that as a function of the type of enantiomer administered, profound differences in the pharmacokinetic profiles, e.g. absorption, distribution, biotransformation and elimination can occur. As a consequence of the enantioselective nature of the drug-organism interaction, major differences in the therapeutic responses can be envisaged depending on whether the drug is administered as a pure enantiomer or as a racemic mixture

Un sistema para la deteccion de antioxidantes volatiles comunmente emitidos desde especias y hierbas medicinales A system for detection of volatile antioxidant commonly emitted from spices and medicinal herbs

<abstract language="eng">An apparatus which allows the direct measurement of the antioxidant capacity of volatiles compounds emitted from some herbs and culinary spices is described. The device comprises: a sample chamber, a mixing chamber, a pump and, a detection system. Volatiles from Clove (Syzygium aromaticum (L.) Merr. & L.M. Perry) were purged and captured into a DPPH-containing solution and changes in the absorbance were recorded on-line. Linear response was observed when temperature was set between 30-53 ºC; nitrogen flow was 15 mL min-1 during 60 min; DPPH concentration was 20 µmol L-1 and a sample size (powdered Clove) ranged between 200-1000 mg

Comparison of rancimat evaluation modes to assess oxidative stability of fish oils

Two Rancimat evaluation modes, the induction period (IP), and the time needed to achieve a selected difference in conductivity (tΔK) were compared for assessing relative stability of anchovy sardine, and hake liver oils. Mean coefficients of variation were 2.5 and 2.4% for IP and tΔK values, respectively, for oils oxidized in the range 55-90°C. Natural logarithms of IP and tΔK values varied linearly with temperature (P&lt; 0.001). A linear relationship (r = 0.999) was established between the IP and tΔK values (P&lt; 0.001). Relative oxidative stability of fish oils was determined with the same degree of confidence by either IP or tΔK values