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

Insights into the antioxidant activity of phenolic compounds: Synthesis and electrochemical study of new series of hydroxycoumarins

The 15th International Electronic Conference on Synthetic Organic Chemistry session Bioorganic, Medicinal and Natural ProductsPhenolic compounds are bioactive substances widely distributed in the vegetable kingdom. They act as natural antioxidants, and their presence contributes to the color, flavor and aroma of food. This group of micronutrients is composed of one or more aromatic benzene rings with one or more hydroxyl groups and their redox properties are related with their chemical structure characteristics. The knowledge of their redox potentials may help the food industry, because when phenolic compounds are oxidized they could affect the quality of the wines, beers, grape juices, etc. Coumarins are a large family of compounds, of natural and synthetic origin, that show important biological activities. Therefore, they occupy an important place in the study of natural products and synthetic organic chemistry. Recent studies pay special attention to their antioxidative, anticarcinogenic and enzymatic inhibition properties. Their preparation, and the versatility of the synthetic methodology, allowed us obtaining a wide family of compounds with substituent in different positions in the molecule. The election of these derivatives has considered the later pharmacological evaluation. The investigation of the properties of these compounds, the study of the structural pattern and the elucidation of their biological role is of great interest for further development of coumarin-like antioxidant drugs. The electrochemical behaviour of a group of differently substituted hydroxycoumarins was investigated using cyclic, differential pulse and square wave voltammetry, in aqueous media at a glassy carbon electrode over the whole pH range. The antioxidant reactivity and capacity were also evaluated through a competition assay with hydroxyl radical (OH•) and DMPO like ORAC-FL methodology. Number and positions of the hydroxyl groups were important factors in the antioxidant activities against peroxyl radical of both types of coumarins derivativesWe are grateful to the Xunta de Galicia (PGIDIT09CSA030203PR) and Ministerio de Sanidad y Consumo (FIS PS09/00501) for the partial financial support. M.J.M. and A.G. also thank Fundação de Ciência e Tecnologia for the fellowship

Study of coumarin-resveratrol hybrids as potent antioxidant compounds

In the present work we synthesized a selected series of hydroxylated 3-phenylcoumarins 5–8, with the aim of evaluating in detail their antioxidant properties. From an in depth study of the antioxidant capacity data (ORAC-FL, ESR, CV and ROS inhibition) it was concluded that these derivatives are very good antioxidants, with very interesting profiles in all the performed assays. The study of the effect of the number and position of the hydroxyl groups on the antioxidant activity was the principal aim of this study. In particular, 7-hydroxy-3-(3'-hydroxy)phenylcoumarin (8) proved to be the most active and effective antioxidant of the selected series in four of the performed assays (ORAC-FL = 11.8, capacity of scavenging hydroxyl radicals = 54%, Trolox index = 2.33 and AI30 index = 0.18). However, the presence of two hydroxyl groups on this molecule did not increase greatly the activity profile. Theoretical evaluation of ADME properties of all the derivatives was also carried out. All the compounds can act as potential candidates for preventing or minimizing the free radical overproduction in oxidative-stress related diseases. OPEN ACCESS Molecules 2015, 20 3291 These preliminary findings encourage us to perform a future structural optimization of this family of compoundsThis project was partially supported by the FONDECYT (projects 1110029 and 1090078), PhD fellowship CONICYT, fellowship for operational expenses (N°21120376), Spanish researchers personal founds, University of Santiago de Compostela and Fundação para a Ciência e Tecnologia (FCT) for the Pest/C-QUI/UI0081/2013. MJ Matos was supported by the fellowship from Fundação para a Ciência e Tecnologia (FCT), POPH (Programa Operacional Potencial Humano) and QREN (Quadro de Referência Estratégica Nacional) (SFRH/BPD/95345/2013). S Vazquez-Rodriguez was supported by the Universidade de Porto postdoctoral grant NORTE-07-0124-FEDER-000065S

Remarkable antioxidant properties of a series of hydroxy-3-arylcoumarins

In the present work we synthesized a series of hydroxy-3-arylcoumarins (compounds 1–9), some of them previously described as MAO-B selective inhibitors, with the aim of evaluating their antioxidant properties. Theoretical evaluation of ADME properties of all the derivatives was also carried out. From the ORAC-FL, ESR and CV data it was concluded that these derivatives are very good antioxidants, with a very interesting hydroxyl, DPPH and superoxide radicals scavenging profiles. In particular compound 9 is the most active and effective antioxidant of the series (ORAC-FL = 13.5, capacity of scavenging hydroxyl radicals = 100%, capacity of scavenging DPPH radicals = 65.9% and capacity of scavenging superoxide radicals = 71.5%). Kinetics profile for protection fluorescein probe against peroxyl radicals by addition of antioxidant molecule 9 was also performed. Therefore, it can operate as a potential candidate for preventing or minimizing the free radicals overproduction in oxidative-stress related diseasesThe current work was supported by Mecesup (Project UCH-0601), CONICYT-Chile (Project N 24110059), Fundação para a Ciência e Tecnologia (Project PTDC/QUI-QUI/113687/2009) and personal funds from the researchers. M.J. Matos thanks Fundação para a Ciência e Tecnologia (SFRH/BD/61262/2009) Ph.D. Grant, F. Pérez-Cruz thanks CONICYT-Chile PhD. grant, Becas-Chile and Fulbright doctoral stay fellowships and S. Vazquez-Rodriguez thanks Ministerio de Educación y Ciencia (AP2008-04263) PhD. GrantS

Polyphenolic Composition and Antioxidant Activity (ORAC, EPR and Cellular) of Different Extracts of Argylia radiata Vitroplants and Natural Roots

Plant biochemistry studies have increased in recent years due to their potential to improve human health. Argylia radiata is an extremophile plant with an interesting polyphenolic profile. However, its biomass is scarce and occasionally available. Argylia in vitro biomass was obtained from tissue culture and compared with in vivo roots regarding its polyphenolic and flavonoid content. Different solvents were used to prepare extracts from the in vitro tissue of callus and aerial plant organs and in vivo roots. UPLC-MS/MS was used to assess the chemical composition of each extract. ORAC-FL and scavenging of free radicals (DPPH and OH) methods were used to determine the antioxidant capacity of extracts. Furthermore, the biological activity of the extracts was established using the cellular antioxidant activity method. The vitroplants were a good source of polyphenols (25–68 mg GAE/100 g tissue FW), and methanol was the most efficient solvent. Eight polyphenolic compounds were identified, and their antioxidant properties were investigated by different chemical methods with EPR demonstrating its specific scavenging activity against free radicals. All extracts showed cellular dose-dependent antioxidant activity. The methanolic extract of vitroplants showed the highest cellular antioxidant activity (44.6% and 51%) at 1 and 10 µg/mL of extract, respectively. Vitroplants of A. radiata are proposed as a biotechnological product as a source of antioxidant compounds with multiple applications

Novel Phenazine 5,10-Dioxides Release •OH in Simulated Hypoxia and Induce Reduction of Tumour Volume In Vivo

Phenazine 5,10-dioxides (PDOs) are a new class of bioreductive cytotoxins, which could act towards tumours containing hypoxic regions. The PDOs selective-hypoxic bioreduction was probed in vitro; however, the mechanism of action has not been completely explained. Besides, PDOs in vivo antitumour activities have not been demonstrated hitherto. We study the mechanism of hypoxic/normoxic cytotoxicity of PDO representative members. Electron spin resonance is used to confirm •OH production, alkaline comet assay to determine genotoxicity, and gel electrophoresis and flow cytometry to analyze DNA fragmentation and cell cycle distribution. Chemically induced rat breast tumours are employed to evaluate in vivo activities. For the most selective cytotoxin, 7(8)-bromo-2-hydroxyphenazine 5,10-dioxide (PDO1), exclusive hypoxic •OH production is evidenced, while for the unselective ones, •OH is produced in both conditions (normoxia and simulated hypoxia). In normoxia (Caco-2 cells), PDO1 induces cell-cycle arrest and DNA fragmentation but does not significantly induce apoptosis neither at IC50 nor IC80. No difference in the comet-assay scores are observed in normoxia and simulated hypoxia being the unselective 2-amino-7(8)-bromophenazine 5,10-dioxide (PDO2) the most genotoxic. The in vivo efficacy with the absence of systemic toxicity of PDO1 and PDO2 is checked out. Results from this study highlight the potential of PDOs as new therapeutics for cancer

Chemical and biological analysis of 4-acyloxy-3-nitrocoumarins as trypanocidal agents

Chagas disease is the most widespread contagious tropical disease in Latin America, being an important public health problem. Treatments against this disease are still very ineffective, presenting several side effects. Therefore, the search for alternative therapeutic solutions is urgent. In the present work, we evaluate the trypanocidal activity and the mechanism of action of a select series of synthetic 4-acyloxy-3-nitrocoumarins. All the coumarin derivatives showed moderate trypanocidal activity in trypomastigotes, along with low cytotoxicity. In addition, compound 1 decreased the number of infected Vero cells in an intracellular T. cruzi model. Electron spin resonance and electrochemical studies showed the formation of nitro radical anions. The Fukui index provided additional information to elucidate the proposed reduction mechanism. Furthermore, in vitro radical formation studies demonstrated the potential of these compounds to achieve higher concentrations of intracellular free radicals, proposing oxidative stress as a possible trypanocidal mechanism. Furthermore, no correlation was observed between the diffusion of these compounds, which shows that lipophilicity is not a predominant factor for activity. Elsevier Ltd. All rights reservedThis project was partially supported by the University of Porto and University of Santiago de Compostela. MJM would like to thank Xunta de Galicia (Galician Plan of Research, Innovation and Growth 2011–2015, Plan I2C, ED481B 2014/086–0 and ED481B 2018/007) and Fundação para a Ciência e Tecnologia (CEECIND/02423/2018 and UIDB/00081/2020). FS would like to thank FONDECYT 1190340 and REDES170126, COA would like to thank FONDECYT 1190340, JDM would like to thank FONDECYT 1170126 and ANID/PCI REDES 170126, and MMB would like to thank FONDECYT Postdoctoral 3190449S

New heterobimetallic ferrocenyl derivatives are promising antitrypanosomal agents

In the search for a more effective chemotherapy for the treatment of Chagas´ disease and human African trypanosomiasis, caused by Trypanosoma cruzi and Trypanosoma brucei parasites, respectively, the use of organometallic compounds may be a promising strategy. In this work, eight new heterobimetallic compounds are described including four 5-nitrofuryl containing thiosemicarbazones as bioactive ligands (HL1-HL4) and dppf = 1,1′-bis(diphenylphosphino) ferrocene as an organometallic co-ligand. Complexes of the formula [MII(L)(dppf)](PF6) with M = Pd or Pt were synthesized and fully characterized in the solid state and in solution, including the determination of the molecular structure of four of them by single crystal X-ray diffraction methods. Most compounds showed activity in the low micromolar or submicromolar range against both parasites, with the platinum compounds being more active than the palladium analogues. Activity was significantly increased by generation of the M-dppf compounds (3-24 fold increase with respect to free ligands HL for T. cruzi and up to 99 fold increase with respect to HL for T. brucei). The inclusion of the organometallic co-ligand also led to lower toxicity in mammalian cells and higher selectivity towards both parasites when compared to the free HL compounds. The complexes interact with DNA and affect the redox metabolism of the parasites. Furthermore, the most active and selective compound of the new series showed no in vivo toxicity in zebrafish embryos.Fil: Rodríguez Arce, Esteban. Universidad de la República; UruguayFil: Putzu, Eugenia. Universidad de la República; UruguayFil: Lapier, Michel. Universidad de Chile; ChileFil: Maya, Juan Diego. Universidad de Chile; ChileFil: Olea Azar, Claudio. Universidad de Chile; ChileFil: Echeverría, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Medeiros, Andrea. Instituto Pasteur de Montevideo; Uruguay. Universidad de la República; UruguayFil: Sardi, Florencia. Instituto Pasteur de Montevideo; UruguayFil: Comini, Marcelo. Instituto Pasteur de Montevideo; UruguayFil: Risi, Gastón. Instituto Pasteur de Montevideo; UruguayFil: Salinas, Gustavo. Instituto Pasteur de Montevideo; UruguayFil: Abad Villamor, Ana Isabel. Instituto Superior Técnico; PortugalFil: Pessoa, João Costa. Instituto Superior Técnico; PortugalFil: Otero, Lucía. Universidad de la República; UruguayFil: Gambino, Dinorah. Universidad de la República; Urugua