A Water-Soluble Manganese(II) Octanediaoate/Phenanthroline Complex Acts as an Antioxidant and Attenuates Alpha-Synuclein Toxicity

The overproduction of reactive oxygen species (ROS) induces oxidative stress, a well-known process associated with aging and several human pathologies, such as cancer and neurodegenerative diseases. A large number of synthetic compounds have been described as antioxidant enzyme mimics, capable of eliminating ROS and/or reducing oxidative damage. In this study, we investigated the antioxidant activity of a water-soluble 1,10-phenantroline-octanediaoate Mn2+-complex on cells under oxidative stress, and assessed its capacity to attenuate alpha-synuclein (aSyn) toxicity and aggregation, a process associated with increased oxidative stress. This Mn2+-complex exhibited a significant antioxidant potential, reducing intracelular oxidation and increasing oxidative stress resistance in S. cerevisiae cells and in vivo, in G. mellonella, increasing the activity of the intracellular antioxidant enzymes superoxide dismutase and catalase. Strikingly, the Mn2+-complex reduced both aSyn oligomerization and aggregation in human cell cultures and, using NMR and DFT/molecular docking we confirmed its interaction with the C-terminal region of aSyn. In conclusion, the Mn2+-complex appears as an excellent lead for the design of new phenanthroline derivatives as alternative compounds for preventing oxidative damages and oxidative stress - related diseases.

Ferroin in dyes degradation by Fenton-like process: a chemical waste recycling perspective

Literature describes the formation of Fe (II)-phenanthroline complex (ferroin) as a stop way for Fenton processes, ceasing radicals yielding. Antagonistically, this study presents evidences that ferroin can be activated by UVA in mildly acidic media in photo-Fenton-like process. Because ferroin is the main waste from total iron determination in environmental samples, a recycling approach is suggested. Based on the best practices of waste management planning, an application of the proposed method for treating another chemical waste is presented. Titrimetric ammonia determination waste containing 2.67 mg L−1 methyl red azo dye and 1.33 mg L−1 methylene blue was degraded at the optimized experimental conditions: pH = 5.2–5.4; [H2O2] = 310 mg L−1; [Ferroin] = 1.4 mg L−1; temperature = 36 ± 1 °C; reaction time = 165 min under UV-A irradiation. Attenuation of most intense spectroscopic bands for the dyes achieved 94% (510 nm) and 96% (665 nm) for methyl red and methylene blue, respectively, with degradation of ferroin itself. The present work brings empirical evidence that is possible to recycling ferroin as photo-Fenton-like process catalyst, besides to determine the best conditions for providing less acidic treated effluents with negligible suspended solid concentration, better than obtained from classical photo-Fenton processes.

Cobalt Graphitic Carbon Nanoparticles for Catalytic Hydrogenation of 2,4-Dinitrophenol

Cobalt carbon nanoparticles CoCNPs were prepared by pyrolysis of cobalt phenanthroline complex at different pyrolysis temperature and time of pyrolysis and used for the catalytic hydrogenation of 2,4-dinitrophenol. CoCNPs (1) and (3) were prepared by heating at 600 ºC and 800 °C respectively, while (2) was prepared by heating at 600 °C with an additional intermediate stage at 300 °C. The structures and chemical properties of the three catalysts were correlated with their catalytic activities. Among the three studied catalysts, the highest rate constant was obtained for (2) while the highest conversion was achieved by (3). Our data show that an increase in oxygen content of the cobalt carbon nano-catalyst reduces the catalytic activity, while an increase in pyrolysis temperature improves the conversion yield.

Nickel-phenanthroline Complex Supported on Mesoporous Carbon as a Catalyst for Carboxylation under CO2 Atmosphere

Carbon dioxide is a highly potential renewable C1 source for synthesis of fine chemicals. Utilization of CO2 in carboxylation reactions requires catalysts, such as: nickel complex for CO2 activation. However, the use of homogeneous catalysts in the reaction is still less efficient due to the difficulty of separating the product and catalyst from reaction mixture. Therefore, it is necessary to heterogenize the nickel complex in a solid support such as mesoporous carbon. In this report, mesoporous carbon (MC) prepared from phloroglucinol and formaldehyde through soft template method was used as a solid support for Ni-phenanthroline complex (Ni-phen). The catalyst was characterized by Fourier Transform Infra Red (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscope - Energy Dispersive X-Ray (SEM-EDX), and Surface Area Analyzer (SAA). The result of SAA characterization showed that the pore diameter of MC was 6.7 nm and Ni-phen/MC was 5.1 nm which indicates that the materials have meso-size pores. Ni-phen/MC material was then used as a heterogeneous catalyst in the carboxylation reaction of phenylacetylene under an ambient CO2 pressure. The reactions were carried out in several variations of conditions such as temperature, time and catalyst types. Based on the results of the reaction, the best conditions were obtained at 25 °C for 8 h of reaction time using Ni-phen/MC catalyst. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Hydroxyl Radical Generation by the H2O2/CuII/Phenanthroline System under Both Neutral and Alkaline Conditions: An EPR/Spin-Trapping Investigation

The copper–phenanthroline complex CuI(Phen)2 was the first artificial nuclease studied in biology. The mechanism responsible for this activity involves CuII(Phen)2 and H2O2. Even if H2O2/Cu systems have been extensively studied in biology and oxidative chemistry, most of these studies were carried out at physiological pH only, and little information is available on the generation of radicals by the H2O2/CuII-Phen system. In the context of paper pulp bleaching to improve the bleaching ability of H2O2, this system has been investigated, mostly at alkaline pH, and more recently at near-neutral pH in the case of dyed cellulosic fibers. Hence, this paper aims at studying the production of radicals with the H2O2/CuII-Phen system at near-neutral and alkaline pHs. Using the EPR/spin-trapping method, HO• formation was monitored to understand the mechanisms involved. DMPO was used as a spin-trap to form DMPO–OH in the presence of HO•, and two HO• scavengers were compared to identify the origin of the observed DMPO–OH adduct, as nucleophilic addition of water onto DMPO leads to the same adduct. H2O2 decomposition was enhanced by the addition of CuII–Phen (and only slightly by addition of CuSO4), reaching a level similar to the Fenton reagent at near-neutral pH. This evidences the role of Phen, which improves the effect of CuII by tuning the electronic structure and structural properties of the corresponding CuII complexes.

APPLICATION OF WATER BEADS AS A NOVEL AND SIMPLE SORBENT FOR SMARTPHONE-BASED COLORIMETRIC DETERMINATION OF IRON IN WATER

This work proposes a novel approach for colorimetric assays using ubiquitous and inexpensive water beads (WBs) made of a superabsorbent polymer (sodium polyacrylate). The high-water absorption capacity by the WBs was exploited for the preconcentration of iron ions from samples of tap, well, and lake waters. Moreover, the WBs also worked as a substrate for colorimetric detection of iron by the classical reaction of formation of Fe(II)-phenanthroline complex. Digital images acquired with a smartphone were used to obtain the color intensity of the WBs containing the orange color complex. The WBs were able to uptake and preconcentrate iron ions, allowing colorimetric detection with good linearity (R2 = 0.9978) and limits of detection (LOD) and quantification (LOQ) of 0.02 and 0.07 mg L-1, respectively. The proposed method provided recoveries ranging from 93 to 111% for a sample of well water spiked with 0.15 mg L-1 of iron.

Inner filter effect between upconversion nanoparticles and Fe(ii)–1,10-phenanthroline complex for the detection of Sn(ii) and ascorbic acid (AA)

Based on the inner filter effect (IFE), we use UCNPs to develop a dual-function sensors, which can realize sensitive and selective detection for the Sn(ii) and ascorbic acid (AA).