Effect of Cu(2+)-complexation on the scavenging ability of chrysin towards photogenerated singlet molecular oxygen (O2((1)Δg)). Possible biological implications

The protective effects of baicalin and chrysin against emamectin benzoate-induced toxicity in Wistar albino rats

The aim of this study was to investigate the effects of baicalin, chrysin and their combinations against emamectin benzoate-induced toxicity in rats. For this purpose, sixty four rats were divided into evenly 8 groups with 6-8-week-old male Wistar albino rats, weighing 180-250 g, in each group. While the first group was kept as a control (corn oil), the remaining 7 groups were administered with emamectin benzoate (10 mg/kg bw), baicalin (50 mg/kg bw) and chrysin (50 mg/kg bw) alone or together for 28 days. Oxidative stress parameters, serum biochemical parameters and blood/tissue (liver, kidney, brain, testis and heart) and tissue histopathology were investigated. Compared to the control group, the emamectin benzoate-intoxicated rats had significantly higher tissue/plasma concentrations of nitric oxide (NO) and malondialdehyde (MDA), as well as lower tissue glutathione (GSH) concentrations and antioxidant enzyme activity (glutathione peroxidase/GSH-Px, glutathione reductase/GR, glutathione-S-transferase/GST, superoxide dismutase/SOD, catalase/CAT). Biochemical analysis showed that emamectin benzoate administration significantly increased serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) activities, as well as triglyceride, cholesterol, creatinine, uric acid and urea levels, and decreased serum total protein and albumin levels. The histopathological examination of the liver, kidney, brain, heart and testis tissues of the emamectin benzoate-intoxicated rats demonstrated necrotic changes. Baicalin and/or chrysin reversed the biochemical and histopathological alterations induced by emamectin benzoate on these tested organs. Therefore, baicalin and chrysin (alone or in combination) could offer protection against emamectin benzoate-induced toxicity.

Efficient degradation of typical pharmaceuticals in water using a novel TiO2/ONLH nano-photocatalyst under natural sunlight

Photocatalytic degradation of typical pharmaceuticals in natural sunlight and in actual water is of great significance. In this study, the oxygen or nitrogen linked heptazine-base polymer (ONLH) was successfully incorporated with TiO₂ nanoparticles and formed a TiO₂/ONLH nanocomposite which was responded to the natural sunlight. Under natural sunlight, the TiO₂/ONLH can effectively degrade ten types of pharmaceuticals. In particular, fluoroquinolone containing N-piperazinyl, and cardiovascular drugs containing long aromatic side chains were easily degraded. The half-life of the best degradation performance of propranolol was less than 5 min. The rate constants of propranolol using the TiO₂/ONLH were approximately six- and eight-fold higher than those of pristine TiO₂ and ONLH, respectively. Two reactive species (OH and O₂^-) facilitated the rapid degradation of propranolol, which occurred primarily through the hydroxyl radical addition, ring-opening, and ipso substitution reactions. An acute toxicity test using luminescent bacteria indicated that the toxicity of the propranolol reaction solution gradually decreased with lower total organic carbon (TOC). According to the toxicity evaluation of monomer products, the TiO₂/ONLH also reduced the generation of toxic transformation products. The effects of actual water/wastewater have further shown the TiO₂/ONLH might be applied for the removal of pharmaceuticals in wastewater.

Experimental and Theoretical Study of the Stability of the Complex Fisetin-Cu(II) and A Comparative Study of Free Ligand and Complex Interaction with Molecular Singlet Oxygen

In this work, the flavonol fisetin was selected in order to study its reactivity against Cu(II), a metal ion of interest in biological media and industry. The stoichiometry and apparent formation constant of the complex in ethanolic medium at 25°C were evaluated using spectrophotometric techniques. The resulting stoichiometry was a 1:1 ligand:metal complex, and a log K = 5.17 ± 0.12 was determined. Since two possible chelation sites can be proposed for the complex formation, quantum chemistry calculations were performed on these structures. Calculations suggest that the hydroxyl-keto site is more stable for the complex formation than the catechol site. Flavonoids could exert protection against oxidative damage caused by reactive oxygen species, and this biological activity could be affected by chelation with metal ions. This led us to perform a study on the interaction of both, free flavonoid and complex, with reactive oxygen species. Our results showed both compounds quench molecular singlet oxygen photogenerated with visible light, mainly in a physical fashion. In order to analyze a possible protective effect of flavonoid and its complex against oxidative damage in biological environments, the amino acid tryptophan was selected as a model oxidation system. Free flavonoid does not have a marked protective effect, whereas its complex showed a relevant protective effect.

Degradation of Ofloxacin by Perylene Diimide Supramolecular Nanofiber Sunlight-Driven Photocatalysis

This study describes a promising sunlight-driven photocatalyst for the treatment of ofloxacin and other fluoroquinolone antibiotics in water and wastewater. Perylene diimide (PDI) supramolecular nanofibers, which absorb a broad spectrum of sunlight, were prepared via a facile acidification polymerization protocol. Under natural sunlight, the PDI photocatalysts achieved rapid treatment of fluoroquinolone antibiotics, including ciprofloxacin, enrofloxacin, norfloxacin, and ofloxacin. The fastest degradation was observed for ofloxacin, which had a half-life of 2.08 min for the investigated conditions. Various light sources emitting in the UV-vis spectrum were tested, and blue light was found to exhibit the fastest ofloxacin transformation kinetics due to the strong absorption by the PDI catalyst. Reactive species, namely, h⁺, ¹O₂, and O₂^•-, comprised the primary photocatalytic mechanisms for ofloxacin degradation. Frontier electron density calculations and mass spectrometry were used to verify the major degradation pathways of ofloxacin by the PDI-sunlight photocatalytic system and identify the transformation products of ofloxacin, respectively. Degradation mainly occurred through demethylation at the piperazine ring, ketone formation at the morpholine moiety, and aldehyde reaction at the piperazinyl group. An overall mechanism was proposed for ofloxacin degradation in the PDI-sunlight photocatalytic system, and the effects of water quality constituents were examined to determine performance in real water/wastewater systems. Ultimately, the aggregate results from this study highlight the suitability of the PDI-sunlight photocatalytic system to treat antibiotics in real water and wastewater systems.

From San Luis, A Few Words of Gratitude

The Photochemical Research Group from San Luis (Argentina) highlights the contributions of Dr. Norman Andino García to the development of the group as a way to show him our gratitude for all his support.