Photochemistry of oxazolidinones antibacterial drugs

The photochemistry of six N3-(3-fluoro-4-dialkylaminophenyl)-oxazolidinones known for their antimicrobial activity has been examined. All of these compounds are defluorinated in water (dec ≈ 0.25) and in methanol (dec ≈ 0.03), reasonably via the triplet. The chemical processes observed are reductive defluorination and solvolysis, depending on the structural variation introduced (thus, tethering the dialkylamino group to the aromatic ring and introducing a highly polar group in the oxazolidinone moiety have an effect). A likely mechanism involves the fragmentation of the C-F bond yielding the corresponding triplet phenyl cation. This intermediate either is reduced or, under appropriate conditions, intersystem crosses to the singlet state that adds the solvent

A Kinetic Approach to Photomineralization of Methane in Air by Membranes Based on TiO2/WO3

Photomineralization of methane in air (10.0-1,000 ppm (mass/volume) of C) at 100% relative humidity (dioxygen as oxygen donor), was systematically studied at 318 ± 3 K, in an annular laboratory-scale reactor, by photocatalytic membranes immobilising titanium dioxide and tungsten trioxide as co-photocatalysts. Kinetics of both substrate disappearance, to yield intermediates, and total organic carbon (TOC) disappearance, to yield carbon dioxide, were followed. A kinetic model was employed, from which, by a set of differential equations, four final optimised parameters, k1 and K1, k2 and K2, were calculated, able to fit the whole kinetic profile adequately. Modelling of quantum yields, as a function of substrate concentration and irradiance, as well as of concentration of photocatalysts, was carried out very satisfactorily. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or intermediates leading to mineralization, were considered, paralleled by second competition kinetics involving superoxide radical anion. When using appropriate blends of the two photocatalysts, limiting quantum yields ∞ values increase considerably and approach the maximum allowable value for the investigated molecule, in a much wider range of irradiances than that shown by the single catalysts mainly at low irradiances. This may be interpreted by strong competition kinetics of superoxide radicals generated by the catalyst defects, in the corresponding range of high irradiances. By this way, operation at high irradiance values is possible, without losing any efficiency for the mineralization process

The Microalgal Diatoxanthin Inflects the Cytokine Storm in SARS-CoV-2 Stimulated ACE2 Overexpressing Lung Cells

Contact between SARS-CoV-2 and human lung cells involves the viral spike protein and the human angiotensin-converting enzyme 2 (ACE2) receptor on epithelial cells, the latter being strongly involved in the regulation of inflammation as well as blood pressure homeostasis. SARS-CoV-2 infection is characterized by a strong inflammatory response defined as a "cytokine storm". Among recent therapeutic approaches against SARS-CoV-2 targeting the dramatic inflammatory reaction, some natural products are promising. Diatoms are microalgae able to produce bioactive secondary metabolites, such as the xanthophyll diatoxanthin (Dt). The aim of this study is to demonstrate the anti-inflammatory effects of Dt on the A549-hACE2 lung cell line, exploring its interaction with the ACE2 receptor, as well as depicting its role in inhibiting a cytokine storm induced by the SARS-CoV-2 spike glycoprotein. Results showed that Dt enhanced the cell metabolism, e.g., the percent of metabolically active cells, as well as the ACE2 enzymatic activity. Moreover, Dt strongly affected the response of the SARS-CoV-2 spike glycoprotein-exposed A549-hACE2 cells in decreasing the interleukin-6 production and increasing the interleukin-10 release. Moreover, Dt upregulated genes encoding for the interferon pathway related to antiviral defense and enhanced proteins belonging to the innate immunity response. The potential interest of Dt as a new therapeutic agent in the treatment and/or prevention of the severe inflammatory syndrome related to SARS-CoV-2 infection is postulated

Light and drugs: the photochemistry of fluoroquinolone antibiotics

Light-related adverse side-effects of drugs are now an important source of concern. In order that the mechanism underlying to such effects is recognised, an in-depth photochemical study must be carried out. The case of some fluoroquinolone antibiotics (norfloxacin, enoxacin, lomefloxacin) is discussed as a representative example. These drugs undergo heterolytic fragmentation of the C—F bond leading to aryl cations. Quantum yields in neutral water range from 0.001 to 0.5 depending on the charge transfer degree of the ππ* state. Lower values are obtained at both acidic and basic pH. There is indication that the excited state involved in most of this reactions is a relatively long-lived triplet. The aryl cations undergo intra- or intermolecular reactions, and are presumably involved in the reported photo-toxic effect

Functions containing a heteroatom different from oxygen

The main photochemical reactions of chromophores containing nitrogen, phosphorus, silicon, sulfur and halogen atoms are briefly reviewe