Photoinduced oxidation of an indole derivative: 2-(1'H-indol-2'-yl)-[1,5]naphthyridine

The UV-induced oxidation of 2-(1'H-indol-2'-yl)-[1,5]naphthyridine acetonitrile solution in the presence of air leads to the formation of 2-(1,5-naphthyridin-2-yl)-4H-3,1-benzoxazin-4-one as a major product and N-(2-formylphenyl)-1,5-naphthyridine-2-carboxamide as a minor one. The probable reaction mechanisms are different for the two photoproducts and may involve both the reaction with singlet oxygen generated by the excited substrate or the reaction of the excited substrate with the ground state oxygen molecule. Electronic absorption and IR spectra indicate that both photoproducts are formed as mixtures of syn and anti-rotameric forms. The obtained results indicate an efficient and easy method for the synthesis of molecules with a benzoxazinone structure.

Persistent phototransformation products of vardenafil (Levitra®) and sildenafil (Viagra®)

As pharmaceutically active compounds (PhACs) are increasingly detected in the aquatic environment, the importance of investigating their transformation products-products of naturally occurring hydrolysis, biodegradation, and solar-mediated photochemical reactions - for persistence and ecotoxicity remains an important part of assessing the pharmaceutical's environmental impact and fate. In this study, the solar phototransformation of vardenafil (active ingredient in Levitra®) and sildenafil (Viagra®), two structurally similar compounds used to treat erectile dysfunction, was studied, with special attention to potentially persistent phototransformation (PT) products. PT products for vardenafil are identified here for the first time. Dilute solutions were prepared in buffered (pH=7.4) aqueous solutions, both with and without Suwanee River humic acid (SRHA) and fulvic acid (SRFA), and exposed to simulated sunlight. The PT products were identified via Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (LC-ESI-MS) and confirmed by MS/MS. Both SRHA and SRFA were observed to lead to more extensive degradation of VRD while having minimal effect on SLD. At least two PT products, SLD-392 and VRD-392, were observed to be notably persistent, indicating their potential impact in the aquatic environment and highlighting the need for investigations of transformation products in natural water samples.

Sildenafil and tadalafil in simulated chlorination conditions: ecotoxicity of drugs and their derivatives

Chlorination experiments on two drugs (sildenafil and tadalafil) were performed mimicking the conditions of a typical wastewater treatment process. The main transformation products were isolated by chromatographic techniques (Thin Layer Chromatography (TLC), Column Chromatography (CC), High Performance Liquid Chromatography (HPLC)) and fully characterized employing Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) analyses. The environmental effects of the parent compounds and transformation products were evaluated using an overall toxicity approach that considered aquatic acute and chronic toxicity on Brachionus calyciflorus and Ceriodaphnia dubia as well as mutagenesis and genotoxicity on bacterial strains. The results revealed that both parent drugs did not show high acute and chronic toxicity for the organisms utilized in the bioassays while, chronic exposure to chlorine derivatives caused inhibition of growth population on rotifers and crustaceans. A mutagenic potential was found for all the compounds investigated.