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The photosensitized reaction of nitrobenzene and its derivatives, including dinitrobenzene, has been extensively investigated in an aqueous alkaline medium using Benzophenone as a sensitizer under visible light irradiation. A 100 W tungsten lamp was employed for the purpose of irradiation. The presence of the strongly electron-withdrawing NO2 group leads to polarization of the C–H bond. In this process, the triplet excited state of benzophenone initiates H+ abstraction from the polarized C–H bond of nitrobenzene (NB) and meta-dinitrobenzene (m-DNB) through exciplex formation. Proton abstraction results in the formation of free radicals for both NB and m-DNB, followed by dimerization of the free radicals. The observed rate of the reaction follows the order m-DNB > NB. However, no photochemical reaction was observed for p-dinitrobenzene (p-DNB). Various parameters such as pH, substrate concentration, sensitizer concentration, light intensity, solvent effect, and the rate of the photochemical reaction were investigated. The quantum efficiency of the product was determined using a potassium ferrioxalate actinometer. The formation of the product occurs through exciplex formation from the triplet excited state. The possible products, namely 2,2'-dinitro biphenyl and 2,2'-4,4'-tetranitro biphenyl, were confirmed using UV–visible spectrophotometry and mass spectrometry. Finally, a proposed reaction mechanism was suggested based on the experimental findings. [ABSTRACT FROM AUTHOR]

The photosensitized reaction of isomeric bromoanilines in an alkaline medium under visible light using methylene blue as a photosensitizer was investigated. It was observed that bromoanilines do not form exciplex with methylene blue, and the reaction rate remains consistent in the pH range of 6 to 12. This reaction involves the heterolytic cleavage of the C–Br bond, leading to the formation of anilinium cations and resulting in amino phenols in methanolic solutions or anisidine in other conditions. The position of the halogen atom does not significantly impact the reaction. The study utilized UV-visible spectroscopy for analysis for product characterization. Methanol did not exhibit a free radical scavenging effect on bromoanilines. Additionally, the influence of various parameters such as pH, sensitizer and substrate concentrations, and light intensity on the reaction rate was explored. The quantum efficiency of the photosensitized reaction was calculated, and a reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

Flavin mononucleotide (FMN) is a dye belonging to the flavin family. These dyes produce photosensitized degradation of organic compounds via reaction with the excited states of the dye or with reactive oxygen species photogenerated from the triplet of the dye. This article presents a new polymeric dye (FMN–CS) composed of the photosensitizer FMN covalently bonded to chitosan polysaccharide (CS). FMN–CS obtained has a molecular weight of 230 × 103 g mol−1 and a deacetylation degree of 74.8%. The polymeric dye is an environmentally friendly polymer with spectroscopic and physicochemical properties similar to those of FMN and CS, respectively. Moreover, under sunlight, it is capable of generating 1O2 with a quantum yield of 0.31. FMN–CS, like CS, is insoluble in basic media. This allows easy recovery of the polymeric dye once the photosensitized process has been carried out and makes FMN–CS a suitable photosensitizer for the degradation of pollutants in contaminated waters. To evaluate whether FMN–CS may be used for pollutant degradation, the photosensitized degradation of two trihydroxybenzenes by FMN–CS was studied. [ABSTRACT FROM AUTHOR]

Gefitinib (GFT) is a selective epidermal growth factor receptor (EGFR) inhibitor clinically used for the treatment of patients with non-small cell lung cancer. Bioactivation by mainly Phase I hepatic metabolism leads to chemically reactive metabolites such as O-Demethyl gefitinib (DMT-GFT), 4-Defluoro-4-hydroxy gefitinib (DF-GFT), and O-Demorpholinopropyl gefitinib (DMOR-GFT), which display an enhanced UV-light absorption. In this context, the aim of the present study is to investigate the capability of gefitinib metabolites to induce photosensitivity disorders and to elucidate the involved mechanisms. According to the neutral red uptake (NRU) phototoxicity test, only DF-GFT metabolite can be considered non-phototoxic to cells with a photoirritation factor (PIF) close to 1. Moreover, DMOR-GFT is markedly more phototoxic than the parent drug (PIF = 48), whereas DMT-GFT is much less phototoxic (PIF = 7). Using the thiobarbituric acid reactive substances (TBARS) method as an indicator of lipid photoperoxidation, only DMOR-GFT has demonstrated the ability to photosensitize this process, resulting in a significant amount of TBARS (similar to ketoprofen, which was used as the positive control). Protein photooxidation monitored by 2,4-dinitrophenylhydrazine (DNPH) derivatization method is mainly mediated by GFT and, to a lesser extent, by DMOR-GFT; in contrast, protein oxidation associated with DMT-GFT is nearly negligible. Interestingly, the damage to cellular DNA as revealed by the comet assay, indicates that DMT-GFT has the highest photogenotoxic potential; moreover, the DNA damage induced by this metabolite is hardly repaired by the cells after a time recovery of 18 h. This could ultimately result in mutagenic and carcinogenic effects. These results could aid oncologists when prescribing TKIs to cancer patients and, thus, establish the conditions of use and recommend photoprotection guidelines. [ABSTRACT FROM AUTHOR]

Gefitinib (GFT) is a selective epidermal growth factor receptor (EGFR) inhibitor clinically used for the treatment of patients with non-small cell lung cancer. Bioactivation by mainly Phase I hepatic metabolism leads to chemically reactive metabolites such as O-Demethyl gefitinib (DMT-GFT), 4-Defluoro-4-hydroxy gefitinib (DF-GFT), and O-Demorpholinopropyl gefitinib (DMOR-GFT), which display an enhanced UV-light absorption. In this context, the aim of the present study is to investigate the capability of gefitinib metabolites to induce photosensitivity disorders and to elucidate the involved mechanisms. According to the neutral red uptake (NRU) phototoxicity test, only DF-GFT metabolite can be considered non-phototoxic to cells with a photoirritation factor (PIF) close to 1. Moreover, DMOR-GFT is markedly more phototoxic than the parent drug (PIF = 48), whereas DMT-GFT is much less phototoxic (PIF = 7). Using the thiobarbituric acid reactive substances (TBARS) method as an indicator of lipid photoperoxidation, only DMOR-GFT has demonstrated the ability to photosensitize this process, resulting in a significant amount of TBARS (similar to ketoprofen, which was used as the positive control). Protein photooxidation monitored by 2,4-dinitrophenylhydrazine (DNPH) derivatization method is mainly mediated by GFT and, to a lesser extent, by DMOR-GFT; in contrast, protein oxidation associated with DMT-GFT is nearly negligible. Interestingly, the damage to cellular DNA as revealed by the comet assay, indicates that DMT-GFT has the highest photogenotoxic potential; moreover, the DNA damage induced by this metabolite is hardly repaired by the cells after a time recovery of 18 h. This could ultimately result in mutagenic and carcinogenic effects. These results could aid oncologists when prescribing TKIs to cancer patients and, thus, establish the conditions of use and recommend photoprotection guidelines.

A water soluble porphyrin, dimethoxophosphorus(V)tetraphenylporphyrin (MP(V)TPP) photosensitized folic acid decomposition in aqueous solution, resulting in the formation of a strongly fluorescent pteridine compound. The quantum yield of folic acid decomposition by photoexcited MP(V)TPP could be determined by a flurometry. A possible mechanism of the initial process of this photodecomposition is direct oxidation through an electron transfer from folic acid to the excited singlet state of MP(V)TPP. It is considered that this electron transfer proceeds as a diffusion-controlled reaction. The quantum yields of the electron transfer and the following process of folic acid decomposition could be determined. In deuterium oxide, folic acid decomposition through the photosensitized singlet oxygen generation by MP(V)TPP was also observed. A fluorometry based on the formation of a strong fluorescent compound through the oxidized decomposition of folic acid may be applied to evaluate the biomolecule damaging-activity of photosensitizers. In addition, a protocol of this assay is proposed. This simple photosensitized reaction in aqueous solution may be used for a first screening of a photosensitizer for phototherapy. [ABSTRACT FROM AUTHOR]

Abstract: Photosensitized diastereodifferentiating addition of methanol to (R)-(+)-(Z)-limonene in a microreactor was investigated. The quantity of photoproducts, cis- and trans-4-isopropenyl-1-methoxy-1-methylcyclohexane, increases with increasing period of irradiation by a mercury lamp, and the diastereomeric excess (de) of the photoadduct is slightly larger than that obtained in a batch reaction system. The reaction rate constants for the production of the cis and trans isomers were successfully obtained by using the steady state approximation. The larger de value in the microreactor was found to result from the suppression of the sequential side reaction processes. The feasibility of microreaction system for the photoreaction will be discussed. [Copyright &y& Elsevier]