We have previously shown that α-linolenic acid (ALA), a (n-3) PUFA exerts in vitro antiinflammatory effects in the intestine. In this study, we aimed to evaluate its effect on inflammatory and oxidative stress in a colitis model. Colitis was induced in 2 groups at d 0 by intrarectal injection of 2-4-6-trinitrobenzen sulfonic acid (TNBS), whereas the control group received the vehicle. Rats we fed 450 mg . kg(-1) . d(-1) of ALA (TNBS+ALA) while the other colitic group (TNBS) and the control group were fed an isocaloric corn oil formula for 14 d (from d -7 to d 7). RBC fatty acid composition was assessed. Oxidative stress was studied by measuring urinary 8-isoprostanes (8-IP) and colon glutathione (GSH) concentration and inducible nitric oxide synthase (iNOS) expression. Colitis was assessed histologically, by production of proinflammatory mediators, including cytokines, leukotrienes B(4) (LTB(4)), and cyclooxygenase-2 (COX-2) and by nuclear factor-κB (NF-κB) activation. The ALA-rich diet significantly increased the RBC levels of ALA, eicosapentaenoic acid, and docosapentaenoic acid (n-3) compared with the TNBS group (P < 0.01 for all). The beneficial effect of ALA supplementation on oxidative stress was reflected by lower urinary 8-IP levels (P < 0.05), a normalized colon GSH concentration (P < 0.01), and reduced colon iNOS expression (P < 0.05) compared with the TNBS group. ALA also protected against colon inflammation as assessed by lower tumor necrosis factor-α secretion and mRNA level (P < 0.05), reduced NF-κB activation (P = 0.01), and lower colon lipid mediator concentrations such as LTB(4) and COX-2 (P < 0.05) compared with the TNBS group. These findings show that an ALA-rich formula is beneficial to TNBS-induced colitic rats via inhibition of oxidative and inflammatory stress.

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The photochemistry of anthraquinone-2-sulfonate (AQ2S) was studied as a function of pH, combining laser flash photolysis and steady-state irradiation experiments, with the additional help of a computational study of energy levels. Two out of the three transient species produced upon irradiation of AQ2S can be involved into the degradation of dissolved molecules, and also AQ2S in its ground state is degraded. The reactive transients are less stable but often more reactive under acidic conditions, which modulates the pH trend of the photodegradation of the adopted organic substrates (furfuryl alcohol, benzene, nitrobenzene). The ability of the excited states of irradiated AQ2S to simulate the reactivity of singlet oxygen upon degradation of furfuryl alcohol, and that of the hydroxyl radical by producing phenol from benzene, can have important consequences. Furfuryl alcohol and benzene are widely adopted probe molecules for the respective quantification of singlet oxygen and the hydroxyl radical in many systems, among which are natural waters under irradiation. This study shows that the interference of AQ2S on singlet oxygen determination would be higher in acidic or basic than in approximately neutral conditions, while in the case of the hydroxyl radical the interference would increase with pH. Processes analogous to those studied could account for the interference of coloured dissolved organic matter on the quantification of singlet oxygen, observed in previous studies.

The triplet state of anthraquinone-2-sulphonate (AQ2S) is able to oxidise bromide to Br(•)/Br(2)(-•), with rate constant (2-4)⋅10(9)M(-1)s(-1) that depends on the pH. Similar processes are expected to take place between bromide and the triplet states of naturally occurring chromophoric dissolved organic matter ((3)CDOM*). The brominating agent Br(2)(-•) could thus be formed in natural waters upon oxidation of bromide by both (•)OH and (3)CDOM*. Br(2)(-•) would be consumed by disproportionation into bromide and bromine, as well as upon reaction with nitrite and most notably with dissolved organic matter (DOM). By using the laser flash photolysis technique, and phenol as model organic molecule, a second-order reaction rate constant of ~3⋅10(2)L(mg C)(-1)s(-1) was measured between Br(2)(-•) and DOM. It was thus possible to model the formation and reactivity of Br(2)(-•) in natural waters, assessing the steady-state [Br(2)(-•)]≈10(-13)-10(-12)M. It is concluded that bromide oxidation by (3)CDOM* would be significant compared to oxidation by (•)OH. The (3)CDOM*-mediated process would prevail in DOM-rich and bromide-rich environments, the latter because elevated bromide would completely scavenge (•)OH. Under such conditions, (•)OH-assisted formation of Br(2)(-•) would be limited by the formation rate of the hydroxyl radical. In contrast, the formation rate of (3)CDOM* is much higher compared to that of (•)OH in most surface waters and would provide a large (3)CDOM* reservoir for bromide to react with. A further issue is that nitrite oxidation by Br(2)(-•) could be an important source of the nitrating agent (•)NO(2) in bromide-rich, nitrite-rich and DOM-poor environments. Such a process could possibly account for significant aromatic photonitration observed in irradiated seawater and in sunlit brackish lagoons.

Three dimensionally ordered macroporous layered double hydroxides (3-DOM LDH) have been synthesized using sacrificial polystyrene (PS) colloidal crystal templates impregnated by divalent and trivalent metal salts. LDH spatially confined coprecipitation occurs during soaking in NaOH solution, and the PS template is subsequently removed by dissolution to preserve the hydroxyl structure. This synthetic process can be applied to a wide range of LDH compositions (MII: Mg, Ni, Co, Zn and MIII: Al, Cr). On the basis of XRD, SEM, TEM, chemical analysis, nitrogen adsorption, XAS experiments, and TGA, structural, textural, and thermal properties of these new nanostructured LDH particles are described. In particular, the study shows that both macro- and mesoporosity can be present and that the macroporosity is maintained after calcination at temperatures as high as 800 °C, giving rise to the presence of macroporous metal and mixed metal oxides. The photocatalytic activity experiments indicate that decatungstate intercalated into the 3-DOM LDH exhibits a higher photocatalytic activity for the photodegradation of 2,6-dimethylphenol than the decatungstate intercalated into the standard coprecipitated LDH parent material.

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5,10,15,20-Tetrakis(2,6-dichloro-3-chlorosulfophenyl)porphyrin and its tin and zinc complexes were synthesized with high yields and fully characterized. The corresponding water-soluble 5,10,15,20-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrins were obtained by hydrolysis with water. An extensive photophysical study of the new water soluble porphyrinic compounds was carried out including absorption and fluorescence spectra, fluorescence quantum yields, triplet absorption spectra, triplet lifetimes, triplet and singlet oxygen quantum yields. These sensitizers were successfully used in the photodegradation of 4-chlorophenol and 2,6-dimethylphenol. A comparison is made of their efficiencies, and some mechanistic considerations are highlighted.