RESUMO
ortho-Carborane (1,2-C2B10H12) was found to be a carrier of protons in both mitochondrial and artificial lipid membranes, suggesting that this dicarborane can reversibly release hydrogen ions and diffuse through the membranes in neutral and anionic forms. Similar to conventional uncouplers (e.g. 2,4-dinitrophenol), o-carborane stimulated mitochondrial respiration and decreased the membrane potential at concentrations of tens of micromoles. Protonophoric activity of o-carborane was observed both by a fluorometric assay using pyranine-loaded liposomes and electrical current measurements across planar lipid bilayers. Substantial contribution of the proton flux to the o-carborane-mediated current was proved by a shift of the zero current voltage upon imposing a pH gradient across the membrane. Meta-carborane (1,7-C2B10H12) lacked the protonophoric activity in line with its reduced C-H acidity. The results suggest that weak C-H acids can exhibit protonophoric activity in the biological environment. The finding of a new class of protonophoric compounds is of substantial interest due to promising anti-obesity and anti-diabetic properties of uncouplers.
Assuntos
Boranos/química , Compostos de Boro/farmacologia , Ácidos de Lewis/farmacologia , Bicamadas Lipídicas/química , Membranas Mitocondriais/química , Desacopladores/farmacologia , Animais , Sulfonatos de Arila/química , Compostos de Boro/química , Concentração de Íons de Hidrogênio , Cinética , Ácidos de Lewis/química , Lipossomos/química , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitocôndrias Hepáticas/química , Mitocôndrias Hepáticas/metabolismo , Fosfatidilcolinas/química , Ratos , Desacopladores/química , Valinomicina/farmacologiaRESUMO
In recent years, cellulose has received increasing attention as a potential material for the production of biofuels and bio-based chemicals. In this study, a new process for the efficient conversion of cellulose into 5-hydroxymethylfurfural (HMF) was developed by the use of AlCl3 as the catalyst in DMSO-ionic liquid ([BMIM]Cl) mixtures. Various reaction parameters such as reaction time, reaction temperature, solvent and catalyst dosage were investigated in detail. A high HMF yield of 54.9% was obtained from cellulose at 150°C after 9h in a mixed solvent of DMSO-[BMIM]Cl (10 wt.%). More importantly, the catalytic system could be reused for several times despite of the slight loss of its catalytic activity.