Photocatalytic degradation of cholesterol-lowering statin drugs by TiO2-based catalyst. Kinetics, analytical studies and toxicity evaluation

摘要

The photocatalytic degradation of simvastatin, lovastatin, and pravastatin, cholesterol-lowering statin drugs, by TiO2-based catalyst in aqueous solutions has been studied. In all cases the degradation was found to be efficient and was clearly owing to the formation of hydroxyl radicals. When present in their open forms, the life times were evaluated, in aerated conditions, to 8.1 ± 1.2,10.4 ± 1.3 and 19,2 ± 2.1 min for simvastatin, lovastatin and pravastatin respectively. In their lactone forms, in non-aerated conditions, the life times were found to be higher: 12.4 ± 1.1 and 15.6 ± 2.0 min for simvastatin and lovastatin. Several primary and secondary photoproducts were elucidated by means of LC-MS technique. They were obtained as a result of the addition of the hydroxyl radical to the double bonds leading to the formation of different hydroxy derivatives. Under prolonged irradiation, efficient mineralization of statin solutions was observed by means of total organic carbon (TOC) evolution. A detailed mechanism for the degradation of statins and the formation of photo-products is proposed and discussed, together with toxicity evaluation. It is stressed that photocatalysis appears to be an alternative to other chemical or biological methods for statins removal in aqueous solutions.