Synthetic Mn(III) porphyrins as biomimetic catalysts of CYP450: Degradation of antibiotic norfloxacin in aqueous medium.

Norfloxacin (NOR) is a synthetic broad-spectrum fluoroquinolone antibiotic classified as an emerging contaminant. Here, we investigate Mn(III) porphyrin-catalyzed NOR degradation using peroxides or peracids (H2O2, t-BuOOH, or Oxone®) as oxidants. We evaluate three Mn(III) porphyrins: the 1st-generation tetraphenylporphyrin and 2nd -generation porphyrins bearing halogen atoms at the ortho-positions of the porphyrin macrocycle meso-aryl groups. Experiments were carried out in aqueous medium under mild conditions. NOR degradation was 67%. Products were proposed by mass spectrometry (MS) analysis. Oxone® was the best oxidant for NOR degradation despite its possible decomposition in the reaction medium. The second-generation Mn(III) porphyrins were more resistant than the first-generation Mn(III) porphyrin, indicating that the bulky groups introduced into the porphyrin macrocycle meso-aryl groups led to more robust catalysts. The degradation products did not present cytotoxic behavior under the employed conditions. In conclusion, Mn(III) porphyrin-catalyzed NOR degradation is a promising strategy to degrade fluoroquinolones and other pollutants.

Efficient atrazine degradation catalyzed by manganese porphyrins: Determination of atrazine degradation products and their toxicity evaluation by human blood cells test models.

Atrazine (ATZ) is an herbicide that has been considered an environmental pollutant worldwide. ATZ contaminates groundwaters and can persist in soils for up to a year causing several environmental and health problems. This study aimed to investigate ATZ degradation catalyzed by manganese porphyrins as biomimetic cytochrome P450 models. We used PhIO, PhI(OAc)2, H2O2, t-BuOOH, m-CPBA, or Oxone® as oxidant under mild conditions and evaluated a range of manganese porphyrins as catalyst. Concerning oxidant, iodosylbenzene provided the best result-ATZ degradation catalyzed by one of the studied manganese porphyrins in acetonitrile was as high as 47%. We studied the same catalyst/oxidant systems in natural water from a Brazilian river as solvent and obtained up to 100% ATZ degradation when iodobenzene diacetate was the oxidant, regardless of the manganese porphyrin. Besides the already known ATZ degradation products, we also identified unexpected degradation compounds (ring-opening products). Toxicity tests showed that the latter products were capable of proliferate blood cells because they did not show toxicity under the evaluated conditions.

Ciprofloxacin degradation by first-, second-, and third-generation manganese porphyrins.

A range of hydrophobic first-, second-, and third-generation manganese porphyrins (MnPs) was investigated as cytochrome P450 models for degradation of the antibiotic ciprofloxacin (CIP). The experiments were carried out under mild conditions; oxidants such as iodosylbenzene (PhIO), H2O2, and meta-chloroperbenzoic acid were employed. The PhIO system yielded the best results: CIP degradation ranged between 56% and 76%. CIP degradation was not directly related to MnP generation. The second-generation MnP afforded the best result with the advantage that it required less preparation effort as compared to the third-generation MnP. Some new degradation products in MnP-mediated ciprofloxacin degradation were proposed, and the products of the reaction are not cytotoxic under the conditions evaluated.