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Antihypertensive drugs are among the most prescribed drugs. Olmesartan acid, of the sartan class, belongs to a relatively new generation of antihypertensive drugs called angiotensin II receptor blockers. There are very few studies on the presence and fate of sartans in the environment, despite them being marketed in huge quantities, metabolized in low percentages, and detected in wastewater and water bodies. This paper presents a study on the less abundant and more polar fractions that have been neglected in previous studies, which led to the isolation by chromatographic methods of thirteen degradation byproducts (DPs), six of which are new, identified by nuclear magnetic resonance and mass spectrometry. A mechanism of degradation from the parent drug was proposed. The ecotoxicity of olmesartan acid and identified compounds was evaluated in Aliivibrio fischeri bacteria and Raphidocelis subcapitata algae to assess acute and chronic toxicity. For 75% of the DPs, acute and chronic exposure to the compounds, at concentrations of 5 mg/L, inhibited population growth in the algae and decreased bioluminescence in the bacteria.

Recently, many studies highlighted the consistent finding of irbesartan in effluents from wastewater treatment plants (WWTPs) and in some rivers and lakes in both Europe and North America, suggesting that no N80% can be removed by specific treatments. The present investigation attempts to study the chemical fate of irbesartan in a simulated chlorination step, mimicking the conditions of a WWTP. A total of six disinfection by-products were identified, five were completely new, and separated on a C-18 column by employing a gradient HPLC method. Initially, a complete mass fragmentation pathway of the drug was established with the help of MS/ TOF, and subsequently, the disinfection by-products were subjected to MS/TOF mass studies to obtain their mass and fragment pattern. The MS results helped to assign tentative structures to the disinfection products, which were verified through 1D and 2D NMR experiments. The chemical structures of the new compounds have been justified by a proposed mechanism of formation. A preliminary ecotoxicity assessment with the crus- tacean Daphnia magna showed that some of the identified by-products were up to 12-times more toxic than irbesartan.

Diclofenac (DCF) is the most widely prescribed non-steroidal anti-inflammatory drug in the world and it has been detected in drinking and surface waters. In this paper, the effect of chlorination process on DCF in aqueous solutions was investigated and the structures of 14 isolated degradation by-products (DPs), of which nine are new, have been determined from combining mass spectrometry and nuclear magnetic resonance data and justified by a proposed mechanism of formation beginning from the parent drug. Some degradation by-products show only one phenyl, others are dimers or trimers of the parental compound, which has undergone oxidative decarboxylation of the side chain and/or chlorination of this or one or both aromatic rings. Ecotoxicological bioassays evidenced the following sensitivities D. magna < R. subcapitata < A. fischeri. The isolated DPs (DP1−8, except for DP9) exhibited effects ≥ 50 % in the exposed microalgae and crustaceans showing toxicities mainly ranked from slight to acute.

In recent years, many studies have reported the frequent detection of antihypertensive agents such as sartans (olmesartan, valsartan, irbesartan and candesartan) in the influents and effluents of wastewater treatment plants (WWTPs) and in the superficial waters of rivers and lakes in both Europe and North America. In this paper, the degradation pathway for candesartan (CAN) was investigated by simulating the chlorination process that is normally used to reduce microbial contamination in a WWTP. Twelve isolated degradation byproducts (DPs), four of which were isolated for the first time, were separated on a C-18 column by employing a gradient HPLC method, and their structures were identified by combining nuclear magnetic resonance and mass spectrometry and comparing the results with commercial standards. On the basis of these results, a mechanism of formation starting from the parent drug is proposed. The ecotoxicity of CAN and its DPs was studied by conducting a battery of ecotoxicity tests, bioassays were performed using Aliivibrio fischeri (bacterium), Daphnia magna (planktonic crustacean) and Raphidocelis subcapitata (alga). The ecotoxicity results shed new light on the increased toxicity of DPs compared with the parent compound.

The discovery of various sartans, which are among the most used antihypertensive drugs in the world, is increasingly frequent not only in wastewater but also in surface water and, in some cases, even in drinking or groundwater. In this paper, the degradation pathway of olmesartan acid, one of the most used sartans, was investigated by simulating the chlorination process normally used in a wastewater treatment plant to reduce similar emerging pollutants. The structures of nine isolated degradation byproducts (DPs), eight of which were isolated for the first time, were separated via chromatography column and HPLC methods, identified by combining nuclear magnetic resonance and mass spectrometry, and justified by a proposed mechanism of formation beginning from the parent drug. Ecotoxicity tests on olmesartan acid and its nine DPs showed that 50% of the investigated byproducts inhibited the target species Aliivibrio fischeri and Raphidocelis subcapitata, causing functional decreases of 18% and 53%, respectively.

In recent years, many studies have highlighted the consistent finding of amoxicillin in waters destined for wastewater treatment plants, in addition to superficial waters of rivers and lakes in both Europe and North America. In this paper, the amoxicillin degradation pathway was investigated by simulating the chlorination process normally used in a wastewater treatment plant to reduce similar emerging pollutants at three different pH values. The structures of 16 isolated degradation byproducts (DPs), one of which was isolated for the first time, were separated on a C-18 column via a gradient HPLC method. Then, combining mass spectrometry (MALDI-MS/TOF) and nuclear magnetic resonance, we compared commercial standards and justified a proposed formation mechanism beginning from the parent drug. Microbial growth inhibition bioassays with Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus were performed to determine the potential loss of antibacterial activity in isolated degradation byproducts. An increase of antibacterial activity in the DPs was observed compared to the parent compound.