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. 2021 Jun 5;26(11):3422.
doi: 10.3390/molecules26113422.

Secondary Effects of Hypochlorite Treatment on the Emerging Pollutant Candesartan: The Formation of Degradation Byproducts and Their Toxicological Profiles

Giovanni Luongo  1 , Lorenzo Saviano  2 , Giovanni Libralato  2 , Marco Guida  2 , Antonietta Siciliano  2 , Lucio Previtera  3 , Giovanni Di Fabio  1 , Armando Zarrelli  1
Affiliations

Secondary Effects of Hypochlorite Treatment on the Emerging Pollutant Candesartan: The Formation of Degradation Byproducts and Their Toxicological Profiles

Giovanni Luongo et al. Molecules. .

Abstract

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.

Keywords: Aliivibrio fischeri; Daphnia magna; Raphidocelis subcapitata; battery toxicity test; candesartan; chlorination; degradation byproducts; hypochlorite; water treatment.

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Conflict of interest statement

The authors declare no conflict of financial interests.

Figures

Figure 1
Figure 1
Chemical structures of Candesartan and its degradation byproducts.
Figure 2
Figure 2
Plausible mechanism for the formation of DP1–DP12.
Figure 3
Figure 3
Toxic units (TU) for D. magna (Dm), R. subcapitata (Rs) and A. fischeri (Af) exposed to CAN and their DPs (A). Class weight scores (CWS %) for the selected battery tests (B).
Scheme 1
Scheme 1
Isolation of the different identified compounds.
See this image and copyright information in PMC

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