Enantioselective toxicity, degradation and transformation of the chiral insecticide fipronil in two algae culture

Yingjuan Ou; Zhiyong Yan; Guofeng Shi; Ziling Yu; Yixiang Cai; Ruixue Ma

doi:10.1016/j.ecoenv.2022.113424

Enantioselective toxicity, degradation and transformation of the chiral insecticide fipronil in two algae culture

Ecotoxicol Environ Saf. 2022 Apr 15:235:113424. doi: 10.1016/j.ecoenv.2022.113424. Epub 2022 Mar 18.

Authors

Yingjuan Ou¹, Zhiyong Yan², Guofeng Shi³, Ziling Yu³, Yixiang Cai¹, Ruixue Ma⁴

Affiliations

¹ College of Resources and Environment, Hunan Agricultural University, Changsha 410028, China.
² College of Resources and Environment, Hunan Agricultural University, Changsha 410028, China. Electronic address: 1577781546@qq.com.
³ State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China.
⁴ State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China. Electronic address: maruixue@scies.org.

PMID: 35313125
DOI: 10.1016/j.ecoenv.2022.113424

Abstract

The occurrence of pesticides and their metabolites in the environment can alter the ecological relationships between aquatic food chains. Fipronil is a broad-spectrum insecticide which release in the environment may harm the non-target organisms. However, the toxicity and biotransformation of its two enantiomers are far from fully understood. The present study aimed to investigate the aquatic toxicity and environmental behavior of fipronil at enantiomeric level using two freshwater algae, Scenedesmus quaclricauda (S. quaclricauda), and Chlorella vulgaris (C. vulgaris) through an integrative approach the transformation process of the individual enantiomer isolated and in racemic form. The 72 h-EC₅₀ values of rac-, R-, S-fipronil varied from 3.27 to 7.24 mg L^-1 with R-fipronil posing a more significant effect on algal growth inhibition. Chlorophyll a was more susceptible to fipronil exposure than chlorophyll b and carotenoids. Enantioselective alterations on physiological and biochemical parameters (chlorophyll a, chlorophyll b, carotenoids, and the activities of antioxidant enzyme catalase (CAT) and superoxide dismutase (SOD)) were also observed. The half-lives (T_1/2) of R-fipronil and S-fipronil in algae culture were 3.4-3.5 d and 4.0-4.9 d, respectively. By the end of the 17-d exposure, the enantiomer fractions (EFs) increased to 0.59, indicating a preferential depuration of R-fipronil. The metabolites monitoring showed the fipronil sulfide was the main metabolite followed by fipronil sulfone. The results revealed that the enantiomers of fipronil pose enantiospecific behaviors induced by these two algae, with the R-enantiomer more toxic to algal growth and favorable in degradation. These analyses are beneficial for understanding the ecological effect of chiral pesticide in aquatic environment, and the enantiomeric differences of the toxicity, degradation and the formation of toxic metabolites could be helpful for the eco-environmental risk evaluation.

Keywords: Algae; Aquatic toxicity; Enantioselectivity; Insecticide; Metabolites.

MeSH terms

Chlorella vulgaris* / metabolism
Chlorophyll A
Insecticides* / chemistry
Pyrazoles
Stereoisomerism

Substances

Insecticides
Pyrazoles
fipronil
Chlorophyll A