Enantioselective Toxic Effects of Prothioconazole toward Scenedesmus obliquus

Abstract

Prothioconazole (PTC) is a broad-spectrum triazole fungicide with one asymmetric center and consists of two enantiomers, R-(−)-PTC and S-(+)-PTC. To address the concern of its environmental safety, the enantioselective toxic effects of PTC on Scendesmus obliquus (S. obliquus) were investigated. PTC racemates (Rac-PTC) and enantiomers exhibited dose-dependent acute toxicity effects against S. obliquus at a concentration from 1 to 10 mg·L−1. The 72 h-EC50 value of Rac-, R-(−)-, and S-(+)-PTC is 8.15, 16.53, and 7.85 mg·L−1, respectively. The growth ratios and photosynthetic pigment contents of the R-(−)-PTC treatment groups were higher than the Rac- and S-(+)-PTC treatment groups. Both catalase (CAT) activities and esterase activities were inhibited in the Rac- and S-(+)-PTC treatment groups at high concentrations of 5 and 10 mg·L−1, and the levels of malondialdehyde (MDA) were elevated, which exceeded the levels in algal cells for the R-(−)-PTC treatment groups. PTC could disrupt the cell morphology of S. obliquus and induce cell membrane damage, following the order of S-(+)-PTC ≈ Rac-PTC > R-(−)-PTC. The enantioselective toxic effects of PTC on S. obliquus provide essential information for its ecological risk assessment.

The Effects of the Fungicide Myclobutanil on Soil Enzyme Activity

“…Recent data in the literature reveal the enantioselective effects of pesticides and/or of their metabolites on both target and non-target organisms, with enantioselectivity differing between toxicological effects or species [72]. Regarding triazole fungicides, enantiose-lective environmental and human health effects were observed for difenoconazole [10], hexaconazole [11], mefentrifluconazole [12], prothioconazole [13], tebuconazole [14], and triticonazole [9].…”

“…Literature data show that both the antifungal activity and non-target toxicity of several triazole fungicides are enantioselective [10][11][12][13][14][15][16][17][18]. There was no enantioselectivity of triticonazole stereoisomers in their interaction with soil enzymes, but such selectivity was recorded for the two steroisomers in the interactions with plasma proteins and human cytochromes [9].…”

“…Considering the DT 50 values for myclobutanil in soil, 11.0-19.2 days [11][12][13], the present study was implemented over a period of 28 days to cover the dissipation half-life. Moreover, numerous studies in the specialized literature mention this period as appropriate for experiments seeking to evaluate the effects of pesticides on the activity of soil enzymes under laboratory conditions.…”