Exploration of Enantioselective Effects of MDPV on Zebrafish Embryogenesis ^†

Abstract

Introduction: Synthetic cathinones (SC) are an emerging class of neuroactive contaminants increasingly detected in aquatic systems due to their widespread recreational use. Their continuous release at ng–µg L⁻¹ levels is particularly concerning, as these compounds are specifically designed to alter neural function, raising the likelihood of subtle yet ecologically relevant effects in non-target organisms. Among them, 3,4-methylenedioxypyrovalerone (MDPV) is one of the most-reported SC in wastewater and surface waters. Nevertheless, its chiral nature has been largely overlooked in ecotoxicological studies, despite growing evidence that enantiomers can differ markedly in biological activity, potentially leading to underestimated environmental risks. Objective: The ecotoxicological impact of racemic MDPV ((R,S)-MDPV) and its separate enantiomers ((R)-MDPV and (S)-MDPV) were examined using zebrafish (Danio rerio) as a model, focusing on survival and embryonic development. Methodology: Zebrafish embryos, at approximately 3-hours post-fertilization (hpf), were exposed over 96 h to environmentally relevant concentrations of MDPV forms (0.18−2.8 μg L⁻¹). Each treatment and control group included 50 animals distributed across 5 replicates. Mortality was assessed at multiple developmental stages (7, 24, 48, 72, and 96 h), along with cumulative mortality. Developmental endpoints included spontaneous movements (24 h), heartbeat (48 h), and hatching rate (48 and 72 h), quantified using stereomicroscopy and video analysis. Results: MDPV showed concentration and enantioselective effects, with (S)-MDPV being the most toxic. Behavioral and cardiac responses varied across forms, while hatching depended on concentration and time without a clear enantioselective pattern. Conclusions: MDPV disrupts early zebrafish development, impairing survival and embryonic development in a concentration-dependent and enantioselective manner, with (S)-MDPV demonstrating greater toxicity. These findings emphasize the importance of considering chirality in the environmental risk assessment of psychoactive contaminants such as SC, as enantiomer-specific effects may influence organism fitness, survival, and broader ecological outcomes.