Alkyl-Chain Extension and Terminal Amine Substitution Shape Cardiotoxic Profiles of Methylenedioxy Cathinones in Zebrafish Embryos
Ouwais Aljabasini, Niki Tagkalidou, Martalu D. Pazos, Guillermo García-Díez, Eva Prats, Roger Seco, Xavier Berzosa, Raúl López‐arnau, Demetrio Raldúa
Pharmaceuticals August 7, 2026 DOI: 10.3390/ph19081243 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Experimental study using zebrafish embryos (New Approach Methodology) Peer reviewed |
|---|---|
| Population | Wild-type short-fin zebrafish (Danio rerio) embryos and eleutheroembryos |
| Interventions | Methylone Butylone Pentylone Dimethylone Dibutylone Dipentylone Dihexylone Diheptylone |
| Duration | Acute exposure for cardiac assessment at 3 days post-fertilization; 120 min locomotor assessment at 5 days post-fertilization |
| Measures | high-speed video microscopy and dynamic pixel-based analysis (atrial chronotropy, atrioventricular conduction); automated video tracking of basal locomotor activity |
| Key findings | Alkyl-chain extension and terminal amine substitution shaped cardiac and neurobehavioral toxicity in a structure-dependent manner. Negative chronotropy increased with chain length (methylone < butylone < pentylone), with diheptylone and dihexylone producing the strongest atrial-rate inhibition; diheptylone showed the lowest AV-block midpoint and complete lethality at 1000 µM. Locomotor activity was predominantly hypoactive, with sustained late-phase inhibition for dipentylone, dihexylone, and diheptylone. |
Abstract
Background/Objectives: Synthetic cathinones are a rapidly evolving class of new psychoactive substances whose structural diversity complicates toxicological risk assessment. Methylenedioxy cathinones occupy a pharmacological space between MDMA-like entactogens and more dopaminergic stimulant cathinones, but their direct cardiac liabilities remain poorly characterized. This study aimed to compare the cardiotoxic and neurobehavioral profiles of methylone, butylone, pentylone and their N,N-dimethyl analogues, and to determine how alkyl-chain extension and terminal amine substitution shape functional toxicity.
Methods: Wild-type short-fin zebrafish (Danio rerio) embryos were used as a multiparametric New Approach Methodology. Cardiac rhythmicity was assessed in 3 days post-fertilization embryos after acute exposure to methylone, butylone, pentylone, dimethylone, dibutylone, dipentylone, dihexylone and diheptylone by high-speed video microscopy and dynamic pixel-based analysis, focusing on atrial chronotropy and atrioventricular conduction. Basal locomotor activity was evaluated in 5 days post-fertilization eleutheroembryos over 120 min using automated video tracking.
Results: Negative chronotropy increased with alkyl-chain extension, with the monoalkyl subset following the rank order methylone < butylone < pentylone. Among dialkyl analogues, dihexylone and, especially, diheptylone produced the strongest atrial-rate inhibition. AV conduction impairment was more heterogeneous but became prominent among higher-liability analogues, with diheptylone showing the lowest AV-block midpoint descriptor and complete lethality at 1000 µM. Locomotor profiling revealed predominantly hypoactive phenotypes, with sustained late-phase inhibition especially for dipentylone, dihexylone and diheptylone.
Conclusions: Alkyl-chain extension and terminal amine substitution shaped cardiac and neurobehavioral toxicity in a structure-dependent manner. The zebrafish workflow provides a structure-oriented framework for prioritizing emerging methylenedioxy cathinones with comparatively higher functional cardiac liability.