Dose–response toxicity and locomotor effects of Mucuna pruriens-based phytotherapeutic combinations in pesticide-exposed Drosophila melanogaster

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Background Mucuna pruriens contains L-3,4-dihydroxyphenylalanine (L-DOPA) and other bioactive constituents with potential relevance to motor dysfunction; however, the safety of crude extracts and the behavioural effects of multi-botanical formulations remain insufficiently characterized. This study evaluated the concentration-dependent toxicity of crude M. pruriens seed extract and its locomotor effects, alone and in combination with Cucurbita pepo and Arachis hypogaea , in pesticide-exposed adult male Drosophila melanogaster . Methods For toxicity assessment, flies were exposed for 7 days to diets containing 0.1%–2.0% (w/v) M. pruriens . Each treatment comprised nine vials containing 20 flies per vial, giving 180 flies per treatment. Mortality, survival, hazard ratios, no-observed-effect level (NOEL), lowest-observed-effect level (LOEL), and model-derived median lethal concentration (LC 50 ) were determined. Locomotor impairment was induced using paraquat at 10 or 20 mM or glyphosate at 0.5%, 1.0%, or 2.0% (w/v). Negative geotaxis was evaluated in three independent experimental runs, with four vials per treatment per run and 10 flies per vial, giving 12 vial-level experimental units and 120 flies per treatment. Vial-level area under the climbing-response curve (AUC) was used as the primary locomotor endpoint. Results Seven-day mortality increased from 13.9% in negative control to 45.6% at 2.0% M. pruriens . The operational NOEL and LOEL were 0.1% and 0.5%, respectively. Logistic modelling estimated an LC 50 of 2.06% (95% CI, approximately 1.71%–2.41%); this estimate was model-dependent and extrapolated because mortality remained below 50%. Paraquat and glyphosate significantly reduced vial-level locomotor AUC relative to the negative control. Treatment with 0.1% M. pruriens , alone or in combination with C. pepo and/or A. hypogaea , produced partial locomotor improvement relative to pesticide-only baselines, but none of the treatments restored performance to the negative-control level. Conclusion Crude M. pruriens seed extract exhibited concentration-dependent toxicity, while the 0.1% concentration was associated with partial locomotor improvement in pesticide-exposed D. melanogaster . The findings provide preliminary toxicological and behavioural evidence but do not establish direct neuronal protection or a molecular neuroprotective mechanism. Further studies should include appropriate vehicle and solvent controls, higher concentrations to improve LC 50 estimation, fixed-total-dose combination formulations, phytochemical standardization, and mechanistic assessment of oxidative stress, mitochondrial integrity, and dopaminergic neurons.

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