Nobsathian_2026_Aquat.Toxicol_299_107938

Combretum trifoliatum Vent. is a promising botanical pesticide, but its environmental fate and non-target aquatic biosafety remain undefined. This study assessed acute toxicity, neurobehavioral disruption, enzymatic detoxification, and aqueous persistence of C. trifoliatum ethanolic leaf and twigs extract and its major constituent camphor using adult zebrafish (Danio rerio). HPLC analysis identified camphor as the predominant compound (24.66% w/w). The crude extract exhibited low acute toxicity (96-h shared LC50 = 193.4 mg/L), whereas camphor was markedly more toxic (96-h shared LC50 = 29.00 mg/L). Sublethal exposure elicited sexually dimorphic neurobehavioral effects: males became hypoactive while females showed hyperactivity, with sex-specific alterations in spatial preference and swimming patterns. These behavioral changes coincided with cholinergic disruption, as AChE was inhibited in males but induced in females. Glutathione S-transferase activity remained unchanged, while carboxylesterase was selectively induced only in females exposed to the crude extract, indicating matrix-dependent metabolic responses. Aqueous persistence trials revealed a pronounced lag phase of -13 days with negligible camphor degradation (>96% recovery), followed by rapid first-order decay with a post-lag half-life of 5.80 days, resulting in an overall DT50 of 18.57 days. Despite low acute mortality, the prolonged environmental persistence and sex-dependent neurobehavioral and enzymatic impacts warrant rigorous risk assessment before widespread use.