Abstract

Trans-cinnamaldehyde (CIN), the main component of cinnamon essential oil, is a promising sustainable alternative to synthetic pesticides. Despite its use, ecotoxicological data on non-target species remain fragmented. This study systematically evaluates CIN’s acute toxicity across multiple trophic levels to characterize the biological sensitivity and environmental response of key organisms. Aquatic assays measured bioluminescence inhibition in Aliivibrio fischeri and immobilization in Daphnia magna. Terrestrial evaluations included lethality tests on Eisenia fetida and root elongation in Allium cepa. Additionally, the impact on soil and river microbial communities was analyzed via Biolog EcoPlates™. Significant dose–response relationships were observed across all bioindicators (p < 0.0001). A. fischeri was the most sensitive species (EC50 = 1.428 mg·L−1), followed by D. magna (EC50 = 4.533 mg·L−1). In terrestrial models, A. cepa (EC50 = 11.644 mg·L−1) exhibited higher sensitivity than E. fetida (LC50 = 412.519 mg·kg−1). Microbial metabolic activity showed dose-dependent inhibition, particularly affecting carbohydrate and polymer degradation at high concentrations. These findings define the first ecotoxicological benchmarks for CIN, establishing EC10 and EC50 values under standardized conditions. These data provide the necessary toxicological constraints to ensure environmental safety in future field-scale applications of this natural compound.

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