Insecticidal and Biochemical Effects of <i>Cinnamomum cassia</i> (L.) Bark Essential Oil Against <i>Anopheles stephensi</i>, <i>Artemia salina</i>, and <i>Eudrilus</i><i>eugeniae</i>

Cinnamomum cassia (L.) bark essential oil (CC-EO) has shown potential as a natural insecticide. However, its toxicity across different species, including disease vectors and bioindicator organisms, has not been fully explored. This study aimed to evaluate the toxicity of CC-EO against human disease vector mosquitoes and aquatic and soil bioindicator species. The mosquitocidal effects of CC-EO were tested on Anopheles stephensi larvae, pupae, and adults. In addition, its impact on Artemia salina and Eudrilus eugeniae was assessed. Chemical composition of CC-EO was analyzed via GC-MS, and its insecticidal activity was further supported by molecular docking studies. CC-EO exhibited significant mosquitocidal activity, with 24-h mortality rates of 53.33% in larvae and 84% in adults. At 48 h, these rates increased to 96% in larvae and 97.33% in adults. Mortality in pupae ranged from 70.66% to 85.33%. Enzyme assays revealed a decrease in insect catalase levels and an increase in glutathione S-transferase. Minimal effects were observed on A. salina (25.33% and 54.66% mortality at 24 and 48 h, respectively), and no toxicity was observed in E. eugeniae. GC-MS analysis identified (E)-cinnamaldehyde as the primary active compound, with molecular docking studies suggesting strong insecticidal potential. CC-EO demonstrates significant mosquitocidal activity against larvae, pupae, and adults of A. stephensi, with minimal toxicity to nontarget organisms, A. salina and E. eugeniae, highlighting its potential for eco-friendly mosquito control.