Target Enzymes of Origanum majorana and Rosmarinus officinalis Essential Oils in Black Cutworm (Agrotis ipsilon): In Vitro and In Silico Studies

In this study, in vitro and in silico approaches were employed to assess the toxicity of marjoram (Origanum majorana) and rosemary (Rosmarinus officinalis) essential oils (EOs) to A. ipsilon larvae. The study determined the activities of ATPases in the larvae after treatment with the LC20 and LC70 of each EO. α-esterase and glutathione-S-transferase (GST) activities were also determined after treatment with LC10 and LC30 of each EO. Furthermore, molecular docking was employed to determine the binding affinity of terpinene-4-ol and α-pinene, the major constituents of O. majorana, and R. officinalis EOs, respectively, compared to the co-crystallized ligand of α-esterase, diethyl hydrogen phosphate (DPF). Toxicity assays revealed that O. majorana EO was more toxic than R. officinalis EO to the A. ipsilon larvae at 96 h post-treatment. However, the LC20 and LC70 of the latter significantly inhibited the activity of the Na+-K+ pump at almost all intervals. The same concentrations significantly inhibited the Mg2+/Ca2+-ATPase and Ca2+ pump at 96 h post-treatment. In contrast, O. majorana EO showed a variable effect on the Na+-K+ pump across different time intervals. On the other hand, LC10 and LC30 of both EOs showed varied effects on α-esterase and GST over time. Molecular docking revealed energy scores of -4.51 and -4.29 kcal/mol for terpinene-4-ol and α-pinene, respectively, compared to a score of -4.67 for PDF. Our study demonstrated the toxicity of the tested EOs to A. ipsilon, suggesting their potential efficacy as insecticides.