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  • Mechanisms of action of essential oils on enzymes relevant to insect and nematode development
    Publication . Martins, Mariana Barreto; Castilho, Paula Cristina Machado Ferreira
    Insects, such as the Mediterranean fruit fly (Medfly, Ceratitis capitata) and the armyworm (Mynthimna unipuncta), and nematodes, such as the root-knot nematode (RKN, Meloidogyne incognita) and the pine wood nematode (PWN, Bursaphelenchus xylophilus), are major agricultural pests. Botanical pesticides such as essential oils (EOs) have proven effective in controlling agricultural pests due to their repellent, anti-feeding properties, etc. Therefore, the objective of this study was to evaluate the potential of aromatic plants in controlling the pests C. capitata, M. unipuncta, M. incognita, and B. xylophilus by studying their mechanisms of action on the neural and digestive enzymes. This study focused on the EOs of Origanum vulgare, Thymus vulgaris, Ocimum gratissimum, Mentha pulegium, and Cinnamomum cassia, mainly composed of carvacrol, thymol, eugenol, pulegone, and trans-cinnamaldehyde, respectively, as several studies have mentioned their insecticidal and/or nematicidal effects. Theirinteractions with enzymes relevant to insect and nematode development, namely acetylcholinesterase (AChE), α- and β-glucosidase, were investigated using crude enzyme extracts obtained from the selected species. Enzyme activity and soluble protein content were quantified using standard assays, and SDS-PAGE was performed to attempt protein identification. In vitro inhibition assays with the EOs and their major components were then conducted to assess inhibitory activity and provide insights into potential mechanisms of action. The results revealed that all tested EOs inhibited AChE but had no effect on the digestive enzymes. Among the EOs studied, M. pulegium EO showed the strongest inhibition of AChE in both Medfly (IC50 = 0.022 mg/mL) and PWN (IC50 = 0.1209 mg/mL). C. cassia EO was particularly effective against armyworm (IC₅₀ = 0.0020 mg/mL) and RKN (IC₅₀ = 0.0197 mg/mL). These findings suggest that these EOs primarily exert their toxic effects through interference with the nervous system, supporting their potential as sustainable alternatives to synthetic pesticides in environmentally friendly pest management.
    2025-11-29Master thesis Embargoed access Show more