Rice weevils (Sitophilus oryzae) are pests that feed on grain products. One strategy employed in the safe pest management is the use of essential oils from plant materials as biopesticide. Monoterpene compounds, present in essential oils, are generally less acutely toxic than other conventional insecticides and are known to possess biopesticide activity against octopaminergic receptors (OAR). Tyramine receptor (TyrR) is a desired biopesticide target due to its absence in vertebrates and its role in insect’s physiological and cellular response. In this study, the biochemical basis of monoterpenes and SoTyrR interactions were determined using in silico methods: ensemble docking, 3DQSAR analysis, and toxicity prediction. Ensemble docking results showed that the lead compounds has binding affinity of − 4.2 to − 6.8 kcal/mol. Four monoterpene compounds: terpinolene, carvacrol, carene, and pulegone were considered top hits based on their favorable binding affinity. Furthermore, hydrophobic interactions of monoterpenes with residues Asp114, Val404, Lys189, Leu190, Tyr196, Phe397, and Tyr401 stabilized the observed docking poses. Upon consolidation of docking and 3DQSAR results, we functionalized top hit ligands and showed significant increase in the average binding affinity of candidate compounds, ranging from − 4.7 to − 8.3 kcal/mol. A carene derivative exhibited the highest binding energy of − 8.3 kcal/mol with a calculated Ki of 0.547 μM which surpassed the known activators of OAR. The top hit modified ligands were also clear of toxicity risks as predicted by Osiris Property Explorer. This work could provide insights in the development of effective biopesticides for rice weevils that is less toxic than conventional pesticides.

The interaction and mechanism of monoterpenes with tyramine receptor (SoTyrR) of rice weevil (Sitophilus oryzae)

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