In silico docking studies of non-azadirachtin limonoids against ecdysone receptor of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae)

Abstract

Although specific binding of 20-hydroxyecdysone (20E) and its analogs (ecdysteroids) to the ecdysone receptor ligand-binding domain (EcR-LBD) in insects has been well documented, information on the EcR-ligand binding in Helicoverpa armigera is limited. Hence, an attempt has been made to screen effective natural plant-based agonists from a library of 25 non-azadirachtin neem limonoids and was compared with the commercially available insecticide, tebufenozide, through in silico approach. Results indicated that six compounds, namely nimbolide, azadirone, nimolinone, meliacinol, nimbocinol, azadiradione, efficiently docked with the active site of H. armigera EcR-LBD. The binding energies of top-ranked six molecules ranged from −10.54 to −12.22 kcal/mol, which was superior to the third-generation insect growth regulator (IGR), tebufenozide RH5992. Two factors are especially important in binding: (1) the residues Cys 508 and Asn 504, which are the most common in hydrogen-bonding interactions and (2) hydrophobic pocket residues—Asn 504, Met 507, Val 416, Tyr 408 and Thr 343. We also recognized one aromatic ring, 3–7 vicinal acceptors and 1–3 distal hydrophobic groups as minimum pharmacophoric feature. A significant correlation coefficient of 0.6823 was observed supporting positively the docking studies. These data could help in the application of natural compounds as alternatives to chemicals in pest management.