Evaluating the insecticidal efficacy of geranium (Pelargonium graveolens) essential oil and its nanoemulsion form against three stored products pests and molecular docking simulations

The geranium essential oil (GEO) has potential as insecticide. It's volatility and low stability limit its use, which can be overcome by nanoemulsion. This study aimed to formulate and characterize a nanoemulsion (GEO-N) of the GEO and examine insecticidal activity against Tribolium castaneum, Sitophilus granarius, Oryzaephilus surinamensis. The components of the GEO were determined as citronellol (30.76 %), geraniol (14.57 %), citronellyl formate (9.67 %) using GC-MS analysis. The GEO-N (1.5:0.3:0.15:98.05 (w/w) GEO:Tween 80:Ethanol:water) was synthesized using an ultrasonic homogenizer. The GEO-N has uniform spherical shape and size of 100 nm-200 nm, its droplet particle size, zeta-potential value, and polydispersity index were 178.2 nm, -15.3 mV, and 0.205, respectively. A concentration of 500 mg/L of GEO-N caused 53.33 %, 20.00 %, and 80 % mortality in T. castaneum, S. granarius, and O. surinamensis, respectively, after 7 days. A concentration of 1000 mg/L of GEO-N resulted in 100 %, 70 %, and 100 % mortality in T. castaneum, S. granarius, and O. surinamensis, respectively, after 7 days. Molecular docking studies have highlighted the interactions of cyclohexanol and 5-methyl-2-(1-methylethyl)-, (1.alpha.,2.alpha.,5.alpha.)- compounds with T. castaneum proteins (PDB ID: 5CQG, 7LT2, and 6V3T). These compounds were identified as promising candidates for use as an ointment applied to the insect cuticle as insecticide.