Exploring the bio-insecticidal activity of Eucalyptus globulus essential oil/β-cyclodextrin inclusion complexes: In vitro and in silico assessment against Ephestia kuehniella larvae

Abstract

Owing to their beneficial functional capabilities, essential oils were largely used. However, their low aqueous solubility, instability, and high volatility urged scientists to their encapsulation with cyclodextrins (CDs) to tackle their shortcomings. In this study, the co-precipitation method was used to prepare β-CD/Eucalyptus globulus essential oil (EGEO) inclusion complexes (ICs). β-CD/EGEO ICs were prepared at ratios (w:w) 1:2 and 1:4 with an encapsulation efficiency of 93 and 96%, respectively. The ICs characterization using the Fourier transform Infrared spectroscopy, differential scanning calorimetry, X-ray powder diffraction, Dynamic Light Scattering, and Laser Doppler Velocimetry confirmed the formation of β-CD/EGEO ICs. The insecticidal activity of the free EGEO and ICs was explored and displayed that the complex β-CD/EGEO 1:4 had the highest activity with the lowest LC50 against Ephestia kuehniella larvae (5.03 ± 1.16 mg/g) when compared to the free oil (8.38 ± 1.95 mg/g). Molecular docking simulations stipulated that the compound α-Bisabolene epoxide had the best docking score (ΔG = −7.4 Kcal/mol) against the selected insecticidal target α-amylase. Additionally, toxicity evaluation of the studied essential oil suggested that it could be safely used as a potent bioinsecticide as compared to chemical insecticides. This study reveals that the formation of β-CD/EGEO ICs enhanced the oil activity and stability and could be a promising and safe tool to boost its application in food or pharmaceutical fields.