Towards Sustainable Pest Management: Toxicity, Biochemical Effects, and Molecular Docking Analysis of Ocimum basilicum (Lamiaceae) Essential Oil on Agrotis ipsilon and Spodoptera littoralis (Lepidoptera: Noctuidae)

Abstract

Over the last decade, essential oils (EOs) have become potential ingredients for insecticide formulations due to their widespread availability and perceived safety. Therefore, this study aimed to evaluate the toxicity and biochemical efficacy of basil (Ocimum basilicum) (Lamiaceae) against two destructive pests Noctuidae, Agrotis ipsilon (Hufnagel) and Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). In addition, a molecular docking study was performed to gain insight into the binding pattern between glutathione S-transferase (GST) and linalool, the main component of EO. GC-MS analysis of O. basilicum EO revealed that linalool is the most abundant compound (29.34%). However, the toxicity tests showed no significant difference between the values of LC₅₀ of O. basilicum EO to A. ipsilon and S. littoralis. On the other hand, the sublethal experiments indicated that treating the second instar larvae with LC₁₅ or LC₅₀ values of O. basilicum EO significantly prolonged the larval duration in both insects, compared to the control. Regarding the biochemical effect of O. basilicum EO, the treatments significantly impacted the activity of detoxification enzymes. A notable elevation in glutathione S-transferase (GST) activity was recorded in A. ipsilon larvae compared with a reduction in S. littoralis larvae. The molecular docking analysis revealed that linalool bonded with the amino acid serine (SER 9) of GST, indicating its binding affinity with the enzyme. The obtained results could offer valuable insights into the mode of action of O. basilicum and can encourage the adoption of sustainable pest control practices that incorporate essential oils.

Keywords: Detoxifying enzymes; Essential oils; Glutathione S-transferase (GST); Molecular docking; Noctuidae pests; Toxicity.

Fig. 1

Chemical structure of the main bioactive compounds of basil EO, O. basilicum

Fig. 2

Sex ratio of the emerged adults of Agrotis ipsilon and Spodoptera littoralis after treating the 2nd instar larvae with LC₁₅ and LC₅₀ of Ocimum basilicum essential oil

Fig. 3

2D and 3D molecular docking simulation of the interactions between the s-Hexylglutathione ligand (GTX) in the enzyme binding pocket and linalool with the active site of the receptor of GST (PDB ID: 1PN9)