Chemical characterization, insecticidal activity and in silico study of Tephrosia vogelii Hook.f. (Fabaceae) flower essential oil on Solenopsis saevissima (Smith, 1855) (Hymenoptera: Formicidae)

Abstract

Pest control is one of the main challenges in sustainable agriculture. A promising pest-control method in these systems is the use of plants with insecticidal properties. This study aimed to identify the chemical components of Tephrosia vogelii Hook.f. (Fabaceae) and evaluate the potential of flower essential oil to control fire ant, Solenopsis saevissima (Smith, 1855) (Hymenoptera: Formicidae), a significant pest of strawberry crops. The essential oil analysis revealed the presence of farnesol, α-pinene, nerolidol, spathulenol, ocimene, and limonene as major constituents. The oil demonstrated strong insecticidal activity, with LC₅₀ and LC₉₀ values of 0.105 and 0.298 mL/L, respectively, in S. saevissima, suggesting a possible neurotoxic effect with rapid action. In bioassays, a neutral detergent was used to solubilize the essential oil, proving an effective and economical alternative to traditional solubilizers. In addition, to support a possible mechanism of action, docking against acetylcholinesterase (AChE; PDB 4EY6) was performed: farnesol exhibited the best affinity (ΔG = −7.1 kcal/mol; Ki ≈ 6.20 µM), followed by nerolidol (−6.8) and, with lower affinities, α-pinene (−6.3) and limonene (−6.2). These results suggest a cholinergic contribution to the observed toxicity, to be confirmed with enzymatic assays and insect AChE models.