A Fusarium Oxysporum-derived Compound Exhibits Potential Insecticidal Activity against Cotton Bollworm: Evidence from In Silico and In Vitro Analyses

Fungal derived secondary metabolites serve as promising alternatives to traditional insecticides due to their eco-friendly nature and specific modes of action. This study investigates the insecticidal potential of a secondary metabolite derived from Fusarium oxysporum using in silico and in vitro approaches. The objectives include the purification of the bioactive compound, followed by computational and experimental evaluations to assess its insecticidal efficacy.

The initial purification involved mass spectroscopic analysis, followed by structural elucidation using Varian 500 NMR. The compound was tested for insecticidal potential using third instar nymphs of Helicoverpa armigera. From stock solution prepared in sterile dimethyl sulfoxide (DMSO) test concentrations of 100, 250, 500, and 1000 µg mL-1 were prepared. Imidacloprid in powder form was used as the standard insecticide in this experiment, also at concentrations of 100, 250, 500, and 1000 µg mL-1. Computational analyses, including molecular docking, molecular dynamics simulations and binding free energy calculations, were performed to explore the compound’s interaction with the target receptor.

The compound derived from F. oxysporum was identified as 6-butyl-3-(1-hydroxyethyl)-2-methyl-2H-pyran-5-carbonyl carbamic acid having an exact mass of 283 and molecular formula C14H21NO5. The fungal compound, administered at concentrations of 100, 200, and 250 µg mL-1, exhibited mortality rates of 30%, 56.6%, and 63.3%, respectively. In comparison, the standard drug, imidacloprid, demonstrated mortality rates of 30%, 50%, and 60% at the respective concentrations. At a concentration of 500 µg mL-1, the fungal compound inhibited the growth of 8 larvae in each test plate, resulting in an 80% mortality rate while, the standard at this concentration caused the death of 8 larvae in two petriplates and 7 larvae in the third, resulting in a mortality rate of 76.6%. At the highest applied concentration (1000 µg mL-1), both the fungal compound and the standard exhibited 100% mortality by inhibiting the growth of every larva in all petriplates. The docking analysis predicted -5.3 binding energy that represents the selected compound having significant binding affinity for the target receptor. Similarly, the compound showed stable dynamics with the enzyme and reported robust binding energies.

The findings highlight the potential of 6-butyl-3-(1-hydroxyethyl)-2-methyl-2H-pyran-5-carbonyl carbamic acid as a bioactive fungal metabolite for eco-friendly pest control, warranting further investigations into its mechanism of action, field efficacy, and environmental safety. Future work will focus on chemical synthesis to produce the compound in sufficient quantities for comprehensive biological evaluations, including detailed toxicity profiling, selectivity assessments and environmental safety studies. Additionally, field trials will be conducted to evaluate its real-world efficacy in pest management.

This study demonstrates that 6-butyl-3-(1-hydroxyethyl)-2-methyl-2H-pyran-5-carbonyl carbamic acid exhibits potent insecticidal activity against Helicoverpa armigera, with efficacy comparable to imidacloprid.