VOLUME 19 NUMBER 1 (January to June 2026)

In vitro and in silico evaluation of phytochemicals from water lettuce (Pistia stratiotes L.) as glutathione S-transferase (GST) inhibitors in the fall armyworm, Spodoptera frugiperda (J.E. Smith)

Plant-derived natural products are widely recognized as valuable resources for pharmaceutical and crop-protection development. This study evaluated the inhibitory effects of phytochemicals from water lettuce (Pistia stratiotes L.) on glutathione S-transferase (GST). GST is a detoxification enzyme associated with insecticide resistance in pests such as the fall armyworm, Spodoptera frugiperda (J.E. Smith) (SfGST). Methanol extracts of P. stratiotes were evaluated using a GST inhibition assay, followed by literature-based selection of known compounds from P. stratiotes. Homology modeling, structural validation, and molecular docking of 11 compounds were conducted to evaluate binding interactions with SfGST. The in vitro assay showed that the crude methanol extract exhibited notable GST inhibitory activity, with an IC₅₀ of 93.30 μg/mL, suggesting potential as a natural inhibitor. In silico results indicated that all 11 compounds exhibited more negative binding affinities than glutathione, with vicenin-2 showing the highest affinity (–9.0 kcal/mol). Molecular dynamics simulations indicated that vicenin-2 acts as a non-covalent inhibitor, inducing moderate structural perturbations and localized flexibility in SfGST. These changes were evident in altered root-mean-square-deviation (RMSD), solvent-accessible surface area (SASA), radius of gyration (Rg), and root-mean-square fluctuation (RMSF) profiles of the enzyme-ligand complex over the 50-ns trajectory. The in silico findings corroborated the in vitro GST inhibitory activity, supporting that enzyme inhibition may be attributed to these phytochemicals. These results highlight the potential of phytochemicals from P. stratiotes as candidates for environmentally sustainable pest management. Field-based evaluations are recommended to confirm the laboratory findings and to explore the applicability of these phytochemicals within integrated pest management (IPM) programs.