Insecticidal and Bactericidal Activities of Vahl and Molecular Docking Analysis of Insect Acetylcholinesterase.

Objectives: This study focused on the phytochemical, insecticidal, and bactericidal activities of Vahl, as well as molecular docking analysis of an acetylcholinesterase (AChE) inhibitor as a promising natural insecticide.

Materials And Methods: The leaves of were successively extracted with n-hexane, acetone, and methanol. Silica gel column chromatography of the methanol extract yielded compound 1. The insecticidal properties of the extracts and compound 1 were evaluated in terms of contact toxicity against . Bactericidal activity was achieved by photodynamic inactivation of fecal coliforms (FCs) and enterococci in water using extracts and compound one as natural photosensitizers. Compound 1 was analyzed for physicochemical and pharmacokinetic parameters and molecular docking against the AChE protein (6XYU).

Results: Compound 1 was characterized as emodin (1,3,8-trihydroxy-6-methylanthracene-9,10-dione) using 1D-2D-H-C nuclear magnetic resonance and mass spectrometry. Insecticidal properties showed that emodin exhibited the highest toxicity with an lethal concentration 50 (LC) = 5.00 mg/mL compared with all extracts. The n-hexane extract showed the highest insecticidal activity (LC = 177.48 mg/mL) compared with the methanol (LC = 195.08 mg/mL) and acetone (LC = 374.14 mg/mL) extracts. Complete inhibition of fecal enterococci by photosensitization was observed after 60 min of light exposure to emodin-treated water at all concentrations (1-5 mg/mL) and 120 minutes for FCs under the same conditions. Based on the docking score, the binding energy of emodin (-6.38 kcal/mol) was close to that of the marketed insecticide pirimiphos-methyl (-6.25 kcal/mol).

Conclusion: In addition, emodin was subjected to insecticide probability prediction and absorption, distribution, metabolism, excretion, and toxicity analysis and was found to be satisfactory as a natural insecticide. Emodin is a promising candidate for insecticidal pest control.