Bioactive flavonoids from Leucosceptrum canum with nematicidal efficacy and mechanistic insights through acetylcholinesterase inhibition and docking study.

Leucosceptrum canum, a rare Himalayan plant, shows significant bioactive properties, with its nematicidal potential investigated here for the first time. This study isolated and characterized flavonoids from L. canum, assessing their efficacy against the plant-parasitic nematode Meloidogyne incognita. Bioassay-guided fractionation identified three active flavonoids: Pectolinarigenin, 5,6,7-Trihydroxy-4'-methoxyflavone and Acacetin, structurally elucidated using spectroscopic techniques and literature comparisons. The flavonoids exhibited dose-dependent nematicidal activity, with percent mortalities after 96 h of 100 %, 92 %, and 59 %, respectively. LC₅₀ values of Pectolinarigenin (11.79 μg/mL), 5,6,7-Trihydroxy-4'-methoxyflavone (230.54 μg/mL), and Acacetin (679.67 μg/mL) were recorded, comparable to the standard nematicide Nimitz (LC₅₀: 0.01 μg/mL). These flavonoids also showed strong to moderate acetylcholinesterase (AChE) inhibitory activity, with IC₅₀ values of 17.09, 86.72, and 142.2 μg/mL, respectively, nearing the efficacy of standard, physostigmine (IC₅₀: 19.37 μg/mL), suggesting a neuromuscular mechanism of action. The enzyme kinetics analysis of pectolinarigenin revealed it to be a reversible inhibitor of AChE exhibiting mixed-type inhibition, with inhibition constant of 15.94 μg/mL. Molecular docking revealed strong binding affinities (-7.8 to -7.2 kcal/mol) at the AChE active site, highlighting key hydrogen bonds and hydrophobic interactions. ADMET analysis confirmed favorable pharmacokinetic and safety profiles, underscoring the potential of these flavonoids as eco-friendly nematicidal alternatives. This study establishes L. canum as a valuable source of flavonoids with dual nematicidal and AChE inhibitory properties, supported by integrated in vitro and in silico studies. It underscores the untapped phytochemical wealth of Himalayan flora for sustainable nematode management.