Evaluation of nematicidal activity and in silico functional interpretations of Diploknema butyracea saponins against Meloidogyne incognita

Biodiesel from non-edible oils has recently picked up significant momentum along with the valorization of unutilized residues. The present study investigates the extraction of saponins (Mi-saponin A and Mi-saponin B) from an under-utilized resource, Diploknema butyracea seed cake, and its application against a serious agricultural nematode pest, Meloidogyne incognita. The results showed that LC₅₀ values for J2 juvenile immobility were 4.98, 1.74, and 4.28 mg mL⁻¹ for D. butyracea saponins, prosapogenin, and sapogenin, respectively,  at 72 h of exposure. The monodesmodic saponins were found to be more effective than bidesmodic saponins. According to ESI–MS, ¹H NMR, ¹³C NMR, and 2D NMR analyses, the structures of prosapogenin and sapogenin were interpreted as "3-O-β-D-glucopyranosyl protobassic acid" and "bassic acid," respectively. In silico analysis against S-adenosylmethionine synthetase (SAMS-1), a major player in controlling cholesterol biosynthesis and lipid metabolism in nematodes, also confirmed the hypothesis. The higher binding ability of prosapogenin with SAMS-1 receptor site confirmed the hypothesis, and it was significantly higher than saponin and sapogenin. The study demonstrated that hampering lipid metabolism in nematodes is the possible mode of action for saponin bioactivity.