New nematicidal compounds from Mentha spicata L. against Meloidogyne incognita.

Meloidogyne incognita (root-knot nematode) is one of the most destructive pests of crops worldwide. Injudicious use of synthetic nematicides has led to environmental toxicity, development of resistance, and disruption of ecological balance, necessitating the need for safer and effective alternatives. Essential oil from Mentha spicata (Spearmint) has been reported to have nematicidal activity but the activity of its polar constituents is unexplored against the nematodes, infesting agricultural crops. Six compounds, stigmasterol (1), β-sitosterol-3-O-β-D-glucoside (2), 3β,13β-dihydroxy-urs-11-en-28-oic acid (3), 5,6-dihydroxy-7,8,4′-trimethoxyflavone (4), 5,6,4′-trihydroxy-7,8,3′-trimethoxyflavone (5), and 5,6,4′-trihydroxy-7,8-dimethoxyflavone (6), were isolated from methanolic extract of Mentha spicata (spearmint) and identified by NMR (1D & 2D) spectral analysis. Compound 3 was identified for the first time from genus Mentha. In vitro nematicidal activity of pure compounds (2 and 4–6) was carried out against Meloidogyne incognita, and results showed significant mortality (LC50 values ranging between 62.64 and 74.19 ppm after 96 h). Molecular docking study revealed the favourable binding of the test compounds with acetylcholinesterase enzyme, facilitated by H-bond, electrostatic interactions, and hydrophobic interactions. The binding energy of the tested compounds with the target protein was found highest in 5 (− 10.0 kcal/mol) and 6(− 9.9 kcal/mol) followed by 2 (− 9.2 kcal/mol) and 4 (− 8.9 kcal/mol). The minimum binding energy was recorded in carbofuran (−7.5 kcal/mol), a positive control, and was also corroborated with in vitro nematicidal activity. This study showed the potent nematicidal activity of compounds (2 and 4–6), which can be further used for the development of nematicides against M. incognita in agriculture. [ABSTRACT FROM AUTHOR]