Keerthiraj_2021_Chem.Biodivers__

Root-knot nematode, Meloidogyne incognita is one of the most destructive nematodes worldwide. Essential oils (EOs) are being extensively utilized as eco-benign bionematicides, although the precise mechanism of action remains unclear. Pogostemon cablin Benth. is well known as "Patchouli", a native to South East Asia, having huge demand due to its huge ethno-pharmacological properties. Chemical composition and potential nematicidal effect of EOs hydrodistilled from the leaves of P. cablin grown at three different locations in India are comprehensively investigated to correlate their mechanism of action for target specific binding affinities toward nematode proteins. Aromatic volatile Pogostemon essential oils (PEO) from Northern India (PEO-NI), Southern India (PEO-SI) and North Eastern India (PEO-NEI) were analysed by Gas Chromatography-Mass Spectrometry (GC-MS) to characterize forty volatile compounds. Maximum thirty-three components were identified in PEO-NEI. Sesquiterpenes are predominant with higher content of alpha -guaiene (2.3-24.4%), patchoulol (6.1-32.7%) and alpha -bulnesene (5.9-27.1%). Patchoulol was the major component in PEO-SI (32.7+/-1.2%) and PEO-NEI (29.2+/-1.1%), while, alpha -guaiene in PEO-NI (24.4+/-1.2%). In vitro nematicidal assay revealed significant nematicidal action (LC 50 44.6-87.0 microg mL -1 ) against juveniles of M. incognita within 24 h exposure. Mortality increases with increasing time to 48 h (LC 50 33.6-71.6 microg mL -1 ) and 72 h (LC 50 27.7-61.2 microg mL -1 ). Molecular modelling and in silico studies revealed multi-modal inhibitive action of alpha -bulnesene (-22 to -13 kJ mol -1 ) and alpha -guaiene (-22 to -12 kJ mol -1 ) against three target proteins namely, acetyl cholinesterase (AChE), odorant response gene-1 (ODR1), odorant response gene-3 (ODR3). Most preferable binding mechanism was observed against AChE due to pi-alkyl, pi-sigma and hydrophobic interactions. Structure nematicidal activity relationship suggested the presence of hydroxyl group for nematicidal activity is nonessential, rather highly depends on synergistic composition of sequiterpene hydrocarbons.