Aliphatic ketones from Ruta chalepensis (Rutaceae) induce paralysis on root knot nematodes

This paper reports on the use of Ruta chalepensis L. extracts as a potential nematicide against root knot nematodes Meloidogyne incognita and Meloidogyne javanica. The essential oil (REO) and methanol extract (RME) of R. chalepensis were tested against second-stage juveniles, with REO inducing paralysis in both species (EC50/1d = 77.5 and 107.3 mg/L) and RME being selective for M. incognita (EC50/1d = 1001 mg/L). Chemical characterization of extracts was done by means of GC-MS and LC-MS, revealing mainly aliphatic ketones and coumarins, respectively. The first-ranking volatile nematicidal component in terms of individual activity against both species was 2-undecanone (EC50 = 20.6 and 22.5 mg/L for M. incognita and M. javanica, respectively). This fact together with its high concentration in the most active extract found in this study, namely, REO (2926 mg/kg), categorizes 2-undecanone among the nematicidal principles of R. chalepensis. On the contrary, coumarins rutin and 8-methoxypsoralen were not found to be nematicidal at concentrations of 500 mg/L. Interestingly, M. incognita was found more sensitive than M. javanica.