Evaluation of nematicidal activity of ethanol extracts of Euphorbiaceae plants and constituents from Euphorbia fischeriana to Meloidogyne incognita (Kofoid and White) Chitwood

Ethanol extracts of 20 plant species (Euphorbiaceae) were assessed for nematicidal activity against the root-knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood. Out of these, four extracts: Croton tiglium, Euphorbia fischeriana, Leptopus chinensis and Ricinus communis caused 100% mortalities of the root-knot nematode at 1000 μg/ml for 72 h. The ethanol extract of E. fischeriana exhibited nematicidal activity against M. incognita with a 72-h LC50 value of 69.0 μg/ml. Six nematicidal constituents were isolated from E. fischeriana as 1-(2, 4-dihydroxy-6-methoxy-3-methylphenyl)ethanone (1), jolkinolide A (2), jolkinolide B (3), 12-deoxyphorbol 13-(9Z)-octadecenoate 20-acetate (4), 17-hydroxyjolkinolide A (5), and 17-hydroxyjolkinolide B (6). Compound 4 and 1 exhibited strong toxicity against M. incognita with 72-h LC50 values of 48.6 μg/ml and 87.8 μg/ml, respectively. The other four compounds, compound 5 (LC50 = 354.6 μg/ml), 6 (LC50 = 539.4 μg/ml), 2 (LC50 = 627.7 μg/ml) and 3 (LC50 = 825.2 μg/ml), also possessed toxicity against M. incognita. The above findings suggested that the four ethanol extracts and constituents of E. fischeriana especially compound 4 and 1 may be explored as natural potential nematicides.