Gas Chromatography-Mass Spectrometric Analysis of Nematicidal Essential Oil ofValeriana amurensis P Smirn ex Kom (Valerianaceae) Roots and its Activity against Heterodera avenae

Purpose: To investigate the chemical composition and nematicidal activity of the essential oil of Valeriana amurensis roots against cereal cyst nematodes (Heterodera avenae).Methods: The essential oil of V. amurensis roots was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromaotography-mass spectrometry (GC-MS). The nematicidal activity of the essential oil and its major constituents was determined against second stage juveniles of H. avenae.Results: A total of 33 components of the essential oil were identified. The major constituents were bornyl acetate (12.5 %), patchoulol (11.6 %), caryophyllene (8.2 %), 3-methylvaleric acid (7.3 %) and isovaleric acid (6.5 %). The essential oil exhibited nematicidal activity against H. avenae with a medium lethal concentration (LC50) value of 311.6 μg/mL. The major constituents, isovaleric acid and 3- methylvaleric acid, exhibited nematicidal activity against H. avenae with LC50 of 218.2 and 683.8 μg/mL, respectively.Conclusion: The study indicates that the essential oil of V. amurensis roots and its two major constituents, isovaleric acid and 3-methylvaleric acid, have a potential to be developed to natural nematicides for the control of cereal cyst nematodes.Keywords: Valeriana amurensis, Heterodera avenae, Nematicidal activity, Isovaleric acid, 3- Methylvaleric acid, Essential oil, Cereal cyst nematodes

Nematicidal Activity of the Essential Oil of Rhododendron anthopogonoides Aerial Parts and its Constituent Compounds against Meloidogyne incognita

Hydrodistilled essential oil from Rhododendron anthopogonoides Maxim. (Ericaceae) aerial parts was analysed by gas chromatography-mass spectrometry (GC-MS). A total of 42 compounds, accounting for 95.48% of the total oil, were identified. The main constituents of the essential oil were benzyl acetone (34.41%), nerolidol (10.19%), 1,4-cineole (8.41%), β-caryophyllene (5.63%), γ-elemene (5.10%), and spathulenol (3.06%). Four constituents were isolated from the essential oil based on fractionation. The essential oil of R. anthopogonoides possessed nematicidal activity against the root knot nematode (Meloidogyne incognita) with an LC50 value of 130.11 μg/ml. The main compound of the essential oil, benzyl acetone, exhibited nematicidal activity against M. incognita with an LC50 value of 74.17 μg/ ml while 1,4-cineole, nerolidol, and β-caryophyllene were not nematicidal at a concentration of 5 mg/ml. The essential oil of R. anthopogonoides and benzyl acetone show potential for their development as possible natural nematicides for the control of the root knot nematode

Secondary metabolites with nematicidal and antimicrobial activity from nematophagous fungi and Ascomycetes

Screening of nematode-trapping fungi for antimicrobial and nematicidal activities gave three new antimicrobial metabolites from cultures of five Arthrobotrys strains. The compounds exhibited no nematicidal activities towards Caenorhabditis elegans and Meloidogyne incognita. From trap-forming submerged cultures of Arthrobotrys conoides, linoleic acid was isolated as a nematicidal principle. Its production increased with the number of traps formed in both Arthrobotrys oligospora and Arthrobotrys conoides. Nematoctonus robustus and Nematoctonus concurrens produced pleurotin, dihydropleurotinic acid, and leucopleurotin, metabolites previously isolated from cultures of Hohenbuehelia species, suggesting that the same biosynthetic pathways function in both the teleomorph and anamorph. Several strains of Ascomycetes had nematicidal activities; linoleic acid was responsible for the activity in cultures of a Chlorosplenium species, 14-epicochlioquinone B in cultures of Neobulgaria pura, and two naphthalenes derived from the melanin biosynthetic pathway in Daldinia concentrica. 5-Pentyl-2-furaldehyde, previously known as a metabolite from a Basidiomycete, was produced by an unidentified Australian Ascomycete. More than 30 mostly new metabolites have been isolated from cultures of Lachnum papyraceum, many being chlorinated. Under different conditions the fungus incorporated bromine instead of chlorine. Key words: nematophagous fungi, natural nematicides, linoleic acid, chlorinated secondary metabolites.