Nacobbus aberrans ranks among the “top ten” plant-parasitic nematodes of phytosanitary importance. It causes significant losses in commercial interest crops in America and is a potential risk in the European Union. The nematicidal and phytotoxic activities of seven plant extracts against N. aberrans and Solanum lycopersicum were evaluated in vitro, respectively. The chemical nature of three nematicidal extracts (EC50,48h ≤ 113 µg mL−1) was studied through NMR analysis. Plant extracts showed nematicidal activity on second-stage juveniles (J2): (≥87%) at 1000 µg mL−1 after 72 h, and their EC50 values were 71.4–468.1 and 31.5–299.8 µg mL−1 after 24 and 48 h, respectively. Extracts with the best nematicidal potential (EC50,48h < 113 µg mL−1) were those from Adenophyllum aurantium, Alloispermum integrifolium, and Tournefortia densiflora, which inhibited L. esculentum seed growth by 100% at 20 µg mL−1. Stigmasterol (1), β-sitosterol (2), and α-terthienyl (3) were identified from A. aurantium, while 1, 2, lutein (4), centaurin (5), patuletin-7-β-O-glucoside (6), pendulin (7), and penduletin (8) were identified from A. integrifolium. From T. densiflora extract, allantoin (9), 9-O-angeloyl-retronecine (10), and its N-oxide (11) were identified. The present research is the first to report the effect of T. densiflora, A. integrifolium, and A. aurantium against N. aberrans and chemically characterized nematicidal extracts that may provide alternative sources of botanical nematicides.

BACKGROUND: While searching for novel small molecules for new organic pesticide agents against plant-parasitic nematodes, we found that the hexane extract from the roots of Senecio sinuatos and its main secondary metabolite, 3⊎-angeloyloxy-6⊎hydroxyfuranoeremophil-1(10)-ene (1), possess nematicidal activity against the second stage juvenile (J2) of Meloidogyne incognita and Nacobbus aberrans. Both species reduce yield of various vegetable crops. These results encouraged us to synthesize esters 3-9 formed by diol 2, obtained by alkaline hydrolysis of 1 and acetic anhydride, benzoic acid, 2-nitrobenzoic acid, 2-bromobenzoic acid, 4-nitrobenzoic acid, 4-bromobenzoic acid, and 4-methoxybenzoic acid, respectively. The nematicidal activity of these esters was evaluated and compared with that of the free benzoic acids.RESULTS: Natural product 1 and derivatives 2-9 were obtained and characterized by their physical and spectroscopic properties, including one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) experiments; X-ray diffraction analysis established their absolute configuration. The nematicidal activity of compounds 1-9 was assessed in vitro against M. incognita and N. aberrans J2 and was compared to activity shown by benzoic acid, 2-nitrobenzoic acid, 2-bromobenzoic acid, 4-nitrobenzoic acid, 4-bromobenzoic acid, and 4-methoxybenzoic acid. The esters suppressed nematodes more than free benzoic acid. Nacobbus aberrans J2 were suppressed, with compounds 5, 6, and 8 being the most active.CONCLUSION: Esters formed by 3⊎,6⊎-dihydroxyfuranoeremophil-1(10)-ene and orthoor para-substituted benzoic acids containing electron acceptor groups had nematicidal activity against N. aberrans. These compound can potentially serve as a model for the development of new organic nematicidal agents.

The main diterpenoid of Acacia schaffneri, 7,8-seco-7,8-oxacassa-13,15-dien-7-ol-17-al (1), has two aldehydes of which one is protected as a ε-lactol.The free aldehyde resisted to afford the carboxylic acid using reagents with different oxidative strength, although 1 gave oxime 2 when treated with hydroxylamine, β-hydroxyketone 3 after addition of acetone, aldo-ε-lactone 4 whereby only the lactol was oxidized when using Jones reagent, and epoxyformate 5 after Baeyer-Villiger treatment. Hydrolysis of 5 with NaHCO3 gave 6. Structures 2-6 followed from physical and spectral data including X-ray diffraction. All compounds showed antiproliferative activity similar to some chemotherapeutic drugs against C2C12, L929, SiHa, and MDA-MB-231 cell lines. RESULTS AND DISCUSSIONDiterpenoid 1 was obtained in adequate amounts for the preparation of 2-6 from the aerial parts of A.schaffneri. 1 Nucleophilic addition of hydroxylamine to 1 gave 2 in 66% yield, while aldol condensation of 1 with acetone in basic medium led to β-hydroxyketone 3 in 43% yield. The corresponding 1 H NMR spectra did not evidence both syn and anti oximes for 2, nor the absolute configuration (AC) of C-17 in the case of 3. However, the anti oxime geometry in 2 and the (17S) AC in 3 followed from the X-ray diffraction (XRD) studies detailed below. Although 3 was not the only expected condensation product, the γ,δ-unsaturated carbonyl compound could not be obtained even when using large excesses of acetone and NaOH.

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