Aqueous extracts of Crambe abyssinica seed cake: Chemical composition and potential for nematode control

Abstract

Plants of the family Brassicaceae are known to produce compounds with nematicidal activity, such as glucosinolates. Although these compounds may find application in the control of plant-parasitic nematodes, they are generally obtained as hydroalcoholic extracts, which can be toxic to plants and the environment. This study investigated the chemical composition of aqueous extracts of crambe (Crambe abyssinica Hochst ex Re Fries) seed cake and their efficiency in controlling the root-knot nematode Meloidogyne javanica (Treub) Chitwood in soybean (Glycine max (L.) Merrill). Four extraction methods were used: water extraction at 25 °C, water extraction at 100 °C, autoclave treatment of a crambe cake/water mixture, autoclave treatment of crambe cake followed by water extraction at room temperature. Compounds were determined by high-performance liquid chromatography and nuclear magnetic resonance spectroscopy. Extracts were diluted to 5, 10, 15, 20, and 25% (v/v) in distilled water for determination of their effects on M. javanica egg hatching and juvenile mortality (in vitro) and nematode reproduction on soybean (in vivo). Chromatographic analysis identified the following nematicidal compounds (100 g−1): gallic acid (250.15 mg), syringic acid (201.46 mg), hydroxybenzoic acid (175.05 mg), chlorogenic acid (129.81 mg), ferulic acid (41.82 mg), trans-cinnamic acid (28.40 mg), and coumaric acid (16.75 mg). Sucrose and epiprogoitrin were detected in a proportion of 56.73 to 43.27%. All extracts reduced egg hatching and increased juvenile mortality, reaching a plateau at a concentration of about 5%. Extract concentrations of 5% and higher decreased nematode reproduction, with the maximum effect estimated to occur at 13%. Crambe cake extracts also increased plant height, shoot fresh weight, and root fresh weight. The compounds from aqueous extracts of crambe seed cake, acting together or separately, may be responsible for the suppressive effects of nematodes and plant growth promoters.