Nematicidal effect of Raphasatin from Raphanus sativus against Meloidogyne incognita

The nematicidal activity of radish bulb (Raphanus sativus) methanol (RME) and aqueous extracts (RAE) was tested against the second stage (J₂) root knot nematode Meloidogyne incognita model. The EC₅₀ of RME after 3 d of J₂ immersion in test solutions was 312 ± 65 μg/ml. However, no activity was noted for RAE (EC₅₀ > 1,000 μg/ml). The chemical composition analysis of the methanol extract carried out by the GC–MS technique showed that 4-methylthio-3-butenyl isothiocyanate (raphasatin) was the most abundant compound at 20%. This pure compound strongly induced J₂ paralysis with an EC₅₀ of 1.3 ± 0.2 μg/ml after 24 hr. Comparison with other 11 selected isothiocyanates with structure similarity showed that the double bond at position 3 of the alkyl side chain is important for nematicidal activity, followed by the sulfur group at position 5 and the benzyl group at position 2. In addition, raphasatin showed the highest nematicidal activity with the corresponding lowest antioxidant activity of about 92 ± 18 μg/ml. In conclusion, the results of this investigation reveal that R. sativus and its major compound raphasatin can be integrated into the pest management system.