Nematicidal Carboxylic Acids and Aldehydes from Melia azedarach Fruits

Melia azedarach is a species gaining scientific interest mostly concerning its range of biological activities against agricultural target pests. The nematicidal melia methanol extract (MME) obtained from the fruits, acting against the phytonematode Meloidogyne incognita, is herein reported to contain hexadecanoic, acetic, and hexanoic acids as well as furfural, 5-hydroxymethylfurfural, 5-methylfurfural, and furfurol. All compounds were tested individually for nematicidal activity against the nematode second-stage juveniles, in paralysis experiments. The nematicidal activity was studied both after nematodes' immersion in treatment solutions and after exposure to test substance vapors. Clear dose and time response relationships were established at the dose ranges of 31.2-500 and 1-100 mu g/mL, concerning the aldehydes and carboxylic acids, respectively, implementing analogous predominance of nematicidal activity. Nevertheless, no synergistic effects were observed in respective mixture interaction bioassays among furfural, 5-hydroxymethylfurfural, 5-methylfurfural, and furfurol. Furfural was the most active bionematicidal compound reported herein for the first time as a natural constituent of M. azedarach.