Design, Synthesis, Nematicidal, and Fungicidal Activities of Novel Azo and Azoxy Compounds.

Bursaphelenchus xylophilus ( B. xylophilus ) and Meloidogyne are parasitic nematodes that have caused severe ecological and economic damage in pinewood and crops, respectively. Jietacins (jietacin A and B) were found to have excellent biological activity against B. xylophilus . Based on our tremendous demand for chemicals against B. xylophilus , a novel scaffold based on the azo and azoxy groups was designed, and a series of compounds were synthesized. In the bioassay, Ia , IIa , IIc , IId , and IVa exhibited higher activity against B. xylophilus in vitro than avermectin (LC 50 = 2.43 μg·mL -1 ) with LC 50 values of 1.37, 1.12, 0.889, 1.56, and 1.10 μg·mL -1 , respectively. Meanwhile, Ib , Ic , IIc , and IVa showed good inhibition effects against Meloidogyne in vivo at the concentrations of 80 and 40 μg·mL -1 with inhibition rates of 89.0% and 81.6%, 95.6% and 75.7%, 96.3% and 41.2%, and 86.8% and 78.7%, respectively. In fungicidal activity in vitro , IIb and IVa exhibited excellent effect against Botryosphaeria dothidea with the inhibition of 82.59% and 85.32% at the concentration of 10 μg·mL -1 , while the inhibition of Ia was 83.16% against Rhizoctonia solani at the concentration of 12.5 μg·mL -1 . Referring to the biological activity against B. xylophilus , a 3D-QASR model was built in which the electron-donating group and small group at the 4-phenylhydrazine were favorable for the activity. In general, the novel azoxy compounds, especially IIc possess great potential for application in the prevention of B. xylophilus .