In an attempt to find the biorational pesticides, 20 novel chalcone derivatives containing a piperazine fragment were designed and synthesized. Their fungicidal activities and preliminarily action mechanism against Rhizoctonia solani were evaluated. Strikingly, the biological activity of compound D2 was obtained by optimizing the structure of the system. Subsequently, the practical value of compound D2 was ascertained by the relative surveys on in vivo anti-R. solani and anti-Colletotrichum gloeosporioides. The results revealed by scanning electron microscopy demonstrated that compound D2 could induce irregular and shrivelled growth of mycelium and rupture of the mycelium surface. This study indicates that chalcone derivatives containing a piperazine skeleton had better inhibitory effect on plant fungi, providing further complementary research on new pesticides.

Structure of some commercial agents.

Twenty 1,4-pentadiene-3-one derivatives containing quinazolinone (W1–W20) were designed and synthesized. The bioactivity test results showed that some compounds had antifungal activities in vitro. W12 showed excellent bioactivity against Sclerotinia sclerotiorum (S. sclerotiorum) and Phomopsis sp., with EC50 values of 0.70 and 3.84 μg/mL, which are higher than those of the control drug azoxystrobin at 8.15 and 17.25 μg/mL. In vivo activity tests were carried out on oilseed rape and kiwifruit. The protective effect of W12 on oilseed rape infected with S. sclerotiorum (91.7 and 87.3%) was better than that of azoxystrobin (90.2 and 79.8%) at 100 and 50 μg/mL, respectively, and the protective effect on kiwifruit infected with Phomopsis sp. (96.2%) was better than that of azoxystrobin (94.6%) at 200 μg/mL. Scanning electron microscopy results showed the hyphae of S. sclerotiorum treated with compound W12 abnormally collapsed and shriveled, inhibiting the growth of mycelium and, thus, laying the inhibiting effect on S. sclerotiorum. The results of the mechanism research showed that the action of W12 changed the mycelial morphology of S. sclerotiorum, affected the permeability of cells, increased the leakage of cytoplasm and allowed the cell membrane to break down. This study shows that 1,4-pentadiene-3-one derivatives containing quinazolinone have good effects on plant fungi and the potential for becoming new fungicides.

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