Synthesis and <i>In Vitro</i> and <i>In Vivo</i> Biological Activity Evaluation and Quantitative Proteome Profiling of Oxadiazoles Bearing Flexible Heterocyclic Patterns

Abstract

A novel series of simple 1,3,4-oxadiazoles that bear flexible heterocyclic patterns was prepared, and their biological activities in plant pathogenic bacteria, fungi, oomycetes, and <i>Meloidogyne incognita in vitro</i> and <i>in vivo</i> were screened to explore low-cost and versatile antimicrobial agents. Screening results showed that compounds, such as <b>A</b>_<b>0</b>, <b>B</b>_<b>0</b>, and <b>C</b>_<b>4</b>, were bioactive against <i>Xanthomonas oryzae</i> pv <i>oryzae in vitro</i> and <i>in vivo</i>, and such bioactivities were superior to those of commercial agents bismerthiazol and thiodiazole copper. Their antibacterial mechanisms were further investigated by quantitative proteomics and concentration-dependent scanning electron microscopy images. Antifungal results indicated that compound <b>A</b>_<b>0</b> displayed a selective and better antifungal effect on <i>Botrytis cinerea</i> with inhibition rate of 96.8% at 50 μg/mL. Nematocidal bioassays suggested that compound <b>D</b>_<b>1</b> had good <i>in vitro</i> nematocidal activity toward <i>M. incognita</i> at 24, 48, and 72 h, with the corresponding insecticidal efficiency of 48.7%, 64.1%, and 87.2% at 40 μg/mL. <i>In vivo</i> study further confirmed that compounds <b>D</b>_<b>1</b> and <b>F</b>_<b>2</b> showed nematocidal actions at 80 μg/mL with a disease index of 1.5. Given these advantages, this kind of molecular frameworks could be a suitable platform for exploring highly efficient agrochemicals.