Synthesis and biological activities of novel chalcone derivatives containing pyrazole oxime ethers

A series of novel chalcone derivatives containing pyrazole oxime ethers were designed and synthesized. The structures of all the target compounds were determined by NMR and HRMS. The structure of H5 was further confirmed via single-crystal X-ray diffraction analysis. The results of biological activity test showed that some of the target compounds exhibited significant antiviral and antibacterial activities. The test results of EC50 value against tobacco mosaic virus showed that H9 had the best curative and protective effect, and the EC50 value of curative activity of H9 was 166.9 μg/mL, which was superior to ningnanmycin (NNM) 280.4 μg/mL, the EC50 value of protective activity of H9 was 126.5 μg/mL, which was superior to ningnanmycin 227.7 μg/mL. Microscale thermophoresis (MST) experiments demonstrated that H9 (Kd = 0.0096 ± 0.0045 μmol/L) exhibited a strong binding ability with tobacco mosaic virus capsid protein (TMV-CP), which was far superior to ningnanmycin (Kd = 1.2987 ± 0.4577 μmol/L). In addition, molecular docking results showed that the affinity of H9 to TMV protein was significantly higher than ningnanmycin. The results of against bacterial activity showed that H17 has a good inhibiting effect against Xanthomonas oryzae pv. oryzae (Xoo), the EC50 value of H17 was 33.0 μg/mL, which was superior to the commercial drugs thiodiazole copper (68.1 μg/mL) and bismerthiazol (81.6 μg/mL), and the antibacterial activity of H17 was verified by scanning electron microscopy (SEM).