Antibacterial and antiviral activities and action mechanism of flavonoid derivatives with a benzimidazole moiety

Abstract

A class of novel benzimidazole-containing flavonoid derivatives were constructed. Antibacterial bioassay showed that most of the target compounds displayed good inhibitory effects against Xanthomonas axonopodis pv. citri (Xac), Ralstonia solanacearum (Rs) and Xanthomonas oryzae pv. oryzae (Xoo). Remarkably, compound 4e showed outstanding antibacterial activity against Rs, with the EC50 14.5 µg/mL, which was better than thiodiazole-copper (118.9 µ/mL), bismerthiazol (55.1 µg/mL) and myricetin (82.3 µg/mL). At the same time, the mechanism of compound 4e was confirmed by scanning electron microscopy (SEM). Antiviral bioassay results demonstrated that compound 4n showed remarkable curative, protective and inactivating activities against tobacco mosaic virus (TMV), with a 500 µg/mL effective concentration of 54.1, 57.6 and 75.3%, respectively. The test results revealed that these values were better than or close to ningnanmycin (49.0, 55.8 and 82.7%, respectively). Microscale thermophoresis (MST) also showed that the binding of compound 4n to TMV coat protein (TMV-CP) gave a Kd value of 1.049 ± 0.582 µmol/L, which was better than that of ningnanmycin (1.058 ± 0.286 µmol/L). This study showed that benzimidazole-containing flavonoid derivatives are promising agricultural antibacterial and antiviral agents.