Novel chalcone derivatives containing a 1,2,4-triazine moiety: design, synthesis, antibacterial and antiviral activities

A series of novel chalcone derivatives containing the 1,2,4-triazine moiety were synthesized and their structures were confirmed by 1H NMR, 13C NMR and elemental analyses. Antiviral bioassays revealed that most of the compounds exhibited good antiviral activity against tobacco mosaic virus (TMV) at a concentration of 500 μg mL−1. The designated compound 4l was 50% effective in terms of curative and protective activities against TMV with 50% effective concentrations (EC50) of 10.9 and 79.4 μg mL−1, which were better than those of ningnanmycin (81.4 and 82.2 μg mL−1). Microscale thermophoresis (MST) also showed that the binding of compound 4l to coat protein (TMV-CP) yielded a Kd value of 0.275 ± 0.160 μmol L−1, which was better than that of ningnanmycin (0.523 ± 0.250 μmol L−1). At the same time, molecular docking studies for 4l with TMV-CP (PDB code:1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP. Meanwhile, compound 4a demonstrated excellent antibacterial activities against Ralstonia solanacearum (R. solanacearum), with an EC50 value of 0.1 μg mL−1, which was better than that of thiodiazole-copper (36.1 μg mL−1) and bismerthiazol (49.5 μg mL−1). The compounds act by causing folding and deformation of the bacterial cell membrane as observed using scanning electron microscopy (SEM). The chalcone derivatives thus synthesized could become potential alternative templates for novel antiviral and antibacterial agents.