A total of 22 quinazoline thioether
derivatives incorporating a
1,2,4-triazolo[4,3-a]pyridine moiety were designed,
synthesized, and evaluated as antimicrobial agents in agriculture.
Among these compounds, the chemical structure of compound 6l was further confirmed via single-crystal X-ray diffraction analysis.
The bioassay results revealed that some of the compounds possessed
noticeable in vitro antibacterial activities against the tested phytopathogenic
bacteria. For example, compounds 6b and 6g had EC50 values as low as 10.0 and 24.7 μg/mL against Xanthomonas axonopodis pv. citri (Xac), respectively, which were significantly better
than that of the commercial agrobactericide bismerthiazol (56.9 μg/mL).
Particularly, compound 6b was also found to be capable
of suppressing the pathogenic bacterium Xanthomonas
oryzae pv. oryzae (Xoo) approximately 12-fold more potent than control bismerthiazol, in
terms of their EC50 values (7.2 versus 89.8 μg/mL).
Importantly, the most active compound 6b turned out to
be one with the highest hydrophilicity and the lowest molecular weight
within the series. In vivo bioassays further showed the application
prospect of 6b as a promising plant bactericide for controlling Xoo. Additionally, in vitro antifungal activities of these
compounds were also evaluated at the concentration of 50 μg/mL.
Overall, the present study demonstrated the potential of 1,2,4-triazolo[4,3-a]pyridine-bearing quinazoline thioether derivatives as
efficient agricultural antibacterial agents for crop protection.
A total of 20 1,2,4-triazole Mannich base derivatives bearing the 6-fluoroquinazolinylpiperidinyl moiety were designed, synthesized, and evaluated as antimicrobial agents against phytopathogenic bacteria and fungi according to the molecular hybridization strategy. Of note, the structure of target compound 4h was clearly confirmed through single-crystal X-ray diffraction analysis. The turbidimetric assays indicated that some compounds exhibited excellent antibacterial efficacies in vitro against Xanthomonas oryzae pv. oryzae (Xoo). For example, compounds 4c, 4f, 4j, and 7j had EC 50 values of 23.6, 18.8, 23.4, and 24.3 μg/ mL, respectively, which were far superior to that of agrobactericide bismerthiazol (EC 50 = 92.4 μg/mL). In particular, compound 4f demonstrated a potent anti-Xoo activity approximately five times more active than that of bismerthiazol. Moreover, in vivo assays showed the excellent protective and curative activities of compound 4f against rice bacterial blight, having the potential as an alternative bactericide for controlling Xoo. The structure−activity relationship analysis showed a good pesticide-likeness concerning compound 4f, following Tice's criteria. The anti-Xoo mechanism of compound 4f was preliminarily explored by scanning electron microscopy measurements in living bacteria. Finally, several compounds also exhibited good antifungal activities in vitro against Gibberella zeae at 50 μg/mL. In short, the presented work showed the potential of 6-fluoroquinazolinylpiperidinyl-containing 1,2,4triazole Mannich base derivatives as effective bactericides for controlling Xoo.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.