Novel pyridinium salt derivatives as potential inhibitors for photosystem I

BACKGROUND Photosystem I (PS I) is a plastocyanin‐ferredoxin oxidoreductase within the photosynthetic electron transport chain and represents a key target for herbicide development. RESULTS Pyridinium salt compounds A and B were designed and synthesized with active substructural insertion and combination strategies. Bioassays revealed that most compounds exhibited > 70% inhibition of growth in Portulaca oleracea and Echinochloa crusgalli when applied to germinated seeds at a concentration of 10 μg mL –1 . Compound B8 demonstrated 90–100% postemergence herbicidal activity on E. crusgalli , Eleusine indica , Setaria viridis , Amaranthus retroflexus , P. oleracea and Abutilon theophrasti . Meanwhile, B8 not only demonstrated electrochemical characteristics associated with PS I inhibitory activity and a negatively charged surface, but also promoted the accumulation of reactive oxygen species in Portulaca oleracea roots. At a concentration of 0.25 mM, B8 exhibited superior safety profiles in zebrafish embryos compared to paraquat. Furthermore, density functional theory calculations corroborated the redox reactivity and molecular orbital properties of B8 , showed strong consistency with experimental observations. CONCLUSION Compound B8 had herbicidal activity similar to paraquat with lower toxicity to zebrafish embryos. Therefore, B8 represents a promising lead candidate for new PS I targeted herbicides.