The present study was carried out to design and synthesize a number of novel aromatic carboxamide derivatives of dehydroabietylamine. The preliminary antifungal assay indicated that most of title compounds displayed moderate to good antifungal activity toward the six fungal strains
in vitro. Compounds
3i,
3q,
4b and
4d showed significant antifungal activity against
Sclerotinia sclerotiorum, with EC
50 values ranging from 0.067 ~ 0.393 mg/L. Compounds
3i,
4b and
4d also showed pronounced mycelial growth inhibition activities against
B. cinerea and
A. solani. Furthermore, in the
in vivo assay, compound
4b exhibited brilliant protective activity against
S. sclerotiorum-infected rape leaves. Meanwhile, the
in vivo bioassay on tomato plants infected by
B. cinerea showed that compound
3i and
4d displayed excellent protective activity at 200 mg/L, which were near to boscalid. Primary mechanistic study revealed that
4b could inhibit sclerotia formation as well as reduce the exopolysaccharide level. SEM and TEM analysis indicated that
4b possessed a strong ability to destroy the surface morphology of mycelia, cell structure and seriously interfere with the growth of the fungal pathogen. In addition,
4b exhibited good inhibitory activity (IC
50 = 23.3 ± 1.6 μM) toward succinate dehydrogenase (SDH). Molecular modeling study confirmed the binding modes between compound
4b and SDH. The above antifungal results and fungicidal mechanism study revealed that this class of dehydroabietylamine derivatives could be potential SDH inhibitors and lead compounds for novel fungicides development.
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