Preliminary Study On Fungicidal Mechanism Of Benzimidazolone Derivative

N-acylated derivatives of benzimidazole are a type of newly reported antifungal chemicals. The synthesis and antifungal activity of benzimidazolones, as well as the relationship between structure and activity, have invsitigated by our research team in recent years, whereas its fungicidal mechanism has never been reported up to now. Here we report the antifungal spectrum, mode of action, and its preliminary fungicidal mechanism of 3-acetyl-6-nitro-1-(prop-1-en-2-yl)-1H-benzo[d]imidazol-2(3H)-one, an optimum compound synthesized in our lab. The results are as follows:(1) The antifungal activity of the title compound against several strains of plant pathogenic fungi, such as Curvularia lunata, Verticillium dahlia and Fusarium graminearum were evaluated, and the results indicated that the title compound exhibited broad spectrum against all tested fungi. The most sensitive strain observed in the test of mycelia growth was Botrytis cinerea, and its median inhibitory concentration was 6.97 μg/mL. Meamwhile, the title compound had most inhibitory effect against the spore germination of Fusarium oxysporum, and its IC50 was 0.83 μg/mL.(2) Benzimidazolones exhibited different mode of action from that of benzimidazole fungicide. Carbendazim could effectively inhibit the growth of mycelia whereas it only has moderate effect on the spore germination of plant pathogenic fungi. On the contrary, benzimidazolones predominately inhibit the germination of spore. The IC50 values of title compound against the spore germination of Fusarium oxysporum, Colletotrichum gloesporioides, Botrytis cinerea and Curvularia lunata were 0.83、6.05、10.56 and 33.79 μg/mL, respectively. Furthermore, no cross-resistance was observed between title compound and carbendazim, which means that the two chemicals have different fungicidal mechanism.(3) The inhibitory effect of title compound against tested strain could effectively reduced by the addition of exogenous glucose, and glucose is a key role in the process of respiration, so it indicated that benzimidazolones may interfere with the respiration of fungi.(4) The results of electron microscope indicated that the intergrity of cell wall was only slightly changed by the title compound, which means that this chemical was not directly targeted on the cell wall. Meanwhile, the tests of membrane permeability indicated that the treatment of title compound resulted in the leakage of electrolyte, which means that the cell membrane was disrupted by the chemical.(5) After treated by the title compound, the content of reducing sugar, chitosan and soluable protein in mycelium was different with those of blank check, and all the variation is related with the content of reducing sugar, so it was hypothesized that the title compound could interfere with the respiration of fungi.