A series of dehydrozingerone derivatives were synthesized, and their fungicidal activities and action mechanism against Colletotrichum musae were evaluated. The bioassay result showed that most compounds exhibited excellent fungicidal activity in vitro at 50 μg mL −1 . Compounds 13, 16, 18, 19, and 27 exhibited broad-spectrum fungicidal activity; especially, compounds 19 and 27 were found to have more potent fungicidal activity than azoxystrobin. The EC 50 values of compounds 19 and 27 against Rhizoctonia solani were 0.943 and 0.161 μg mL −1 respectively. Moreover, compound 27 exhibited significant in vitro bactericidal activity against Xanthomonas oryzae pv. oryzae, with an EC 50 value of 11.386 μg mL −1 , and its curative effect (49.64%) and protection effect (51.74%) on rice bacterial blight disease was equivalent to that of zhongshengmycin (42.90%, 40.80% respectively). Compound 27 could also effectively control gray mold (87.10%, 200 μg mL −1 ) and rice sheath blight (100%, 200 μg mL −1 ; 82.89%, 100 μg mL −1 ) in vivo. Preliminary action mechanism study showed that compound 27 mainly acted on the cell membrane and significantly inhibited ergosterol biosynthesis in Colletotrichum musae.
Natural products are an important source of pesticide discovery. A series of N-amino-maleimide derivatives containing hydrazone group were designed and synthesized based on the structure of linderone and methyllinderone which were isolated from Lindera erythrocarpa Makino. According to the bioassay results, compounds 2 and 3 showed 60% inhibition against mosquito (Culex pipiens pallens) at 0.25 µg·mL−1. Furthermore, the results of antifungal tests indicated that most compounds exhibited much better antifungal activities against fourteen phytopathogenic fungi than linderone and methyllinderone and some compounds exhibited better antifungal activities than commercial fungicides (carbendazim and chlorothalonil) at 50 µg·mL−1. In particular, compound 12 exhibited broad-spectrum fungicidal activity (>50% inhibitory activities against 11 phytopathogenic fungi) and compounds 12 and 14 displayed 60.6% and 47.9% inhibitory activity against Rhizoctonia cerealis at 12.5 µg·mL−1 respectively. Furthermore, compound 17 was synthesized, which lacks N-substituent at maleimide and its poor antifungal activity against Sclerotinia sclerotiorum and Rhizoctonia cerealis at 50 µg·mL−1 showed that the backbone structure of N-amino-maleimide derivatives containing hydrazone group was important to the antifungal activity.
In order to find pesticides with insecticidal and antifungal activities, a series of novel benzoyl pyrimidinylurea derivatives were designed and synthesized. All target compounds were identified by 1H-NMR spectroscopy and HRMS. Insecticidal and antifungal activity of these compounds were evaluated and the structure-activity relationships (SAR) were clearly and comprehensively illustrated. Compound 7, with low toxicity to zebrafish (LC50 = 378.387 µg mL−1) showed 100% inhibition against mosquito (Culex pipiens pallens) at 0.25 µg mL−1. Both compounds 19 and 25 exhibited broad-spectrum fungicidal activity (>50% inhibitory activities against 13 phytopathogenic fungi), which were better than those of the commercial pesticide pyrimethanil (>50% inhibitory activities against eight phytopathogenic fungi). Furthermore, compounds 19 and 25 exhibited protective activity against Sclerotinia sclerotiorum on leaves of Brassica oleracea L. during in vivo experiments.
Applications of supramolecular materials in plant protection
have
attracted significant interest in recent years. To develop a feasible
method to improve the efficacy and reduce the usage of chemical pesticides,
the effect of calix[4]arene (C4A) inclusion on enhancing the insecticidal
activity of commercial insecticides was investigated. Results showed
that all three tested insecticides (chlorfenapyr, indoxacarb, and
abamectin) with distinct molecular sizes and modes of action were
able to form stable 1:1 host–guest complexes with C4A through
simple preparation steps. The insecticidal activities of the complexes
against Plutella xylostella were effectively
enhanced compared to the guest molecule, with the synergism ratio
being up to 3.05 (for indoxacarb). An obvious correlation was found
between the enhanced insecticidal activity and the high binding affinity
between insecticide and C4A, while the improvement in water solubility
may not be a determining factor. The work would provide hints for
the further development of functional supramolecular hosts as synergists
in pesticide formulations.
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