BACKGROUND Nanopesticides have been proved to be a powerful and promising tool to solve the issues in agriculture. The purpose of the present study was to develop ecofriendly nanopesticide systems by the strategy of comprehensive utilization of two natural biomass resources (bagasse and turpentine oil) because of their incomparable advantages. RESULTS In this research, a series of nanocellulose carriers ETOCN‐1–ETOCN‐4 (ETOCN, esterified TEMPO‐oxidized cellulose nanofibers) with different degrees of substitution were prepared and characterized by Fourier‐transform infrared (FTIR), X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Then, 21 1,3,4‐thiadiazole‐amide compounds 8a–8u containing gem‐dimethylcyclopropane ring were designed, synthesized and characterized. A preliminary bioassay indicated that compound 8i (R = p‐Br Ph) exhibited broad‐spectrum antifungal activity against the tested fungi. Furthermore, drug‐loading complexes 8i/ETOCN‐1–8i/ETOCN‐4 were fabricated by integration of nanocellulose‐based carriers ETOCN‐1–ETOCN‐4 with bioactive compound 8i, and the drug‐loading capacities, microstructures and sustained‐releasing performance of these complexes were also investigated. According to the observation of scanning electron microscopy (SEM) images of complex 8i/ETOCN‐2, the small‐molecule drug and the carrier formed a well‐distributed and compact complex, which led to the excellent drug‐loading capacity and sustained‐releasing performance in the ethanol/water (1:1, v/v) system. CONCLUSIONS Complexes 8i/ETOCN‐1–8i/ETOCN‐4 deserved further study as the promising candidates for the development of nanopesticides. © 2022 Society of Chemical Industry.

For exploring novel natural product-derived herbicides, 16 novel α-campholenic aldehyde-based 4methyl-1,2,4-triazole-thioether compounds were designed, synthesized, and characterized by FT-IR, 1 H NMR, 13 C NMR, ESI-MS and elemental analysis. The preliminary bioassay showed that, at 100 µg/mL, most of the target compounds displayed significant inhibition activity against root-growth of rape(Brassica campestris L.), with inhibition rates of 85.0%～98.2%(A-class activity level), much better than that of the positive control flumioxazin. In addition, an effective and reasonable 3D-QSAR model was established by CoMFA method in SYBYL-X 2.1.1 software. It was found that, the steric field was the major factor towards the herbicidal activity of the target compounds against B. campestris L., and the introduction of bulky groups into m-and p-position of the benzene ring was favourable to increase the herbicidal activity. This kind of title compounds deserved further study as potential leading compounds for the discovery and development of novel herbicidal agents.

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In an attempt to search for natural renewable product-based antifungal agents, eighteen 1,3,4-thiadiazole-urea compounds containing gem-dimethylcyclopropane ring structure were designed and synthesized. The antifungal activity of the target compounds against six plant pathogens was preliminarily evaluated at the concentration of 50 mg/L. As a result, the inhibitory rates of (＋)-cis-1-(4-bromophenyl)-3-(5-((2,2-dimethyl-3-propylcyclopropyl)methyl)-1,3,4-thiadiazol-2-yl) urea (7i) against Colletotrichum orbicular, Bipolaris maydis and Alternaria solani were 91.2%, 85.0% and 60.1%, respectively, which was better than that of the positive control chlorothalonil. Furthermore, a reasonable and effective 3D-quantitative structure-activity relationship (3D-QSAR) model (r 2 ＝0.990, q 2 ＝0.517) was established by the comparative molecular field analysis method (CoMFA). The binding mode between the target compounds and succinate dehydrogenase (SDH) was investigated by molecular docking, and the cation-π interaction between the key residue Arg and the benzene ring was quantitatively analyzed. The gem-dimethylcyclopropane and thiadiazole-urea-benzene moieties of the target compounds probably made major contributions to the antifungal activity by frontier molecular orbital calculation.