Fabrication of Host-Guest Complexes between Adamantane-Functionalized 1,3,4-Oxadiazoles and β-Cyclodextrin with Improved Control Efficiency against Intractable Plant Bacterial Diseases.

Supramolecular chemistry provides huge potentials and opportunities in agricultural pest management. In an attempt to develop highly bioactive, eco-friendly, and biocompatible supramolecular complexes for managing intractable plant bacterial diseases, herein, a type of interesting adamantane-functionalized 1,3,4-oxadiazole was rationally prepared to facilitate the formation of supramolecular complexes via β-cyclodextrin-adamantane host-guest interactions. Initial antibacterial screening revealed that most of these adamantane-decorated 1,3,4-oxadiazoles were obviously bioactive against three typically destructive phytopathogens. The lowest EC 50 values could reach 0.936 ( III 18 ), 0.889 ( III 18 ), and 2.10 ( III 19 ) μg/mL against the corresponding Xanthomonas oryzae pv. oryzae ( Xoo ), Xanthomonas axonopodis pv. citri ( Xac ), and Pseudomonas syringae pv. actinidiae ( Psa ). Next, the representative supramolecular binary complex III 18 @β-CD (binding mode 1:1) was successfully fabricated and characterized by 1 H nuclear magnetic resonance (NMR), isothermal titration calorimetry (ITC), high-resolution mass spectrometry (HRMS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Eventually, correlative water solubility and foliar surface wettability were significantly improved after the formation of host-guest assemblies. In vivo antibacterial evaluation found that the achieved supramolecular complex could distinctly alleviate the disease symptoms and promote the control efficiencies against rice bacterial blight (from 34.6-35.7% ( III 18 ) to 40.3-43.6% ( III 18 @β-CD)) and kiwi canker diseases (from 41.0-42.3% ( III 18 ) to 53.9-68.0% ( III 18 @β-CD)) at 200 μg/mL (active ingredient). The current study can provide a feasible platform and insight for constructing biocompatible supramolecular assemblies for managing destructive bacterial infections in agriculture.