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

Abstract

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.

Photo‐Stimuli Smart Supramolecular Self‐Assembly of Azobenzene/β‐Cyclodextrin Inclusion Complex for Controlling Plant Bacterial Diseases

“…However, after UV irradiation, cis ‐type 3a’ did not match the structure of β ‐CD and slipped out of the cavity, thereby inclusion complex gradually disassembles. [ 29 ]…”

“…[17,27,28] This contribution suggests that rational fabrication of cyclodextrins-based binary complexes has significant application prospects to improve the bioavailability and stability of the active ingredients and endows novel delivery systems to reasonably release active ingredients. [29][30][31][32] Azobenzene analogs are a family of compounds that can be encapsulated by loading cyclodextrins with noncovalent interactions. [33,34] This type of molecule has a unique photoresponsive property that coexists in both cis-and transconfigurations, and can be reversed under different illumination conditions.…”

Pursuing Green and Efficient Agriculture from Molecular Assembly: A Review of Solid-State Forms on Agrochemicals

“…(c) The supramolecular complexes of β-cyclodextrin–adamantane host–guest interactions prepared 1,3,4-oxadiazole (III 18 @β-CD) with better efficacy. Reprinted with permission from ref . Copyright 2022 American Chemical Society.…”

“…Specifically, the clathrate hydrate constituted by Btz and β-CD and γ-CD, when contrasted with the commercially available Btz sodium salt, demonstrates a reduction in the dissolution rate by 13 times and 16 times and in solubility by 183 times and 117 times, respectively. Furthermore, the adamantane-functionalized 1,3,4-oxadiazole (III18) and β-CD supramolecular complex exhibits superior water solubility and leaf wettability, substantially diminishing disease symptoms and enhancing control efficiencies against rice bacterial blight (from 34.6–35.7% (III18) to 40.3–43.6% (III18@β-CD)) and kiwi canker diseases (from 41.0–42.3% (III18) to 53.9–68.0% (III18@β-CD)) . This work underscores the potential to guide the judicious design of environmentally considerate and biocompatible supramolecular structures for fungi control.…”

“…Furthermore, the adamantane-functionalized 1,3,4-oxadiazole (III18) and β-CD supramolecular complex exhibits superior water solubility and leaf wettability, substantially diminishing disease symptoms and enhancing control efficiencies against rice bacterial blight (from 34.6−35.7% (III18) to 40.3−43.6% (III18@β-CD)) and kiwi canker diseases (from 41.0−42.3% (III18) to 53.9−68.0% (III18@β-CD)). 225 This work underscores the potential to guide the judicious design of environmentally considerate and biocompatible supramolecular structures for fungi control.…”