Diversity in the supramolecular interactions of 5,6-dichloro-2-(trifluoromethyl)-1H-benzimidazole with modified cyclodextrins: Implications for physicochemical properties and antiparasitic activity

Enhancing Giardicidal Activity and Aqueous Solubility through the Development of "RetroABZ", a Regioisomer of Albendazole: In Vitro, In Vivo, and In Silico Studies

Parasitic diseases, including giardiasis caused by Giardia lamblia (G. lamblia), present a considerable global health burden. The limited effectiveness and adverse effects of current treatment options underscore the necessity for novel therapeutic compounds. In this study, we employed a rational design strategy to synthesize retroalbendazole (RetroABZ), aiming to address the limitations associated with albendazole, a commonly used drug for giardiasis treatment. RetroABZ exhibited enhanced in vitro activity against G. lamblia trophozoites, demonstrating nanomolar potency (IC50 = 83 nM), outperforming albendazole (189 nM). Moreover, our in vivo murine model of giardiasis displayed a strong correlation, supporting the efficacy of RetroABZ, which exhibited an eleven-fold increase in potency compared to albendazole, with median effective dose (ED50) values of 5 µg/kg and 55 µg/kg, respectively. A notable finding was RetroABZ's significantly improved water solubility (245.74 µg/mL), representing a 23-fold increase compared to albendazole, thereby offering potential opportunities for developing derivatives that effectively target invasive parasites. The molecular docking study revealed that RetroABZ displays an interaction profile with tubulin similar to albendazole, forming hydrogen bonds with Glu198 and Cys236 of the β-tubulin. Additionally, molecular dynamics studies demonstrated that RetroABZ has a greater number of hydrophobic interactions with the binding site in the β-tubulin, due to the orientation of the propylthio substituent. Consequently, RetroABZ exhibited a higher affinity compared to albendazole. Overall, our findings underscore RetroABZ's potential as a promising therapeutic candidate not only for giardiasis but also for other parasitic diseases.

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 EC₅₀ values could reach 0.936 (III₁₈), 0.889 (III₁₈), and 2.10 (III₁₉) 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 III₁₈@β-CD (binding mode 1:1) was successfully fabricated and characterized by ¹H 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% (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)) 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.

Anisotropic Amorphous X-ray Diffraction Attributed to the Orientation of Cyclodextrin

The beauty of cyclic molecules is reflected in their host-guest complexation reactions, as well as their unique X-ray diffraction patterns. Cyclodextrins, the longest known host molecules with rigid ring structures, show anisotropic X-ray diffraction characteristic of their single-molecule structure, rather than their intermolecular relationships. Amorphous derivatives of α-cyclodextrin exhibit broad and strong halo diffractions in the solid, melted, and dilute solution states. The diffraction angle corresponds to the intramolecular distance between neighboring glycosidic oxygen atoms located at the vertices of a regular hexagonal array. Because the hexagon is parallel to the aperture plane of the rigid cyclic molecule, the diffraction appears only in the direction parallel to this plane. The anisotropy was confirmed by stretching an amorphous thermoplastic polymer threaded through the inclusion cavities of a sequence of cyclodextrins. The resultant unique anisotropic X-ray diffraction suggests the possible use of rigid cyclic molecules as molecular orientation probes.