Experimental and computational study of the complexation of adamantyl glycosides with β-cyclodextrin

β-Cyclodextrin-optimized supramolecular nanovesicles enhance the droplet/foliage interface interactions and inhibition of succinate dehydrogenase (SDH) for efficient treatment of fungal diseases

BACKGROUND

Plant fungal diseases present a major challenge to global agricultural production. Despite extensive efforts to develop fungicides, particularly succinate dehydrogenase inhibitors (SDHIs), their effectiveness is often limited by poor retention of fungicide droplets on hydrophobic leaves. The off-target losses and unintended release cause fungal resistance and severe environmental pollution.

RESULTS

To update the structure of existing SDHIs and synchronously realize the efficient utilization, we have employed a sophisticated supramolecular strategy to optimize a structurally novel SDH inhibitor (AoH25), creating an innovative supramolecular SDH fungicide (AoH25@β-CD), driven by the host-guest recognition principle between AoH25 and β-cyclodextrin (β-CD). Intriguingly, AoH25@β-CD self-assembles into biocompatible supramolecular nanovesicles, which reinforce the droplet/foliage (liquid-solid) interface interaction and the effective wetting and retention on leaf surfaces, setting the foundation for enhancing fungicide utilization. Mechanistic studies revealed that AoH25@β-CD exhibited significantly higher inhibition of SDH (IC50 = 1.56 µM) compared to fluopyram (IC50 = 244.41 µM) and AoH25 alone (IC50 = 2.29 µM). Additionally, AoH25@β-CD increased the permeability of cell membranes in Botryosphaeria dothidea, facilitating better penetration of active ingredients into pathogenic cells. Further experimental outcomes confirmed that AoH25@β-CD was 88.5% effective against kiwifruit soft rot at a low-dose of 100 µg mL-1, outperforming commercial fungicides such as fluopyram (52.4%) and azoxystrobin (65.4%). Moreover, AoH25@β-CD showed broad-spectrum bioactivity against oilseed rape sclerotinia, achieving an efficacy of 87.2%, outstripping those of fluopyram (48.7%) and azoxystrobin (76.7%).

CONCLUSION

This innovative approach addresses key challenges related to fungicide deposition and resistance, improving the bioavailability of agricultural chemicals. The findings highlight AoH25@β-CD as a novel supramolecular SDH inhibitor, demonstrating its potential as an efficient and sustainable solution for plant disease management.

Synthesis and Immunological Evaluation of Mannosylated Desmuramyl Dipeptides Modified by Lipophilic Triazole Substituents

Muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine, MDP) is the smallest peptidoglycan fragment able to trigger an immune response by activating the NOD2 receptor. Structural modification of MDP can lead to analogues with improved immunostimulating properties. The aim of this work was to prepare mannosylated desmuramyl peptides (ManDMP) containing lipophilic triazole substituents to study their immunomodulating activities in vivo. The adjuvant activity of the prepared compounds was evaluated in the mouse model using ovalbumin as an antigen and compared to the MDP and referent adjuvant ManDMPTAd. The obtained results confirm that the α-position of D-isoGln is the best position for the attachment of lipophilic substituents, especially adamantylethyl triazole. Compound 6c exhibited the strongest adjuvant activity, comparable to the MDP and better than referent ManDMPTAd.

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.

Unravelling binding effects in cyclodextrin inclusion complexes with diamondoid ammonium salt guests

A hydrophobic tornado – complexation of diamondoid ammonium salts with cyclodextrins in water.

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

Muramyl dipeptide is the minimal structure of peptidoglycan with adjuvant properties. Replacement of the N-acetylmuramyl moiety and increase of lipophilicity are important approaches in the preparation of muramyl dipeptide analogues with improved pharmacological properties. Mannose receptors present on immunocompetent cells are pattern-recognition receptors and by mannose ligands binding they affect the immune system. Here we present the design, synthesis and biological evaluation of novel mannosylated desmuramyl peptide derivatives. Mannose was coupled to dipeptides containing a lipophilic adamantane on N- or C-terminus through a glycolyl or hydroxyisobutyryl linker. Adjuvant activities of synthesized compounds were investigated in the mouse model using ovalbumin as an antigen. Their activities were compared to the previously described mannosylated adamantane-containing desmuramyl peptide and peptidoglycan monomer. Tested compounds exhibited adjuvant activity and the strongest enhancement of IgG production was stimulated by compound 21 (Man-OCH₂-ᴅ-(1-Ad)Gly-ʟ-Ala-ᴅ-isoGln).

Functional self-assembled nanovesicles based on β-cyclodextrin, liposomes and adamantyl guanidines as potential nonviral gene delivery vectors

Multicomponent self-assembled supramolecular nanovesicles based on an amphiphilic derivative of β-cyclodextrin and phosphatidylcholine liposomes (PC-liposomes) functionalized with four structurally different adamantyl guanidines were prepared and characterized. Incorporation efficiency of the examined adamantyl guanidines as well as size and surface charge of the prepared supramolecular nanovesicles was determined. Changes in the surface charge of the prepared nanovesicles confirmed that guanidinium groups were exposed on the surface. ITC and 1H NMR spectroscopy complemented by molecular dynamics (MD) simulations were used to elucidate the structural data and stability of the inclusion complexes of β-cyclodextrin and adamantyl guanidines (AG1-5). The results are consistent and point to a significant contribution of the guanylhydrazone residue to the complexation process for AG1 and AG2 with β-cyclodextrin. In order to evaluate the potential of the self-assembled supramolecular nanomaterial as a nonviral gene delivery vector, fluorescence correlation spectroscopy was used. It showed that the prepared nanovesicles functionalized with adamantyl guanidines AG1-4 effectively recognize and bind the fluorescently labelled DNA. Furthermore, gel electrophoretic assay confirmed the formation of nanoplexes of functionalized nanovesicles and plasmid DNA. These findings together suggest that the designed supramolecular nanovesicles could be successfully applied as nonviral gene delivery vectors.

Azaadamantyl nitroxide spin label: complexation with β-cyclodextrin and electron spin relaxation

An iodoacetamide azaadamantyl spin label was studied in fluid solution and in 9:1 trehalose:sucrose glass. In 9:1 toluene:CH₂Cl₂ solution at 293 K, the isotropic nitrogen hyperfine coupling is 19.2 G, T₁ is 0.37 µs and T₂ is 0.30-0.35 µs. Between about 80 and 150 K 1/T_m in 9:1 trehalose:sucrose is approximately independent of temperature demonstrating that the absence of methyl groups decreases 1/T_m relative to that which is observed in spin labels with methyl groups on the alpha carbons. Spin lattice relaxation rates between about 80 and 293 K in 9:1 trehalose:sucrose are similar to those observed for other nitroxide spin labels, consistent with the expectation that relaxation is dominated by Raman and local mode processes. Although complexation of the azaadamantyl spin label with β-cyclodextrin slows tumbling in aqueous solution by about a factor of 10, it has little impact on 1/T₁ or 1/T_m in 9:1 trehalose:sucrose between 80 and 293 K.

Adamantylated organosilatranes: design, synthesis, and potential appraisal in surface modification and anti-protozoal activity

A series of organosilatranes tethered with the privileged adamantane motif has been prepared and their pharmacokinetic profiles were scrutinized.