Complexation of several benzimidazole-type fungicides with alpha- and beta-cyclodextrins

Computational Insights into Cyclodextrin Inclusion Complexes with the Organophosphorus Flame Retardant DOPO

Cyclodextrins (CDs) were used as green char promoters in the formulation of organophosphorus flame retardants (OPFRs) for polymeric materials, and they could reduce the amount of usage of OPFRs and their release into the environment by forming [host:guest] inclusion complexes with them. Here, we report a systematic study on the inclusion complexes of natural CDs (α-, β-, and γ-CD) with a representative OPFR of DOPO using computational methods of molecular docking, molecular dynamics (MD) simulations, and quantum mechanical (QM) calculations. The binding modes and energetics of [host:guest] inclusion complexes were analyzed in details. α-CD was not able to form a complete inclusion complex with DOPO, and the center of mass distance [host:guest] distance amounted to 4-5 Å. β-CD and γ-CD allowed for a deep insertion of DOPO into their hydrophobic cavities, and DOPO was able to frequently change its orientation within the γ-CD cavity. The energy decomposition analysis based on the dispersion-corrected density functional theory (sobEDAw) indicated that electrostatic, orbital, and dispersion contributions favored [host:guest] complexation, while the exchange-repulsion term showed the opposite. This work provides an in-depth understanding of using CD inclusion complexes in OPFRs formulations.

Nanobiosensors and nanoformulations in agriculture: new advances and challenges for sustainable agriculture

In the current scenario of climate change, global agricultural systems are facing remarkable challenges in order to increase production, while reducing the negative environmental impact. Nano-enabled technologies have the potential to revolutionise farming practices by increasing the efficiency of inputs and minimising losses, as well as contributing to sustainable agriculture. Two promising applications of nanotechnology in agriculture are nanobiosensors and nanoformulations (NFs). Nanobiosensors can help detect biotic and abiotic stresses in plants before they affect plant production, while NFs can make agrochemicals, more efficient and less polluting. NFs are becoming new-age materials with a wide variety of nanoparticle-based formulations such as fertilisers, herbicides, insecticides, and fungicides. They facilitate the site-targeted controlled delivery of agrochemicals enhancing their efficiency and reducing dosages. Smart farming aims to monitor and detect parameters related to plant health and environmental conditions in order to help sustainable agriculture. Nanobiosensors can provide real-time analytical data, including detection of nutrient levels, metabolites, pesticides, presence of pathogens, soil moisture, and temperature, aiding in precision farming practices, and optimising resource usage. In this review, we summarise recent innovative uses of NFs and nanobiosensors in agriculture that may boost crop protection and production, as well as reducing the negative environmental impact of agricultural activities. However, successful implementation of these smart technologies would require two special considerations: (i) educating farmers about appropriate use of nanotechnology, (ii) conducting field trials to ensure effectiveness under real conditions.

A micellar-enhanced fluorescence photoinduced four-way calibration method for the determination of multiclass pesticides in lemon juice

In this work, a four-way multivariate calibration method for the simultaneous determination of four pesticides - carbendazim (CBZ), thiabendazole (TBZ), pirimiphos-methyl (PMM), and clothianidin (CLT) - in lemon juice is presented. Third-order data were acquired by registering the photoinduced fluorescence of the analytes as excitation-emission matrices at different times of UV-light irradiation, in the presence of organized media (direct micelles) as fluorescence enhancers. The optimal experimental conditions (pH 11.5 and 32 mmol L-1 hexadecyltrimethylammonium chloride surfactant) were determined through a central composite design using the response surface methodology. The analytes were individually calibrated, except for TBZ and CBZ due to the inner filter effect of TBZ on CBZ. Test samples containing all analytes and imidacloprid (as potential interference) were analysed. PARAFAC was utilized to evaluate both the trilinearity and quadrilinearity of the third-order data and four-way arrays, respectively. PMM was successfully determined with quadrilinear PARAFAC decomposition, whereas CLT, TBZ, and CBZ were satisfactorily modelled using U-PLS/RTL due to the loss of quadrilinearity caused by different phenomena. The profitable applicability of the analytical method in the CBZ, TBZ, PMM, and CLT determination in lemon juice samples was demonstrated, achieving limits of detection below the maximum residue levels reported by the European Commission, and mean recoveries at 90 ± 5%.

Synthesis, in vitro biological assessment, and molecular docking study of benzimidazole-based thiadiazole derivatives as dual inhibitors of α-amylase and α-glucosidase

The clinical significance of benzimidazole-containing drugs has increased in the current study, making them more effective scaffolds. These moieties have attracted strong research interest due to their diverse biological features. To examine their various biological significances, several research synthetic methodologies have recently been established for the synthesis of benzimidazole analogs. The present study aimed to efficiently and quickly synthesize a new series of benzimidazole analogs. Numerous spectroscopic techniques, including ¹H-NMR, ¹³C-NMR, and HREI-MS, were used to confirm the synthesized compounds. To explore the inhibitory activity of the analogs against α-amylase and α-glucosidase, all derivatives (1-17) were assessed for their biological potential. Compared to the reference drug acarbose (IC₅₀ = 8.24 ± 0.08 µM), almost all the derivatives showed promising activity. Among the tested series, analog 2 (IC₅₀ = 1.10 ± 0.10 & 2.10 ± 0.10 µM, respectively) displayed better inhibitory activity. Following a thorough examination of the various substitution effects on the inhibitory capacity of α-amylase and α-glucosidase, the structure-activity relationship (SAR) was determined. We looked at the potential mechanism of how active substances interact with the catalytic cavity of the targeted enzymes in response to the experimental results of the anti-glucosidase and anti-amylase. Molecular docking provided us with information on the interactions that the active substances had with the various amino acid residues of the targeted enzymes for this purpose.

Chemical modification of β-cyclodextrin towards hydrogel formation

β-CD is a cyclic oligosaccharide, which has trunked cone like structure. The unique structure makes it efficient for numerous applications. Though, the native β-CD has many issues like low solubility, absence of sufficient functionalities and lower complexation ability with guest molecules. One of the most effective paths to increase the efficiency of cyclodextrins is the generation of polycyclodextrins. In this perspective article, we have summarized the recent reports on the synthetic methods towards the modification of β-CD. Besides, this article reviews the current improvements of two types of β-CD centered supramolecular hydrogels: one is supramolecular hydrogels prepared from CD-based poly(pseudo)rotaxanes and the other is supramolecular hydrogels developed through the host-guest interaction between small guest molecules and CDs. The Polycyclodextrins have established noteworthy applications in several areas ranging from adsorbents for organic pollutants removal to effective carriers of bioactive agents.

Reduced Graphene Oxide as a Platform for the Immobilization of Amino-Cyclodextrins

In the present work, we reported on a method to combine amino β-cyclodextrins (CD1) with reduced graphene oxide (obtained by the electrochemical reduction of graphene oxide, erGO) to produce a glassy carbon electrode (GCE) modified with both CD1 and erGO (CD1-erGO/GCE). This procedure avoids the use of organic solvents such as hydrazine or long reaction times and high temperatures. The material combining both CD1 and erGO (CD1-erGO/GCE) was characterized by SEM, ATR-FTIR, Raman, XPS, and electrochemical techniques. As proof-of-concept, the determination of the pesticide carbendazim was carried out. The spectroscopic measurements, especially XPS, proved that CD1 was covalently attached to the surface of the erGO/GCE electrode. The attachment of cyclodextrin at the reduced graphene oxide produced an increase in the electrochemical behavior of the electrode. The cyclodextrin-functionalized reduced graphene oxide, CD1-erGO/GCE, showed a larger sensitivity (1.01 μA/μM) and a lower limit of detection for carbendazim (LOD = 0.50 μM) compared with the non-functionalized material, erGO/GCE, (sensitivity = 0.63 μA/μM and LOD = 4.32 μM, respectively). Overall, the results of the present work show that this simple method is suitable to attach cyclodextrins to graphene oxide, maintaining their inclusion abilities.

Conductometric Studies of Formation the Inclusion Complexes of Phenolic Acids with β-Cyclodextrin and 2-HP-β-Cyclodextrin in Aqueous Solutions

An attempt was made to evaluate the possibility of creating and assessing the stability of inclusion complexes of selected phenolic acids [trans-4-hydroxycinnamic acid (trans-p-coumaric acid), trans-3,4-dihydroxycinnamic acid (trans-caffeic acid), trans-4-hydroxy-3-methoxycinnamic acid, (trans-ferulic acid) and trans-3-phenylacrylic acid (trans-cinnamic acid)] with β-cyclodextrin and 2-HP-β-cyclodextrin in aqueous solutions in a wide temperature range 283.15 K-313.15 K. On the basis of the values of the limiting molar conductivity (Λ_CDNaDod), calculated from the experimental data, the values of the formation constants and the thermodynamic functions of formation (standard enthalpy, entropy, and Gibs standard enthalpy) of the studied complexes were determined. It has been found that the stability of the studied complexes increases with lowering of the molar mass of cyclodextrin and lowering of the temperature.

pH-Responsive templates modulate the dynamic enzymatic synthesis of cyclodextrins

Product selection in the dynamic enzymatic synthesis of cyclodextrins can be controlled by changing the pH. Using cyclodextrin glucanotransferase to make labile the glycosidic linkages in cyclodextrins (CDs), we generate a dynamic combinatorial library of interconverting linear and cyclic α-1,4-glucans. Templates can be employed to favour the selective production of specific CDs and, herein, we show that by using ionisable templates, the synthesis of α-CD or β-CD can be favoured by simply changing the pH. Using 4-nitrophenol as the template, β-CD is the preferred product at low pH, while α-CD is the preferred product at high pH. Furthermore, a new methodology is described for the simulation of product distributions in dynamic combinatorial libraries with ionisable templates at any given pH.

Supramolecular Hydrogels: Design Strategies and Contemporary Biomedical Applications

Self-assembly of supramolecular hydrogels is driven by dynamic, non-covalent interactions between molecules. Considerable research effort has been exerted to fabricate and optimise supramolecular hydrogels that display shear-thinning, self-healing, and reversibility, in order to develop materials for biomedical applications. This review provides a detailed overview of the chemistry behind the dynamic physicochemical interactions that sustain hydrogel formation (hydrogen bonding, hydrophobic interactions, ionic interactions, metal-ligand coordination, and host-guest interactions). Novel design strategies and methodologies to create supramolecular hydrogels are highlighted, which offer promise for a wide range of applications, specifically drug delivery, wound healing, tissue engineering and 3D bioprinting. To conclude, future prospects are briefly discussed, and consideration given to the steps required to ultimately bring these biomaterials into clinical settings.

Soft Materials by Design: Unconventional Polymer Networks Give Extreme Properties

Hydrogels are polymer networks infiltrated with water. Many biological hydrogels in animal bodies such as muscles, heart valves, cartilages, and tendons possess extreme mechanical properties including being extremely tough, strong, resilient, adhesive, and fatigue-resistant. These mechanical properties are also critical for hydrogels' diverse applications ranging from drug delivery, tissue engineering, medical implants, wound dressings, and contact lenses to sensors, actuators, electronic devices, optical devices, batteries, water harvesters, and soft robots. Whereas numerous hydrogels have been developed over the last few decades, a set of general principles that can rationally guide the design of hydrogels using different materials and fabrication methods for various applications remain a central need in the field of soft materials. This review is aimed at synergistically reporting: (i) general design principles for hydrogels to achieve extreme mechanical and physical properties, (ii) implementation strategies for the design principles using unconventional polymer networks, and (iii) future directions for the orthogonal design of hydrogels to achieve multiple combined mechanical, physical, chemical, and biological properties. Because these design principles and implementation strategies are based on generic polymer networks, they are also applicable to other soft materials including elastomers and organogels. Overall, the review will not only provide comprehensive and systematic guidelines on the rational design of soft materials, but also provoke interdisciplinary discussions on a fundamental question: why does nature select soft materials with unconventional polymer networks to constitute the major parts of animal bodies?

Synthesis and Characterization of Phenolic Acid/Hydroxypropyl-β-Cyclodextrin Inclusion Complexes

The objective of this study was to synthesize and characterize inclusion complexes of phenolic acids with hydroxypropyl-β-cyclodextrin (HP-β-CD). The inclusion complexes were prepared by the freeze-drying method and characterized using a variety of analytical techniques, including ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffractometry. The results of all these approaches indicated that phenolic acids were able to form an inclusion complex with HP-β-CD, and the phenolic acids/HP-β-CD inclusion compounds exhibited different spectroscopic features and properties based on the phenolic acids employed. The use of the HP-β-CD matrix allowed for higher encapsulation efficiency and afforded capsules with distinct shapes.

Advances in controlled release pesticide formulations: Prospects to safer integrated pest management and sustainable agriculture

As the world is striving hard towards sustainable agricultural practices for a better tomorrow, one of the primary focuses is on effective pest management for enhanced crop productivity. Despite newer and potent chemicals as pesticides, there are still substantial crop losses, and if by any means this loss can be tackled; it will alleviate unwanted excessive use of chemical pesticides. Scientific surveys have already established that pesticides are not being utilized by the crops completely rather a significant amount remains unused due to various limiting factors such as leaching and bioconversion, etc., resulting in an adverse effect on human health and ecosystems. Concerted efforts from scientific diaspora toward newer and innovative strategies are already showing promise, and one such viable approach is controlled release systems (CRS) of pesticides. Moreover, to bring these smart formulations within the domain of current pesticide regulatory framework is still under debate. It is thus, paramount to discuss the pros and cons of this new technology vis-à-vis the conventional agrarian methods. This review deliberates on the developmental updates in this innovative field from the past decades and also appraises the challenges encumbered. Additionally, critical information and the foreseeable research gaps in this emerging area are highlighted.

Crystal structure of bis-[2-(1H-benzimidazol-2-yl-κN 3)aniline-κN]bis-(nitrato-κO)cadmium(II)

In the title compound, [Cd(NO3)2(C13H11N3)2], the CdII atom lies on a twofold rotation axis and is coordinated by four N atoms and two O atoms, provided by two bidentate 2-(1H-benzimidazol-2-yl)aniline ligands, and two nitrato O atoms, forming a distorted octa-hedral geometry [range of bond angles around the Cd atom = 73.82 (2)-106.95 (8)°]. In the ligand, the dihedral angle between the aniline ring and the benzimidazole ring system is 30.43 (7)°. The discrete complex mol-ecule is stabilized by an intra-molecular N-H⋯O hydrogen bond. In the crystal, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules, forming a three-dimensional network.

Safe nanotechnologies for increasing the effectiveness of environmentally friendly natural agrochemicals

Natural compounds and living organisms continue to play a limited role in crop protection, and few of them have reached the market, despite their attractiveness and the efforts made in research. Very often these products have negative characteristics compared to synthetic compounds, e.g., higher costs of production, lower effectiveness, lack of persistence, and inability to reach and penetrate the target plant. Conversely, nanotechnologies are having an enormous impact on all human activities, including agriculture, even if the production of some nanomaterials is not environmentally friendly or could have adverse effects on agriculture and the environment. Thus, certain nanomaterials could facilitate the development of formulated natural pesticides, making them more effective and more environmentally friendly. Nanoformulations can improve efficacy, reduce effective doses, and increase shelf-life and persistence. Such controlled-release products can improve delivery to the target pest. This review considers certain available nanomaterials and nanotechnologies for use in agriculture, discussing their properties and the feasibility of their use in sustainable crop protection, in particular, in improving the effectiveness of natural bio-based agrochemicals. © 2019 Society of Chemical Industry.

Synthesis and characterization of a new cyclodextrin derivative with improved properties to design oral dosage forms

This work aimed to synthesize a novel β-cyclodextrin derivative, itaconyl-β-cyclodextrin to evaluate whether albendazole inclusion complexes with the new β-cyclodextrin derivative-improved albendazole dissolution efficiency and its anthelminthic activity. The new derivative was thoroughly evaluated and characterized, and an average degree of substitution of 1.4 per cyclodextrin molecule was observed. Albendazole:itaconyl-β-cyclodextrin complexes were prepared by spray drying procedures and investigated using phase solubility diagrams, dissolution efficiency, X-ray diffraction, differential scanning calorimetry, Fourier transform infrared, scanning electronic microscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy. Phase solubility diagrams and mass spectrometry studies showed that the inclusion complex was formed in an equimolar ratio. Stability constant values were 602 M^-1 in water, and 149 M^-1 in HCl 0.1 N. Nuclear magnetic resonance experiments of the inclusion complex showed correlation signals between the aromatic and propyl protons of albendazole and the itaconyl-β-cyclodextrin inner protons. The studies indicated solid structure changes of albendazole included in itaconyl-β-cyclodextrin. The maximum drug release was reached at 15 min, and the inclusion complex solubility was 88-fold higher than that of the pure drug. The in vitro anthelmintic activity assay showed that the complex was significantly more effective than pure albendazole.

Synthesis, Characterization, and Antifungal Activity of Novel Benzo[4,5]imidazo[1,2-d][1,2,4]triazine Derivatives

A series of novel fused heterocyclic compounds bearing benzo[4,5]imidazo[1,2-d][1,2,4]triazine 4a–4w were designed and conveniently synthesized via the intermediates 2-(halogenated alkyl)-1H-benzo[d]imidazoles 2a, 2b, and 2-((1-(substituted phenyl)hydrazinyl)alkyl)-1H-benzo[d]imidazoles 3a–3g. The structures of all target compounds were characterized by FT-IR, ¹H NMR, ¹³C NMR, and EI-MS, of which, the structure of compound 4n was further determined by the single crystal X-ray diffraction. The crystal structure of 4n was crystallized in the triclinic crystal system, space group P1¯ with a = 9.033 (6) Å, b = 10.136 (7) Å, c = 10.396 (7) Å, α = 118.323 (7)°, β = 91.750 (8)°, γ = 104.198 (7)°, Z = 2, V = 800.2 (9) ų; total R indices: R₁ = 0.0475, wR₂ = 0.1284. The antifungal activity of title compounds 4a–4w in vitro against the phytopathogenic fungi Botrytis cinerea (B. cinerea), Rhizoctonia solani (R. solani) and Colletotrichum capsici (C. capsici) were evaluated, the bioassay results demonstrated that most of the title compounds exhibited obvious fungicidal activities at 50 μg/mL. This work indicated that benzo[4,5]imidazo[1,2-d][1,2,4]triazine derivatives could be considered as a new leading structure in searching for novel agricultural fungicides.

Cyclodextrin-based host–guest supramolecular hydrogel and its application in biomedical fields

CD-based host–guest supramolecular hydrogels and their potential biomedical application.

Selection and Characterization of DNA Aptamers for Electrochemical Biosensing of Carbendazim

This article reports a novel aptamer-based impedimetric detection of carbendazim, a commonly used benzimidazole fungicide in agriculture. High affinity and specificity DNA aptamers against carbendazim were successfully selected using systematic evolution of ligand by exponential enrichment (SELEX). The dissociation constants (K_ds) of the selected DNA aptamers after 10 in vitro selection cycles were characterized using fluorescence-based assays showing values in the nanomolar range. The aptamer which showed the highest degree of affinity and conformation change was used to fabricate an electrochemical aptasensor via self-assembly of thiol-modified aptamer on gold electrodes. The aptasensor exploits the specific recognition of carbendazim by the aptamer immobilized on the gold surface which leads to conformational changes in the aptamer structure. This conformational change alters the access of a ferrocyanide/ferricyanide redox couple to the aptasensor surface. The aptasensor response is thus measured by following the increase in the electron transfer resistance of the redox couple using Faradaic electrochemical impedance spectroscopy. This method allowed a selective and sensitive label-free detection of carbendazim within a range of 10 pg/mL-10 ng/mL with a limit of detection of 8.2 pg/mL. The aptasensor did not show cross reactivity with other commonly used pesticides such as fenamiphos, isoproturon, atrazine, linuron, thiamethoxam, trifluralin, carbaryl, and methyl parathion. Moreover, the aptasensor has been applied in different spiked food matrixes showing high recovery percentages. We believe that the proposed aptasensor is a promising alternative to the currently used methods for carbendazim monitoring.

β-Cyclodextrin functionalized carbon quantum dots as sensors for determination of water-soluble C60 fullerenes in water

A selective photoluminescence method based on Carbon Quantum Dots (CQDs) functionalized with carboxymethyl-β-cyclodextrin for the direct determination of water-soluble C₆₀ fullerene has been developed.

Complexation of synthetic CDM-AM copolymer with natamycin and carbendazim to improve solubility and fungicidal activity

The β-cyclodextrin-acrylamide (CDM-AM) copolymer was prepared from acrylamide and β-CD maleate (CDM) using K2S2O8 as initiator. The effects of the CDM-AM copolymer on the solubility and fungicidal activity of natamycin (NM) and carbendazim (MBC) were investigated. The stability constant of NM·CDM-AM and MBC·CDM-AM complexes at 303 K were of 10,725.45 M(-1) and 3000.89 M(-1), respectively. The complexes were characterized using phase solubility diagrams, NMR spectra and FT-IR spectra. The analysis of the biological activities of these two complexes indicated that they possessed enhancing fungicidal activities compared to NM and MBC alone.

Encapsulation of biocides by cyclodextrins: toward synergistic effects against pathogens

Host-guest chemistry is useful for the construction of nanosized objects. Some of the widely used hosts are probably the cyclodextrins (CDs). CDs can form water-soluble complexes with numerous hydrophobic compounds. They have been widespread used in medicine, drug delivery and are of interest for the biocides encapsulation. Indeed, this enables the development of more or less complex systems that release antimicrobial agents with time. In this paper, the general features of CDs and their applications in the field of biocides have been reviewed. As the key point is the formation of biocide-CD inclusion complexes, this review deals with this in depth and the advantages of biocide encapsulation are highlighted throughout several examples from the literature. Finally, some future directions of investigation have been proposed. We hope that scientists studying biocide applications receive inspiration from this review to exploit the opportunities offered by CDs in their respective research areas.