Synthesis, fungicidal activity, structure-activity relationships (SARs) and density functional theory (DFT) studies of novel strobilurin analogues containing arylpyrazole rings

Impacts of UV light on the effects of either conventional or nano-enabled azoxystrobin on Daphnia magna

Agri-chemicals such as fungicides are applied in natural settings and hence are exposed to the environment's ultraviolet (UV) light. Recently, many fungicides in commerce are being modified as nano-enabled formulations to increase agricultural productivity and reduce potential off-target effects. The present study investigated the impacts of sunlight-grade UV emission on the effects of either conventional or nano-enabled azoxystrobin (Az or nAz, respectively), a commonly applied agricultural fungicide, on Daphnia magna. Daphnids were exposed to increasing concentrations of Az or nAz under either full-spectrum (Vis) or full-spectrum Vis + UV (Vis + UV) lighting regimes to evaluate LC50s. Az LC50 was calculated at 268.8 and 234.2 μg/L in Vis or Vis + UV, respectively, while LC50 for nAz was 485.6 and 431.0 μg/L under Vis or Vis + UV light, respectively. Daphnids were exposed to 10% LC50 of either Az or nAz under Vis or Vis + UV lighting regime for 48 h or 21 d (acute and chronic, respectively). By 48 h, both Az and nAz reduced O2 consumption and increased TBARS. Heart rate was increased in Az-exposed daphnids but not in nAz groups. Neither of the two chemicals impacted thoracic limb activity. In 21 d exposures, Az significantly reduced biomass production and fecundity, but nAz groups were not significantly different from controls. The results of the present study demonstrate that conventional Az is more toxic to D. magna at lethal and sub-lethal levels in acute and chronic exposures, and sunlight strength UV can potentiate both acute and chronic effects of Az and nAz on D. magna.

Pouteria caimito fruit derived nanoparticles inhibited the apple ring rot disease as well as extended the shelf-life of sliced apples

Background

Apple disease, exaggerated by Botryosphaeria dothidea, is a foremost intimidating problem for extending the apple fruit shelf-life and producing substantial economic losses for cultivators and distributors. Alternate sources are urgently needed to prevent or inhibit the ring rot infection of apple fruit instigated by Botryosphaeria dothidea.

Objective

In this current study, we premeditated to make novel organic nanoparticles as of Pouteria caimito fruit extract and calcium chloride (PCNP), which were used to evaluate the preventive outcome of Botryosphaeria dothidea-caused apple disease on postharvest apple fruits.

Results

Our findings corroborated that the fruit derived nanoparticle had been confirmed for quality and size by altered estimations such as fourier transform infrared (FTIR), UV-vis spectroscopic analysis, scanning electron microscope and energy dispersive X-ray (SEM and EDX) estimation, and dynamic light scattering (DLS) analysis. In addition, we have investigated the excellent inhibitory action of the pathogen infection in apples initiated by Botryosphaeria dothidea. The protective enzymes function was pointedly improved in nanoparticle-treated apple fruits once equated with those of control apple fruits. The catalase (CAT) and superoxide dismutase (SOD) activities were pointedly improved in nanoparticle-treated fruits when compared to those of control fruits. The shelf-life extension studies were conducted for 7 days with a fresh-cut apple. The total soluble solid, pH, weight loss, and sensory studies were analyzed, and they proved the extension of sliced apple shelf life up to 7 days.

Conclusions

The discoveries of this study provided a well-organized, harmless, and environment-friendly substitute to control the apple disease as well as the durability postponement of sliced apples 7 days or may longer.

Comprehensive Overview of β-Methoxyacrylate Derivatives as Cytochrome bc1 Inhibitors for Novel Pesticide Discovery

β-Methoxyacrylate derivatives represent a new class of pesticides, which have attracted increasing attention owing to their unique structure, broad biological activity, and unique mechanisms of action. They inhibit mitochondrial respiration via preventing electron transfer at the Qo site of the cytochrome bc₁ complex and thus are identified as cyt bc₁ inhibitors. A variety of β-methoxyacrylate derivatives have been reported by many research groups for discovery of novel pesticides with improved expected activities. This review focuses on development of β-methoxyacrylate derivatives with great significance as pesticides such as fungicides, acaricides, insecticides, herbicides, and antiviral agents. In addition, the structure-activity relationships (SARs) of β-methoxyacrylate derivatives are summarized. Moreover, the cause of resistance to β-methoxyacrylate fungicides and some solutions are also introduced. Finally, the development trend of β-methoxyacrylate derivatives as pesticides is explored. We hope the review will give a guide to develop novel β-methoxyacrylate pesticides in the future.

Synthesis, DFT Analyses, Antiproliferative Activity, and Molecular Docking Studies of Curcumin Analogues

With 19.3 million new cases and almost 10 million deaths in 2020, cancer has become a leading cause of death today. Curcumin and its analogues were found to have promising anticancer activity. Inspired by curcumin’s promising anticancer activity, we prepared three semi-synthetic analogues by chemically modifying the diketone function of curcumin to its pyrazole counterpart. The curcumin analogues (3a−c) were synthesized by two different methods, followed by their DFT analyses to study the HOMO/LUMO configuration to access the stability of compounds (∆E = 3.55 to 3.35 eV). The curcumin analogues (3a−c) were tested for antiproliferative activity against a total of five dozen cancer cell lines in a single (10 µM) and five dose (0.001 to 100 µM) assays. 3,5-Bis(4-hydroxy-3-methoxystyryl)-1H-pyrazole-1-yl-(phenoxy)ethanone (3b) and 3,5-bis(4-hydroxy-3-methoxystyryl)-1H-pyrazole-1-yl-(2,4-dichlorophenoxy)ethanone (3c) demonstrated the most promising antiproliferative activity against the cancer cell lines with growth inhibitions of 92.41% and 87.28%, respectively, in a high single dose of 10 µM and exhibited good antiproliferative activity (%GIs > 68%) against 54 out of 56 cancer cell lines and 54 out of 60 cell lines, respectively. The compound 3b and 3c demonstrated the most potent antiproliferative activity in a 5-dose assay with GI50 values ranging between 0.281 and 5.59 µM and 0.39 and 0.196 and 3.07 µM, respectively. The compound 3b demonstrated moderate selectivity against a leukemia panel with a selectivity ratio of 4.59. The HOMO-LUMO energy-gap (∆E) of the compounds in the order of 3a > 3b > 3c, was found to be in harmony with the anticancer activity in the order of 3c ≥ 3b > 3a. Following that, all of the curcumin analogues were molecular docked against EGFR, one of the most appealing targets for antiproliferative activity. In a molecular docking simulation, the ligand 3b exhibited three different types of interactions: H-bond, π-π-stacking and π-cationic. The ligand 3b displayed three H-bonds with the residues Met793 (with methoxy group), Lys875 (with phenolic group) and Asp855 (with methoxy group). The π-π-stacking interaction was observed between the phenyl (of phenoxy) and the residue Phe997, while π-cationic interaction was displayed between the phenyl (of curcumin) and the residue Arg841. Similarly, the ligand 3c displayed five H-bonds with the residue Met793 (with methoxy and phenolic groups), Lys845 (methoxy group), Cys797 (phenoxy oxygen), and Asp855 (phenolic group), as well as a halogen bond with residue Cys797 (chloro group). Furthermore, all the compound 3a−c demonstrated significant binding affinity (−6.003 to −7.957 kcal/mol) against the active site of EGFR. The curcumin analogues described in the current work might offer beneficial therapeutic intervention for the treatment and prevention of cancer. Future anticancer drug discovery programs can be expedited by further modifying these analogues to create new compounds with powerful anticancer potentials.

Experimental and Quantum Chemical Studies of Nicotinamide-Oxalic Acid Salt: Hydrogen Bonding, AIM and NBO Analysis

The computational modeling supported with experimental results can explain the overall structural packing by predicting the hydrogen bond interactions present in any cocrystals (active pharmaceutical ingredients + coformer) as well as salts. In this context, the hydrogen bonding synthons, physiochemical properties (chemical reactivity and stability), and drug-likeliness behavior of proposed nicotinamide-oxalic acid (NIC-OXA) salt have been reported by using vibrational spectroscopic signatures (IR and Raman spectra) and quantum chemical calculations. The NIC-OXA salt was prepared by reactive crystallization method. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) techniques were used for the characterization and validation of NIC-OXA salt. The spectroscopic signatures revealed that (N7-H8)/(N23-H24) of the pyridine ring of NIC, (C═O), and (C-O) groups of OXA were forming the intermolecular hydrogen bonding (N-H⋯O-C), (C-H⋯O═C), and (N-H⋯O═C), respectively, in NIC-OXA salt. Additionally, the quantum theory of atoms in molecules (QTAIM) showed that (C10-H22⋯O1) and (C26-H38⋯O4) are two unconventional hydrogen bonds present in NIC-OXA salt. Also, the natural bond orbital analysis was performed to find the charge transfer interactions and revealed the strongest hydrogen bonds (N7-H8⋯O5)/(N23-H24⋯O2) in NIC-OXA salt. The frontier molecular orbital (FMO) analysis suggested more reactivity and less stability of NIC-OXA salt in comparison to NIC-CA cocrystal and NIC. The global and local reactivity descriptors calculated and predicted that NIC-OXA salt is softer than NIC-CA cocrystal and NIC. From MESP of NIC-OXA salt, it is clear that electrophilic (N7-H8)/(N23-H24), (C6═O4)/(C3═O1) and nucleophilic (C10-H22)/(C26-H38), (C6-O5)/(C3-O2) reactive groups in NIC and OXA, respectively, neutralize after the formation of NIC-OXA salt, confirming the presence of hydrogen bonding interactions (N7-H8⋯O5-C6) and (N23-H24⋯O2-C3). Lipinski's rule was applied to check the activeness of salt as an orally active form. The results shed light on several features of NIC-OXA salt that can further lead to the improvement in the physicochemical properties of NIC.

Structure-antioxidant activity relationships of dendrocandin analogues determined using density functional theory

Quantum-chemical calculations based on the density functional theory (DFT) at the B3LYP/6-311 + + G(2d,2p)//B3LYP/6-31G(d,p) level were employed to study the relationship between the antioxidant properties and chemical structures of six dendrocandin (DDCD) analogues in the gas phase and two solvents (methanol and water). The hydrogen atom transfer (HAT), electron-transfer-proton-transfer (ET-PT), and sequential proton-loss-electron-transfer (SPLET) mechanisms are explored. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), reactivity indices (η, μ, ω, ω +, and ω - ), and molecular electrostatic potentials (MEPs) were also evaluated. The results suggest that the D ring plays an important role in mediating the antioxidant activity of DDCDs. For all the studied compounds, indicating that HAT was identified as the most favorable mechanism, whereas the SPLET mechanism was the most thermodynamically favorable pathway in polar solvents. The results of our study should aid in the development of new or modified antioxidant compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11224-022-01895-2.

Natural Compound-derived Cytochrome bc1 Complex Inhibitors as Antifungal Agents

The high incidence of fungal pathogens has become a global issue for crop protection. A promising strategy to control fungal plant infections is based on the use of nature-inspired compounds. The cytochrome bc1 complex is an essential component of the cellular respiratory chain and is one of the most important fungicidal targets. Natural products have played a crucial role in the discovery of cytochrome bc1 inhibitors, as proven by the development of strobilurins, one of the most important classes of crop-protection agents, over the past two decades. In this review, we summarize advances in the exploration of natural product scaffolds for the design and development of new bc1 complex inhibitors. Particular emphasis is given to molecular modeling-based approaches and structure-activity relationship (SAR) studies performed to improve the stability and increase the potency of natural precursors. The collected results highlight the versatility of natural compounds and provide an insight into the potential development of nature-inspired derivatives as antifungal agents.

Fungicidal Effect of Pyraclostrobin against Botrytis cinerea in Relation to Its Crystal Structure

Pyraclostrobin (PYR) is a commonly used strobilurin fungicide, which inhibits mitochondrial respiration at the ubiquinol oxidation center site of the cytochrome bc1 complex. Little information is available regarding the crystal structure of PYR on its fungicidal effect. In this study, the crystal structures of eight PYRs (PYR-A to H) from different sources are determined by using high-resolution X-ray powder diffraction (XRPD) and model construction with the Pawley refinement module. The effects of PYRs on mycelium growth, the kinetics of mycelial growth, conidial germination, and tube elongation of conidia of Botrytis cinerea from tomato are compared. The level of organic acids in the mitochondrial tricarboxylic acid cycle of PYR-treated B. cinerea is analyzed. The results show that PYR-A to PYR-H have their own unique character of XRPD patterns, but the crystal morphology of eight PYRs presents in the triclinic crystal system and space group P1̅. PYR-D with the eclipsed conformation and rational edge angles α (72.599°) and β (98.612°) in the crystal cell shows the highest inhibitory effect against mycelium growth with EC₅₀ as 3.383 μg mL^-1, the best time-dependent effects on the mycelium growth kinetics, and the strongest inhibition on tube elongation of conidia, whereas PYR-E with anticonformation is the worst. Moreover, a significant accumulation of fumarate, malate, and oxalate in the PYR-D-treated mycelium is observed. These findings reinforce the need for a definite crystal structure of PYR to limit usage and mitigate future selection pressure for gray mold management.