Ametoctradin is a potent Qo site inhibitor of the mitochondrial respiration complex III

Off-target effects of statins: molecular mechanisms, side effects and the emerging role of kinases

Statins are one of the most important classes of drugs. In this analytical review, we elucidate the intricate molecular mechanisms and toxicological rationale regarding both the on- (targeting 3-hydroxy-3-methylglutaryl-coenzyme A reductase [HMGCR]) and off-target effects of statins. Statins interact with a number of membrane kinases, such as epidermal growth factor receptor (EGFR), erb-b2 receptor tyrosine kinase 2 (HER2) and MET proto-oncogene, receptor tyrosine kinase (MET), as well as cytosolic kinases, such as SRC proto-oncogene, non-receptor tyrosine kinase (Src) and show inhibitory activity at nanomolar concentrations. In addition, they interact with calcium ATPases and peroxisome proliferator-activated receptor α (PPARα/NR1C1) at higher concentrations. Statins interact with mitochondrial complexes III and IV, and their inhibition of coenzyme Q10 synthesis also impairs the functioning of complexes I and II. Statins act as inhibitors of kinases, calcium ATPases and mitochondrial complexes, while activating PPARα. These off-target effects likely contribute to the side effects observed in patients undergoing statin therapy, including musculoskeletal symptoms and hepatic effects. Interestingly, some off-target effects of statins could also be the cause of favourable outcomes, relating to repurposing statins in conditions such as inflammatory disorders and cancer.

Rational design, synthesis, and antimicrobial evaluation of novel 1,2,4-trizaole-substituted 1,3,4-oxadiazole derivatives with a dual thioether moiety

In this paper, a series of novel 1,2,4-trizaole-substituted 1,3,4-oxadiazole derivatives with a dual thioether moiety were constructed. The synthetic compounds were characterized by 1H NMR, 13C NMR, HRMS, and single crystal diffraction. The antimicrobial activities of title compounds against fungi (Pyricutaria oryzae Cav., Phomopsis sp., Botryosphaeria dothidea, cucumber Botrytis cinerea, tobacco Botrytis cinerea, blueberry Botrytis cinerea) and bacteria (Xanthomonas oryzae pv. oryzicola, Xoc; Xanthomonas axonopodis pv. citri, Xac) revealed these compounds possessed excellent antibacterial activity through mycelial growth rate method and turbidity method, respectively. Among them, compounds 7a, 7d, 7g, 7k, 7l, and 7n had the antibacterial inhibition rate of 90.68, 97.86, 93.61, 97.70, 97.26, and 92.34%, respectively. The EC50 values of 7a, 7d, 7g, 7k, 7l, and 7n were 58.31, 48.76, 58.50, 40.11, 38.15, and 46.99 μg/mL, separately, superior to that of positive control pesticide thiodiazole copper (104.26 μg/mL). The molecular docking simulation of compound 7l and glutathione s-transferase also confirmed its good activity. The in vivo bioassay toward Xac infected citrus leaves was also performed to evaluate the potential of compounds as efficient antibacterial reagent. Further study of antibacterial mechanism was also carried out, including extracellular polysaccharide production, permeability of bacterial membrane, and scanning electron microscope observations. The excellent antibacterial activities of these compounds provided a strong support for its application for preventing and control plant diseases.

Mycoremediation of the novel fungicide ametoctradin by different agricultural soils and accelerated degradation utilizing selected fungal strains

Accelerating safety assessments for novel agrochemicals is imperative, advocating for in vitro setups to present pesticide biodegradation by soil microbiota before field studies. This approach enables metabolic profile generation in a controlled laboratory environment eliminating extrinsic factors. In the current study, ten different soil samples were utilized to check their capability to degrade Ametoctradin by their microbiota. Furthermore, five different fungal strains (Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Lasiodiplodia theobromae, and Penicillium chrysogenum) were utilized to degrade Ametoctradin in aqueous media. A degradation pathway was established using the metabolic patterns created during the biodegradation of Ametoctradin. In contrast to 47% degradation (T1/2 of 34 days) when Ametoctradin was left in the soil samples, the fungal strain Aspergillus fumigatus demonstrated 71% degradation of parent Ametoctradin with a half-life (T1/2) of 16 days. In conclusion, soil rich in microorganisms effectively cleans Ametoctradin-contaminated areas while Fungi have also been shown to be an effective, affordable, and promising way to remove Ametoctradin from the environment.

The Interaction Mechanism of Picolinamide Fungicide Targeting on the Cytochrome bc1 Complex and Its Structural Modification

Picolinamide fungicides, structurally related to UK-2A and antimycin-A, bind into the Qi-site in the bc1 complex. However, the detailed binding mode of picolinamide fungicides remains unknown. In the present study, antimycin-A and UK-2A were selected to study the binding mode of picolinamide inhibitors with four protonation states in the Qi-site by integrating molecular dynamics simulation, molecular docking, and molecular mechanics Generalized Born surface area (MM/GBSA) calculations. Subsequently, a series of new picolinamide derivatives were designed and synthesized to further understand the effects of substituents on the tail phenyl ring. The computational results indicated that the substituted aromatic rings in antimycin-A and UK-2A were the pharmacophore fragments and made the primary contribution when bound to a protein. Compound 9g-hydrolysis formed H-bonds with Hie201 and Ash228 and showed an IC50 value of 6.05 ± 0.24 μM against the porcine bc1 complex. Compound 9c, with a simpler chemical structure, showed higher control effects than florylpicoxamid against cucumber downy mildew and expanded the fungicidal spectrum of picolinamide fungicides. The structural and mechanistic insights obtained from the present study will provide a valuable clue for the future designing of new promising Qi-site inhibitors.

Nickel Catalyzed Selective Arylation of Geminal Dinitriles: Direct Access to α-Cyano Carbonyl Compounds

The catalytic intermolecular arylation of disubstituted geminal dinitriles with in situ generated arylnickel complexes is disclosed. This method efficiently provides various all-carbon substituted α-cyanocarbonyl compounds without additives and an inert atmosphere. It also demonstrates the arylation of R-BINOL and S-BINOL derived geminal dinitriles, preserving optical purity. Mechanistic studies proved that the in situ generated organonickel complex is involved in arylation.

Natural terpene-based derivatives to control postharvest sclerotinia rot and the involved potential mechanism

In an effort to develop novel postharvest preservatives of satisfactory environmental compatibility from natural monoterpene, a series of terpene-based derivatives containing oxime ester were designed and prepared. In this research, the inhibitory effect of target compounds against S. sclerotiorum were evaluated though in vitro and in vivo tests. It was investigated that most compounds exhibited promising antifungal activity, especially compound 4k with EC50 value of 3.02 μg/mL, which was significantly superior to commercial fungicide trifloxystrobin. Notably, compound 4k improved the physicochemical quality of carrot including weight loss, contents of titratable acidity, ascorbic acid, carotenoid, malondialdehyde, and enzymes activities, ensuring post-harvest preservation. Simultaneously, the mycelial morphology, ultrastructure, cell wall permeability, and defense/respiration-related enzymes of S. sclerotiorum were destructed. The preliminary toxicity evaluation of target compounds indicated that the prepared target compounds possessed safety and low toxicity. Additionally, the essential chemical features for activity and interaction mode between molecule and cytochrome bc1 complex were inquired by computer-aid technology. The study provided meaningful insight into formulation of natural terpene-based fresh-keeping agent to resist postharvest decay infected by S. sclerotiorum.

Ametoctradin resistance risk and its resistance-related point mutation in PsCytb of Phytophthora sojae confirmed using ectopic overexpression

Ametoctradin is mainly used to treat plant oomycetes diseases, but the mechanism and resistance risk of ametoctradin in Phytophthora sojae remain unknown. This study determined the ametoctradin sensitivity of 106 P. sojae isolates and found that the frequency distribution of the median effective concentration (EC50) of ametoctradin was unimodal with a mean value of 0.1743 ± 0.0901 μg/mL. Furthermore, ametoctradin-resistant mutants had a substantially lower fitness index compared with that of wild-type isolates. Although ametoctradin did not show cross-resistance to other fungicides, negative cross-resistance to amisulbrom was found. In comparison to sensitive isolates, the control efficacy of ametoctradin to resistant mutants was lower, implying a low to moderate ametoctradin resistance risk in P. sojae. All ametoctradin-resistant mutants contained a S33L point mutation in PsCytb. A system with overexpression of PsCytb in the nucleus was established. When we ectopically overexpressed S33L-harboring PsCytb, P. sojae developed ametoctradin resistance. We hypothesized that the observed negative resistance between ametoctradin and amisulbrom could be attributed to conformational changes in the binding cavity of PsCytb at residues 33 and 220.

Prediction of drug-induced mitochondrial dysfunction using succinate-cytochrome c reductase activity, QSAR and molecular docking

There is increasing evidence that links mitochondrial off-target effects with organ toxicities. For this reason, predictive strategies need to be developed to identify mitochondrial dysfunction early in the drug discovery process. In this study, as a major mechanism of mitochondrial toxicity, first, the inhibitory activity of 35 compounds against succinate-cytochrome c reductase (SCR) was investigated. This in vitro study led to the generation of consistent experimental data for a diverse range of compounds, including pharmaceutical drugs and fungicides. Next, molecular docking and protein-ligand interaction fingerprinting (PLIF) analysis were used to identify significant residues and protein-ligand interactions for the Q_o site of complex III and Q site of complex II. Finally, this data was used for the development of QSAR models using a regression-based approach to highlight structural and chemical features that might be responsible for SCR inhibition. The statistically validated QSAR models from this work highlighted the importance of low aqueous solubility, low ionisation, fewer 6-membered rings and shorter hydrocarbon alkane chains in the molecular structure for increased inhibition of SCR, hence mitochondrial toxicity. PLIF analysis highlighted two key residues for inhibitory activity of the Q_o site of complex III: His 161 as H-bond acceptor and Pro 270 for arene interactions. Currently, there are limited structure-activity models published in the scientific literature for the prediction of mitochondrial toxicity. We believe this study helps shed light on the chemical space for the inhibition of mitochondrial electron transport chain (ETC).

Efficacy of Fungicides Used to Manage Downy Mildew in Cucumber Assessed with Multiple Meta-Analysis Techniques

A nationwide, quantitative synthesis of fungicide efficacy data on management of cucurbit downy mildew (CDM) caused by Pseudoperonospora cubensis is needed to broadly evaluate fungicide performance. Three-level meta-analysis, three-level meta-regression, and network meta-analyses were conducted on data from 46 cucumber (Cucumis sativus) CDM fungicide efficacy studies conducted in the eastern United States retrieved from Plant Disease Management Reports published between 2009 and 2018. Three response variables were examined in each analysis: disease severity, marketable yield, and total yield, from which percent disease control and percent yield return compared with nontreated controls was calculated. Moderator variables used in the three-level meta-analysis or three-level meta-regression included year, disease pressure, number of fungicide applications, and slicing or pickling cucumbers. In the network meta-analysis, fungicides were grouped by common combinations of Fungicide Resistance Action Committee Codes and modes of action. Overall, fungicides significantly (P < 0.001) reduced disease severity and increased marketable and total yields, resulting in a mean 54.0% disease control and 61.9% marketable and 73.3% total yield return. Subgroup differences were observed for several fungicide applications, control plot disease severity, and cucumber type for marketable yield. Based on the meta-regression analysis for disease severity by year, fungicide efficacy has been decreasing from 2009 to 2018, potentially indicating broad development of fungicide resistance over time. Treatments containing quinone inside inhibitors, pyridinylmethyl-benzamides, and protectants and treatments containing oxysterol binding protein inhibitors and protectants most effectively reduced disease severity. The most effective fungicide combinations for disease control did not always result in the highest yield return.

Discovery of Novel Cytochrome bc1 Complex Inhibitor Based on Natural Product Neopeltolide

Background:

Natural products (NPs) are important sources for the design of new drugs and agrochemicals. Neopeltolide, a marine NP, has been identified as a potent Qo-site inhibitor of cytochrome bc1 complex.

Methods:

In this study, a series of neopeltolide derivatives was designed and synthesized by the simplification of its 14-membered macrolactone ring with a diphenyl ether fragment. The enzymatic inhibition bioassays and mycelium growth inhibition experiments against a range of fungi were performed to determine their fungicidal activities.

Results:

The derivatives have potent activity against the porcine bc1 complex. Compound 8q showed the best activity with an IC50 value of 24.41 nM, which was 8-fold more effective than that of positive control azoxystrobin. Compound 8a exhibited a 100% inhibitory rate against Zymoseptoria tritici and Alternaria solani at a 20 mg/L dose.

Conclusion:

Computational results indicated that compounds with suitable physicochemical properties, as well as those forming a hydrogen bond with His161, would have good fungicidal activity. These data could be useful for the design of bc1 complex inhibitors in the future.

Discovery of Biphenyl-Sulfonamides as Novel β-N-Acetyl-d-Hexosaminidase Inhibitors via Structure-Based Virtual Screening

Novel insecticidal targets are always in demand due to the development of resistance. OfHex1, a β-N-acetyl-d-hexosaminidase identified in Ostrinia furnacalis (Asian corn borer), is involved in insect chitin catabolism and has proven an ideal target for insecticide development. In this study, structure-based virtual screening, structure simplification, and biological evaluation are used to show that compounds with a biphenyl-sulfonamide skeleton have great potential as OfHex1 inhibitors. Specifically, compounds 10k, 10u, and 10v have K_i values of 4.30, 3.72, and 4.56 μM, respectively, and thus, they are more potent than some reported nonglycosyl-based inhibitors such as phlegmacin B₁ (K_i = 26 μM), berberine (K_i = 12 μM), 2 (K_i = 11.2 μM), and 3 (K_i = 28.9 μM). Furthermore, inhibitory kinetic assessments reveal that the target compounds are competitive inhibitors with respect substrate, and based on toxicity predictions, most of them have potent drug properties. The obtained results indicate that the biphenyl-sulfonamide skeleton characterized by simple chemical structure, synthetic tractability, potent activity, and low toxicity has potential for further development in pest management targeting OfHex1.

Expanding the Chemical Space of Succinate Dehydrogenase Inhibitors via the Carbon-Silicon Switch Strategy

The carbon-silicon switch strategy has become a key technique for structural optimization of drugs to widen the chemical space, increase drug activity against targeted proteins, and generate novel and patentable lead compounds. Flubeneteram, targeting succinate dehydrogenase (SDH), is a promising fungicide candidate recently developed in China. We describe the synthesis of novel SDH inhibitors with enhanced fungicidal activity to enlarge the chemical space of flubeneteram by employing the C-Si switch strategy. Several of the thus formed flubeneteram-silyl derivatives exhibited improved fungicidal activity against porcine SDH compared with the lead compound flubeneteram and the positive controls. Disease control experiments conducted in a greenhouse showed that trimethyl-silyl-substituted compound W2 showed comparable and even higher fungicidal activities compared to benzovindiflupyr and flubeneteram, respectively, even with a low concentration of 0.19 mg/L for soybean rust control. Furthermore, compound W2 encouragingly performed slightly better control than azoxystrobin and was less active than benzovindiflupyr at the concentration of 100 mg/L against soybean rust in field trials. The computational results showed that the silyl-substituted phenyl moiety in W2 could form strong van der Waals (VDW) interactions with SDH. Our results indicate that the C-Si switch strategy is an effective method for the development of novel SDH inhibitors.

Catalytic Reactions and Energy Conservation in the Cytochrome bc1 and b6f Complexes of Energy-Transducing Membranes

This review focuses on key components of respiratory and photosynthetic energy-transduction systems: the cytochrome bc1 and b6f (Cytbc1/b6f) membranous multisubunit homodimeric complexes. These remarkable molecular machines catalyze electron transfer from membranous quinones to water-soluble electron carriers (such as cytochromes c or plastocyanin), coupling electron flow to proton translocation across the energy-transducing membrane and contributing to the generation of a transmembrane electrochemical potential gradient, which powers cellular metabolism in the majority of living organisms. Cytsbc1/b6f share many similarities but also have significant differences. While decades of research have provided extensive knowledge on these enzymes, several important aspects of their molecular mechanisms remain to be elucidated. We summarize a broad range of structural, mechanistic, and physiological aspects required for function of Cytbc1/b6f, combining textbook fundamentals with new intriguing concepts that have emerged from more recent studies. The discussion covers but is not limited to (i) mechanisms of energy-conserving bifurcation of electron pathway and energy-wasting superoxide generation at the quinol oxidation site, (ii) the mechanism by which semiquinone is stabilized at the quinone reduction site, (iii) interactions with substrates and specific inhibitors, (iv) intermonomer electron transfer and the role of a dimeric complex, and (v) higher levels of organization and regulation that involve Cytsbc1/b6f. In addressing these topics, we point out existing uncertainties and controversies, which, as suggested, will drive further research in this field.

Selective Synthesis of β-Ketonitriles via Catalytic Carbopalladation of Dinitriles

A practical, convenient, and highly selective method of synthesizing β-ketonitriles from the Pd-catalyzed addition of organoboron reagents to dinitriles has been developed. This method provides excellent functional-group tolerance, a broad scope of substrates, and the convenience of using commercially available substrates. The method is expected to show further utility in future synthetic procedures.

Design, synthesis, and fungicidal evaluation of novel oxysterol binding protein inhibitors for combatting resistance associated with oxathiapiprolin

Oxathiapiprolin, the first successful oxysterol binding protein (OSBP) inhibitor for oomycete control, is regarded as an important milestone in the history of fungicide discovery. However, its interaction with OSBP remain unclear. Moreover, some plant pathogenic oomycetes have developed medium to high resistance to oxathiapiprolin. In this paper, the three-dimensional (3D) structure of OSBP from Phytophthora capsici (pcOSBP) was built, and its interaction with oxathiapiprolin was systematically investigated by integrating molecular docking, molecular dynamics simulations, and molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) calculations. The computational results showed that oxathiapiprolin bound to pcOSBP forms H-bonds with Leu73, Lys74, Ser69, and water molecules. Then, based on its interaction with pcOSBP, oxathiapiprolin was structurally modified to discover new analogs with high fungicidal activity and a low risk of resistance. Fortunately, compound 1e was successfully designed and synthesized as the most potent candidate, and it showed a much lower resistance risk (RF < 1) against LP3-M and LP3-H in P. capsici. The present work indicated that the piperidinyl-thiazole-isoxazoline moiety is useful for further optimization. Furthermore, compound 1e could be used as a lead compound for the discovery of new OSBP inhibitors.

Diacetoxy iodobenzene mediated regioselective synthesis and characterization of novel [1,2,4]triazolo[4,3-a]pyrimidines: apoptosis inducer, antiproliferative activities and molecular docking studies

Prompt and regioselective synthesis of eleven novel [1,2,4]triazolo[4,3-a]pyrimidines 2a-2k, via intramolecular oxidative-cyclization of 2-(2-arylidenehydrazinyl)-4-methyl-6-phenylpyrimidine derivatives 1a-1k has been demonstrated here using diacetoxy iodobenzene (DIB) as inexpensive and ecofriendly hypervalent iodine(III) reagent in CH₂Cl₂ at room temperature. Regiochemistry of final product has been established by developing single crystal and studied X-ray crystallographic data for two derivatives 2c and 2h without any ambiguity. These prominent [1,2,4]triazolo[4,3-a]pyrimidines were evaluated for human osteosarcoma bone cancer (MG-63) and breast cancer (MCF-7) cell lines using MTT assay to find potent antiproliferative agent and also on testicular germ cells to find potent apoptotic inducing activities. All compounds show significant cytotoxicity, particularly 3-(2,4-dichlorophenyl)-5-methyl-7-phenyl-[1,2,4]triazolo[4,3-a]pyrimidine (2g) was found significant apoptotic inducing molecule, as well as the most potent cytotoxic agent against bone cancer (MG-63) and breast cancer (MCF-7) cell lines with GI₅₀ value 148.96 µM and 114.3 µM respectively. Molecular docking studies has been carried out to see the molecular interactions of synthesized compounds with the protein thymidylate synthase (PBD ID: 2G8D).Communicated by Ramaswamy H. Sarma.

Design and synthesis of potent inhibitors of bc1 complex based on natural product neopeltolide

Neopeltolide, a natural product isolated from deep-water sponge specimen of the family neopeltidae, has been proven to be a novel inhibitor of cytochrome bc₁. In this study, a series of neopeltolide derivatives was designed by replacing the 14-membered macrolactone with indole ring and confirmed by ¹H NMR, ¹³C NMR, and HRMS. Based on the binding mode of 12h with bc₁ complex, the IC₅₀ values of compounds 16a-f (ranging from 0.70 to 1.46 μM) were improved significantly than the ester derivatives 12a-u by replacing the ester with amide linker. Subsequently, the molecular docking results indicated that compound 16e could form a π-π interaction with Phe274 and two H-bonds with Glu271 and His161 and the latter H-bond was found to account for its high activity. The present work accelerates the discovery of novel bc₁ complex inhibitors to deal with the resistance that the existing bc₁ complex inhibitors are facing and provides a valuable idea for the design of new fungicides.

Natural Product Neopeltolide as a Cytochrome bc1 Complex Inhibitor: Mechanism of Action and Structural Modification

The marine natural product neopeltolide was isolated from a deep-water sponge specimen of the family Neopeltidae. Neopeltolide has been proven to be a new type of inhibitor of the cytochrome bc₁ complex in the mitochondrial respiration chain. However, its detailed inhibition mechanism has remained unknown. In addition, neopeltolide is difficult to synthesize because of its very complex chemical structure. In the present work, the binding mode of neopeltolide was determined for the first time by integrating molecular docking, molecular dynamics simulations, and molecular mechanics Poisson-Boltzmann surface area calculations, which showed that neopeltolide is a Q_o site inhibitor of the bc₁ complex. Then, according to guidance via inhibitor-protein interaction analysis, structural modification was carried out with the aim to simplify the chemical structure of neopeltolide, leading to the synthesis of a series of new neopeltolide derivatives with much simpler chemical structures. The calculated binding energies (Δ G_cal) of the newly synthesized analogues correlated very well ( R² = 0.90) with their experimental binding free energies (Δ G_exp), which confirmed that the computational protocol was reliable. Compound 45, bearing a diphenyl ether fragment, was successfully designed and synthesized as the most potent candidate (IC₅₀ = 12 nM) against porcine succinate cytochrome c reductase. The molecular modeling results indicate that compound 45 formed a π-π interaction with Phe274 and two hydrogen bonds with Glu271 and His161. The present work provides a new starting point for future fungicide discovery to overcome the resistance that the existing bc₁ complex inhibitors are facing.

Features of interactions responsible for antifungal activity against resistant type cytochrome bc1: A data-driven analysis based on the binding free energy at the atomic level

Quinone outside inhibitors (QoIs), which inhibit the mitochondrial respiratory system by binding to the Qo site of Complex III in fungi, are widely used as pesticides with broad spectrum antifungal activity. However, excessive use of QoIs leads to pesticide resistance through mutation of amino acid residues in the Qo site. Recently, metyltetraprole, a novel QoI that is effective against wild-type and resistant mutant fungi, was developed. Interestingly, metyltetraprole has a very similar structure to other QoIs, azoxystrobin and pyraclostrobin, which do not act on resistant mutants. However, it is unknown how slight structural differences in these inhibitors alter their effectiveness towards fungi with amino acid mutations in the Qo site of Complex III. Therefore, we studied the features of interactions of inhibitors effective towards resistant mutants by quantitatively comparing the interaction profiles of three QoIs at the atomic level. First, we reproduced the binding affinity by the thermodynamic integration (TI) method, which treated explicitly environmental molecules and considered the pseudo-binding pathway. As such, a good correlation (R2 = 0.74) was observed between the binding free energy calculated using the TI method and experimentally observed pIC50 value in 12 inhibitor-target pairs, including wild-type and mutant Complex III in two fungal species, Zymoseptoria tritici and Pyrenophora teres. Trajectory analysis of this TI calculation revealed that the effectiveness against resistant mutant fungi strongly depended on the interaction of constituent parts of the inhibitor disposed near the active center of the target protein. Specifically, the key in the effectiveness against resistant mutant fungi is that the corresponding component part, tetrazolinone moiety of metyltetraprole, traded off Coulomb and van der Waals interactions in response to subtle changes in the binding pose.

Design, synthesis and fungicidal evaluation of novel pyraclostrobin analogues

A series of novel pyraclostrobin derivatives were designed and prepared as antifungal agents. Their antifungal activities were tested in vitro with five important phytopathogenic fungi, namely, Batrylis cinerea, Phytophthora capsici, Fusarium sulphureum, Gloeosporium pestis and Sclerotinia sclerotiorum using the mycelium growth inhibition method. Among these compounds, 5s displayed IC₅₀ value of 0.57 μg/mL against Batrylis cinerea and 5k-II displayed IC₅₀ value of 0.43 μg/mL against Sclerotinia sclerotiorum, which were close to that of the positive control pyraclostrobin (0.18 μg/mL and 0.15 μg/mL). Other compounds 5f, 5k-II, 5j, 5m and 5s also exhibited strong antifungal activity. Further enzymatic assay demonstrated compound 5s inhibited porcine bc₁ complex with IC₅₀ value of 0.95 μM. The statistical results from an integrated computational pipeline demonstrated the predicted total binding free energy for compound 5s is the highest. Consequently, compound 5s with the biphenyl-4-methoxyl side chain could serve as a new motif as inhibitors of bc₁ complex and deserve to be further investigated.

Recent Developments and Applications of the MMPBSA Method

The Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) approach has been widely applied as an efficient and reliable free energy simulation method to model molecular recognition, such as for protein-ligand binding interactions. In this review, we focus on recent developments and applications of the MMPBSA method. The methodology review covers solvation terms, the entropy term, extensions to membrane proteins and high-speed screening, and new automation toolkits. Recent applications in various important biomedical and chemical fields are also reviewed. We conclude with a few future directions aimed at making MMPBSA a more robust and efficient method.

Growth inhibition of fungus Phycomyces blakesleeanus by anion channel inhibitors anthracene-9-carboxylic and niflumic acid attained through decrease in cellular respiration and energy metabolites

Increasing resistance of fungal strains to known fungicides has prompted identification of new candidates for fungicides among substances previously used for other purposes. We have tested the effects of known anion channel inhibitors anthracene-9-carboxylic acid (A9C) and niflumic acid (NFA) on growth, energy metabolism and anionic current of mycelium of fungus Phycomyces blakesleeanus. Both inhibitors significantly decreased growth and respiration of mycelium, but complete inhibition was only achieved by 100 and 500 µM NFA for growth and respiration, respectively. A9C had no effect on respiration of human NCI-H460 cell line and very little effect on cucumber root sprout clippings, which nominates this inhibitor for further investigation as a potential new fungicide. Effects of A9C and NFA on respiration of isolated mitochondria of P. blakesleeanus were significantly smaller, which indicates that their inhibitory effect on respiration of mycelium is indirect. NMR spectroscopy showed that both A9C and NFA decrease the levels of ATP and polyphosphates in the mycelium of P. blakesleeanus, but only A9C caused intracellular acidification. Outwardly rectifying, fast inactivating instantaneous anionic current (ORIC) was also reduced to 33±5 and 21±3 % of its pre-treatment size by A9C and NFA, respectively, but only in the absence of ATP. It can be assumed from our results that the regulation of ORIC is tightly linked to cellular energy metabolism in P. blakesleeanus, and the decrease in ATP and polyphosphate levels could be a direct cause of growth inhibition.

Discovery of cytochrome bc1 complex inhibitors inspired by the natural product karrikinolide

Novel and potent inhibitors targeting the cytochrome bc₁ complex were discovered from the natural product karrikinolide for the first time.

The Novel Oomycide Oxathiapiprolin Inhibits All Stages in the Asexual Life Cycle of Pseudoperonospora cubensis - Causal Agent of Cucurbit Downy Mildew

Oxathiapiprolin is a new oomycide (piperidinyl thiazole isoxazoline class) discovered by DuPont which controls diseases caused by oomycete plant pathogens. It binds in the oxysterol-binding protein domain of Oomycetes. Growth chambers studies with detached leaves and potted plants showed remarkable activity of oxathiapiprolin against Pseudoperonospora cubensis in cucurbits. The compound affected all stages in the asexual life cycle of the pathogen. It inhibited zoospore release, cystospore germination, lesion formation, lesion expansion, sporangiophore development and sporangial production. When applied to the foliage as a preventive spray no lesions developed due to inhibition of zoospore release and cystospore germination, and when applied curatively, at one or two days after inoculation, small restricted lesions developed but no sporulation occurred. When applied later to mature lesions, sporulation was strongly inhibited. Oxathiapiprolin suppressed sporulation of P. cubensis in naturally-infected leaves. It exhibited trans-laminar activity, translocated acropetaly from older to younger leaves, and moved from the root system to the foliage. Seed coating was highly effective in protecting the developed cucumber plants against downy mildew. UV microscopy observations made with cucumber leaves infected with P. cubensis revealed that inhibition of mycelium growth and sporulation induced by oxathiapiprolin was associated with callose encasement of the haustoria.