Novel Sulfoximine Derivatives Containing Cyanoguanidine and Nitroguanidine Moieties: Design, Synthesis, and Bioactivities

A total of 32 novel sulfoximines bearing cyanoguanidine and nitroguanidine moieties were designed and synthesized by a rational molecule design strategy. The bioactivities of the title compounds were evaluated and the results revealed that some of the target compounds possessed excellent antifungal activities against six agricultural fungi, including Sclerotinia sclerotiorum, Fusarium graminearum, Phytophthora capsici, Botrytis cinerea, Rhizoctonia solani, and Pyricularia grisea. Among them, compounds 8e1 and 8e4 exhibited significant efficacy against P. grisea with EC50 values of 2.72 and 2.98 μg/mL, respectively, which were much higher than that of commercial fungicides boscalid (47.95 μg/mL). Interestingly, in vivo assays determined compound 8e1 possessed outstanding activity against S. sclerotiorum with protective and curative effectiveness of 98 and 95.6% at 50 μg/mL, which were comparable to those of boscalid (93.2, 91.9%). The further preliminary mechanism investigation disclosed that compound 8e1 could damage the structure of the cell membrane of S. sclerotiorum, increase its permeability, and suppress its growth. Overall, the findings enhanced that these novel sulfoximine derivatives could be potential lead compounds for the development of new fungicides.

Eudistomins Y-Inspired Design and Divergent Optimization of Heteroaryl Ketones for New Antifungal Leads

The discovery of structurally distinct leads is imperative in modern agrochemical science. Inspired by eudistomins Y and the framework-related pharmaceuticals, aryl heteroaryl ketone was drawn as a common model intriguing the design and divergent synthesis of 14 kinds of heteroaryl ketones aligned with their oxime derivatives. Antifungal function-oriented phenotypical screen protruded benzothiazolyl-phenyl oxime 5a as a promising model, and the concomitant modification led to benzothiazolyl oxime 5am (EC50 = 5.17 μM) as a superior lead than fluoxastrobin (EC50 = 7.54 μM) against Sclerotinia sclerotiorum. Scaffold hopping of the phenyl subunit identified benzothiazolyl-pyridyl oxime as a novel antifungal scaffold accompanied by acquiring oxime 5bm with remarkable activity (EC50 = 3.57 μM) against Pyricularia oryzae. Molecular docking showed that candidate 5am could form more hydrogen bonds with the amino acid residues of actin than metrafenone. This compound also demonstrated better curative efficacy than that of fluoxastrobin and metrafenone in controlling the plant disease caused by S. sclerotiorum. These results rationalize the discovery of antifungal candidates based on aryl heteroaryl ketone.

Molecular Mechanistic Insights into Dipeptidyl Peptidase-IV Inhibitory Peptides to Decipher the Structural Basis of Activity

Dipeptidyl peptidase-IV (DPP-IV) inhibiting peptides have attracted increased attention because of their possible beneficial effects on glycemic homeostasis. However, the structural basis underpinning their activities has not been well understood. This study combined computational and in vitro investigations to explore the structural basis of DPP-IV inhibitory peptides. We first superimposed the Xaa-Pro-type peptide-like structures from several crystal structures of DPP-IV ligand-protein complexes to analyze the recognition interactions of DPP-IV to peptides. Thereafter, a small set of Xaa-Pro-type peptides was designed to explore the effect of key interactions on inhibitory activity. The intramolecular interaction of Xaa-Pro-type peptides at the first and third positions from the N-terminus was pivotal to their inhibitory activities. Residue interactions between DPP-IV and residues of the peptides at the fourth and fifth positions of the N-terminus contributed significantly to the inhibitory effect of Xaa-Pro-type tetrapeptides and pentapeptides. Based on the interaction descriptors, quantitative structure-activity relationship (QSAR) studies with the DPP-IV inhibitory peptides resulted in valid models with high R2 values (0.90 for tripeptides; 0.91 for tetrapeptides and pentapeptides) and Q2 values (0.33 for tripeptides; 0.68 for tetrapeptides and pentapeptides). Taken together, the structural information on DPP-IV and peptides in this study facilitated the development of novel DPP-IV inhibitory peptides.

Site-Specifically Modified Peptide Inhibitors of Protein Tyrosine Phosphatase 1B and T-Cell Protein Tyrosine Phosphatase with Enhanced Stability and Improved In Vivo Long-Acting Activity

Protein tyrosine phosphatase 1B (PTP1B) and TC-PTP can function in a coordinated manner to regulate diverse biological processes including insulin and leptin signaling, T-cell activation, and tumor antigen presentation, which makes them potential targets for several therapeutic applications. We have previously demonstrated that the lipidated BimBH3 peptide analogues were a new class of promising PTP1B inhibitors with once-weekly antidiabetic potency. Herein, we chemically synthesized two series of BimBH3 analogues via site-specific modification and studied their structure-activity relationship. The screened analogues S2, S6, A2-14, A2-17, A2-20, and A2-21 exhibited an improved PTP1B/TC-PTP dual inhibitory activity and achieved good stability in the plasma of mice and dogs, which indicated long-acting potential. In mouse models of type 2 diabetes mellitus (T2DM), the selected analogues S6, S7, A2-20, and A2-21 with an excellent target activity and plasma stability generated once-weekly therapeutic potency for T2DM at lower dosage (0.5 μmol/kg). In addition, evidence was provided to confirm the cell permeability and targeted enrichment of the BimBH3 analogues. In summary, we report here that site-specific modification and long fatty acid conjugation afforded cell-permeable peptidomimetic analogues of BimBH3 with enhanced stability, in vivo activity, and long-acting pharmacokinetic profile. Our findings could guide the further optimization of BimBH3 analogues and provide a proof-of-concept for PTP1B/TC-PTP targeting as a new therapeutic approach for T2DM, which may facilitate the discovery and development of alternative once-weekly anti-T2DM drug candidates.

Design, Synthesis, Antibacterial Activity, and Mechanisms of Novel Benzofuran Derivatives Containing Disulfide Moieties

The unsatisfactory effects of conventional bactericides and antimicrobial resistance have increased the challenges in managing plant diseases caused by bacterial pests. Here, we report the successful design and synthesis of benzofuran derivatives using benzofuran as the core skeleton and splicing the disulfide moieties commonly seen in natural substances with antibacterial properties. Most of our developed benzofurans displayed remarkable antibacterial activities to frequently encountered pathogens, including Xanthomonas oryzae pv oryzae (Xoo), Xanthomonas oryzae pv oryzicola (Xoc), and Xanthomonas axonopodis pv citri (Xac). With the assistance of the three-dimensional quantitative constitutive relationship (3D-QSAR) model, the optimal compound V40 was obtained, which has better in vitro antibacterial activity with EC50 values of 0.28, 0.56, and 10.43 μg/mL against Xoo, Xoc, and Xac, respectively, than those of positive control, TC (66.41, 78.49, and 120.36 μg/mL) and allicin (8.40, 28.22, and 88.04 μg/mL). Combining the results of proteomic analysis and enzyme activity assay allows the antibacterial mechanism of V40 to be preliminarily revealed, suggesting its potential as a versatile bactericide in combating bacterial pests in the future.

Design, Synthesis, and Herbicidal Evaluation of Pyrrolidinone-Containing 2-Phenylpyridine Derivatives as Novel Protoporphyrinogen Oxidase Inhibitors

In this work, a series of pyrrolidinone-containing 2-phenylpyridine derivatives were synthesized and evaluated as novel protoporphyrinogen IX oxidase (PPO, EC 1.3.3.4) inhibitors for herbicide development. At 150 g ai/ha, compounds 4d, 4f, and 4l can inhibit the grassy weeds of Echinochloa crus-galli (EC), Digitaria sanguinalis (DS), and Lolium perenne (LP) with a range of 60 to 90%. Remarkably, at 9.375 g ai/ha, these compounds showed 100% inhibition effects against broadleaf weeds of Amaranthus retroflexus (AR) and Abutilon theophrasti (AT), which were comparable to the performance of the commercial herbicides flumioxazin (FLU) and saflufenacil (SAF) and better than that of acifluorfen (ACI). Molecular docking analyses revealed significant hydrogen bonding and π-π stacking interactions between compounds 4d and 4l with Arg98, Asn67, and Phe392, respectively. Additionally, representative compounds were chosen for in vivo assessment of PPO inhibitory activity, with compounds 4d, 4f, and 4l demonstrating excellent inhibitory effects. Notably, compounds 4d and 4l induced the accumulation of reactive oxygen species (ROS) and a reduction in the chlorophyll (Chl) content. Consequently, compounds 4d, 4f, and 4l are promising lead candidates for the development of novel PPO herbicides.

Design, Synthesis, Antifungal Activity, and Molecular Docking Studies of Novel Chiral Isoxazoline-Benzofuran-Sulfonamide Derivatives

Succinate dehydrogenase (SDH) is one of the most important molecular targets for the development of novel fungicides. With the emerging problem of resistance in plant fungal pathogens, novel compounds with high fungicidal activity need to be developed, but the study of chiral pesticides for the inhibition of highly destructive plant pathogens has been rarely reported in recent years. Therefore, a series of novel chiral isoxazoline-benzofuran-sulfonamide derivatives were designed to investigate potential novel antifungal molecules. The chiral target compound 3a was cultured as a single crystal and confirmed using X-ray diffraction. All the target compounds were tested for antifungal activity, and compounds 3c, 3i, 3s, and 3r were found to have significant antifungal effects against S. sclerotiorum with EC50 values of 0.42 mg/L, 0.33 mg/L, 0.37 mg/L, and 0.40 mg/L, respectively, which were superior to the commercial fungicide fluopyram (EC50 = 0.47 mg/L). The IC50 value of compound 3i against the SDH of S. sclerotiorum was 0.63 mg/mL, which was further demonstrated by enzyme activity assays. Scanning electron microscopy showed that 3i had a significant inhibitory effect on S. sclerotiorum. In addition, the fluorescence quenching analysis assay indicated that compound 3i had a similar effect with the positive control fluopyram. Molecular docking exhibited that target compounds with chiral configuration had better affinity than racemic configuration, and 3i possessed stronger action than fluopyram, which was in keeping with the in vitro test results. These results would provide a basis and reference for the development of novel chiral fungicides.

Potent Inhibition of E. coli DXP Synthase by a gem-Diaryl Bisubstrate Analog

New antimicrobial strategies are needed to address pathogen resistance to currently used antibiotics. Bacterial central metabolism is a promising target space for the development of agents that selectively target bacterial pathogens. 1-Deoxy-d-xylulose 5-phosphate synthase (DXPS) converts pyruvate and d-glyceraldehyde 3-phosphate (d-GAP) to DXP, which is required for synthesis of essential vitamins and isoprenoids in bacterial pathogens. Thus, DXPS is a promising antimicrobial target. Toward this goal, our lab has demonstrated selective inhibition of Escherichia coli DXPS by alkyl acetylphosphonate (alkylAP)-based bisubstrate analogs that exploit the requirement for ternary complex formation in the DXPS mechanism. Here, we present the first DXPS structure with a bisubstrate analog bound in the active site. Insights gained from this cocrystal structure guided structure-activity relationship studies of the bisubstrate scaffold. A low nanomolar inhibitor (compound 8) bearing a gem-dibenzyl glycine moiety conjugated to the acetylphosphonate pyruvate mimic via a triazole-based linker emerged from this study. Compound 8 was found to exhibit slow, tight-binding inhibition, with contacts to E. coli DXPS residues R99 and R478 demonstrated to be important for this behavior. This work has discovered the most potent DXPS inhibitor to date and highlights a new role of R99 that can be exploited in future inhibitor designs toward the development of a novel class of antimicrobial agents.

Synthesis, Stereochemical Resolution, and Analogue Synthesis of Variabiline, an Aporphine Alkaloid That Sensitizes Acinetobacter baumannii and Klebsiella pneumoniae to Colistin

Increasing antimicrobial resistance, coupled with the absence of new antibiotics, has led physicians to rely on colistin, a polymyxin with known nephrotoxicity, as the antibiotic of last resort for the treatment of infections caused by Gram-negative bacteria. One approach to increasing antibiotic efficacy and thereby reducing dosage is the use of small-molecule potentiators that augment antibiotic activity. We recently identified the aporphine alkaloid (±)-variabiline, which lowers the minimum inhibitory concentration of colistin in Acinetobacter baumannii and Klebsiella pneumoniae. Herein, we report the first total synthesis of (±)-variabiline to confirm structure and activity, the resolution, and evaluation of both enantiomers as colistin potentiators, and a structure-activity relationship study that identifies more potent variabiline derivatives. Preliminary mechanistic studies indicate that (±)-variabiline and its derivatives potentiate colistin by targeting the Gram-negative outer membrane.

Potential Mechanisms of Casein Hexapeptide YPVEPF on Stress-Induced Anxiety and Insomnia Mice and Its Molecular Effects and Key Active Structure

The hexapeptide YPVEPF with strong sleep-enhancing effects could be detected in rat brain after a single oral administration as we previously proved. In this study, the mechanism and molecular effects of YPVEPF in the targeted stress-induced anxiety mice were first investigated, and its key active structure was further explored. The results showed that YPVEPF could significantly prolong sleep duration and improve the anxiety indexes, including prolonging the time spent in the open arms and in the center. Meanwhile, YPVEPF showed strong sleep-enhancing effects by significantly increasing the level of the GABA/Glu ratio, 5-HT, and dopamine in brain and serum and regulating the anabolism of multiple targets, but the effects could be blocked by bicuculline and WAY100135. Moreover, the molecular simulation results showed that YPVEPF could stably bind to the vital GABAA and 5-HT1A receptors due to the vital structure of Tyr-Pro-Xaa-Xaa-Pro-, and the electrostatic and van der Waals energy played dominant roles in stabilizing the conformation. Therefore, YPVEPF displayed sleep-enhancing and anxiolytic effects by regulating the GABA-Glu metabolic pathway and serotoninergic system depending on distinctive self-folding structures with Tyr and two Pro repeats.

Design and Discovery of α-Oximido-arylacetamides as Novel Antifungal Leads

The discovery of novel and easily accessible antifungal compounds is an imperative issue in agrochemical innovation. Our continuing research with the o-aminophenyloxazoline (NHPhOx) scaffold demonstrated the viability of introducing phenylacetamides for identifying novel antifungal leads. An antifungal function-oriented molecular evaluation was conducted for the previously identified lead R-LE008. Fine-tuning of the α-position and scaffold hopping of acid segment and NHPhOx enables α-oximido-arylacetamide as a novel antifungal model. The concomitant function-oriented diversification produces a panel of antifungal leads CN19, CN21b, CN28, and CN31 against Sclerotinia sclerotiorum and Botrytis cinerea. The crucial and multidimensional effect of the configuration of the acquired amides on the antifungal performance is demonstrated specifically by the separable CN21 isomers. The Z-isomer (CN21b), with an EC50 value of 0.97 μM against B. cinerea, is significantly more potent than its E-isomer (CN21a) and the positive control boscalid. More importantly, compound CN21b can efficiently inhibit resistant B. cinerea strains. CN21b demonstrates a better in vivo preventative effect (82.1%) than those of CN21a (48.1%) and boscalid (55.1%) at 100 μM. CN21b showed a distinct binding model from those of the boscalid and CN21a in the molecular docking simulation. A further morphological investigation by scanning electron microscopy revealed the different mycelia shrinkage of B. cinerea treated by CN21 isomers. The easy accessibility and cost-effectiveness demonstrated the practical potential of α-oximido-phenylacetamide containing NHPhOx as a new model for agrochemical innovation.

Design and Enantioselective Synthesis of Chiral Pyranone Fused Indole Derivatives with Antibacterial Activities against Xanthomonas oryzae pv oryzae for Protection of Rice

A new class of chiral pyranone fused indole derivatives were prepared by means of N-heterocyclic carbene (NHC) organocatalysis and demonstrated notable antibacterial activity against Xanthomonas oryzae pv oryzae (Xoo). Bioassays showed that compounds (3S,4R)-5b, (3S,4R)-5d, and (3S,4R)-5l exhibited promising in vitro efficacy against Xoo, with EC50 values of 9.05, 9.71, and 5.84 mg/L, respectively, which were superior to that of the positive controls with commercial antibacterial agents, bismerthiazol (BT, EC50 = 27.8 mg/L) and thiodiazole copper (TC, EC50 = 70.1 mg/L). Furthermore, single enantiomer (3S,4R)-5l was identified as an optimal structure displaying 55.3% and 52.0% curative and protective activities against Xoo in vivo tests at a concentration of 200 mg/L, which slightly surpassed the positive control with TC (curative and protective activities of 47.2% and 48.8%, respectively). Mechanistic studies through molecular docking analysis revealed preliminary insights into the distinct anti-Xoo activity of the two single enantiomers (3S,4R)-5l and (3R,4S)-5l, wherein the (3S,4R)-configured stereoisomer could form a more stable interaction with XooDHPS (dihydropteroate synthase). These findings underscore the significant anti-Xoo potential of these chiral pyranone fused indole derivatives, and shall inspire further exploration as promising lead structures for a novel class of bactericides to combat bacterial infections and other plant diseases.

Advances in Separation, Biological Properties, and Structure-Activity Relationship of Triterpenoids Derived from Camellia oleifera Abel

Extensive research has been conducted on Camellia oleifera Abel., a cultivar predominantly distributed in China, to investigate its phytochemical composition, owning to its potential as an edible oil crop. Pentacyclic triterpene saponins, as essential active constituents, play a significant role in contributing to the pharmacological effects of this cultivar. The saponins derived from C. oleifera (CoS) offer a diverse array of bioactivity benefits, including antineoplastic/bactericidal/inflammatory properties, cardiovascular protection, neuroprotection, as well as hypoglycemic and hypolipidemic effects. This review presents a comprehensive analysis of the isolation and pharmacological properties of CoS. Specially, we attempt to reveal the antitumor structure-activity relationship (SAR) of CoS-derived triterpenoids. The active substitution sites of CoS, namely, C-3, C-15, C-16, C-21, C-22, C-23, and C-28 pentacyclic triterpenoids, make it a unique and highly valuable substance with significant medicinal and culinary applications. As such, CoS can play a critical role in transforming people's lives, providing unique medicinal benefits, and contributing to the advancement of both medicine and cuisine.

Nanoscale Luminescence Imaging/Detection of Single Particles: State-of-the-Art and Future Prospects

Single-particle-level measurements, during the reaction, avoid averaging effects that are inherent limitations of conventional ensemble strategies. It allows revealing structure-activity relationships beyond averaged properties by considering crucial particle-selective descriptors including structure/morphology dynamics, intrinsic heterogeneity, and dynamic fluctuations in reactivity (kinetics, mechanisms). In recent years, numerous luminescence (optical) techniques such as chemiluminescence (CL), electrochemiluminescence (ECL), and fluorescence (FL) microscopies have been emerging as dominant tools to achieve such measurements, owing to their diversified spectroscopy principles, noninvasive nature, higher sensitivity, and sufficient spatiotemporal resolution. Correspondingly, state-of-the-art methodologies and tools are being used for probing (real-time, operando, in situ) diverse applications of single particles in sensing, medicine, and catalysis. Herein, we provide a concise and comprehensive perspective on luminescence-based detection and imaging of single particles by putting special emphasis on their basic principles, mechanistic pathways, advances, challenges, and key applications. This Perspective focuses on the development of emission intensities and imaging based individual particle detection. Moreover, several key examples in the areas of sensing, motion, catalysis, energy, materials, and emerging trends in related areas are documented. We finally conclude with the opportunities and remaining challenges to stimulate further developments in this field.

Structurally Modified Polysaccharides: Physicochemical Properties, Biological Activities, Structure-Activity Relationship, and Applications

Polysaccharides are an important class of biomolecules derived from several sources. However, the inherent structure of polysaccharides prevents them from exhibiting favorable physicochemical properties, which restricts their development in agriculture, industry, food, and biomedicine. This paper systematically summarizes the changes in the primary and advanced structures of modified polysaccharides, and focuses on the effects of various modification methods on the hydrophobicity, rheological properties, emulsifying properties, antioxidant activity, hypoglycemic, and hypolipidemic activities of polysaccharides. Then there is a list the applications of modified polysaccharides in treating heavy metal pollutants, purifying water resources, improving beverage stability and bread quality, and precisely delivering the drug. When summarized and reviewed, the information above can shed further light on the relationship between polysaccharide structure and function. Determining the structure-activity relationship provides a scientific basis for the direction of molecular modifications of polysaccharides.

Critical Review of Pd-Catalyzed Reduction Process for Treatment of Waterborne Pollutants

Catalyzed reduction processes have been recognized as important and supplementary technologies for water treatment, with the specific aims of resource recovery, enhancement of bio/chemical-treatability of persistent organic pollutants, and safe handling of oxygenate ions. Palladium (Pd) has been widely used as a catalyst/electrocatalyst in these reduction processes. However, due to the limited reserves and high cost of Pd, it is essential to gain a better understanding of the Pd-catalyzed decontamination process to design affordable and sustainable Pd catalysts. This review provides a systematic summary of recent advances in understanding Pd-catalyzed reductive decontamination processes and designing Pd-based nanocatalysts for the reductive treatment of water-borne pollutants, with special focus on the interactions and transformation mechanisms of pollutant molecules on Pd catalysts at the atomic scale. The discussion begins by examining the adsorption of pollutants onto Pd sites from a thermodynamic viewpoint. This is followed by an explanation of the molecular-level reaction mechanism, demonstrating how electron-donors participate in the reductive transformation of pollutants. Next, the influence of the Pd reactive site structure on catalytic performance is explored. Additionally, the process of Pd-catalyzed reduction in facilitating the oxidation of pollutants is briefly discussed. The longevity of Pd catalysts, a crucial factor in determining their practicality, is also examined. Finally, we argue for increased attention to mechanism study, as well as precise construction of Pd sites under batch synthesis conditions, and the use of Pd-based catalysts/electrocatalysts in the treatment of concentrated pollutants to facilitate resource recovery.

Herbicide Safeners: From Molecular Structure Design to Safener Activity

Herbicide safeners, highly effective antidotes, find widespread application in fields for alleviating the phytotoxicity of herbicides to crops. Designing new herbicide safeners remains a notable issue in pesticide research. This review focuses on discussing and summarizing the structure-activity relationships, molecular structures, physicochemical properties, and molecular docking of herbicide safeners in order to explore how different structures affect the safener activities of target compounds. It also provides insights into the application prospects of computer-aided drug design for designing and synthesizing new safeners in the future.

Organic Semiconducting Polymers for Augmenting Biosynthesis and Bioconversion

Solar-driven biosynthesis and bioconversion are essential for achieving sustainable resources and renewable energy. These processes harness solar energy to produce biomass, chemicals, and fuels. While they offer promising avenues, some challenges and limitations should be investigated and addressed for their improvement and widespread adoption. These include the low utilization of light energy, the inadequate selectivity of products, and the limited utilization of inorganic carbon/nitrogen sources. Organic semiconducting polymers offer a promising solution to these challenges by collaborating with natural microorganisms and developing artificial photosynthetic biohybrid systems. In this Perspective, we highlight the latest advancements in the use of appropriate organic semiconducting polymers to construct artificial photosynthetic biohybrid systems. We focus on how these systems can enhance the natural photosynthetic efficiency of photosynthetic organisms, create artificial photosynthesis capability of nonphotosynthetic organisms, and customize the value-added chemicals of photosynthetic synthesis. By examining the structure-activity relationships and emphasizing the mechanism of electron transfer based on organic semiconducting polymers in artificial photosynthetic biohybrid systems, we aim to shed light on the potential of this novel strategy for artificial photosynthetic biohybrid systems. Notably, these coupling strategies between organic semiconducting polymers and organisms during artificial photosynthetic biohybrid systems will pave the way for a more sustainable future with solar fuels and chemicals.

2-Amino-5-arylethynyl-thiophen-3-yl-(phenyl)methanones as A1 Adenosine Receptor Positive Allosteric Modulators

A1 adenosine receptor (A1AR) agonists have cerebroprotective, cardioprotective, antinociceptive, and other pharmaceutical applications. We explored the structure-activity relationship of 5-arylethynyl aminothiophenes as A1AR positive allosteric modulators (PAMs). The derivatives were compared in binding and functional assays at the human A1AR, indicating that some fluoro-substituted analogues have enhanced PAM activity. We identified substitution of the terminal phenyl ring in 12 (2-F-Ph), 15 (3,4-F2-Ph, MRS7935), and 21 (2-CF3-Ph) as particularly enhancing the PAM activity. 15 was also shown to act as an A1 ago-PAM with EC50 ≈ 2 μM, without activity (30 μM) at other ARs. Molecular modeling indicated that both the 5-arylethynyl and the 4-neopentyl groups are located in a region outside the receptor transmembrane helix bundle that is in contact with the phospholipid bilayer, consistent with the preference for nonpolar substitution of the aryl moiety. Although they are hydrophobic, these PAMs could provide potential drug candidate molecules for engaging protective A1ARs.

N-Biphenyl Pyrrolinones and Dibenzofurans as RNA-Binding Protein LIN28 Inhibitors Disrupting the LIN28-Let-7 Interaction

The RNA-binding protein LIN28 is a regulator of miRNA let-7 biogenesis. Inhibitors of LIN28 are highly sought after given the central role that LIN28 plays in tumorigenesis and development of cancer stem cells as well as LIN28's association with poor clinical prognosis. Although LIN28 inhibitors of different scaffolds have been reported, the potential of most LIN28 inhibiting small molecules was not fully explored since very limited structure-activity relationship (SAR) studies have been performed. We previously identified trisubstituted pyrrolinones as a new class of LIN28 inhibitors disrupting the LIN28-let-7 interaction. Here, we performed extensive SAR by evaluating 95 small molecules and identified new trisubstituted pyrrolinones featuring either an N-biphenyl or N-dibenzofuran substituent, overthrowing the existing conclusion that a salicylic acid moiety is indispensable for activity. Exchange of the negatively charged salicylic acid moiety in LIN28 inhibitors with a heterocyclic substituent is beneficial for membrane permeability, leading to increased activity in a cellular assay, and will potentially reduce toxicity.

Structural and Functional Insights into the Biomineralized Zeolite Imidazole Frameworks

Biomineralization is a natural process of mineral formation mediated by biomacromolecules, allowing access to hierarchical structures integrating biological, chemical, and material properties. In this contribution, we comprehensively investigate the biomineralization of zeolite imidazole frameworks (ZIFs) for one-step synthesis of an enzyme-MOF biocomposite, in terms of differential crystallization behaviors, fine microstructure of resultant ZIF biominerals, the enzyme's conformation evolution, and protective effect of ZIF mineral. We discover that the biomineralization ability is ZIF organic linker dependent and the biocatalytic function is highly related to the ZIF mineral species and their distinguishable topologies and defect structures. Importantly, a side-by-side analysis suggests that the protective effect of ZIF mineral toward the hosted enzyme is highly associated with the synergistic effect of size dimension and chemical microenvironment of the ZIF pores. This work provides important insight into the ZIF-dependent biomineralization behaviors and highlights the important role of the ZIF microstructure in its biocatalytic activity and durability, which has been underestimated previously.

Synthesis and Insecticidal Activity Study of Azidopyridryl Containing Dichlorolpropene Ether Derivatives

Pyridalyl, as a novel insecticide with an unknown mode of action, has shown excellent control efficacy against lepidopterous larvae and thrips. Previous modifications of this compound have mostly focused on the pyridine moiety, with limited information available about modifications to other parts of pyridalyl. In this paper, we report the synthesis and insecticidal activity of a series of azidopyridryl-containing dichlorolpropene ether derivatives, based on modifications to the middle alkyl chain of pyridalyl. Screening results for insecticidal activity indicate that our synthesized compounds show moderate to high activities at the tested concentrations against P. xylostella. Particularly, compound III-10 exhibits a LC50 value of 0.831 mg L-1, compared to the LC50 value of pyridalyl at 2.021 mg L-1. Furthermore, compound III-10 also displays a relatively broad insecticidal spectrum against Lepidoptera pests M. separata, C. suppressalis, O. nubilalis, and C. medinalis. Finally, in field trials, III-10 demonstrates better control efficiency against Chilo suppressalis compared to pyridalyl. Overall, our findings suggest that the modification of the middle alkyl chain of pyridalyl may be a promising approach for developing insecticides with improved efficacy.

Antifungal Function Oriented Scaffold Hopping for the Discovery of Oxazolyl-oxazoline as a Novel Model against Fusarium graminearum

Discovery of novel structural models is extremely important in agrochemical innovation. Scaffold hopping was conducted, and 16 kinds of novel models were synthesized and biologically evaluated. Oxazolyl-oxazoline 25 showed a promising in vitro potential against Fusarium graminearum with EC50 value of 18.25 μM, which was 2.4 times more potent than that of carbendazim (EC50 = 43.06 μM). The antifungal structure-activity relationship (SAR) revealed that compound 25am had the most promising antifungal activity against F. graminearum, with an EC50 value of 13.46 μM, which was 3.2 more potent than that of carbendazim. Different from carbendazim, the candidate 25am could form five hydrogen bonds with the amino acid residues in β-tubulin in the molecular docking and could effectively inhibit the carbendazim-resistant F. graminearum strain. Scanning electron microscopy (SEM) revealed that compound 25am induced the mycelia of F. graminearum slight collapse. This work suggests that compound 25am should be prioritized for further evaluation for new antifungal agents.

Discovery of Fungicidal Hydrazide Lead Compounds Derived from Sinapic Acid and Mycophenolic Acid

Structure optimization based on natural products has become an effective way to develop new green fungicides. In this project, thirty-two novel NPs-derived hydrazide compounds were designed and synthesized by introducing the bioactive hydrazide substructure into sinapic acid and mycophenolic acid. The fungicidal bioassays indicated that the obtained hydrazide compounds showed excellent and selective fungicidal activity against specific pathogens, especially compounds C8, D7, and D8 with EC50 values of 0.63, 0.56, and 0.43 μg mL-1 against M. oryzae, respectively. SAR indicated that the introduction of 4-fluoro, 4-chloro, and 2,4-difluoro groups was conducive to improving the fungicidal activity, while the extension of the hydrazide bridge would affect the selectivity for inhibitory activity. Subsequently, the effects of hydrazide compounds on rice seedling and zebrafish growth were also investigated. The fungicidal mechanism implied that treatment with compound B4 would cause significant changes in metabolites of plasma membrane-related linolenic acid metabolism, arachidonic acid metabolism, and α-linolenic acid metabolism pathways, which further led to the wrinkled hyphae and the blurred plasma membrane and cytoplasm. Finally, the frontier molecular orbitals and charge distribution were calculated to analyze the differences in bioactivity from a structural perspective. These results provide important guidance for the development and practical application of novel fungicides.

The Chemistry Behind the Folin-Ciocalteu Method for the Estimation of (Poly)phenol Content in Food: Total Phenolic Intake in a Mediterranean Dietary Pattern

The Folin-Ciocalteu assay is a reference method for the quantification of total (poly)phenols in food. This review explains the fundamental mechanism of the redox reaction on which the method is based and looks at some of the practical considerations concerning its application. To accurately estimate the antioxidant capacity of (poly)phenolic compounds, a thorough knowledge of their structural characteristics is essential, as the two are closely associated. Therefore, to help researchers interpret the results of the Folin-Ciocalteu method, this review also summarizes some of the main phenolic structural features. Finally, we have used the Folin-Ciocalteu method to estimate the total phenolic intake associated with high adherence to a Mediterranean diet, ranked as one of the healthiest dietary patterns, which is characterized by a high consumption of (poly)phenol-rich food such as wine, virgin olive oil, fruits, vegetables, whole grains, nuts, and legumes.

Discovery of Potent and Selective CB2 Agonists Utilizing a Function-Based Computational Screening Protocol

Nowadays, the identification of agonists and antagonists represents a great challenge in computer-aided drug design. In this work, we developed a computational protocol enabling us to design/screen novel chemicals that are likely to serve as selective CB2 agonists. The principle of this protocol is that by calculating the ligand-residue interaction profile (LRIP) of a ligand binding to a specific target, the agonist-antagonist function of a compound is then able to be determined after statistical analysis and free energy calculations. This computational protocol was successfully applied in CB2 agonist development starting from a lead compound, and a success rate of 70% was achieved. The functions of the synthesized derivatives were determined by in vitro functional assays. Moreover, the identified potent CB2 agonists and antagonists strongly interact with the key residues identified using the already known potent CB2 agonists/antagonists. The analysis of the interaction profile of compound 6, a potent agonist, showed strong interactions with F2.61, I186, and F2.64, while compound 39, a potent antagonist, showed strong interactions with L17, W6.48, V6.51, and C7.42. Still, some residues including V3.32, T3.33, S7.39, F183, W5.43, and I3.29 are hotspots for both CB2 agonists and antagonists. More significantly, we identified three hotspot residues in the loop, including I186 for agonists, L17 for antagonists, and F183 for both. These hotspot residues are typically not considered in CB1/CB2 rational ligand design. In conclusion, LRIP is a useful concept in rationally designing a compound to possess a certain function.

Herbicidal Activity of Beflubutamid Analogues as PDS Inhibitors and SAR Analysis and Degradation Dynamics in Wheat

In this work, a series of beflubutamid (BF) analogues' postemergent herbicidal activity was evaluated, and the structure-activity relationship (SAR) was discussed. At a dosage of 300 g ai/ha, compounds (Rac)-6h and (Rac)-6q showed excellent herbicidal activity against Amaranthus retroflexus, Abutilon theophrasti, and Medicago sativa, with inhibition rates of 90, 100, and 80% and 100, 100, and 100%, respectively, comparable to that of commercial herbicide BF, which showed inhibition rates of 90, 100, and 100%, respectively. Notably, at dosages of 150 and 300 g ai/ha, the chiral compounds (S)-6h and (S)-6q exhibited higher herbicidal activities than their racemates. Molecular docking results indicated that compounds (S)-BF and (S)-6h have stronger binding affinities with Oryza sativa phytoene desaturase (OsPDS), resulting in a higher herbicidal activity. Additionally, the degradation dynamics half-life of (S)-BF in wheat was determined to be 77.02 h. Consequently, compounds (S)-6h and (S)-6q are promising lead candidates for the development of highly effective herbicides.

Leveraging the MMV Pathogen Box to Engineer an Antifungal Compound with Improved Efficacy and Selectivity against Candida auris

Fungal infections pose a significant and increasing threat to human health, but the current arsenal of antifungal drugs is inadequate. We screened the Medicines for Malaria Venture (MMV) Pathogen Box for new antifungal agents against three of the most critical Candida species (Candida albicans, Candida auris, and Candida glabrata). Of the 14 identified hit compounds, most were active against C. albicans and C. auris. We selected the pyrazolo-pyrimidine MMV022478 for chemical modifications to build structure-activity relationships and study their antifungal properties. Two analogues, 7a and 8g, with distinct fluorine substitutions, greatly improved the efficacy against C. auris and inhibited fungal replication inside immune cells. Additionally, analogue 7a had improved selectivity toward fungal killing compared to mammalian cytotoxicity. Evolution experiments generating MMV022478-resistant isolates revealed a change in morphology from oblong to round cells. Most notably, the resistant isolates blocked the uptake of the fluorescent dye rhodamine 6G and showed reduced susceptibility toward fluconazole, indicative of structural changes in the yeast cell surface. In summary, our study identified a promising antifungal compound with activity against high-priority fungal pathogens. Additionally, we demonstrated how structure-activity relationship studies of known and publicly available compounds can expand the repertoire of molecules with antifungal efficacy and reduced cytotoxicity to drive the development of novel therapeutics.

"AMP plus": Immunostimulant-Inspired Design Based on Chemotactic Motif-(PhHAhPH)n

Ability to stimulate antimicrobial immunity has proven to be a useful therapeutic strategy in treating infections, especially in the face of increasing antibiotic resistance. Natural antimicrobial peptides (AMPs) exhibiting immunomodulatory functions normally encompass complex activities, which make it difficult to optimize their therapeutic benefits. Here, a chemotactic motif was harnessed as a template to design a series of AMPs with immunostimulatory activities plus bacteria-killing activities ("AMP plus"). An amphipathic peptide ((PhHAhPH)n) was employed to improve the antimicrobial impact and expand the therapeutic potential of the chemotactic motif that lacked obvious bacteria-killing properties. A total of 18 peptides were designed and evaluated for their structure-activity relationships. Among the designed, KWH2 (1) potently killed bacteria and exhibited a narrow antimicrobial spectrum against Gram-negative bacteria and (2) activated macrophages (i.e., inducing Ca2+ influx, cell migration, and reactive oxygen species production) as a macrophage chemoattractant. Membrane permeabilization is the major antimicrobial mechanism of KWH2. Furthermore, the mouse subcutaneous abscess model supported the dual immunomodulatory and antimicrobial potential of KWH2 in vivo. The above results confirmed the efficiency of KWH2 in treating bacterial infection and provided a viable approach to develop immunomodulatory antimicrobial materials with desired properties.

Structures and Biological Activities of Secondary Metabolites from the Trichoderma genus (Covering 2018-2022)

Trichoderma, a genus with more than 400 species, has a long history of use as an industrial bioreactor, biofertilizer, and biocontrol agent. It is considered a significant source of secondary metabolites (SMs) that possess unique structural features and a wide range of bioactivities. In recent years, numerous secondary metabolites of Trichoderma, including terpenoids, polyketides, peptides, alkaloids, and steroids, have been identified. Most of these SMs displayed antimicrobial, cytotoxic, and antifungal effects. This review focuses on the structural diversity, biological activities, and structure-activity relationships (SARs) of the SMs isolated from Trichoderma covered from 2018 to 2022. This study provides insights into the exploration and utilization of bioactive compounds from Trichoderma species in the agriculture or pharmaceutical industry.

Discovery of 2-Naphthol from the Leaves of Actephila merrilliana as a Natural Nematicide Candidate

To identify natural nematicides that can replace chemical nematicides, 2-naphthol with high activity against Meloidogyne incognita was isolated from Actephila merrilliana. The nematicidal activity of 2-naphthol against M. incognita was 100% at 100 μg/mL with an EC50 value of 38.00 μg/mL. Moreover, 2-naphthol had a significant negative effect on egg incubation. 2-Naphthol effectively inhibited the invasion of M. incognita into crops in both a pot experiment and field trial. In addition, the structure-activity relationship indicated that the naphthalene ring and its β-site hydroxyl group were the key pharmacophores for the nematicidal activity of 2-naphthol. Nematodes were stimulated by 2-naphthol to produce excessive reactive oxygen species, which may be the underlying mechanism of 2-naphthol nematicidal activity. A systemic evaluation of 2-naphthol in tomato plants demonstrated that 2-naphthol remained mainly fixed in the roots after being absorbed by the crop and was not transported to the stems or leaves. Thus, 2-naphthol can be developed as a natural nematicide candidate.

Morpholine Derivatives in Agrochemical Discovery and Development

Derivatives of morpholine are biologically active organic compounds with special structures discovered in multiple drugs. As a result of the terminal pharmacophore of action and extraordinary activity, they attracted fair attention with regard to pesticide innovation and development. Analysis of brief structure-activity relationships and the summarization of the characteristics of pesticides containing morpholine fragments with efficient activity are key steps in the development of novel pesticides. This review primarily overviews morpholine compounds with insecticidal, fungicidal, herbicidal, antiviral, and plant growth regulation properties to provide educational insight for the creation of new morpholine-containing compounds.

Synthesis and Biological Profiling of Novel Strigolactone Derivatives for Arabidopsis Growth and Development

The artificially synthesized strigolactone (SL) analogue GR24 is currently the most widely used reference compound in studying the biological functions of SLs. To elucidate the structure-activity relationship and find more promising derivatives with unique molecular profiles, we design and synthesized three series of novel GR24 derivatives and explored their activities in hypocotyl and root development of Arabidopsis. Among the 50 synthesized compounds, A11a, A12a, and A20d were found to have high activities comparable to GR24 for hypocotyl and/or primary root elongation inhibition in Arabidopsis. Some new analogues have been discovered to exhibit unique activities: (1) A20c, A21e, and A21o are specific inhibitors in primary root elongation; (2) A21c, A26c, and A27a exhibit a high promotion effect on Arabidopsis primary root elongation; and (3) A27e possesses the most unique profiles completely opposite to GR24 that promotes both hypocotyl elongation and primary root development. Moreover, we revealed that the AtD14 receptor does not affect the inhibitory effect of SL analogues in Arabidopsis root development. The ligand-receptor interactions for the most representative analogues A11a and A27e were deciphered with a long time scale molecular dynamics simulation study, which provides the molecular basis of their distinct functions, and may help scientists design novel phytohormones.

Natural Alkaloid Waltherione F-Derived Hydrazide Compounds Evaluated in an Agricultural Fungicidal Field

In this project, quinoline and quinolone-containing hydrazide compounds were designed and synthesized by introducing a bioactive hydrazide group into the skeleton of waltherione F. The fungicidal activity revealed that some hydrazide compounds exhibited excellent and broad-spectrum fungicidal activity; especially, compounds E8, E12, and E16 showed more than 90% or even 100% inhibition rates against most pathogens at 50 μg·mL-1. The fungicidal mechanism indicated that compound E8 may affect the normal function of the plasma membrane, further generating changes in the morphology and subcellular structure of mycelia. Simultaneously, Fusarium graminearum may resist the E8-treated stress through the metabolic pathways related to l-glutamate, l-glutamine, and glutathione. Finally, the effect of compound E8 on wheat seedling's growth and the toxicity to zebrafish were accomplished. These results will provide important guidance to discover novel fungicidal lead compounds and explore new targets, which are effective ways to alleviate the increasingly severe drug resistance.

Identification of a Non-Nucleoside Reverse Transcriptase Inhibitor against Human Immunodeficiency Virus-1

The HIV-1 infection epidemic remains a global health problem. Current antiretroviral treatments are effective in controlling the progression of a severe infection. However, the emergence of drug resistance requires an urgent identification of new treatment regimes. HIV-1 reverse transcriptase (RTs) has been a successful therapeutic target owing to its high specificity and potent antiviral properties; therefore, it has become an essential component of current HIV-1 standard treatments. This study identified a new HIV-1 RTs inhibitor (Compound #8) that is structurally unique and greatly effective against HIV-1 through chemical library screening and a medicinal chemistry program by analyzing the structure-activity relationship (SAR). Further analysis of molecular docking and mechanisms of action demonstrated that Compound #8 is a novel type of HIV-1 non-nucleoside reverse transcriptase inhibitor (NNRTI) with a flexible binding mode. Therefore, it exhibits great therapeutic potential when combined with other existing HIV-1 drugs. Our current studies suggest that Compound #8 is a promising novel scaffold for the development of new HIV-1 treatments.

Discovery of Natural Sesquiterpene Lactone 1-O-Acetylbritannilactone Analogues Bearing Oxadiazole, Triazole, or Imidazole Scaffolds for the Development of New Fungicidal Candidates

In recent decades, natural products have been considered important resources for developing of new agrochemicals because of their novel architectures and multibioactivities. Consequently, herein, 1-O-acetylbritannilactone (ABL), a natural sesquiterpene lactone from Inula britannica L., was used as a lead for further modification to discover fungicidal candidates. Six series of ABL-based derivatives containing an oxadiazole, triazole, or imidazole moiety were designed and synthesized, and their antifungal activities were also evaluated in vitro and in vivo. Bioassay results revealed that compounds 8d, 8h, and 8j (EC₅₀ = 61.4, 30.9, and 12.4 μg/mL, respectively) exhibited more pronounced inhibitory activity against Fusarium oxysporum than their precursor ABL (EC₅₀ > 500 μg/mL) and positive control hymexazol (EC₅₀ = 77.2 μg/mL). Derivatives 8d and 11j (EC₅₀ = 19.6 and 41.5 μg/mL, respectively) exhibited more potent antifungal activity toward Cytospora mandshurica than ABL (EC₅₀ = 68.3 μg/mL). Compound 10 exhibited excellent and broad-spectrum antifungal activity against seven phytopathogenic fungal mycelia. Particularly, the inhibitory activity of compound 10 against the mycelium of Botrytis cinerea was more than 10.8- and 2.3-fold those of ABL and hymexazol, respectively. Meanwhile, derivative 10 (IC₅₀ = 47.7 μg/mL) displayed more pronounced inhibitory activity against the spore of B. cinerea than ABL (IC₅₀ > 500 μg/mL) and difenoconazole (IC₅₀ = 80.8 μg/mL). Additionally, the in vivo control efficacy of compound 10 against B. cinerea was further studied using infected tomatoes (protective effect = 58.4%; therapeutic effect = 48.7%). The preliminary structure-activity relationship analysis suggested that the introduction of the 1,3,4-oxadiazole moiety (especially the 1,3,4-oxadiazole heterocycle containing the 4-chlorophenyl, 2-furyl, or 2-pyridinyl group) on the skeleton of ABL was more likely to produce potential antifungal compounds. These findings pave the way for further design and development of ABL-based derivatives as potential antifungal agents.

Discovery of [1,2,3]Triazolo[4,5-c]quinoline Derivatives as a New Class of Ataxia-Telangiectasia Mutated Kinase Inhibitors

Ataxia-telangiectasia mutated (ATM) is an atypical serine/threonine protein kinase which is implicated in the repair of DNA double-strand breaks. Numerous reports have shown that ATM inhibition is an attractive target for radiotherapy and chemotherapy sensitization. Herein we report a new series of ATM kinase inhibitors containing the 1H-[1,2,3]triazolo[4,5-c]quinoline scaffold, which was obtained by virtual screening, structural optimization, and structure-activity relationship studies. Among the inhibitors, A011 was one of the most potent, with an IC₅₀ value of 1.0 nM against ATM. In colorectal cancer cells (SW620 and HCT116), A011 was able to inhibit activation of ATM signaling induced by irinotecan (CPT-11) and ionizing radiation and then increased the sensitivity of colorectal cancer cells to irinotecan and ionizing radiation through increasing G2/M arrest and inducing apoptosis. In the SW620 human colorectal adenocarcinoma tumor xenograft model, A011 sensitized SW620 to CPT-11 by inhibiting ATM activity. Collectively, this work has identified a promising lead in the discovery of potent inhibitors against ATM.

Correlating the Structure and Gene Silencing Activity of Oligonucleotide-Loaded Lipid Nanoparticles Using Small-Angle X-ray Scattering

With three FDA-approved products, lipid nanoparticles (LNPs) are under intensive development for delivering wide-ranging nucleic acid therapeutics. A significant challenge for LNP development is insufficient understanding of structure-activity relationship (SAR). Small changes in chemical composition and process parameters can affect LNP structure, significantly impacting performance in vitro and in vivo. The choice of polyethylene glycol lipid (PEG-lipid), one of the essential lipids for LNP, has been proven to govern particle size. Here we find that PEG-lipids can further modify the core organization of antisense oligonucleotide (ASO)-loaded LNPs to govern its gene silencing activity. Furthermore, we also have found that the extent of compartmentalization, measured by the ratio of disordered vs ordered inverted hexagonal phases within an ASO-lipid core, is predictive of in vitro gene silencing. In this work, we propose that a lower ratio of disordered/ordered core phases correlates with stronger gene knockdown efficacy. To establish these findings, we developed a seamless high-throughput screening approach that integrated an automated LNP formulation system with structural analysis by small-angle X-ray scattering (SAXS) and in vitro TMEM106b mRNA knockdown assessment. We applied this approach to screen 54 ASO-LNP formulations while varying the type and concentration of PEG-lipids. Representative formulations with diverse SAXS profiles were further visualized using cryogenic electron microscopy (cryo-EM) to help structural elucidation. The proposed SAR was built by combining this structural analysis with in vitro data. Our integrated methods, analysis, and resulting findings on PEG-lipid can be applied to rapidly optimize other LNP formulations in a complex design space.

A Comprehensive Investigation of Hydrazide and Its Derived Structures in the Agricultural Fungicidal Field

Hydrazides are present in many bioactive molecules and exhibit a variety of biological activities, such as insecticidal, herbicidal, antifungal, antitumor, and antiviral effects. In this Review, we review the application of hydrazide and its derived structures in the agricultural fungicidal field, including monohydrazides, diacylhydrazines, hydrazide-hydrazones, and sulfonyl hydrazides. In addition, the antifungal mechanism of action of the hydrazide derivatives was analyzed and summarized, mainly involving succinate dehydrogenase inhibitors, laccase inhibitors, and targeting plasma membranes. Finally, based on the structural analysis of the novel fungicidal lead compounds, the structure-activity relationship of the hydrazide derivatives was constructed and the development trend of hydrazide structures in fungicidal applications was prospected. It is hoped that this Review can provide some significant guidance for the development of new hydrazide fungicides in the future.

Cladosporin, A Highly Potent Antimalaria Drug?

Cladosporin, a unique natural product from the fungus Cladosporium cladosporioides, exhibits nanomolar inhibitory activity against Plasmodium falciparum by targeting its cytosolic lysyl-tRNA synthetase (PfKRS) to inhibit protein biosynthesis. Due to its exquisite selectivity towards pathogenic parasites, cladosporin has become a very promising lead compound for developing antiparasitic drugs to treat drug-resistant malaria and cryptosporidiosis infections. Here we review the recent research progress of cladosporin covering aspects of the chemical synthesis, biosynthesis, bioactivity, cellular target and structure-activity relationship.

Insight into Surface Electronic Effects on Pd Nanostructures as Efficient Electrocatalysts

Although the unique properties of nanomaterials have endowed enzyme-mimic catalysts with broad applications, the development of catalysts still relies on trial-and-error strategies without predictive indicators. Surface electronic structures have rarely been studied in enzyme-mimic catalysts. Herein, we present a platform for understanding the impact of surface electronic structures on electrocatalysis toward H₂O₂ decomposition, using the Pd icosahedra (Pd ico), Pd octahedra (Pd oct) and Pd cubic nanocrystals as electrocatalysts. The electronic properties on Pd were modulated with a correlation of surface orientation. We revealed the relationship between the electronic properties and electrocatalytic performance, in which the surface electron accumulation can boost the electrocatalytic activity of the enzyme-mimic catalysts. As a result, the Pd icodimer exhibits the highest electrocatalytic and sensing efficiency. This work offers new perspectives for the investigation of structure-activity relationships and provides an effective knob for utilizing the surface electronic structures to boost the catalytic performance for enzyme-mimics.

Aprosamine Derivatives Active against Multidrug-Resistant Gram-Negative Bacteria

Novel aprosamine derivatives were synthesized for the development of aminoglycoside antibiotics active against multidrug-resistant Gram-negative bacteria. The synthesis of aprosamine derivatives involved glycosylation at the C-8' position and subsequent modification (epimerization and deoxygenation at the C-5 position and 1-N-acylation) of the 2-deoxystreptamine moiety. All 8'-β-glycosylated aprosamine derivatives (3a-h) showed excellent antibacterial activity against carbapenem-resistant Enterobacteriaceae and 16S ribosomal RNA methyltransferase-producing multidrug-resistant Gram-negative bacteria compared to the clinical drug, arbekacin. The antibacterial activity of 5-epi (6a-d) and 5-deoxy derivatives (8a,b and 8h) of β-glycosylated aprosamine was further enhanced. On the other hand, the derivatives (10a,b and 10h) in which the amino group at the C-1 position was acylated with (S)-4-amino-2-hydroxybutyric acid showed excellent activity (MICs 0.25-0.5 μg/mL) against resistant bacteria that produce the aminoglycoside-modifying enzyme, aminoglycoside 3-N-acetyltransferase IV, which induces high resistance against parent apramycin (MIC > 64 μg/mL). In particular, 8b and 8h showed approximately 2- to 8-fold antibacterial activity against carbapenem-resistant Enterobacteriaceae and 8- to 16-fold antibacterial activity against resistant Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci, compared to apramycin. Our results showed that aprosamine derivatives have immense potential in the development of therapeutic agents for multidrug-resistant bacteria.

Structural Simplification of Cryptolepine to Obtain Novel Antifungal Quinoline Derivatives against Phytopathogenic Fungi

A series of quinoline derivatives were designed and synthesized by the structural simplification of cryptolepine and evaluated for their fungicidal activity against six phytopathogenic fungi. Most of these compounds exhibited remarkable activities against Botrytis cinereain vitro. Among them, compounds A18 and L01 showed superior antifungal activity. Significantly, compared to cryptolepine, compound A18 exhibited broad-spectrum inhibitory activities against B. cinerea, Sclerotinia sclerotiorum, Rhizoctonia solani, Phytophthora capsica, Magnaporthe oryzae, and Fusarium graminearum with the respective EC₅₀ values of 0.249, 1.569, 3.915, 0.505, 0.246, and 4.999 μg/mL. Compound L01 displayed the best antifungal activity against B. cinerea with an EC₅₀ value of 0.156 μg/mL. Preliminary mechanistic studies showed that compound A18 could inhibit spore germination, affect the permeability of the cell membrane, increase the content of reactive oxygen species, and affect the morphology of hyphae and cells. Moreover, compound A18 showed excellent in vivo protective effect against B. cinerea, which was more potent than pyrimethanil and equitant to cryptolepine. These results evidenced that compound A18 displayed superior fungicidal activities and could be a potential fungicidal candidate against plant fungal diseases.

Quassinoids from Picrasma chinensis with Insecticidal Activity against Adults and Larvae of Diaphorina citri Kuwayama and Neuroprotective Effect

Eleven new tetracyclic quassinoids, picrachinensin A-K (1-11), along with six known congeners, were isolated from the stems and leaves of Picrasma chinensis. Their structures were elucidated by integrated multiple spectroscopic techniques, single-crystal X-ray diffraction analysis, and electronic circular dichroism. Notably, compounds 3 and 4 are a pair of undescribed epimers, and 8 and 9 are unusual quassinoids with a hydroxymethyl group at C-13. Biologically, compound 7 exhibited insecticidal activity on both adults and larvae of Diaphorina citri Kuwayama even more effectively than the positive control (abamectin), with an LD₅₀ of 55.69 mg/L for adults and a corrected mortality rate of 30.42 ± 2.78% for larvae (100 mg/L). According to preliminary structure-activity relationship investigations, the hydroxymethyl at the C-13 position of quassinoids was beneficial for their insecticidal activity. In addition, compounds 1, 4, and 12 exhibited excellent neuroprotective effect against H₂O₂-induced oxidative injury on SH-SY5Y cells, with more potent activity than the positive control (Trolox), and all the compounds exhibited no cytotoxicity to SH-SY5Y and BV-2 cells at the indicated concentrations.

Comprehensive Characterization of a Systematic Library of Alkyl and Alicyclic Synthetic Cannabinoids Related to CUMYL-PICA, CUMYL-BUTICA, CUMYL-CBMICA, and CUMYL-PINACA

Over 200 synthetic cannabinoid receptor agonists (SCRAs) have been identified as new psychoactive substances. Effective monitoring and characterization of SCRAs are hindered by the rapid pace of structural evolution. Ahead of possible appearance on the illicit drug market, new SCRAs were synthesized to complete a systematic library of cumyl-indole- (e.g., CUMYL-CPrMICA, CUMYL-CPMICA) and cumyl-indazole-carboxamides (e.g., CUMYL-CPrMINACA, CUMYL-CPMINACA), encompassing butyl, pentyl, cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl, and cyclohexylmethyl tails. Comprehensive pharmacological characterization was performed with three assay formats, monitoring the recruitment of either wild-type or C-terminally truncated (βarr2d366) β-arrestin2 to the activated cannabinoid 1 receptor (CB₁) or monitoring G_βγ-mediated membrane hyperpolarization. Altered compound characterization was observed when comparing derived potency (EC₅₀) and efficacy (E_max) values from both assays monitoring the same or a different signaling event, whereas ranges and ranking orders were similar. Structure-activity relationships (SAR) were assessed in threefold, resulting in the identification of the pendant tail as a critical pharmacophore, with the optimal chain length for CB₁ activation approximating an n-pentyl (e.g., cyclopentylmethyl or cyclohexylmethyl tail). The activity of the SCRAs encompassing cyclic tails decreased with decreasing number of carbons forming the cyclic moiety, with CUMYL-CPrMICA showing the least CB₁ activity in all assay formats. The SARs were rationalized via molecular docking, demonstrating the importance of the optimal steric contribution of the hydrophobic tail. While SAR conclusions remained largely unchanged, the differential compound characterization by both similar and different assay designs emphasizes the importance of detailing specific assay characteristics to allow adequate interpretation of potencies and efficacies.

Characterization of a Potential KOR/DOR Dual Agonist with No Apparent Abuse Liability via a Complementary Structure-Activity Relationship Study on Nalfurafine Analogues

Discovery of analgesics void of abuse liability is critical to battle the opioid crisis in the United States. Among many strategies to achieve this goal, targeting more than one opioid receptor seems promising to minimize this unwanted side effect while achieving a reasonable therapeutic profile. In the process of understanding the structure-activity relationship of nalfurafine, we identified a potential analgesic agent, NMF, as a dual kappa opioid receptor/delta opioid receptor agonist with minimum abuse liability. Further characterizations, including primary in vitro ADMET studies (hERG toxicity, plasma protein binding, permeability, and hepatic metabolism), and in vivo pharmacodynamic and toxicity profiling (time course, abuse liability, tolerance, withdrawal, respiratory depression, body weight, and locomotor activity) further confirmed NMF as a promising drug candidate for future development.

Electrochemical Reduction of Halogenated Alkanes and Alkenes Using Activated Carbon-Based Cathodes

Granular activated carbon (GAC) is used to sorb a broad range of halogenated contaminant classes, but spent GAC disposal is costly. Taking advantage of GAC's conductivity, this study evaluated the conversion of the GAC to cathodes for electrochemical reductive dehalogenation of 15 halogenated alkanes and alkenes exhibiting a diversity of structures (type of halogen, number of halogens, functional groups) and including contaminants of practical importance (e.g., trichloroethylene). Alkane degradation rates increased with the number of halogens and in the order: chlorine < bromine < iodine. Quantitative structure-activity relationships (QSARs) correlating experimental first-order degradation rate constants for alkanes with molecular descriptors associated with an outer-sphere one-electron transfer calculated using density functional theory indicated that correlations with molecular descriptors improved in the order: aqueous phase reduction potentials (E^0,aq) < energy of the substrate's lowest unoccupied molecular orbital (E_LUMO) < Marcus theory activation free energies (ΔG^‡) ∼ gas-phase standard reduction free energies (ΔG^0,gas). Chlorinated alkene degradation rates increased with decreasing number of chlorines, and QSAR correlations were opposite those of alkanes, indicating a different reaction mechanism. Degradation timescales ranged from 1 min to 3 h with halides as predominant products. These results suggest that the electrochemical reduction of halogenated alkanes and alkenes can be used to regenerate spent GAC.

Structure and Activity Relationships of the Two-Component Lantibiotic Bicereucin

Identified from the pathogen Bacillus cereus SJ1, the two-component lantibiotic bicereucin is featured by the presence of a series of nonproteogenic amino acids and exhibits potent synergistic activity against a broad spectrum of Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci, as well as hemolytic activity against mammalian cells. In this study, we performed site-directed mutagenesis on the nonproteogenic amino acids as well as truncation of dehydrobutyrine-rich N-terminal residues and evaluated the effects on both biological activities. We identified that D-Ala21 and D-Ala26 of Bsjα and D-Ala23 and D-Ala28 of Bsjβ play an essential role in the antimicrobial activity, while the N-termini of both peptides are important for both activities. We also determined that the integrity of both subunits is essential for hemolytic activity. Finally, we obtained two variants Bsjαt^S17A+Bsjβ and Bsjα^S30A+Bsjβ^T19A, which retained the antimicrobial activity and exhibited greatly decreased hemolytic toxicity. Overall, our results provide a comprehensive understanding of the structure-activity relationships of bicereucin and insights into the mechanism of action thereof, facilitating the further exploration of the molecular basis of the binding receptor of bicereucin and genome mining of potential novel two-component lantibiotics.

Stability, Bioavailability, and Structure-Activity Relationship of Casein-Derived Peptide YPVEPF with a Sleep-Enhancing Effect

YPVEPF (Tyr-Pro-Val-Glu-Pro-Phe) is an outstanding sleep-enhancing peptide derived from casein. This study aimed to evaluate the bioavailability of YPVEPF in vitro and in vivo and to explore its structure-activity relationship through a sleep test and cheminformatics. Our results showed that YPVEPF was unstable against gastrointestinal enzymes and almost totally degraded to YPVEP in vitro. However, the pharmaco-kinetics results in vivo showed that the C_max of YPVEPF was 10.38 ± 4.01 ng/mL at 5 min, and YPVEPF could be detected in the stomach, intestine, and brain at 12.89 ± 0.55, 10.26 ± 0.23, and 2.47 ± 0.55 ng/g, respectively. The main metabolites including YPVEP, YP, PVEPF, and PVEP were identified. We first explored whether the fragment YPVEP also had a strong sleep-enhancing effect, and the sleep-enhancing effects of PVEPF and PVEP (lacking a Tyr residue) significantly decreased compared with those of YPVEPF and YPVEP. Moreover, molecular docking and quantum calculations revealed that the N-terminus Tyr played a dominant role in YPVEPF and YPVEP. They had distinctive self-folding structures and varying electron-withdrawing properties of the groups at the N terminus, allowing different binding modes and electron/proton transfer.

Breaking the Volcano-Shaped Relationship for Highly Efficient Electrocatalytic Nitrogen Reduction: A Computational Guideline

The volcano-shaped relationship is very common in electrocatalytic nitrogen reduction reaction (e-NRR) and is usually caused by the competition between the first and last hydrogenation steps. How to break such a relationship to further improve the catalytic performance remains a great challenge. Herein, using first-principles calculations, we investigate a range of transition-metal (TM)-doped Cu-based single-atom alloys (TM₁-Cu(111)) as catalysts for e-NRR. When the adsorption of N₂ on the catalysts is strong enough, the inert N₂ molecules can be effectively activated for the first hydrogenation step. Meanwhile, the last hydrogenation step is not affected by the scaling relationship and remains easy on all of the catalysts due to the unstable top-site adsorption of NH₂, resulting in the break of the volcano-shaped relationship in e-NRR. Thus, only the first hydrogenation step is identified as the potential determining step. Four TM₁-Cu(111) catalysts (TM = Re, W, Tc, and Mo) are selected as promising catalysts with limiting potential ranging from -0.38 to -0.56 V, showing outstanding e-NRR activity. Besides, the four catalysts also inhibit the competing hydrogen evolution reaction and long-term stability. Our work provides a guideline for breaking the volcano-shaped relationship in e-NRR and significant in the rational design of highly efficient electrocatalysts.