Design, synthesis, anti-infective potency and mechanism study of novel Ru-based complexes containing substituted adamantane as antibacterial agents.

Infections caused by Staphylococcus aureus (S. aureus) are increasing difficult to treat because this pathogen is easily resistant to antibiotics. However, the development of novel antibacterial agents with high antimicrobial activity and low frequency of resistance remains a huge challenge. Here, building on the coupling strategy, an adamantane moiety was linked to the membrane-active Ru-based structure and then developed three novel metalloantibiotics: [Ru(bpy)2(L)](PF6)2 (Ru1) (bpy = 2,2-bipyridine, L = amantadine modified ligand), [Ru(dmb)2(L)](PF6)2 (Ru2) (dmb = 4,4'-dimethyl-2,2'-bipyridine) and [Ru(dpa)2(L)](PF6)2 (Ru3), (dpa = 2,2'-dipyridylamine). Notably, complex Ru1 was identified to be the best candidate agent, showing greater efficacy against S. aureus than most of clinical antibiotics and low resistance frequencies. Mechanism studies demonstrated that Ru1 could not only increase the permeability of bacterial cell membrane and then caused the leakage of bacterial contents, but also promoted the production of reactive oxygen species (ROS) in bacteria. Importantly, complex Ru1 inhibited the biofilm formation, exotoxin secretion and increased the potency of some clinical used antibiotics. In addition, Ru1 showed low toxic in vivo and excellent anti-infective efficacy in two animal infection model. Thus, Ru-based metalloantibiotic bearing adamantane moiety are promising antibacterial agents, providing a certain research basis for the future antibiotics research.

The visualization of the spatial distribution of Cocculus orbiculatus based on air flow-assisted desorption electrospray ionization mass spectrometry imaging.

Cocculus orbiculatus (C. orbiculatus), the root of plants belonging to the Menispermaceae family, has been extensively used to treat various diseases, including malaria and rheumatism. The main chemicals in these plants are alkaloids; however, the spatial distribution of these compounds within the plant roots remains undefined. This study aimed to visualize the spatial distribution of C. orbiculatus using air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI). In total, the spatial distribution of four aporphine alkaloids, five benzyltetrahydroisoquinoline alkaloids, six bisbenzylisoquinoline alkaloids, and one morphinane alkaloid in the cork layer, xylem, and ray of the root of C. orbiculatus was observed; the distribution characteristics of the different compounds in C. orbiculatus were significantly different. This study provides a visualized spatial distribution analysis method for the characterization of metabolites in the root tissue of C. orbiculatus and also provides valuable information for the specificity of the root of C. orbiculatus, which is beneficial for understanding its chemical separation, biosynthesis, and pharmacological activities.

The Research Progress of Bioactive Peptides Derived from Traditional Natural Products in China.

Traditional natural products in China have a long history and a vast pharmacological repertoire that has garnered significant attention due to their safety and efficacy in disease prevention and treatment. Among the bioactive components of traditional natural products in China, bioactive peptides (BPs) are specific protein fragments that have beneficial effects on human health. Despite many of the traditional natural products in China ingredients being rich in protein, BPs have not received sufficient attention as a critical factor influencing overall therapeutic efficacy. Therefore, the purpose of this review is to provide a comprehensive summary of the current methodologies for the preparation, isolation, and identification of BPs from traditional natural products in China and to classify the functions of discovered BPs. Insights from this review are expected to facilitate the development of targeted drugs and functional foods derived from traditional natural products in China in the future.

Structural Characterization and Anti-Inflammatory Activity of a Novel Polysaccharide from Duhaldea nervosa.

In the present study, a novel water-soluble polysaccharide (DNP-1) was isolated and purified from the root of Duhaldea nervosa via column chromatography. Structural analyses indicated that DNP-1 had a linear backbone consisting of (2→1)-linked ß-D- fructofuranosyl residues, ending with a (2→1) bonded α-D-glucopyranose. DNP-1 was a homogeneous polysaccharide with an average molecular weight of 3.7 kDa. Furthermore, the anti-inflammatory activity of DNP-1 was investigated in vitro. The concentration of pro-inflammatory cytokines, including NO, TNF-α, MCP-1, IL-2, and IL-6, in the DNP-1 treatment group was suppressed in LPS-induced RAW 264.7 cells. DNP-1 was able to improve inflammatory injury by inhibiting the secretion of pro-inflammatory cytokines. These investigations into this polysaccharide from the root of Duhaldea nervosa provide a scientific basis for the further development of this plant. The results indicate that this Duhaldea nervosa polysaccharide could be used as a potential natural source for the treatment of inflammatory injury.

The synthesis and antibacterial activity study of ruthenium-based metallodrugs with a membrane-disruptive mechanism against Staphylococcus aureus.

The wide spread of drug-resistant bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA), poses a tremendous threat to global health. Of particular concern, resistance to vancomycin, linezolid, and daptomycin has already been reported in clinical MRSA strains. New antibacterial agents are urgently needed to overcome this crisis. Here, we designed and synthesized a series of ruthenium-based antibacterial agents via targeting bacterial membrane integrity. Structure-activity relationship studies demonstrated that both the lipophilicity/hydrophilicity ratio and biphenyl group play an important role in elevating the antibacterial activity. To characterize the antibacterial mechanism, we combined scanning electron microscopy, propidium iodide dyeing, and DNA leakage assays. The results demonstrated that Ru2 could destroy the integrity of bacterial cell membranes. In addition, Ru2 can efficiently inhibit biofilm formation and α-hemolysin secretion from Staphylococcus aureus. Finally, in both a mouse skin infection model and a G. mellonella wax worm infection model, Ru2 showed significant antibacterial activity in vivo. Moreover, the Ru2 complex was almost non-toxic. Thus, this work demonstrated that ruthenium-based complexes bearing a biphenyl group are promising agents to combat bacterial infection.

The Application of UHPLC-HRMS for Quality Control of Traditional Chinese Medicine.

UHPLC-HRMS (ultra-high-performance liquid chromatography-high resolution mass spectrometry) is a new technique that unifies the application of UHPLC with HRMS. Because of the high sensitivity and good separation ability of UHPLC and the sensitivity of HRMS, this technique has been widely used for structure identification, quantitative determination, fingerprint analysis, and elucidation of the mechanisms of action of traditional Chinese medicines (TCMs) in recent years. This review mainly outlines the advantages of using UHPLC-HRMS and provides a survey of the research advances on UHPLC-HRMS for the quality control of TCMs.

Ruthenium(II) complexes targeting membrane as biofilm disruptors and resistance breakers in Staphylococcus aureus bacteria.

The development of ruthenium-based complexes or antimicrobial peptides are identified as a promising strategy for combating drug-resistant bacteria. In this work, four biphenyl-based antibacterial ruthenium complexes by targeting membrane integrity, which act as antimicrobial peptides mimics, were designed and synthesized. In vitro antimicrobial screening demonstrated that four complexes could absolutely inhibit the growth of Staphylococcus aureus (S. aureus) with MIC values ranging from 15.6 to 100 µg/mL. The most active complex Ru(Ⅱ)-1 (MIC = 15.6 µg/mL) could kill S. aureus through targeting the membrane integrity without detectably resistance frequencies. Further investigation including bacteria biofilm formation, hemolysin activity and checkerboard assay were performed as well. The results revealed that Ru(Ⅱ)-1 could inhibit the biofilm formation and α-hemolysis secretion in S. aureus at subinhibitory concentration. More interestingly, the combination use of Ru(Ⅱ)-1 and five traditional antibiotics showing synergistic effect. Finally, based on the mouse model of S. aureus skin infection, Ru(Ⅱ)-1 showed important antibacterial efficacy against S. aureus in vivo, and almost non-toxic against mouse tissue. Our study indicates that introducing membrane targeting ligands onto ruthenium complexes may be an underappreciated strategy for developing antibacterial agents.

Chemical characterization of extracts of leaves of Kadsua coccinea (Lem.) A.C. Sm. by UHPLC-Q-Exactive Orbitrap Mass spectrometry and assessment of their antioxidant and anti-inflammatory activities.

Kadsua coccinea (K. coccinea) has long been used as a fruit and folk medicine; however, the composition of its leaves and the activities of its constituents have been seldom studied. A total of 98 chemical constituents, including 53 phenolic acids, 41 flavonoids, and 4 lignans, were identified from the plant of kadsua coccinea by UHPLC-Q-Exactive Orbitrap Mass spectrometry. All these chemicals were reported for the first time in leaves, and 95 of them have been reported for the first time in the plant of kadsua coccinea. The biological potential of extracts of K. coccinea leaves (EKL) was evaluated by in vitro antioxidant assay and anti-inflammatory assay. EKL are composed of polysaccharides (60%), polyphenols (26%), and proteins (11%). EKL present decent potent •OH and DPPH scavenging abilities and Fe2+ chelating ability. They also inhibit the secretion of NO, reduce the level of Cox2 in proteins, inhibit the secretion of pro-inflammatory cytokines, such as IL-2 and IL-6, and promote the secretion of anti-inflammatory cytokine IL-10. These results displayed significant antioxidant and anti-inflammatory activities of EKL, which will be very beneficial for further development and investigation of kadsua coccinea leaves.

Dysosma versipellis Extract Inhibits Esophageal Cancer Progression through the Wnt Signaling Pathway.

OBJECTIVE: In this study, we aim to investigate the effect of Dysosma versipellis extract on biological behavior of esophageal cancer cells and its underlying mechanisms. METHODS: A total of 30 BALB/C nude mice (class SPF) were equally and randomly divided into the control group, model group, and Dysosma versipellis group. CP-C cell of esophageal cancer was subcutaneously injected into the model group as well as the Dysosma versipellis group, and the same amount of normal saline into the control group, in order to compare the tumorigenesis of nude mice of three groups. Wnt, ß-catenin, and p-GSK3ß/GSK3ß expression in tumor tissues was detected using Western blot. CP-C cells in logarithmic growth were selected and divided into 4 groups, including the control group, podophyllotoxin group, Wnt activator group, and combined group (mixture of podophyllotoxin and Wnt activator). The cell viability, apoptosis, and invasion ability, Wnt, ß-catenin, and p-GSK3ß/GSK3ß expression level of CP-C cells in each group were detected via MTT assay, flow cytometry, transwell, and Western blot, respectively. RESULTS: The tumorigenesis rates of the control group, model group, and Dysosma versipellis group were 0%, 90% (1 tumor-free mouse), and 80% (2 tumor-free mice), respectively. The tumor mass in the Dysosma versipellis group was significant less than that in the model group. Based on the results of Western blot, Wnt, ß-catenin, and p-GSK3ß/GSK3ß expression of the Dysosma versipellis group was lower than that of the control group. The in vitro viability test indicated that there was a significant difference in cell viability exhibited among four groups. Cell viability level in the 3 groups, including the combined group, blank group, and Wnt activator group, was higher than the podophyllotoxin group at each time point. In vitro apoptosis assay revealed that significant differences in cell apoptosis exhibited among four groups. Cell apoptosis rate was higher in the podophyllotoxin group compared to the remaining three groups. The Wnt activator group showed the lowest cell apoptosis rate. The in vitro invasion assay demonstrated that numbers of transmembrane cell in the 3 groups, involving the combined group, blank group, and Wnt activator group, showed a higher level than the podophyllotoxin group. The results of Western blot manifested that the podophyllotoxin group showed lower level of Wnt, ß-catenin, and p-GSK3ß/GSK3ß expression compared to the other 3 groups. CONCLUSION: Podophyllotoxin in Dysosma versipellis has an excellent antiesophageal cancer effect and is able to inhibit cell viability as well as invasion ability and promote apoptosis of esophageal cancer cells by inhibiting the Wnt signaling pathway, which could be potentially used in future clinical treatment of esophageal cancer.

Synthesis of ruthenium complexes functionalized with benzothiophene and their antibacterial activity against Staphylococcus aureus.

New effective antimicrobial agents with novel modes of action are urgently needed due to the continued emergence of drug-resistant bacteria. Here, three ruthenium complexes functionalized with benzothiophene: [Ru(phen)2(BTPIP)](ClO4)2 (Ru(II)-1), [Ru(dmp)2(BTPIP)](ClO4)2 (Ru(II)-2) and [Ru(dmb)2(BTPIP)](ClO4)2 (Ru(II)-3) (dmb = 4,4'-dimethyl-2,2'-bipyridine, phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline) have been synthesized and their antimicrobial activities in vitro were assessed. Minimum inhibitory concentration (MIC) assays indicated that the three Ru(II)-1, Ru(II)-2 and Ru(II)-3 complexes all showed antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. The most active Ru(II)-3 complex was further tested against biofilms. Furthermore, it was also tested whether complex Ru(II)-3 could serve as an antibacterial adjuvant. Interestingly, the checkerboard data showed that Ru(II)-3 selectively exhibited synergism with aminoglycoside antibiotics. More importantly, the observed synergetic effect might be attributed to the inhibition of the regulatory function of SaCcpA. Finally, in vivo bacterial infection treatment studies through a murine skin infection model and skin irritation test were also conducted. All in all, these results confirmed that ruthenium complexes functionalized with benzothiophene have good antimicrobial activity against Staphylococcus aureus.

Identification of the Constituents of Percutaneous Absorption from Duhaldea nervosa Based on UHPLC-Q-Exactive Orbitrap MS and Microdialysis Technique.

Duhaldea nervosa (D. nervosa) has been used for treatment of bone fracture by external use. Thus, the percutaneous absorption was crucial to the effect of D. nervosa, especially the constituents of percutaneous absorption. However, the constituents in vivo were never investigated to date. In this study, an efficient method was developed for the identification of constituents of percutaneous absorption using UHPLC-Q-Exactive Orbitrap MS and microdialysis technique. A total of 20 constituents including 15 chlorogenic acid analogues, 3 amino acids, and 2 organic acids were unambiguously or tentatively identified based on high-resolution mass data including MS and MS2, chromatography retention time, and bibliography data. To the best of our knowledge, this is the first study to report the constituents of percutaneous absorption from D. nervosa, which will be very helpful for understanding the bioactive compounds and quality control.

SCI: a robust and reliable density-based descriptor to determine multiple covalent bond orders.

Very recently [J. Phys. Chem. A 2018, 122 (11), 3087-3095], we proposed to employ the Pauli energy to identify and determine strong covalent interactions (SCI), whose bond order are equal to or larger than two. This is done through the signature isosurface shape between the two bonding atoms. We discovered that the signature shape for a double, triple, and quadruple covalent bond is like a dumbbell, donut (torus), and four-beats, respectively. Systems with even higher bond orders were examined and confirmed. This work is a follow-up study of our previous work. The dependence of the signature isosurface shape on the choice of methodologies and basis sets is systematically investigated. Its effectiveness and robustness in determining bond orders are highlighted again with more examples. In addition, using the molybdenum dimer in different environments, e.g., in vacuum, sandwiched between molecules, and encapsulated in the C80 cage, as illustrative examples, we show that, generally speaking, bond strength and bond order are two different chemical concepts. For systems containing transition metals, it is not always true that a short metal-metal bond length corresponds to a larger bond order. Put together, these results should provide additional pieces of convincing evidence showing that the SCI index is a robust and reliable density-based descriptor to accurately determine multiple covalent bond orders.

Steric charge.

The steric effect is one of the most widely used chemical concepts in chemistry, yet a generally accepted implementation of its formulation and quantification from a theoretical viewpoint, if even possible, is still an unaccomplished task. Based on the energetics viewpoint of our earlier proposal using the Weizsäcker kinetic energy as a quantification of the energy contribution from the steric effect as well as our recent work using steric force as a reliable local descriptor to account for the origin of the stereoselective propensity in chemical reactions, in this work, we systematically examine the local behavior and general applicability of another closely related quantity, steric charge. To this end, its physical origin and physiochemical properties are formalized and highlighted, and are shown with numerical illustrations and verifications. To showcase its usefulness in appreciating chemical reactivity, we present three case studies of steric charge in this work. In the case of ethane flexible rotation, we found that the eclipsed conformer is more sterically charged than the staggered conformer, leading to the reduced stability and higher energy of the former. For the case of SN2 reactions, a remarkable linear correlation has been obtained between the steric charge on the central atom in the transition state and the reaction barrier height of SN2 reactions, in good agreement with experimental findings. In the case of stereoselectivity properties for the nucleophilic addition of carbonyl compounds, we found that steric charge is equally applicable as steric force to justify the stereoselective origin for the nucleophilic attack to the carbonyl carbon atom with different substituent groups. Put together, our results from the present study should pave the way towards the general use of steric charge, together with steric energy and steric force, as an insightful global and local descriptor to appreciate and quantify chirality and stereoselectivity related phenomena in chemical processes and transformations.

Rapid characterization of chlorogenic acids in Duhaldea nervosa based on ultra-high-performance liquid chromatography-linear trap quadropole-Orbitrap-mass spectrometry and mass spectral trees similarity filter technique.

Duhaldea nervosa (Wallich ex Candolle) A. Anderberg has been traditionally used as a food spice and also in folk medicine for treating traumatic injury and relieving rheumatism, especially accelerating the healing of a fracture. However, so far as we are aware, the chemical constituents have not been fully investigated. In this study, a practical method of mass spectral trees similarity filter, a data-mining technique, was developed and evaluated for the rapid detection and identification complicated constituents based on ultra-high-performance liquid chromatography-linear trap quadropole-Orbitrap-mass spectrometry. Finally, a total of 47 chlorogenic acids, including 19 monoacyl-quinic acids, 22 diacyl-quinic acids, and six triacyl-quinic acids, were unambiguously or tentatively identified based on their accurate mass measurement, chromatographic retention, MSn spectra, and bibliography data. To our best knowledge, it is the first time to report the chlorogenic acids of D. nervosa, which would be beneficial for the further material basis and quality research. Meanwhile, this mass spectral trees similarity filter method could be envisioned to exhibit a wide application for the identification of complicated components from botanical extracts.

Modeling molecular acidity with electronic properties and Hammett constants for substituted benzoic acids.

Molecular acidity is an important physiochemical property essential in many fields of molecular studies, but an efficient and reliable computational approach to make accurate predictions is still missing. In this work, based on our previous studies to use gas phase electronic properties such as molecular electrostatic potential and valence natural atomic orbitals of the acidic atom and leaving proton, we demonstrate here that different approaches can be employed to tackle this problem. To that end, we employ 196 singly, doubly, and triply substituted benzoic acids for the study. We show that two different approaches are possible, one focusing on the carboxyl group through its localized electronic properties and the other on the substituting groups via Hammett constants and their additivity rule. Our present results clearly exhibit that with the linear models built from the singly substituted species, one can accurately predict the pK(a) values for the doubly and triply substituted species with both of these two approaches. The predictions from these approaches are consistent with each other and agree well with the experimental data. These intrinsically different approaches are the two manifestations of the same molecular acidity property, both valid and complementary to each other.