Structures, Activities and Drug-Likeness of Anti-Infective Xanthone Derivatives Isolated from the Marine Environment: A Review

Nucleobase-Coupled Xanthones with Anti-ROS Effects from Marine-Derived Fungus Aspergillus sydowii

A MS/MS-based molecular networking approach compared to the Global Natural Product Social Molecular Networking library, in association with genomic annotation of natural product biosynthetic gene clusters within a marine-derived fungus, Aspergillus sydowii, identified a suite of xanthone metabolites. Chromatographic techniques applied to the cultured fungus led to the isolation of 11 xanthone-based alkaloids, dubbed sydoxanthones F-M. The structures of these alkaloids were elucidated using extensive spectroscopic data, including electronic circular dichroism and single-crystal X-ray diffraction data for configurational assignments. Among these analogues, sydoxanthones F-K exhibit structure features typical of nucleobase-coupled xanthones, with sydoxanthone H being an N-bonded xanthone dimer. Notably, (±)sydoxanthones F (1a/1b), (±)sydoxanthones H (3b/3a), and (±)sydoxanthones J (5b/5a) are enantiomeric pairs, while sydoxanthones G (2), I (4), and K (6) are stereoisomers of 1, 3, and 5, respectively. Furthermore, (+)sydoxanthone H (3a) demonstrated significant rescue of cell viability in H2O2-injuried SH-SY5Y cells by inhibiting reactive oxygen species production, suggesting its potential for neuroprotection.

Discovering targeted inhibitors for Escherichia coli efflux pump fusion proteins using computational and structure-guided approaches

Multidrug resistance pathogens causing infections and illness remain largely untreated clinically. Efflux pumps are one of the primary processes through which bacteria develop resistance by transferring antibiotics from the interior of their cells to the outside environment. Inhibiting these pumps by developing efficient derivatives appears to be a promising strategy for restoring antibiotic potency. This investigation explores literature-reported inhibitors of E. coli efflux pump fusion proteins AcrB-AcrA and identify potential chemical derivatives of these inhibitors to overcome the limitations. Using computational and structure-guided approaches, a study was conducted with the selected inhibitors (AcrA:25-AcrB:59) obtained by data mining and their derivatives (AcrA:857-AcrB:3891) to identify their inhibitory effect on efflux pump using virtual screening, molecular docking and density functional theory (DFT) calculations. The finding indicates that Compound 2 (ZINC000072136376) has shown better binding and a significant inhibitory effect on AcrA, while Compound 3 (ZINC000072266819) has shown stronger binding and substantial inhibition effect on both non-mutant and mutated AcrB subunits. The identified derivatives could exhibit a better inhibitor and provide a potential approach for restoring the actions of resistant antibiotics.

Ehretia Species Phytoconstituents as Potential Lead Compounds against Klebsiella pneumoniae Carbapenemase: A Computational Approach

The evolution of antibiotic-resistant carbapenemase has negatively impacted the management of critical healthcare-associated infections. K. pneumoniae carbapenemase-2- (KPC-2-) expressing bacteria have developed resistance to conventional therapeutic options, including those used as a last resort for life-threatening diseases. In this study, Ehretia species phytoconstituents were screened for their potential to inhibit KPC-2 protein using in silico approaches. Molecular docking was used to identify strong KPC-2 protein binding phytoconstituents retrieved from the literature. The best-docked conformation of the ligands was selected based on their glide energy and binding interactions. To determine their binding free energies, these hit compounds were subjected to molecular mechanics with generalized born and surface area (MM-GBSA) in the PRIME module. Pharmacological assessments of the ligands were performed to evaluate their drug-likeness. Molecular dynamic (MD) simulations were used to analyze the conformational stability of the selected druglike compounds within the active site of the KPC-2 protein. Overall, a total of 69 phytoconstituents were compiled from the literature. Fourteen of these compounds exhibited a stronger binding affinity for the protein target than the reference drugs. Four of these top hit compounds, DB09, DB12, DB28, and DB66, revealed the highest efficacy in terms of drug-likeness properties. The MD simulation established that among the druglike compounds, DB66 attained stable conformations after 150 ns simulation in the active site of the protein. We concluded that DB66 from Ehretia species could play a significant role in therapeutic efforts against KPC-2-expressing bacteria.

Synthesis and bioassay of 3-Aryl -1-(pyridin-4-yl)benzo[4,5]imidazo[1,2-d][1,2,4]- triazin-4(3H)-ones as anti-cancer agents

Four novel 3-Aryl -1-(pyridin-4-yl)benzo[4,5]imidazo[1,2-d][1,2,4]- triazin-4(3H)-ones derivatives (C1 to C4) have been designed, synthesized, and evaluated for their anticancer activity. The structure of compounds was characterized by IR,1H NMR, 13C NMR and high-resolution mass (HRMS). The crystal structures of C1, C2 and C4 were previously determined by single-crystal X-ray analysis.The results from docking experiments with EGFR suggested the binding of the compounds at the active site of EGFR. The new compounds exhibited different levels of cytotoxicity against HCC1937 and MCF7 breast cancer cells. Results of the MTT assay identified C3 as the most cytotoxic of the series against both MCF7 and HCC1937 breast cancer cell lines with IC50 values of 36.4 and 48.2 µM, respectively. In addition to its ability to inhibit cell growth and colony formation ability, C3 also inhibited breast cancer cell migration. Western blotting results showed that C3 treatment inhibited EGFR signaling and induced cell cycle arrest and apoptosis as indicated by the low level of p-EGFR and p-AKT and the increasing levels of p53, p21 and cleaved PARP. Our work represents a promising starting point for the development of a new series of compounds targeting cancer cells.

The Chemical Space of Marine Antibacterials: Diphenyl Ethers, Benzophenones, Xanthones, and Anthraquinones

The emergence of multiresistant bacteria and the shortage of antibacterials in the drug pipeline creates the need to search for novel agents. Evolution drives the optimization of the structure of marine natural products to act as antibacterial agents. Polyketides are a vast and structurally diverse family of compounds that have been isolated from different marine microorganisms. Within the different polyketides, benzophenones, diphenyl ethers, anthraquinones, and xanthones have shown promising antibacterial activity. In this work, a dataset of 246 marine polyketides has been identified. In order to characterize the chemical space occupied by these marine polyketides, molecular descriptors and fingerprints were calculated. Molecular descriptors were analyzed according to the scaffold, and principal component analysis was performed to identify the relationships among the different descriptors. Generally, the identified marine polyketides are unsaturated, water-insoluble compounds. Among the different polyketides, diphenyl ethers tend to be more lipophilic and non-polar than the remaining classes. Molecular fingerprints were used to group the polyketides according to their molecular similarity into clusters. A total of 76 clusters were obtained, with a loose threshold for the Butina clustering algorithm, highlighting the large structural diversity of the marine polyketides. The large structural diversity was also evidenced by the visualization trees map assembled using the tree map (TMAP) unsupervised machine-learning method. The available antibacterial activity data were examined in terms of bacterial strains, and the activity data were used to rank the compounds according to their antibacterial potential. This potential ranking was used to identify the most promising compounds (four compounds) which can inspire the development of new structural analogs with better potency and absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties.

A Review on Bioactive Compounds from Marine-Derived Chaetomium Species

Filamentous marine fungi have proven to be a plentiful source of new natural products. Chaetomium, a widely distributed fungal genus in the marine environment, has gained much interest within the scientific community. In the last 20 years, many potential secondary metabolites have been detected from marine-derived Chaetomium. In this review, we attempt to provide a comprehensive summary of the natural products produced by marine-derived Chaetomium species. A total of 122 secondary metabolites that were described from 2001 to 2021 are covered. The structural diversity of the compounds, along with details of the sources and relevant biological properties are also provided, while the relationships between structures and their bioactivities are discussed. It is our expectation that this review will be of benefit to drug development and innovation.

Marine-Derived Xanthone from 2010 to 2021: Isolation, Bioactivities and Total Synthesis

Marine life has proved to be an invaluable source of new compounds with significant bioactivities, such as xanthones. This review summarizes the advances made in the study of marine-derived xanthones from 2010 to 2021, from isolation towards synthesis, highlighting their biological activities. Most of these compounds were isolated from marine-derived fungi, found in marine sediments, and associated with other aquatic organisms (sponge and jellyfish). Once isolated, xanthones have been assessed for different bioactivities, such as antibacterial, antifungal, and cytotoxic properties. In the latter case, promising results have been demonstrated. Considering the significant bioactivities showed by xanthones, efforts have been made to synthesize these compounds, like yicathins B and C and the secalonic acid D, through total synthesis.

Bioactive Compounds and Their Derivatives: An Insight into Prospective Phytotherapeutic Approach against Alzheimer’s Disease

Alzheimer's disease (AD) is a common neurodegenerative brain disorder that causes cellular response alterations, such as impaired cholinergic mechanism, amyloid-beta (Aβ) AD aggregation, neuroinflammation, and several other pathways. AD is still the most prevalent form of dementia and affects many individuals across the globe. The exact cause of the disorder is obscure. There are yet no effective medications for halting, preventing, or curing AD's progress. Plenty of natural products are isolated from several sources and analyzed in preclinical and clinical settings for neuroprotective effects in preventing and treating AD. In addition, natural products and their derivatives have been promising in treating and preventing AD. Natural bioactive compounds play an active modulatory role in the pathological molecular mechanisms of AD development. This review focuses on natural products from plant sources and their derivatives that have demonstrated neuroprotective activities and maybe promising to treat and prevent AD. In addition, this article summarizes the literature pertaining to natural products as agents in the treatment of AD. Rapid metabolism, nonspecific targeting, low solubility, lack of BBB permeability, and limited bioavailability are shortcomings of most bioactive molecules in treating AD. We can use nanotechnology and nanocarriers based on different types of approaches.

phytochemdb: a platform for virtual screening and computer-aided drug designing

The phytochemicals of medicinal plants are regarded as a rich source of diverse chemical spaces that have been used as supplements and alternative medicines in the millennium. Even in this era of combinatorial chemical drugs, phytomedicines account for a large share of the statistics of newly approved drugs. In the field of computational aided and rational drug design, there is an urgent need to develop and build a useful phytochemical database management system with a user-friendly interface that allows proper data storage, retrieval and management. We showed ‘phytochemdb’, a manually managed database that compiles 525 plants and their corresponding 8093 phytochemicals, aiming to incorporate the activities of phytochemicals from medicinal plants. The database collects molecular formula, three-dimensional/two-dimensional structure, canonical SMILES, molecular weight, no. of heavy atoms, no. of aromatic heavy atoms, fraction Csp3, no. of rotatable bonds, no. of H-bond acceptors, no. of H-bond donors, molar refractivity, topological polar surface area, gastrointestinal absorption, Blood–Brain Barrier (BBB) permeant, P-gp substrate, CYP1A2 inhibitor, CYP2C19 inhibitor, CYP2C9 inhibitor, CYP2D6 inhibitor, CYP3A4 inhibitor, Log Kp, Ghose, Veber, Egan, Muegge, bioavailability scores, pan-assay interference compounds, Brenk, Leadlikeness, synthetic accessibility, iLOGP and Lipinski rule of five with the number of violations for each compound. It provides open contribution functions for the researchers who screen phytochemicals in the laboratory and have released their data. ‘phytochemdb’ is a comprehensive database that gathers most of the information about medicinal plants in one platform, which is considered to be very beneficial to the work of researchers on medicinal plants. ‘phytochemdb’ is available for free at https://phytochemdb.com/.

Synthesis and in vitro assay of hydroxyxanthones as antioxidant and anticancer agents

In the present work, three hydroxyxanthones were synthesized in 11.15–33.42% yield from 2,6-dihydroxybenzoic acid as the starting material. The chemical structures of prepared hydroxyxanthones have been elucidated by using spectroscopic techniques. Afterward, the hydroxyxanthones were evaluated as antioxidant agents through radical scavenging assay; and anticancer agents through in vitro assays against WiDr, MCF-7, and HeLa cancer cell lines. Hydroxyxanthone 3b was categorized as a strong antioxidant agent (IC₅₀ = 349 ± 68 µM), while the other compounds were categorized as moderate antioxidant agents (IC₅₀ > 500 µM). On the other hand, hydroxyxanthone 3a exhibited the highest anticancer activity (IC₅₀ = 184 ± 15 µM) and the highest selectivity (SI = 18.42) against MCF-7 cancer cells. From the molecular docking study, it was found that hydroxyxanthone 3a interacted with the active sites of Topoisomerase II protein through Hydrogen bonding with DG13 and π–π stacking interactions with DA12 and DC8. These findings revealed that hydroxyxanthones are potential candidates to be developed as antioxidant and anticancer agents in the future.

Promising bioactive compounds from the marine environment and their potential effects on various diseases

Background

The marine environment hosts a wide variety of species that have evolved to live in harsh and challenging conditions. Marine organisms are the focus of interest due to their capacity to produce biotechnologically useful compounds. They are promising biocatalysts for new and sustainable industrial processes because of their resistance to temperature, pH, salt, and contaminants, representing an opportunity for several biotechnological applications. Encouraged by the extensive and richness of the marine environment, marine organisms’ role in developing new therapeutic benefits is heading as an arable field.

Main body of the abstract

There is currently much interest in biologically active compounds derived from natural resources, especially compounds that can efficiently act on molecular targets, which are involved in various diseases. Studies are focused on bacteria and fungi, isolated from sediments, seawater, fish, algae, and most marine invertebrates such as sponges, mollusks, tunicates, coelenterates, and crustaceans. In addition to marine macro-organisms, such as sponges, algae, or corals, marine bacteria and fungi have been shown to produce novel secondary metabolites (SMs) with specific and intricate chemical structures that may hold the key to the production of novel drugs or leads. The marine environment is known as a rich source of chemical structures with numerous beneficial health effects. Presently, several lines of studies have provided insight into biological activities and neuroprotective effects of marine algae, including antioxidant, anti-neuroinflammatory, cholinesterase inhibitory activity, and neuronal death inhibition.

Conclusion

The application of marine-derived bioactive compounds has gained importance because of their therapeutic uses in several diseases. Marine natural products (MNPs) display various pharmaceutically significant bioactivities, including antibiotic, antiviral, neurodegenerative, anticancer, or anti-inflammatory properties. The present review focuses on the importance of critical marine bioactive compounds and their role in different diseases and highlights their possible contribution to humanity.

Modelling and targeting mitochondrial protein tyrosine phosphatase 1: a computational approach

The present research scintillates on the homology modelling of rat mitochondrial protein tyrosine phosphatase 1 (PTPMT1) and targeting its activity using flavonoids through a computational docking approach. PTPMT1 is a dual-specificity phosphatase responsible for protein phosphorylation and plays a vital role in the metabolism of cardiolipin biosynthesis, insulin regulation, etc. The inhibition of PTPMT1 has also shown enhanced insulin levels. The three-dimensional structure of the protein is not yet known. The homology modelling was performed using SWISS-MODEL and Geno3D webservers to compare the efficiencies. The PROCHECK for protein modelled using SWISS-MODEL showed 91.6% of amino acids in the most favoured region, 0.7% residues in the disallowed region that was found to be significant compared to the model built using Geno3D. 210 common flavonoids were docked in the modelled protein using the AutoDock 4.2.6 along with a control drug alexidine dihydrochloride. Our results show promising candidates that bind protein tyrosine phosphatase 1, including, prunin (- 8.66 kcal/mol); oroxindin (- 8.56 kcal/mol); luteolin 7-rutinoside (- 8.47 kcal/mol); 3(2H)-isoflavenes (- 8.36 kcal/mol); nicotiflorin (- 8.29 kcal/mol), ranked top in the docking experiments. We predicted the pharmacokinetic and Lipinski properties of the top ten compounds with the lowest binding energies. To further validate the stability of the modelled protein and docked complexes molecular dynamics simulations were performed using Desmond, Schrodinger for 150 ns in conjunction with MM-GBSA. Thus, flavonoids could act as potential inhibitors of PTPMT1, and further, in-vitro and in-vivo studies are essential to complete the drug development process.

Bioactive Marine Xanthones: A Review

The marine environment is an important source of specialized metabolites with valuable biological activities. Xanthones are a relevant chemical class of specialized metabolites found in this environment due to their structural variety and their biological activities. In this work, a comprehensive literature review of marine xanthones reported up to now was performed. A large number of bioactive xanthone derivatives (169) were identified, and their structures, biological activities, and natural sources were described. To characterize the chemical space occupied by marine-derived xanthones, molecular descriptors were calculated. For the analysis of the molecular descriptors, the xanthone derivatives were grouped into five structural categories (simple, prenylated, O-heterocyclic, complex, and hydroxanthones) and six biological activities (antitumor, antibacterial, antidiabetic, antifungal, antiviral, and miscellaneous). Moreover, the natural product-likeness and the drug-likeness of marine xanthones were also assessed. Marine xanthone derivatives are rewarding bioactive compounds and constitute a promising starting point for the design of other novel bioactive molecules.

Marine Bioactive Compounds as Nutraceutical and Functional Food Ingredients for Potential Oral Health

Oral diseases have received considerable attention worldwide as one of the major global public health problems. The development of oral diseases is influenced by socioeconomic, physiological, traumatic, biological, dietary and hygienic practices factors. Currently, the main prevention strategy for oral diseases is to inhibit the growth of biofilm-producing plaque bacteria. Tooth brushing is the most common method of cleaning plaque, aided by mouthwash and sugar-free chewing gum in the daily routine. As the global nutraceutical market grows, marine bioactive compounds are becoming increasingly popular among consumers for their antibacterial, anti-inflammatory and antitumor properties. However, to date, few systematic summaries and studies on the application of marine bioactive compounds in oral health exist. This review provides a comprehensive overview of different marine-sourced bioactive compounds and their health benefits in dental caries, gingivitis, periodontitis, halitosis, oral cancer, and their potential use as functional food ingredients for oral health. In addition, limitations and challenges of the application of these active ingredients are discussed and some observations on current work and future trends are presented in the conclusion section.

An Update on the Anticancer Activity of Xanthone Derivatives: A Review

The annual number of cancer deaths continues increasing every day; thus, it is urgent to search for and find active, selective, and efficient anticancer drugs as soon as possible. Among the available anticancer drugs, almost all of them contain heterocyclic moiety in their chemical structure. Xanthone is a heterocyclic compound with a dibenzo-γ-pyrone framework and well-known to have "privileged structures" for anticancer activities against several cancer cell lines. The wide anticancer activity of xanthones is produced by caspase activation, RNA binding, DNA cross-linking, as well as P-gp, kinase, aromatase, and topoisomerase inhibition. This anticancer activity depends on the type, number, and position of the attached functional groups in the xanthone skeleton. This review discusses the recent advances in the anticancer activity of xanthone derivatives, both from natural products isolation and synthesis methods, as the anticancer agent through in vitro, in vivo, and clinical assays.

Diversity-Oriented Synthesis of Spiropyrrolo[1,2-a]isoquinoline Derivatives via Diastereoselective and Regiodivergent Three-Component 1,3-Dipolar Cycloaddition Reactions: In Vitro and in Vivo Evaluation of the Antidiabetic Activity of Rhodanine Analogues

An efficient diastereoselective route is developed to get access to novel spiropyrrolo[1,2-a]isoquinoline-oxindole skeletons by a one-pot three-component [3 + 2] cycloaddition reaction of (Z)-5-arylidene-1,3-thiazolidine-2,4-diones, isatin derivatives, and 1,2,3,4-tetrahydroisoquinoline (THIQ). Interestingly, the regioselectivity of the reaction is both temperature- and solvent-dependent, allowing the synthesis of two regioisomeric endo-dispiropyrrolo[2,1-a]isoquinolineoxindoles in excellent yield. Unprecedentedly, each isomeric dispiropyrrolo[2,1-a]isoquinolineoxindole endured retro-1,3-dipolar cycloaddition/recycloaddition reactions under thermal or catalytic conditions to regenerate the corresponding regioisomeric counterpart. In addition, DFT calculations were performed at the M062X/6-31++g(d,p) level of theory to unravel the origin of the reversal of regioselectivity and endo-stereoselectivity of the title 1,3-dipolar cycloaddition reactions. Upon treatment of Isatin, THIQ with (Z)-4-arylidene-5-thioxo-thiazolidin-2-ones as dipolarophiles, unusual rhodanine analogues were formed, along with smaller amounts of a dispirooxindole-piperazine. The structure and the relative configuration of these N-heterocycles were unambiguously assigned by spectroscopic techniques and confirmed by four single-crystal structures. In vitro and in vivo studies reveal that the novel rhodanine derivatives exert antidiabetic activity. The binding affinity with the active site of the enzyme α-amylase was studied by molecular docking. Furthermore, the bioavailability assessed through virtual ADME parameters (Absorption, Distribution, Metabolism, Elimination pharmacokinetics) and the excellent fit with the Lipinski and Veber rules predict good drug-likeness properties for a bromo-substituted 2-sulfanylidene-1,3-thiazolidin-4-one.

Xanthone: A Promising Antimycobacterial Scaffold

BACKGROUND

Tuberculosis (TB) is one of the infectious diseases associated with high rate of morbidity and mortality and still remains one of the top-ten leading causes of human death in the world. The development of new anti-TB drugs is mandatory due to the existence of latent infection as well as the expansion of the resistant Mycobacterium tuberculosis (MBT) strains. Xanthones encompass a wide range of structurally diverse bioactive compounds, obtained either naturally or through chemical synthesis. There is a growing body of literature that recognizes the antitubercular activity of xanthone derivatives.

OBJECTIVE

The objective of this review is to highlight the main natural sources along with the critical design elements, structure-activity relationships (SARs), modes of action and pharmacokinetic profiles of xanthone-based anti-TB compounds.

METHODS

In the present review, the anti-TB activity of xanthones reported in the literature from 1972 to date is presented and discussed.

RESULTS

Exploration of xanthone scaffold led to the identification of several members of this class having superior activity against both sensitive and resistant MBT strains with distinctive mycobacterial membrane disrupting properties. However, studies regarding their modes of action, pharmacokinetic properties and safety are limited.

CONCLUSION

Comprehendible data and information are afforded by this review and it would certainly provide scientists with new thoughts and means which will be conducive to design and develop new drugs with excellent anti-TB activity through exploration of xanthone scaffold.

In Silico Repositioning of Dopamine Modulators with Possible Application to Schizophrenia: Pharmacophore Mapping, Molecular Docking and Molecular Dynamics Analysis

We have performed theoretical calculations with 70 drugs that have been considered in 231 clinical trials as possible candidates to repurpose drugs for schizophrenia based on their interactions with the dopaminergic system. A hypothesis of shared pharmacophore features was formulated to support our calculations. To do so, we have used the crystal structure of the D2-like dopamine receptor in complex with risperidone, eticlopride, and nemonapride. Linagliptin, citalopram, flunarizine, sildenafil, minocycline, and duloxetine were the drugs that best fit with our model. Molecular docking calculations, molecular dynamics outcomes, blood-brain barrier penetration, and human intestinal absorption were studied and compared with the results. From the six drugs selected in the shared pharmacophore features input, flunarizine showed the best docking score with D2, D3, and D4 dopamine receptors and had high stability during molecular dynamics simulations. Flunarizine is a frequently used medication to treat migraines and vertigo. However, its antipsychotic properties have been previously hypothesized, particularly because of its possible ability to block the D2 dopamine receptors.

Xanthones Active against Multidrug Resistance and Virulence Mechanisms of Bacteria

The emergence of multidrug and extensively drug-resistant pathogenic bacteria able to resist to the action of a wide range of antibiotics is becoming a growing problem for public health. The search for new compounds with the potential to help in the reversion of bacterial resistance plays an important role in current medicinal chemistry research. Under this scope, bacterial efflux pumps are responsible for the efflux of antimicrobials, and their inhibition could reverse resistance. In this study, the multidrug resistance reversing activity of a series of xanthones was investigated. Firstly, docking studies were performed in the AcrAB-TolC efflux pump and in a homology model of the NorA pump. Then, the effects of twenty xanthone derivatives on bacterial growth were evaluated in Staphylococcus aureus 272123 and in the acrA gene-inactivated mutant Salmonella enterica serovar Typhimurium SL1344 (SE03). Their efflux pump inhibitory properties were assessed using real-time fluorimetry. Assays concerning the activity of these compounds towards the inhibition of biofilm formation and quorum sensing have also been performed. Results showed that a halogenated phenylmethanamine xanthone derivative displayed an interesting profile, as far as efflux pump inhibition and biofilm formation were concerned. To the best of our knowledge, this is the first report of xanthones as potential efflux pump inhibitors.

Antibacterial Secondary Metabolites from Marine-Derived Fungus Aspergillus sp. IMCASMF180035

Four new secondary metabolites, including one spiro[anthracenone-xanthene] derivative aspergiloxathene A (1), one penicillide analogue, Δ^2′-1′-dehydropenicillide (2), and two new phthalide derivatives, 5-methyl-3-methoxyepicoccone (3) and 7-carboxy-4-hydroxy-6-methoxy-5-methylphthalide (4), together with four known compounds, yicathin C (5), dehydropenicillide (6), 3-methoxyepicoccone (7), 4-hydroxy-6-methoxy-5-methylphthalide (8), were identified from the marine-derived fungus Aspergillus sp. IMCASMF180035. Their structures were determined by spectroscopic data, including high-resolution electrospray ionization mass spectrometry (HRESIMS), 1D and 2D nuclear magnetic resonance (NMR) techniques. Compound 1 was identified as the first jointed molecule by xanthene and anthracenone moieties possessing an unprecedented carbon skeleton with spiro-ring system. All compounds were evaluated activities against Staphylococcus aureus, methicillin resistant S. aureus (MRSA), Escherichia coli, Escherichia faecium, Pseudomonas aeruginosa, and Helicobacter pylori. Compound 1 showed significant inhibitory effects against S. aureus and MRSA, with minimum inhibitory concentration (MIC) values of 5.60 and 22.40 µM. Compounds 2 and 6 exhibited potent antibacterial activities against H. pylori, with MIC values of 21.73 and 21.61 µM, respectively.

Analogue discovery of safer alternatives to HCQ and CQ drugs for SAR-CoV-2 by computational design

COVID-19 outbreak poses a severe health emergency to the global community. Due to availability of limited data, the selection of an effective treatment is a challenge. Hydroxychloroquine (HCQ), a chloroquine (CQ) derivative administered for malaria and autoimmune diseases, has been shown to be effective against both Severe Acute Respiratory Syndrome (SARS-CoV-1) and SARS-CoV-2. Apart from the known adverse effects of these drugs, recently the use of CQ and HCQ as a potential treatment for COVID-19 is under flux globally. In this study, we focused on identifying a more potent analogue of HCQ and CQ against the spike protein of SAR-CoV-2 that can act as an effective antiviral agent for COVID-19 treatment. Systematic pharmacokinetics, drug-likeness, basicity predictions, virtual screening and molecular dynamics analysis (200 ns) were carried out to predict the inhibition potential of the analogous compounds on the spike protein. This work identifies the six potential analogues, out of which two compounds, namely 1-[1-(6-Chloroquinolin-4-yl) piperidin-4-yl]piperidin-3-ol and (1R,2R)-2-N-(7-Chloroquinolin-4-yl)cyclohexane-1,2-diamine interact with the active site of the spike protein similar to HCQ and CQ respectively with augmented safety profile.

Characterisation of twelve newly synthesised N-(substituted phenyl)-2-chloroacetamides with QSAR analysis and antimicrobial activity tests

In this study we screened twelve newly synthesised N-(substituted phenyl)-2-chloroacetamides for antimicrobial potential relying on quantitative structure-activity relationship (QSAR) analysis based on the available cheminformatics prediction models (Molinspiration, SwissADME, PreADMET, and PkcSM) and verified it through standard antimicrobial testing against Escherichia coli, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and Candida albicans. Our compounds met all the screening criteria of Lipinski’s rule of five (Ro5) as well as Veber’s and Egan’s methods for predicting biological activity. In antimicrobial activity tests, all chloroacetamides were effective against Gram-positive S. aureus and MRSA, less effective against the Gram-negative E. coli, and moderately effective against the yeast C. albicans. Our study confirmed that the biological activity of chloroacetamides varied with the position of substituents bound to the phenyl ring, which explains why some molecules were more effective against Gram-negative than Gram-positive bacteria or C. albicans. Bearing the halogenated p-substituted phenyl ring, N-(4-chlorophenyl), N-(4-fluorophenyl), and N-(3-bromophenyl) chloroacetamides were among the most active thanks to high lipophilicity, which allows them to pass rapidly through the phospholipid bilayer of the cell membrane. They are the most promising compounds for further investigation, particularly against Gram-positive bacteria and pathogenic yeasts.

From Natural Products to New Synthetic Small Molecules: A Journey through the World of Xanthones

This work reviews the contributions of the corresponding author (M.M.M.P.) and her research group to Medicinal Chemistry concerning the isolation from plant and marine sources of xanthone derivatives as well as their synthesis, biological/pharmacological activities, formulation and analytical applications. Although her group activity has been spread over several chemical families with relevance in Medicinal Chemistry, the main focus of the investigation and research has been in the xanthone family. Xanthone derivatives have a variety of activities with great potential for therapeutic applications due to their versatile framework. The group has contributed with several libraries of xanthones derivatives, with a variety of activities such as antitumor, anticoagulant, antiplatelet, anti-inflammatory, antimalarial, antimicrobial, hepatoprotective, antioxidant, and multidrug resistance reversal effects. Besides therapeutic applications, our group has also developed xanthone derivatives with analytical applications as chiral selectors for liquid chromatography and for maritime application as antifouling agents for marine paints. Chemically, it has been challenging to afford green chemistry methods and achieve enantiomeric purity of chiral derivatives. In this review, the structures of the most significant compounds will be presented.

A Pyranoxanthone as a Potent Antimitotic and Sensitizer of Cancer Cells to Low Doses of Paclitaxel

Microtubule-targeting agents (MTAs) remain a gold standard for the treatment of several cancer types. By interfering with microtubules dynamic, MTAs induce a mitotic arrest followed by cell death. This antimitotic activity of MTAs is dependent on the spindle assembly checkpoint (SAC), which monitors the integrity of the mitotic spindle and proper chromosome attachments to microtubules in order to ensure accurate chromosome segregation and timely anaphase onset. However, the cytotoxic activity of MTAs is restrained by drug resistance and/or toxicities, and had motivated the search for new compounds and/or alternative therapeutic strategies. Here, we describe the synthesis and mechanism of action of the xanthone derivative pyranoxanthone 2 that exhibits a potent anti-growth activity against cancer cells. We found that cancer cells treated with the pyranoxanthone 2 exhibited persistent defects in chromosome congression during mitosis that were not corrected over time, which induced a prolonged SAC-dependent mitotic arrest followed by massive apoptosis. Importantly, pyranoxanthone 2 was able to potentiate apoptosis of cancer cells treated with nanomolar concentrations of paclitaxel. Our data identified the potential of the pyranoxanthone 2 as a new potent antimitotic with promising antitumor potential, either alone or in combination regimens.

Anti-Tumor Xanthones from Garcinia nujiangensis Suppress Proliferation, and Induce Apoptosis via PARP, PI3K/AKT/mTOR, and MAPK/ERK Signaling Pathways in Human Ovarian Cancers Cells

Background

Ovarian cancer (OC) is a serious public health concern in the world. It is important to develop novel drugs to inhibit OC.

Purpose

This study investigated the isolation, elucidation, efficiency, molecular docking, and pharmaceutical mechanisms of xanthones isolated from Garcinia nujiangensis.

Methods

Xanthones were isolated, and purified by different chromatography, including silica gel, reversed-phase silica gel (ODS-C₁₈), and semipreparative HPLC, then identified by analysis of their spectral data. Three xanthones were estimated for their efficiency on the human OC cells HEY and ES-2. 2 was found to be the most potent cytotoxic xanthones of those tested. Further, its mechanisms of action were explored by molecular docking, cell apoptosis, and Western blotting analysis.

Results

Bioassay-guided fractionation of the fruits of Garcinia nujiangensis led to the separation of a new xanthone named nujiangexanthone G (1) and two known xanthones. Among these, isojacareubin (2) exhibited the most potent cytotoxic compound against the HEY and ES-2 cell lines. The analysis of Western blot suggested that 2 inhibited OC via regulating the PARP, PI3K/AKT/mTOR, and ERK/MAPK signal pathways in the HEY cell lines.

Conclusion

In conclusion, isojacareubin (2) might be a potential drug for the treatment of OC.

Rational design of new multitarget histamine H3 receptor ligands as potential candidates for treatment of Alzheimer's disease

Design and development of multitarget-directed ligands (MTDLs) has become a very important approach in the search of new therapies for Alzheimer's disease (AD). In our present research, a number of xanthone derivatives were first designed using a pharmacophore model for histamine H₃ receptor (H₃R) antagonists/inverse agonists, and virtual docking was then performed for the enzyme acetylcholinesterase. Next, 23 compounds were synthesised and evaluated in vitro for human H₃R (hH₃R) affinity and inhibitory activity on cholinesterases. Most of the target compounds showed hH₃R affinities in nanomolar range and exhibited cholinesterase inhibitory activity with IC₅₀ values in submicromolar range. Furthermore, the inhibitory effects of monoamine oxidases (MAO) A and B were investigated. The results showed low micromolar and selective human MAO B (hMAO B) inhibition. Two azepane derivatives, namely 23 (2-(5-(azepan-1-yl)pentyloxy)-9H-xanthen-9-one) and 25 (2-(5-(azepan-1-yl)pentyloxy)-7-chloro-9H-xanthen-9-one), were especially very promising and showed high affinity for hH₃R (K_i = 170 nM and 100 nM respectively) and high inhibitory activity for acetylcholinesterase (IC₅₀ = 180 nM and 136 nM respectively). Moreover, these compounds showed moderate inhibitory activity for butyrylcholinesterase (IC₅₀ = 880 nM and 394 nM respectively) and hMAO B (IC₅₀ = 775 nM and 897 nM respectively). Furthermore, molecular docking studies were performed for hH₃R, human cholinesterases and hMAO B to describe the mode of interactions with these biological targets. Next, the two most promising compounds 23 and 25 were selected for in vivo studies. The results showed significant memory-enhancing effect of compound 23 in dizocilpine-induced amnesia in rats in two tests: step-through inhibitory avoidance paradigm (SIAP) and transfer latency paradigm time (TLPT). In addition, favourable analgesic effects of compound 23 were observed in neuropathic pain models. Therefore, compound 23 is a particularly promising structure for further design of new MTDLs for AD.

Synthesis of a Small Library of Nature-Inspired Xanthones and Study of Their Antimicrobial Activity

A series of thirteen xanthones 3–15 was prepared based on substitutional (appendage) diversity reactions. The series was structurally characterized based on their spectral data and HRMS, and the structures of xanthone derivatives 1, 7, and 8 were determined by single-crystal X-ray diffraction. This series, along with an in-house series of aminated xanthones 16–33, was tested for in-vitro antimicrobial activity against seven bacterial (including two multidrug-resistant) strains and five fungal strains. 1-(Dibromomethyl)-3,4-dimethoxy-9H-xanthen-9-one (7) and 1-(dibromomethyl)-3,4,6-trimethoxy-9H-xanthen-9-one (8) exhibited antibacterial activity against all tested strains. In addition, 3,4-dihydroxy-1-methyl-9H-xanthen-9-one (3) revealed a potent inhibitory effect on the growth of dermatophyte clinical strains (T. rubrum FF5, M. canis FF1 and E. floccosum FF9), with a MIC of 16 µg/mL for all the tested strains. Compounds 3 and 26 showed a potent inhibitory effect on two C. albicans virulence factors: germ tube and biofilm formation.

Yicathins B and C and Analogues: Total Synthesis, Lipophilicity and Biological Activities

Natural products have always been an important source of new hits and leads in drug discovery, with the marine environment being regarded as a significant source of novel and exquisite bioactive compounds. Yicathins B and C are two marine-derived xanthones that have shown antibacterial and antifungal activity. Herein, the total synthesis of these yicathins and six novel analogues is reported for the first time. As marine natural products tend to have very lipophilic scaffolds, the lipophilicity of yicathins and their analogues was evaluated in the classical octanol/water system and a biomimetic model-based system. As the xanthonic nucleus is a "privileged structure", other biological activities were evaluated, namely antitumor and anti-inflammatory activities. An interesting anti-inflammatory activity was identified for yicathin analogues that paves the way for the design of dual activity (anti-infective and anti-inflammatory) marine-inspired xanthone derivatives.

Xanthones, A Promising Anti-Inflammatory Scaffold: Structure, Activity, and Drug Likeness Analysis

Inflammation is the body's self-protective response to multiple stimulus, from external harmful substances to internal danger signals released after trauma or cell dysfunction. Many diseases are considered to be related to inflammation, such as cancer, metabolic disorders, aging, and neurodegenerative diseases. Current therapeutic approaches include mainly non-steroidal anti-inflammatory drugs and glucocorticoids, which are generally of limited effectiveness and severe side-effects. Thus, it is urgent to develop novel effective anti-inflammatory therapeutic agents. Xanthones, a unique scaffold with a 9H-Xanthen-9-one core structure, widely exist in natural sources. Till now, over 250 xanthones were isolated and identified in plants from the families Gentianaceae and Hypericaceae. Many xanthones have been disclosed with anti-inflammatory properties on different models, either in vitro or in vivo. Herein, we provide a comprehensive and up-to-date review of xanthones with anti-inflammatory properties, and analyzed their drug likeness, which might be potential therapeutic agents to fight against inflammation-related diseases.

Recent advances in the synthesis of xanthones and azaxanthones

A useful chemical toolbox for (aza)xanthones from 2012 to 2020 that covers the optimization of known procedures and novel methodologies.

Fatty Acid, Lipid Classes and Phospholipid Molecular Species Composition of the Marine Clam Meretrix lyrata (Sowerby 1851) from Cua Lo Beach, Nghe An Province, Vietnam

This study aims to analyze compositions of fatty acids and phospholipid molecular species in the hard clams Meretrix lyrata (Sowerby, 1851) harvested from Cua Lo beach, Nghe An province, Viet Nam. Total lipid of hard clams Meretrix lyrata occupied 1.7 ± 0.2% of wet weight and contained six classes: hydrocarbon and wax (HW), triacylglycerol (TAG), free fatty acids (FFA), sterol (ST), polar lipid (PoL), and monoalkyl diacylglycerol (MADAG). Among the constituents, the proportion of PoL accounted was highest, at 45.7%. In contrast, the figures for MADAG were lowest, at 1.3%. Twenty-six fatty acids were identified with the ratios of USAFA/SAFA was 2. The percentage of n-3 PUFA (ω-3) and n-6 PUFA (ω-6) was high, occupying 38.4% of total FA. Among PUFAs, arachidonic acid (AA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3), docosapentaenoic acid (DPA, 22:5n-3), and docosahexaenoic acid (DHA, 22:6n-3) accounted for 3.8%, 7.8%, 2.2% and 12.0% of total lipid of the clam respectively. Phospholipid molecular species were identified in polar lipids of the clams consisting six types: phosphatidylethalnolamine (PE, with 28 molecular species), phosphatidylcholine (PC, with 26 molecular species), phosphatidylserine (PS, with 18 molecular species), phosphatidylinositol (PI, with 10 molecular species), phosphatidylglycerol (PG, with only one molecular species), and ceramide aminoethylphosphonate (CAEP, with 15 molecular species). This is the first time that the molecular species of sphingophospholipid were determined, in Meretrix lyrata in particular, and for clams in general. Phospholipid formula species of PE and PS were revealed to comprise two kinds: Alkenyl acyl glycerophosphoethanolamine and Alkenyl acyl glycerophosphoserine occupy 80.3% and 81.0% of total PE and PS species, respectively. In contrast, the percentage of diacyl glycero phosphatidylcholine was twice as high as that of PakCho in total PC, at 69.3, in comparison with 30.7%. In addition, phospholipid formula species of PI and PG comprised only diacyl glycoro phospholipids. PE 36:1 (p18:0/18:1), PC 38:6 (16:0/22:6), PS 38:1 (p18:0/20:1), PI 40:5 (20:1/20:4), PG 32:0 (16:0/16:0) and CAEP 34:2 (16:2/d18:0) were the major molecular species.