Enhanced biological activities of coumarin-functionalized polysaccharide derivatives: Chemical modification and activity assessment.

Natural polysaccharides are abundant and renewable resource, but their applications are hampered by limited biological activity. Chemical modification can overcome these drawbacks by altering their structure. Three series of polysaccharide derivatives with coumarins were synthesized to obtain polysaccharide derivatives with enhanced biological activity. The biological activities were tested, including antioxidant property, antifungal property, and antibacterial property. Based on the results, the inhibitory properties of the coumarin-polysaccharide derivatives were significantly improved over the raw polysaccharide. The IC50 of the inhibition of DPPH, ABTS•+, and superoxide (O2•-) radical-scavenging was 0.06-0.15 mg/mL, 2.3-15.9 µg/mL, and 0.03-0.25 mg/mL, respectively. Compared with the raw polysaccharides, coumarin- polysaccharide derivatives exhibited higher efficacy in inhibiting the growth of tested phytopathogens, showing inhibitory indices of 60.0-93.6 % at 1.0 mg/mL. Chitosan derivatives with methyl and chlorine (Compound 10B and 10C) exhibited significant antibacterial activity against S. aureus (MIC = 31.2 µg/mL), E. coli (MIC = 7.8 µg/mL), and V. harveyi (MIC = 15.6 µg/mL), respectively. The results of the cytotoxicity assay showed no observed cytotoxicity when the RAW 264.7 cells were incubated with the synthesized polysaccharide derivatives at the tested concentrations.

Design, Spectroscopy, and Assessment of Cholinesterase Inhibition and Antimicrobial Activities of Novel Coumarin-Thiadiazole Hybrids.

A novel series of coumarin-thiadiazole hybrids, derived from substituted coumarin-3-carboxylic acids was isolated and fully characterized with the use of a number of spectroscopic techniques and XRD crystallography. Several of the novel compounds showed intensive fluorescence in the visible region, comparable to that of known coumarin-based fluorescence standards. Moreover, the new compounds were tested as potential antineurodegenerative agents via their ability to act as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. Compared to the commercial standards, only a few compounds demonstrated moderate AChE and BuChE activities. Moreover, the novel derivatives were tested for their antimicrobial activity against a panel of pathogenic bacterial and fungal species. Their lack of activity and toxicity across a broad range of biochemical assays, together with the exceptional emission of some hybrid molecules, highlights the possible use of a number of the novel hybrids as potential fluorescence standards or fluorescence imaging agents.

Novel coumarin-functionalized inulin derivatives: Chemical modification and antioxidant activity assessment.

In this paper, a series of target derivatives were synthesized by introducing coumarin into inulin structure using three-step chemical modification, and their structures were characterized by FTIR, 1H NMR, and 13C NMR. At the same time, the antioxidant activities of inulin derivatives were determined, including DPPH-radical scavenging activity, superoxide-radical scavenging activity, PTIO-radical scavenging activity and reducing ability. The test results showed that the antioxidant activities of inulin derivatives containing coumarin were significantly increased. Especially, inulin derivatives showed excellent DPPH radical-scavenging ability (IC50 0.09-0.11 mg/mL). Meanwhile, the scavenging ability of PTIO-radical was increased by more than 80%, and the IC50 values were all between 0.23 and 0.26 mg/mL. At the concentration below 1 mg/mL, the scavenging rate of all inulin derivatives could even reach 100%. This study provides a feasible way to synthesize inulin derivatives with significant activity, which may be developed into new antioxidants in medicine and cosmetics.

O-prenylated carbostyrils as a novel class of 15-lipoxygenase inhibitors: Synthesis, characterization, and inhibitory assessment.

Catalyzed peroxidation of unsaturated lipid in animals and plants intimately is linked to the activity of 15-Lipoxygenase enzymes. Lipoxygenases (LOXs) are well known to play an important role in many acute and chronic syndromes such as inflammation, asthma, cancer, and allergy. In this study, a series of mono prenyloxycarbostyrils were synthesized and evaluated as potential inhibitors of soybean 15-Lipoxygenase (SLO) and their inhibitory potencies were compared to mono prenyloxycoumarins which had been reported in the previous works. The synthetic compounds inhibit lipoxygenase enzyme by competitive mechanism like the prenyloxy coumarins. The results showed that position and length of the prenyl moiety play the important role in lipoxygenase inhibitory activity. Among all of the synthetic compounds (coumarin and carbostyril derivatives), 5-farnesyloxycoumarin and 8-farnesyloxycarbostyril demonstrated the best inhibitory activity by IC50  values of 1.1 µM and 0.53 µM, respectively.

Assessment of Conventional Solvent Extraction vs. Supercritical Fluid Extraction of Khella (Ammi visnaga L.) Furanochromones and Their Cytotoxicity.

BACKGROUND: Khella (Ammi visnaga Lam.) fruits (Apiaceae) are rich in furanochromones, mainly khellin and visnagin, and are thus incorporated in several pharmaceutical products used mainly for treatment of renal stones. METHODS: The objective of this study was to compare the yield of khellin and visnagin obtained using different conventional solvents and supercritical fluid extraction (SCFE) with carbon dioxide (containing 5% methanol as co-solvent). Water, acetone and ethanol (30% and 95%) were selected as conventional solvents. RESULTS: Highest extract yield was obtained from 30% ethanol (15.44%), while SCFE gave the lowest yield (4.50%). However, the percentage of furanochromones were highest in SCFE (30.1%), and lowest in boiling water extract (5.95%). HPLC analysis of conventional solvent extracts showed other coumarins that did not appear in supercritical fluid extraction chromatogram due to non-selectivity of solvent extraction. Ammi visnaga extracts as well as standard khellin and visnagin were tested for their cytotoxic activity using sulforhodamine B assay on breast cancer (MCF-7) and hepatocellular carcinoma (Hep G2) cell lines. Results revealed a strong cytotoxic activity (IC50 < 20 µg/mL) for the SCFE and standard compounds (khellin and visnagin) (IC50 ranging between 12.54 ± 0.57 and 17.53 ± 1.03 µg/mL). However, ethanol and acetone extracts had moderate cytotoxic activity (IC50 20-90 µg/mL) and aqueous extract had a weak activity (IC50 > 90 µg/mL). CONCLUSIONS: Thus, supercritical fluid extraction is an efficient, relatively safe, and cheap technique that yielded a more selective purified extract with better cytotoxic activity.

Predictive QSAR modeling for the antioxidant activity of natural compounds derivatives based on Monte Carlo method.

In this research, QSAR modeling was carried out through SMILES of compounds and on the basis of the Monte Carlo method to predict the antioxidant activity of 79 derivatives of pulvinic acid, 23 of coumarine, as well as nine structurally non-related compounds against three radiation sources of Fenton, gamma, and UV. QSAR model was designed through CORAL software, as well as a newer optimizing method well known as the index of ideality correlation. The full set of antioxidant compounds were randomly distributed into four sets, including training, invisible training, validation, and calibration; this division was repeated three times randomly. The optimal descriptors were picked up from a hybrid model by the combination of the hydrogen-suppressed graph and SMILES descriptors based on the objective function. These models' predictability was assessed on the sets of validation. The results of three randomized sets showed that simple, robust, reliable, and predictive models were achieved for training, invisible training, validation, and calibration sets of all three models. The central decrease/increase descriptors were identified. This simple QSAR can be useful to predict antioxidant activity of numerous antioxidants.

The Application of the Combination of Monte Carlo Optimization Method based QSAR Modeling and Molecular Docking in Drug Design and Development.

In recent years, one of the promising approaches in the QSAR modeling Monte Carlo optimization approach as conformation independent method, has emerged. Monte Carlo optimization has proven to be a valuable tool in chemoinformatics, and this review presents its application in drug discovery and design. In this review, the basic principles and important features of these methods are discussed as well as the advantages of conformation independent optimal descriptors developed from the molecular graph and the Simplified Molecular Input Line Entry System (SMILES) notation compared to commonly used descriptors in QSAR modeling. This review presents the summary of obtained results from Monte Carlo optimization-based QSAR modeling with the further addition of molecular docking studies applied for various pharmacologically important endpoints. SMILES notation based optimal descriptors, defined as molecular fragments, identified as main contributors to the increase/ decrease of biological activity, which are used further to design compounds with targeted activity based on computer calculation, are presented. In this mini-review, research papers in which molecular docking was applied as an additional method to design molecules to validate their activity further, are summarized. These papers present a very good correlation among results obtained from Monte Carlo optimization modeling and molecular docking studies.

DFT/MRCI assessment of the excited-state interplay in a coumarin-schiff Mg2+ fluorescent sensor.

Fluorescent sensors with selectivity and sensitivity to metal ions are an active field in supramolecular chemistry for biochemical, analytical, and environmental problems. Mg2+ is one of the most abundant divalent ions in the cell, and it plays a critical role in many biological processes. Coumarin-based sensors are widely used as desirable fluorophore and binding moieties showing a remarkable sensitivity and fluorometric enhancement for Mg2+ . In this work, density functional theory/multireference configuration interaction (DFT/MRCI) calculations were performed in order to understand the sensing behavior of the organic fluorescent sensor 7-hydroxy-4-methyl-8-((2-(pyridin-2-yl)hydrazono)methyl)-2H-chromen-2-one (PyHC) in ethanol to solvated Mg2+ ions. The computed optical properties reproduce well-reported experimental data. Our results suggest that after photoexcitation of the free PyHC, a photo-induced electron transfer (PET) mechanism may compete with the fluorescence decay to the ground state. In contrast, this PET channel is no longer available in the complex with Mg2+ making the emissive decay more efficient. © 2019 Wiley Periodicals, Inc.

Novel coumarins active against Trypanosoma cruzi and toxicity assessment using the animal model Caenorhabditis elegans.

BACKGROUND: Chagas disease (CD) is a tropical parasitic disease. Although the number of people infected is very high, the only drugs available to treat CD, nifurtimox (Nfx) and benznidazole, are highly toxic, particularly in the chronic stage of the disease. Coumarins are a large class of compounds that display a wide range of interesting biological properties, such as antiparasitic. Hence, the aim of this work is to find a good antitrypanosomal drug with less toxicity. The use of simple organism models has become increasingly attractive for planning and simplifying efficient drug discovery. Within these models, Caenorhabditis elegans has emerged as a convenient and versatile tool with significant advantages for the toxicological potential identification for new compounds. METHODS: Trypanocidal activity: Forty-two 4-methylamino-coumarins were assayed against the epimastigote form of Trypanosoma cruzi (Tulahuen 2 strain) by inhibitory concentration 50% (IC50). Toxicity assays: Lethal dose 50% (LD50) and Body Area were determined by Caenorhabditis elegans N2 strain (wild type) after acute exposure. Structure-activity relationship: A classificatory model was built using 3D descriptors. RESULTS: Two of these coumarins demonstrated near equipotency to Nifurtimox (IC50 = 5.0 ± 1 µM), with values of: 11 h (LaSOM 266), (IC50 = 6.4 ± 1 µM) and 11 g (LaSOM 231), (IC50 = 8.2 ± 2.3 µM). In C. elegans it was possible to observe that Nfx showed greater toxicity in both the LD50 assay and the evaluation of the development of worms. It is possible to observe that the efficacy between Nfx and the synthesized compounds (11 h and 11 g) are similar. On the other hand, the toxicity of Nfx is approximately three times higher than that of the compounds. Results from the QSAR-3D study indicate that the volume and hydrophobicity of the substituents have a significant impact on the trypanocidal activities for derivatives that cause more than 50% of inhibition. These results show that the C. elegans model is efficient for screening potentially toxic compounds. CONCLUSION: Two coumarins (11 h and 11 g) showed activity against T. cruzi epimastigote similar to Nifurtimox, however with lower toxicity in both LD50 and development of C. elegans assays. These two compounds may be a feasible starting point for the development of new trypanocidal drugs.

Proposal for an ecofriendly and economic strategy for efficient radioiodination of coumarin derivatives.

Combination of the calculation of reactivity descriptors and the cold iodine test for some coumarin derivatives was used in order to optimize the radioiodination reaction. The strongly nucleophilic predicted coumarins were subjected to the action of cold iodine. With two coumarins substituted at 3 by the 2-hydroxybenzoyl group, iodination did not occur but a product of intramolecular heterocyclization was obtained. This strategy is useful for economic and environmentally friendly radioiodination.

Radiation Chemical Yield of Hydroxyl Radicals for Accelerator-based Boron Neutron Capture Therapy: Dose Assessment of 10B(n,α)7Li Reaction Using Coumarin-3-Carboxilic Solution.

Evaluation of the characteristics of accelerator-based thermal neutron fields is recognized as an important issue when discussing the effectiveness of boron neutron capture therapy (BNCT). In this study, we propose that the radiation chemical yield (G value) of hydroxyl radicals (Goh•) can be considered a universal parameter for the description of the accelerator-based thermal neutron field. The Goh• of the 10B(n,α)7Li reaction was quantitatively evaluated using an aqueous coumarin-3-carboxylic acid (3CCA) solution, and was discriminated from that of contaminations (i.e., γ rays and fast neutrons). The Goh• of the 10B(n,α)7Li reaction was 0.107 ± 0.004 OH•/100 eV, which is almost equivalent to that exposed to α particles with an energy of 6.0 MeV. Since the Goh• of γ rays from a 60Co source is 2.03 ± 0.05 OH•/100 eV, this lower value suggests that indirect action by the 10B(n,α)7Li reaction is not dominant in BNCT. However, our results indicate that one can assess the 60Co equivalent dose of the 10B(n,α)7Li reaction in water from the Goh• derived using aqueous 3CCA solution in the accelerator-based thermal neutron field.

Molecular Mechanics Simulations and Improved Tight-Binding Hamiltonians for Artificial Light Harvesting Systems: Predicting Geometric Distributions, Disorder, and Spectroscopy of Chromophores in a Protein Environment.

We present molecular mechanics and spectroscopic calculations on prototype artificial light harvesting systems consisting of chromophores attached to a tobacco mosaic virus (TMV) protein scaffold. These systems have been synthesized and characterized spectroscopically, but information about the microscopic configurations and geometry of these TMV-templated chromophore assemblies is largely unknown. We use a Monte Carlo conformational search algorithm to determine the preferred positions and orientations of two chromophores, Coumarin 343 together with its linker and Oregon Green 488, when these are attached at two different sites (104 and 123) on the TMV protein. The resulting geometric information shows that the extent of disorder and aggregation properties and therefore the optical properties of the TMV-templated chromophore assembly are highly dependent on both the choice of chromophores and the protein site to which they are bound. We use the results of the conformational search as geometric parameters together with an improved tight-binding Hamiltonian to simulate the linear absorption spectra and compare with experimental spectral measurements. The ideal dipole approximation to the Hamiltonian is not valid because the distance between chromophores can be very small. We found that using the geometries from the conformational search is necessary to reproduce the features of the experimental spectral peaks.

Safety assessment of Urolithin A, a metabolite produced by the human gut microbiota upon dietary intake of plant derived ellagitannins and ellagic acid.

Urolithins are metabolites produced in the gut following consumption of ellagitannins and ellagic acid rich foods such as pomegranates, nuts and certain berries. Urolithin A (UA) is one of the predominant isoforms of urolithins in humans and has demonstrated compelling biological activities, suggesting potential benefits of direct consumption of UA. However, an evaluation of the safety of direct administration of UA has not yet been published. The aim of this study was to investigate for the first time the genotoxicity, toxicokinetics, and repeated dose safety of orally administered synthetic UA in rats. The battery of genotoxicity assays demonstrated that UA is not genotoxic. The ADME study showed that glucuronidated and sulfonated forms of UA are the predominant metabolites following both oral and i.v. administration. The 28-day (0, 0.175, 1.75, and 5.0% UA mixed in diet) and 90-day studies (0, 1.25, 2.5, and 5.0% UA mixed in diet) showed no alterations in clinical parameters, blood chemistry, or hematology, and did not indicate any target organs, or any specific toxic mechanisms. The NOAEL was the highest dose tested, 5% UA by weight in the diet, or 3451 mg/kg bw/day in males and 3826 mg/kg bw/day in females in the 90-day oral study.

Quantitative assessment of specific carbonic anhydrase inhibitors effect on hypoxic cells using electrical impedance assays.

Carbonic anhydrase IX (CA IX) is an important orchestrator of hypoxic tumour environment, associated with tumour progression, high incidence of metastasis and poor response to therapy. Due to its tumour specificity and involvement in associated pathological processes: tumourigenesis, angiogenesis, inhibiting CA IX enzymatic activity has become a valid therapeutic option. Dynamic cell-based biosensing platforms can complement cell-free and end-point analyses and supports the process of design and selection of potent and selective inhibitors. In this context, we assess the effectiveness of recently emerged CA IX inhibitors (sulphonamides and sulphocoumarins) and their antitumour potential using an electrical impedance spectroscopy biosensing platform. The analysis allows discriminating between the inhibitory capacities of the compounds and their inhibition mechanisms. Microscopy and biochemical assays complemented the analysis and validated impedance findings establishing a powerful biosensing tool for the evaluation of carbonic anhydrase inhibitors potency, effective for the screening and design of anticancer pharmacological agents.

Identification of human UDP-glucuronosyltransferase isoforms involved in the isofraxidin glucuronidation and assessment of the species differences of the reaction.

Isofraxidin, 7-Hydroxy-6.8-dimethoxy-2H-1-benzopyran-2-one, is a major active component of Acanthopanax senticosus, which has been used as Acanthopanax (Ciwujia) injection to treat cardiovascular and cerebrovascular diseases in China for more than thirty years. The purpose of this study was to identify the roles of human UDP-glucuronosyltransferases (UGTs) in isofraxidin glucuronidation in the liver and intestinal microsomes and to reveal the potential species differences by comparing the liver microsomal glucuronidation from different experimental animals. One metabolite was biosynthesized and characterized as isofraxidin-7-O-glucuronide by liquid chromatography tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR). The intrinsic clearances in human liver and intestinal microsomes were 63.8 and 16.4µL/min/mg, respectively. Human liver microsomes displays higher potential for isofraxidin elimination than human intestinal microsomes. The reaction phenotyping analysis was conducted using cDNA-expressed human UGTs and chemical inhibitors. The results indicated that UGT1A1 and UGT1A9 were the main isoforms involved in the formation of isofraxidin-7-O-glucuronide. The isofraxidin glucuronidation in liver microsomes from human (HLM), rat (RLM), mouse (MLM), dog (DLM), monkey (CyLM), minipig (PLM), and guinea pig (GpLM) followed the Michealis-Menten model. The isofraxidin glucuronidation displays species differences in terms of catalytic activities. GpLM had the highest clearance with the CLint value of 152µL/min/mg. CyLM, RLM and MLM exhibit similar catalytic activities in isofraxidin glucuronidation with the intrinsic clearance values of 54.6, 58.0 and 50.2µL/min/mg, respectively, which are higher than those of PLM and DLM (23.9 and 37.7µL/min/mg, respectively). Rat exhibits the most similar intrinsic metabolic clearance (CLint) to human.

Structural Characterization and Assessment of the Cytotoxicity of 2,3-Dihydro-1H-indene Derivatives and Coumarin Glucosides from the Bark of Streblus indicus.

A pair of enantiomers and a pair of 2,3-dihydro-1H-indene epimers, rac-indidene A (rac-1), indidenes B and C (2, 3); four new coumarin glucosides (4-7); and four known coumarin glucosides (8-11) were isolated from the bark of Streblus indicus (Bur.) Corner. The structures of 1-11 were defined by physical data analyses, including MS, NMR, and single-crystal X-ray diffraction. The absolute configurations of the 2,3-dihydro-1H-indene derivatives were defined via experimental and calculated ECD data. rac-Indidene A and indidenes B and C showed inhibitory activity against A549 and MCF-7 tumor cells with IC50 values in the range of 2.2 ± 0.1 to 7.2 ± 0.9 µM.

Assessment of Binding Affinity between Drugs and Human Serum Albumin Using Nanoporous Anodic Alumina Photonic Crystals.

In this study, we report an innovative approach aiming to assess the binding affinity between drug molecules and human serum albumin by combining nanoporous anodic alumina rugate filters (NAA-RFs) modified with human serum albumin (HSA) and reflectometric interference spectroscopy (RIfS). NAA-RFs are photonic crystal structures produced by sinusoidal pulse anodization of aluminum that present two characteristic optical parameters, the characteristic reflection peak (λPeak), and the effective optical thickness of the film (OTeff), which can be readily used as sensing parameters. A design of experiments strategy and an ANOVA analysis are used to establish the effect of the anodization parameters (i.e., anodization period and anodization offset) on the sensitivity of HSA-modified NAA-RFs toward indomethacin, a model drug. To this end, two sensing parameters are used, that is, shifts in the characteristic reflection peak (ΔλPeak) and changes in the effective optical thickness of the film (ΔOTeff). Subsequently, optimized NAA-RFs are used as sensing platforms to determine the binding affinity between a set of drugs (i.e., indomethacin, coumarin, sulfadymethoxine, warfarin, and salicylic acid) and HSA molecules. Our results verify that the combination of HSA-modified NAA-RFs with RIfS can be used as a portable, low-cost, and simple system for establishing the binding affinity between drugs and plasma proteins, which is a critical factor to develop efficient medicines for treating a broad range of diseases and medical conditions.

Synthesis, pharmacological assessment, molecular modeling and in silico studies of fused tricyclic coumarin derivatives as a new family of multifunctional anti-Alzheimer agents.

A series of fused tricyclic coumarin derivatives bearing iminopyran ring connected to various amido moieties were developed as potential multifunctional anti-Alzheimer agents for their cholinesterase inhibitory and radical scavenging activities. In vitro studies revealed that most of these compounds exhibited high inhibitory activity on acetylcholinesterase (AChE), with IC50 values ranging from 0.003 to 0.357 µM which is 2-220 folds more potent than the positive control, galantamine. Their inhibition selectivity against AChE over butyrylcholinesterase (BuChE) has increased about 194 fold compared with galantamine. The developed compounds also showed potent ABTS radical scavenging activity (IC50 7.98-15.99 µM). Specifically, the most potent AChE inhibitor 6n (IC50 0.003 ± 0.0007 µM) has an excellent antioxidant profile as determined by the ABTS method (IC50 7.98 ± 0.77 µM). Moreover, cell viability studies in SK N SH cells showed that the compounds 6m-q have significant neuroprotective effects against H2O2-induced cell death, and are not neurotoxic at all concentrations except 6n and 6q. The kinetic analysis of compound 6n proved that it is a mixed-type inhibitor for EeAChE (Ki1 0.0103 µM and Ki2 0.0193 µM). Accordingly, the molecular modeling study demonstrated that 6m-q with substituted benzyl amido moiety possessed an optimal docking pose with interactions at catalytic active site (CAS) and peripheral anionic site (PAS) of AChE simultaneously and thereby they might prevent aggregation of Aß induced by AChE. Furthermore, in silico ADMET prediction studies indicated that these compounds satisfied all the characteristics of CNS acting drugs. Most active inhibitor 6n is permeable to BBB as determined in the in vivo brain AChE activity. To sum up, the multipotent therapuetic profile of these novel tricyclic coumarins makes them promising leads for developing anti-Alzheimer agents.