Selective Interactions of O-Methylated Flavonoid Natural Products with Human Monoamine Oxidase-A and -B

A set of structurally related O-methylated flavonoid natural products isolated from Senecio roseiflorus (1), Polygonum senegalense (2 and 3), Bhaphia macrocalyx (4), Gardenia ternifolia (5), and Psiadia punctulata (6) plant species were characterized for their interaction with human monoamine oxidases (MAO-A and -B) in vitro. Compounds 1, 2, and 5 showed selective inhibition of MAO-A, while 4 and 6 showed selective inhibition of MAO-B. Compound 3 showed ~2-fold selectivity towards inhibition of MAO-A. Binding of compounds 1–3 and 5 with MAO-A, and compounds 3 and 6 with MAO-B was reversible and not time-independent. The analysis of enzyme-inhibition kinetics suggested a reversible-competitive mechanism for inhibition of MAO-A by 1 and 3, while a partially-reversible mixed-type inhibition by 5. Similarly, enzyme inhibition-kinetics analysis with compounds 3, 4, and 6, suggested a competitive reversible inhibition of MAO-B. The molecular docking study suggested that 1 selectively interacts with the active-site of human MAO-A near N5 of FAD. The calculated binding free energies of the O-methylated flavonoids (1 and 4–6) and chalcones (2 and 3) to MAO-A matched closely with the trend in the experimental IC_50′s. Analysis of the binding free-energies suggested better interaction of 4 and 6 with MAO-B than with MAO-A. The natural O-methylated flavonoid (1) with highly potent inhibition (IC₅₀ 33 nM; Ki 37.9 nM) and >292 fold selectivity against human MAO-A (vs. MAO-B) provides a new drug lead for the treatment of neurological disorders.     

Design,Synthesis and Biological Assessment of Rhodanine-Linked Benzenesulfonamide Derivatives as Selective and Potent Human Carbonic Anhydrase Inhibitors

A novel series of twenty-five rhodamine-linked benzenesulfonamide derivatives (7a–u and 9a–d) were synthesized and screened for their inhibitory action against four physiologically relevant human (h) carbonic anhydrase (CA) isoforms, namely hCA I, hCA II, hCA IX, and hCA XII. All the synthesized molecules showed good to excellent inhibition against all the tested isoforms in the nanomolar range due to the presence of the sulfonamide as a zinc binding group. The target compounds were developed from indol-3-ylchalcone-linked benzenesulfonamide where the indol-3-ylchalcone moiety was replaced with rhodanine-linked aldehydes or isatins to improve the inhibition. Interestingly, the molecules were slightly more selective towards hCA IX and XII compared to hCA I and II. The most potent and efficient ones against hCA I were 7h (K_I 22.4 nM) and 9d (K_I 35.8 nM) compared to the standard drug AAZ (K_I 250.0 nM), whereas in case of hCA II inhibition, the derivatives containing the isatin nucleus as a tail were preferred. Collectively, all compounds were endowed with better inhibition against hCA IX compared to AAZ (K_I 25.8 nM) as well as strong potency against hCA XII. Finally, these newly synthesized molecules could be taken as potential leads for the development of isoform selective hCA IX and XII inhibitors.     

Selective polymerization of functional monomers with Novozym 435

Two novel monomers, ambrettolide epoxide and isopropyl aleuriteate, encompassing functional groups, were obtained in a single step from commercially available materials. Novozym 435 catalyzed ring opening polymerization of ambrettolide epoxide furnished a polymer of M_n = 9.7 kg/mol and PDI = 1.9 while the epoxide groups remained unaffected during the polymerization. Selective polymerization of the primary hydroxyl groups of isopropyl aleuriteate using Novozym 435 was feasible and a polymer with moderate molecular weight (M_n = 5.6 kg/mol, PDI = 3.2) was isolated in moderate yield (43%). Subsequently, copolymerization of isopropyl aleuriteate with ε‐CL in different ratios was performed, resulting in soluble, hydroxy functional polymers with good molecular weights (M_n = 10.4–27.2 kg/mol) in good yield (71–78%). The secondary hydroxy groups in the polymer reacted easily with hexyl isocyanate, showing the potential of isopropyl aleuriteate as a comonomer for the synthesis of functional polyesters. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5968–5978, 2007     

ACE抑制剂的QSAR研究与分子设计

从20种天然氨基酸的41个randic molecular profiles、44个eigenvalue based indices和47个walk and path counts非零描述符分别进行主成分分析,得出一种新的氨基酸描述符——SVREW.将其应用于血管紧张素转化酶抑制三肽结构表征,应用多元线性回归(MLR)及偏最小二乘(PLS)建立定量构效关系模型,同时采用内部与外部双重验证的方法验证模型的稳定性.所建模型复相关系数(Rcum2)、留一法(LOO)交互校验相关系数(Rcv2)和外部样本校验相关系数(Qext2)分别为MLR(0.994,0.974,0.991),P LS(0.949,0.886,0.898).然后利用此多元线性回归方程设计出一系列血管紧张素转化酶抑制三肽化合物并预测了其活性,并且应用分子对接验证所设计药物的合理性.经研究表明SVREW描述符应用于ACE三肽结构表征所建模型的稳定性与预测能力均较好,有望成为多肽定量构效关系研究中一种有效的结构表征方法,并对新药物的发现和研究提供指导.     

Exploiting Atropisomerism to Increase the Target Selectivity of Kinase Inhibitors

Many biologically active molecules exist as rapidly interconverting atropisomeric mixtures. Whereas one atropisomer inhibits the desired target, the other can lead to off‐target effects. Herein, we study atropisomerism as a possibility to improve the selectivities of kinase inhibitors through the synthesis of conformationally stable pyrrolopyrimidines. Each atropisomer was isolated by HPLC on a chiral stationary phase and subjected to inhibitor profiling across a panel of 18 tyrosine kinases. Notably different selectivity patterns between atropisomers were observed, as well as improved selectivity compared to a rapidly interconverting parent molecule. Computational docking studies then provided insights into the structure‐based origins of these effects. This study is one of the first examples of the intentional preorganization of a promiscuous scaffold along an atropisomeric axis to increase target selectivity, and provides fundamental insights that may be applied to other atropisomeric target scaffolds.     

Evaluation of carbonic anhydrase and paraoxonase inhibition activities and molecular docking studies of highly water-soluble sulfonated phthalocyanines

The investigation of carbonic anhydrase and paraoxonase enzyme inhibition properties of water-soluble zinc and gallium phthalocyanine complexes ( 1 and 2 ) are reported for the first time. The binding of p-sulfonylphenoxy moieties to the phthalocyanine structure favors excellent solubilities in water, as well as providing an inhibition effect on carbonic anhydrase (CA) I and II isoenzymes and paraoxonase (PON1) enzyme. According to biological activity results, both complexes inhibited hCA I, hCA II, and PON1. Whereas 1 and 2 showed moderate hCA I and hCA II (off-target cytosolic isoforms) inhibitory activity (Ki values of 26.09 µM and 43.11 µM for hCA I and 30.95 µM and 33.19 µM for hCA II, respectively), they exhibited strong PON1 (associated with high-density lipoprotein [HDL]) inhibitory activity (Ki values of 0.37 µM and 0.27 µM, respectively). The inhibition kinetics were analyzed by Lineweaver–Burk double reciprocal plots. It revealed that 1 and 2 were noncompetitive inhibitors against PON1, hCA I, and hCA II. These complexes can be more advantageous than other synthetic CA and PON inhibitors due to their water solubility. Docking studies were carried out to examine the interactions between hCA I, hCA II, and PON1 inhibitors and metal complexes at a molecular level and to predict binding energies.     

7-Aminoalkoxy-Quinazolines from Epigenetic Focused Libraries Are Potent and Selective Inhibitors of DNA Methyltransferase 1

Inhibitors of epigenetic writers such as DNA methyltransferases (DNMTs) are attractive compounds for epigenetic drug and probe discovery. To advance epigenetic probes and drug discovery, chemical companies are developing focused libraries for epigenetic targets. Based on a knowledge-based approach, herein we report the identification of two quinazoline-based derivatives identified in focused libraries with sub-micromolar inhibition of DNMT1 (30 and 81 nM), more potent than S-adenosylhomocysteine. Also, both compounds had a low micromolar affinity of DNMT3A and did not inhibit DNMT3B. The enzymatic inhibitory activity of DNMT1 and DNMT3A was rationalized with molecular modeling. The quinazolines reported in this work are known to have low cell toxicity and be potent inhibitors of the epigenetic target G9a. Therefore, the quinazoline-based compounds presented are attractive not only as novel potent inhibitors of DNMTs but also as dual and selective epigenetic agents targeting two families of epigenetic writers.     

Synthesis,cytotoxicity, topoisomerase I inhibition and molecular docking of novel phosphoramide mustard sophoridinic acid analogues

A series of novel phosphoramide mustard sophoridinic acid analogues, consisting of nitrogen mustard group and sophoridinic acid scaffold, have been designed, synthesized and evaluated for their topoisomerase inhibitory activity as well as cytotoxicity against six tumor cell lines (SMMC‐7721, LoVo, MCF‐7, K562, S180 and H22) and a normal cell line (L929). Among the compounds tested, five were found to be potent inhibitors and exhibited potent cytotoxicity against S180 and H22 cell lines with IC₅₀ values of 1–4 μM. Further mechanistic studies showed that this class of compounds acted as novel topoisomerase I (Topo I) catalytic inhibitors by preventing the binding of Topo I to DNA and inhibiting the cleavage of DNA, and molecular docking studies revealed that the binding energy for these compounds was comparable to that for classic Topo I inhibitors CPT and HCPT, indicating that the compounds have an interaction with DNA and Topo I.     

Synthesis and biological evaluation of 2-substituted vinylgembisphosphonates against Plasmodium falciparum and Trypanosoma brucei

Abstract

A series of 2-substituted vinylidene-1,1-bisphosphonate esters and their acids were synthesized and tested in vitro for activity against Plasmodium falciparum and Trypanosoma brucei. For each compound, % parasite viability in treated wells was calculated relative to untreated controls for both P. falciparum and T. brucei. Fifty percentage inhibitory concentration (IC₅₀) was also determined for the compounds. Chloroquine and pentamidine were used as positive control drug standards for activity against P. falciparum and T. brucei, respectively. The esters had better antiparasitic activity compared to their corresponding acids. Some of the compounds reduced % parasite viability to as low as 24.3% for P. falciparum and down to 0.602% for T. brucei. Tetraethyl-2-(o-tolyl)-ethene-1,1-bisphosphonate (3b) recorded the best IC₅₀ against T. brucei which was 0.0345?µmol/mL.     

Thiourea Derivatives,Simple in Structure but Efficient Enzyme Inhibitors and Mercury Sensors

In this study six unsymmetrical thiourea derivatives, 1-isobutyl-3-cyclohexylthiourea (1), 1-tert-butyl-3-cyclohexylthiourea (2), 1-(3-chlorophenyl)-3-cyclohexylthiourea (3), 1-(1,1-dibutyl)-3-phenylthiourea (4), 1-(2-chlorophenyl)-3-phenylthiourea (5) and 1-(4-chlorophenyl)-3-phenylthiourea (6) were obtained in the laboratory under aerobic conditions. Compounds 3 and 4 are crystalline and their structure was determined for their single crystal. Compounds 3 is monoclinic system with space group P2₁/n while compound 4 is trigonal, space group R³:H. Compounds (1–6) were tested for their anti-cholinesterase activity against acetylcholinesterase and butyrylcholinesterase (hereafter abbreviated as, AChE and BChE, respectively). Potentials (all compounds) as sensing probes for determination of deadly toxic metal (mercury) using spectrofluorimetric technique were also investigated. Compound 3 exhibited better enzyme inhibition IC₅₀ values of 50, and 60 µg/mL against AChE and BChE with docking score of −10.01, and −8.04 kJ/mol, respectively. The compound also showed moderate sensitivity during fluorescence studies.     

Efficacy of Phytochemicals Derived from Roots of Rondeletia odorata as Antioxidant,Antiulcer, Diuretic,Skin Brightening and Hemolytic Agents—A Comprehensive Biochemical and In Silico Study

Roots of Rondeletia odorata are a rich source of phytochemicals with high antioxidant potential and thus may possess health benefits. This study used the LC-MS technique to identify phytoconstituents in R. odorata roots extract/fractions. Results revealed that n-butanol fraction and ethanolic extract contained total phenolic and flavonoid contents with values of 155.64 ± 0.66 mgGAE/g DE and 194.94 ± 0.98 mgQE/g DE, respectively. Significant potential of antioxidants was observed by DPPH, CUPRAC and FRAP methods while the ABTS method showed moderate antioxidant potential. Maximum % inhibition for urease, tyrosinase and carbonic anhydrase was shown by ethanolic extract (73.39 ± 1.11%), n-butanol soluble fraction (80.26 ± 1.59%) and ethyl acetate soluble fraction (76.50 ± 0.67%) which were comparable with thiourea (standard) (98.07 ± 0.74%), kojic acid (standard) (98.59 ± 0.92%) and acetazolamide (standard) (95.51 ± 1.29%), respectively, while all other extract/fractions showed moderate inhibition activity against these three enzymes. Hemolytic activity was also observed to range from 18.80 ± 0.42 to 3.48 ± 0.69% using the standard (triton X-100) method. In total, 28 and 20 compounds were identified tentatively by LC-MS analysis of ethanolic extract and n-butanol soluble fraction, respectively. Furthermore, molecular docking was undertaken for major compounds identified by LC-MS for determining binding affinity between enzymes (urease, tyrosinase and carbonic anhydrase) and ligands. It was concluded that active phytochemicals were present in roots of R. odorata with potential for multiple pharmacological applications and as a latent source of pharmaceutically important compounds. This should be further explored to isolate important constituents that could be used in treating different diseases.     

Sahlep (Dactylorhiza osmanica): Phytochemical Analyses by LC-HRMS,Molecular Docking,Antioxidant Activity,and Enzyme Inhibition Profiles

Studies have shown an inverse correlation among age-related illnesses like coronary heart disease and cancer and intake of fruit and vegetable. Given the probable health benefits of natural antioxidants from plants, research on them has increased. Dactylorhiza osmanica is consumed as a food and traditional medicine plant in some regions of Turkey, so evaluation of the biological ability of this species is important. In this study, the amount of phenolic content (LC-HRMS), antioxidant activities and enzyme inhibitory properties of an endemic plant, D. osmanica, were investigated. The antioxidant capacities of an ethanol extract of D. osmanica aerial parts (EDOA) and roots (EDOR) were evaluated with various antioxidant methods. Additionally, the enzyme inhibitory effects of EDOA and EDOR were examined against acetylcholinesterase (AChE), α-glycosidase, and α-amylase enzymes, which are associated with common and global Alzheimer’s disease and diabetes mellitus. The IC₅₀ values of EDOA against the enzymes were found to be 1.809, 1.098, and 0.726 mg/mL, respectively; and the IC₅₀ values of EDOR against the enzymes were found to be 2.466, 0.442, and 0.415 mg/mL, respectively. Additionally, LC-HRMS analyses revealed p-Coumaric acid as the most plentiful phenolic in both EDOA (541.49 mg/g) and EDOR (559.22 mg/g). Furthermore, the molecular docking interaction of p-coumaric acid, quercitrin, and vanillic acid, which are the most plentiful phenolic compounds in the extracts, with AChE, α-glucosidase, and α-amylase, were evaluated using AutoDock Vina software. The rich phenolic content and the effective antioxidant ability and enzyme inhibition potentials of EDOA and EDOR may support the plant’s widespread food and traditional medicinal uses.     

New para-para stilbenophanes: synthesis by McMurry coupling, conformational analysis and inhibition of tubulin polymerisation

The synthesis of a new family of methoxy-substituted [2.7]- and [2.8]paracyclophanes linked by 3-oxapentamethylene-1,5-dioxy and hexamethylene-1,6-dioxy bridges has been carried out by using the McMurry methodology. Related indole compounds were also synthesised. Olefin-to-diol ratios depended on the bridge length, the structure of the aromatic ring and the reaction conditions. Macrocyclisation, the methoxy substituents and the presence of a rigid indole moiety restricted the conformational equilibria, as observed by NMR spectroscopy and according to theoretical calculations. The synthesised compounds display micromolar tubulin polymerisation inhibitory activity. The conformational implications on the tubulin polymerisation inhibitory activity derived from the macrocyclisation when compared with combretastatins, closely related stilbenes, are also discussed.     

Glucose 6-Phosphate Dehydrogenase from Trypanosomes: Selectivity for Steroids and Chemical Validation in Bloodstream Trypanosoma brucei

Glucose 6-phosphate dehydrogenase (G6PDH) fulfills an essential role in cell physiology by catalyzing the production of NADPH⁺ and of a precursor for the de novo synthesis of ribose 5-phosphate. In trypanosomatids, G6PDH is essential for in vitro proliferation, antioxidant defense and, thereby, drug resistance mechanisms. So far, 16α-brominated epiandrosterone represents the most potent hit targeting trypanosomal G6PDH. Here, we extended the investigations on this important drug target and its inhibition by using a small subset of androstane derivatives. In Trypanosoma cruzi, immunofluorescence revealed a cytoplasmic distribution of G6PDH and the absence of signal in major organelles. Cytochemical assays confirmed parasitic G6PDH as the molecular target of epiandrosterone. Structure-activity analysis for a set of new (dehydro)epiandrosterone derivatives revealed that bromination at position 16α of the cyclopentane moiety yielded more potent T. cruzi G6PDH inhibitors than the corresponding β-substituted analogues. For the 16α brominated compounds, the inclusion of an acetoxy group at position 3 either proved detrimental or enhanced the activity of the epiandrosterone or the dehydroepiandrosterone derivatives, respectively. Most derivatives presented single digit μM EC₅₀ against infective T. brucei and the killing mechanism involved an early thiol-redox unbalance. This data suggests that infective African trypanosomes lack efficient NADPH⁺-synthesizing pathways, beyond the Pentose Phosphate, to maintain thiol-redox homeostasis.     

Chemical Composition,Biological Activities and In Silico Analysis of Essential Oils of Three Endemic Prangos Species from Turkey

In this study, the essential oils (EOs) obtained from three endemic Prangos species from Turkey (P. heyniae, P. meliocarpoides var. meliocarpoides, and P. uechtritzii) were studied for their chemical composition and biological activities. β-Bisabolenal (12.2%) and caryophyllene oxide (7.9%) were the principal components of P. heyniae EO, while P. meliocarpoides EO contained sabinene (16.7%) and p-cymene (13.2%), and P. uechtritzii EO contained p-cymene (24.6%) and caryophyllene oxide (19.6%), as the most abundant components. With regard to their antioxidant activity, all the EOs were found to possess free radical scavenging potential demonstrated in both DPPH and ABTS assays (0.43–1.74 mg TE/g and 24.18–92.99 mg TE/g, respectively). Additionally, while no inhibitory activity was displayed by P. meliocarpoides and P. uechtritzii EOs against both cholinesterases (acetyl- and butyryl-cholinesterases). Moreover, all the EOs were found to act as inhibitors of tyrosinase (46.34–69.56 mg KAE/g). Molecular docking revealed elemol and α-bisabolol to have the most effective binding affinity with tyrosinase and amylase. Altogether, this study unveiled some interesting biological activities of these EOs, especially as natural antioxidants and tyrosinase inhibitors and hence offers stimulating prospects of them in the development of anti-hyperpigmentation topical formulations.     

Design,Synthesis and Biological Evaluation of Potent Azadipeptide Nitrile Inhibitors and Activity‐Based Probes as Promising Anti‐Trypanosoma brucei Agents

Trypanosoma cruzi and Trypanosoma brucei are parasites that cause Chagas disease and African sleeping sickness, respectively. There is an urgent need for the development of new drugs against both diseases due to the lack of adequate cures and emerging drug resistance. One promising strategy for the discovery of small‐molecule therapeutics against parasitic diseases has been to target the major cysteine proteases such as cruzain for T. cruzi, and rhodesain/TbCatB for T. brucei. Azadipeptide nitriles belong to a novel class of extremely potent cysteine protease inhibitors against papain‐like proteases. We herein report the design, synthesis, and evaluation of a series of azanitrile‐containing compounds, most of which were shown to potently inhibit both recombinant cruzain and rhodesain at low nanomolar/picomolar ranges. A strong correlation between the potency of rhodesain inhibition (i.e., target‐based screening) and trypanocidal activity (i.e., whole‐organism‐based screening) of the compounds was observed. To facilitate detailed studies of this important class of inhibitors, selected hit compounds from our screenings were chemically converted into activity‐based probes (ABPs), which were subsequently used for in situ proteome profiling and cellular localization studies to further elucidate potential cellular targets (on and off) in both the disease‐relevant bloodstream form (BSF) and the insect‐residing procyclic form (PCF) of Trypanosoma brucei. Overall, the inhibitors presented herein show great promise as a new class of anti‐trypanosome agents, which possess better activities than existing drugs. The activity‐based probes generated from this study could also serve as valuable tools for parasite‐based proteome profiling studies, as well as bioimaging agents for studies of cellular uptake and distribution of these drug candidates. Our studies therefore provide a good starting point for further development of these azanitrile‐containing compounds as potential anti‐parasitic agents.     

Phytochemical Profiling,In Vitro Biological Activities,and In Silico Molecular Docking Studies of Dracaena reflexa

Dracaena reflexa, a traditionally significant medicinal plant, has not been extensively explored before for its phytochemical and biological potential. The present study was conducted to evaluate the bioactive phytochemicals and in vitro biological activities of D. reflexa, and perform in silico molecular docking validation of D. reflexa. The bioactive phytochemicals were assessed by preliminary phytochemical testing, total bioactive contents, and GC-MS analysis. For biological evaluation, the antioxidant (DPPH, ABTS, CUPRAC, and ABTS), antibacterial, thrombolytic, and enzyme inhibition (tyrosinase and cholinesterase enzymes) potential were determined. The highest level of total phenolic contents (92.72 ± 0.79 mg GAE/g extract) was found in the n-butanol fraction while the maximum total flavonoid content (110 ± 0.83 mg QE/g extract) was observed in methanolic extract. The results showed that n-butanol fraction exhibited very significant tyrosinase inhibition activity (73.46 ± 0.80) and acetylcholinesterase inhibition activity (64.06 ± 2.65%) as compared to other fractions and comparable to the standard compounds (kojic acid and galantamine). The methanolic extract was considered to have moderate butyrylcholinesterase inhibition activity (50.97 ± 063) as compared to the standard compound galantamine (53.671 ± 0.97%). The GC-MS analysis of the n-hexane fraction resulted in the tentative identification of 120 bioactive phytochemicals. Furthermore, the major compounds as identified by GC-MS were analyzed using in silico molecular docking studies to determine the binding affinity between the ligands and the enzymes (tyrosinase, acetylcholinesterase, and butyrylcholinesterase enzymes). The results of this study suggest that Dracaena reflexa has unquestionable pharmaceutical importance and it should be further explored for the isolation of secondary metabolites that can be employed for the treatment of different diseases.     

In Vitro Evaluation of In Silico Screening Approaches in Search for Selective ACE2 Binding Chemical Probes

New models for ACE2 receptor binding, based on QSAR and docking algorithms were developed, using XRD structural data and ChEMBL 26 database hits as training sets. The selectivity of the potential ACE2-binding ligands towards Neprilysin (NEP) and ACE was evaluated. The Enamine screening collection (3.2 million compounds) was virtually screened according to the above models, in order to find possible ACE2-chemical probes, useful for the study of SARS-CoV2-induced neurological disorders. An enzymology inhibition assay for ACE2 was optimized, and the combined diversified set of predicted selective ACE2-binding molecules from QSAR modeling, docking, and ultrafast docking was screened in vitro. The in vitro hits included two novel chemotypes suitable for further optimization.