Flavones and Related Compounds: Synthesis and Biological Activity

This review focuses on the synthesis and biological activity of flavones and their related flavonoidic compounds, namely flavonols and aurones. Among the biological activities of natural and synthetic flavones and aurones, their anticancer, antioxidant, and antimicrobial properties are highlighted and detailed in this review. Starting from the structures of natural flavones acting on multiple anticancer targets (myricetin, genkwanin, and other structurally related compounds), new flavone analogs were recently designed and evaluated for their anticancer activity. The most representative compounds and their anticancer activity are summarized in this review. Natural flavones recognized for their antimicrobial properties (baicalein, luteolin, quercetol, apigenin, kaempferol, tricin) have been recently derivatized or structurally modulated by chemical synthetic methods in order to obtain new effective antimicrobial flavonoidic derivatives with improved biological properties. The most promising antimicrobial agents are systematically highlighted in this review. The most applied method for the synthesis of flavones and aurones is based on the oxidative cyclization of o-hydroxychalcones. Depending on the reaction conditions and the structure of the precursor, in some cases, several cyclization products result simultaneously: flavones, flavanones, flavonols, and aurones. Based on the literature data and the results obtained by our research group, our aim is to highlight the most promising methods for the synthesis of flavones, as well as the synthetic routes for the other structurally related cyclization products, such as hydroxyflavones and aurones, while considering that, in practice, it is difficult to predict which is the main or exclusive cyclization product of o-hydroxychalcones under certain reaction conditions.

Simulation of the oxidative metabolization pattern of netupitant, an NK1 receptor antagonist, by electrochemistry coupled to mass spectrometry

Considering the frequent use of netupitant in polytherapy, the elucidation of its oxidative metabolization pattern is of major importance. However, there is a lack of published research on the redox behavior of this novel neurokinin-1 receptor antagonist. Therefore, this study was performed to simulate the intensive hepatic biotransformation of netupitant using an electrochemically driven method. Most of the known enzyme-mediated reactions occurring in the liver (i.e., N-dealkylation, hydroxylation, and N-oxidation) were successfully mimicked by the electrolytic cell using a boron-doped diamond working electrode. The products were separated by reversed-phase high-performance liquid chromatography and identified by high-resolution mass spectrometry. Aside from its ability to pinpoint formerly unknown metabolites that could be responsible for the known side effects of netupitant or connected with any new perspective concerning future therapeutic indications, this electrochemical process also represents a facile alternative for the synthesis of oxidation products for further in vitro and in vivo studies.

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Study of the electrochemical behavior of netupitant, an NK₁ receptor antagonist.

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Electrochemical simulation of the phase I oxidative metabolization of netupitant.

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Identification of the generated oxidation species by LC/ESI(+)-MS.

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Separation and identification of electrochemically generated isomers.

Heterocycles 51: Liphophilicity investigation of some thiazole chalcones and aurones by experimental and theoretical methods

Reversed-phase thin-layer chromatography and reversed-phase high-performance liquid chromatography were used for lipophilicity determination of a library of 30 thiazole chalcones and aurones previously synthetized in our laboratory. The experimental lipophilicity data have been compared with theoretical lipophilicity parameters estimated by various computational methods. Good correlations between the experimental and calculated lipophilicity parameters have been found for both investigated classes of compounds. Correlations between the lipophilicity of the thiazole chalcones and aurones and their antiproliferative activity were discussed. The methodologies and data gathered in this study will contribute to the lipophilicity studies of chalcones and aurones derivatives, two important classes of compounds in medicinal chemistry.

Heterocycles 48. Synthesis, Characterization and Biological Evaluation of Imidazo[2,1-b][1,3,4]Thiadiazole Derivatives as Anti-Inflammatory Agents

Non-steroidal anti-inflammatory drugs (NSAIDs) are an important pharmacological class of drugs used for the treatment of inflammatory diseases. They are also characterized by severe side effects, such as gastrointestinal damage, increased cardiovascular risk and renal function abnormalities. In order to synthesize new anti-inflammatory and analgesic compounds with a safer profile of side effects, a series of 2,6-diaryl-imidazo[2,1-b][1,3,4]thiadiazole derivatives 5a⁻l were synthesized and evaluated in vivo for their anti-inflammatory and analgesic activities in carrageenan-induced rat paw edema. Among all compounds, 5c showed better anti-inflammatory activity compared to diclofenac, the standard drug, and compounds 5g, 5i, 5j presented a comparable antinociceptive activity to diclofenac. None of the compounds showed ulcerogenic activity. Molecular docking studies were carried out to investigate the theoretical bond interactions between the compounds and target, the cyclooxygenases (COX-1/COX-2). The compound 5c exhibited a higher inhibition of COX-2 compared to diclofenac.

Understanding the Chromatographic Properties and Cytotoxicity of Hidrazinoselenazole Compounds by Computational Study

Selenium compounds have been proven to possess anti-inflammatory, anti-cancer, anti-bacterial and anti-viral activities. A series of fifteen synthesized hidrazinoselenazole was investigated to assess the chromatographic properties as function of structural features and the cytotoxicity as function of chromatographic properties and/or structural descriptors. The investigated chromatographic properties were retention factor, specific surface area of the solvent and chromatographic hydrophobicity index. The 3D model of the compounds was optimized using Hartree-Fock DFT/B3LYP method, 6-31+G* basis set both in vacuum and water with Spartan software (v.8). Furthermore, several quantitative structure-activity relationship (QSAR) descriptors were calculated with Spartan and Dragon (v. 5.5) software. Full search approach was used to construct simple and multiple linear regression models. No reliable model was identified for specific surface area of the solvent. The models with higher performances in estimation and prediction for retention factor and chromatographic hydrophobicity index proved the ones with Dragon descriptors and molecules optimized in water (retention factor: rloo2 (loo = leave-one-out analysis) = 0.9244; rtr2 (tr = training set) = 0.9652; rts2 (ts = test set) = 0.9606; chromatographic hydrophobicity index: rloo2 = 0.9489; rtr2 = 0.9592; rts2 = 0.9669). The cytotoxicity proved related neither to chromatographic properties nor with compounds� structural characteristics.

In vitro antibacterial activities of p-toluenesulfonyl-hydrazinothiazoles and hydrazinoselenazoles against multi-drug resistant Gram-negative phenotypes

BACKGROUND

Bacterial multidrug resistance (MDR) constitutes a major hurdle in the treatment of infectious diseases worldwide. The present study was designed to evaluate the antibacterial activities of synthetic p-toluenesulfonyl-hydrazinothiazoles against multidrug resistant Gram-negative bacteria.

METHODS

The broth microdilution method was used to determine the minimal inhibitory concentrations (MIC).

RESULTS

The results demonstrated that the best activities were obtained with hydrazinoselenazoles. p-Chloro-benzyliden-selenosemicarbazide, 4-methyl-2-[(4-chloro-benzyliden)-hydrazinyl]-1,3-selenazole, p-chloro-benzoyl-selenosemicarbazide and 4-chloromethyl-2-[(4-chlorobenziliden)-N-acetyl-hydrazinyl]-1,3-selenazole were more active than the choramphenicol on Klebsiella pneumoniae KP63. Tested alone, the lowest MIC value of 16 mg/L was obtained with p-methoxy-benzyliden-selenosemicarbazide against Enterobacter aerogenes ATCC13048, K. pneumoniae ATCC112296 and KP55. Tested in the presence of an efflux pump inhibitor, phenylalanine arginine β-naphthylamide (PAβN), the activity of p-chloro-benzyliden-selenosemicarbazide, 4-methyl-2-[(4-chloro-benzyliden)-hydrazinyl]-1,3-selenazole, p-chloro-benzoyl-selenosemicarbazide and p-methoxy-benzyliden-selenosemicarbazide significantly increased with MIC values below 10 mg/L obtained respectively on 43.8 %, 31.3 %, 62.5 % and 100 % of the 16 tested bacterial strains. The lowest MIC value of 0.5 mg/L in the presence of PAβN was recorded with p-chloro-benzoyl-selenosemicarbazide against Escherichia coli ATCC8739 and KP55 as well as p-methoxy-benzyliden-selenosemicarbazide against E. aerogenes KP55. p-Chloro-benzyliden-selenosemicarbazide and p-chloro-benzoyl-selenosemicarbazide contained the same pharmacophore as p-methoxy-benzyliden-selenosemicarbazide.

CONCLUSION

This study indicates that p-chloro-benzyliden-selenosemicarbazide, p-chloro-benzoyl-selenosemicarbazide and p-methoxy-benzyliden-selenosemicarbazide could be explored more to develop novel antimicrobial drugs to fight MDR bacterial infections.

ATYPICAL FEMORAL FRACTURES AFTER LONG-TERM BISPHOSPHONATES THERAPY: CASE REPORT

We present a 77-year-old woman with no histor of trauma, or associated with low-energy trauma, admitted to our clinic after three weeks of a left femoral fracture threated in Orthopedic Clinic. The patient was in treatment with bisphosphonates over 10 years for osteoporosis.

DISCUSSION AND CONCLUSIONS

The causal re lationship between prolonged bisphosphonate use and the occurrence of atypical femora fractures (AFF) has not yet been established. For the patient at high risk of fracture, it may be beneficial to continue bisphosphonate treatment beyond five years. The absolute risk of atypical femoral fractures is low (about 100 cases per 100,000 person-years among long term users). For most people with osteoporosis, the proven fragility-fracture risk-reduction. benefits of bisphosphonates outweigh the risks of AFF.

Heterocycles 38. Biocatalytic Synthesis of New Heterocyclic Mannich Bases and Derivatives

This paper describes the biocatalytic synthesis of new Mannich bases containing various heterocyclic rings (thiazole, furane, thiophene, pyridine) by applying the lipase catalyzed trimolecular condensation of the corresponding heterocyclic aldehydes with acetone and primary aromatic amines, in mild and eco-friendly reaction conditions. The obtained Mannich bases were acylated to their corresponding N-acetyl derivatives. All compounds were characterized by ¹H-NMR, ¹³C-NMR and MS spectrometry.

The synthesis and antiproliferative activities of new arylidene-hydrazinyl-thiazole derivatives

New and known arylidene-hydrazinyl-thiazole derivatives have been synthesized by a convenient Hantzsch condensation. All compounds were evaluated for their in vitro cytotoxicity on two carcinoma cell lines, MDA-MB231 and HeLa. Significant antiproliferative activity for 2-(2-benzyliden-hydrazinyl)-4-methylthiazole on both MDA-MB-231 (IC50: 3.92 µg/mL) and HeLa (IC50: 11.4 µg/mL) cell lines, and for 2-[2-(4-methoxybenzylidene) hydrazinyl]-4-phenylthiazole on HeLa (IC50: 11.1 µg/mL) cell line is reported. Electrophoresis experiments showed no plasmid DNA (pTZ57R) cleavage in the presence of the investigated thiazoles.

Heterocycles 27. Microwave assisted synthesis and antitumour activity of novel phenothiazinyl-thiazolyl-hydrazine derivatives

A series of new phenothiazinyl-thiazolyl-hydrazine derivatives were synthesized by Hantzsch cyclization of 1-(10-ethyl-10H-phenothiazin-3-yl)-methylidene-thiosemicarbazide with α-halocarbonyl derivatives. Comparison between classical and microwave assisted synthesis emphasizes the great advantages induced by microwaves irradiation which afforded high reaction yields in much shorter reaction time. Structural assignments were based on spectroscopic methods (high resolution NMR, FTIR, MS). The new compounds were tested in vitro for their antiproliferative activity against tumor cell lines using spectrometric methods. Most of the compounds exhibit cytotoxicity against hepatic and colon tumor cells in a dose-dependent mode and a relationship between the structure and their biological activity was observed.

Synthesis of some p-toluenesulfonyl-hydrazinothiazoles and hydrazino-bis-thiazoles and their anticancer activity

A series of novel p-toluenesulfonyl-hydrazinothiazoles and hydrazino-bis-thiazoles derivatives (2a-f, 3a-f and 5-8) were synthesized by initial condensation of p-toluenesulfonylthiosemicarbazide 1 with a series of α-halogenocarbonyls in acetone or dimethylformamide (DMF)/acetone, mixture. All our synthesized compounds were submitted for further acylation reaction in the presence of acetic anhydride. The structures of newly synthesized derivatives 2a-f, 3a-f and 5-8 were confirmed by IR, (1)H-NMR, EIMS spectral data and elemental analysis. Compounds 2a, 2c, 2d, 2e and 3a showed significant anticancer activities (IC(50)<10 μM) on both prostate DU-145 and hepatocarcinoma Hep-G2 cancer cell lines.

Heterocycles 21. Reaction of 2-phenyl-thiazol-4-carbaldehyde with 2-bromoacetophenone

The condensation reaction of 2-phenyl-thiazol-4-carbaldehyde with 2-bromoacetophenone was performed in basic catalysis, resulting in a mixture of 2,3-epoxy-1-phenyl-3-(2-phenyl-thiazol-4-yl)-propan-1-one (1), 1-phenyl-3-(2-phenyl-thiazol-4-yl)-propane-1,2-dione (2) and 2-phenyl-4,5-bis-(2-phenyl-thiazol-4-yl)-3-hydroxy-furane (4). The isolated solids were structurally investigated by spectroscopic methods, i.e. infrared spectroscopy, mass spectrometry and NMR. In solution the dicarbonylic derivative 2 undergoes a tautomeric process, resulting in the enol 2-hydroxy-1-phenyl-3-(2-phenyl-thiazol-4-yl)-prop-2-en-1-one 3. Compounds 3 and 4 were transformed in the corresponding acetyl derivatives 5 and 6, respectively, by reacting them with acetic anhydride. For the furane 4 the single crystal X-ray diffraction structure was determined.

Importance of hepatitis C coinfection in the development of QT prolongation in HIV-infected patients

BACKGROUND

Case reports and unblinded studies suggest that human immunodeficiency virus (HIV) disease is associated with QT prolongation and torsade de pointes ventricular tachycardia. Hepatitis C coinfection is common in patients with HIV disease, and cirrhosis is also associated with QT prolongation. We therefore undertook a systematic analysis of the role of liver injury, nutritional state, and coinfection with hepatitis C in the etiology of QT prolongation in HIV disease.

METHODS

We performed a blinded, controlled retrospective cohort study of 1648 patients over a 3-year period at a university-affiliated municipal hospital. All electrocardiograms were included if patients with HIV disease had measurements of CD4 count and viral load within 3 months and serum electrolytes within 30 days (n = 816). Control subjects were chosen randomly from the general medicine service (n = 832). QT interval was measured in lead II and corrected for heart rate by Bazett's formula (QTc).

RESULTS

QTc was slightly but significantly longer in patients with HIV disease than in controls (443 +/- 37 vs 436 +/- 36 milliseconds, P < .001). Patients with hepatitis C had more pronounced QTc prolongation (452 +/- 41 vs 437 +/- 35 milliseconds, P < .001). CD4 count, HIV viral load, and HIV medications had no effect on QTc. When patients with hepatitis C were excluded from the analysis, there was no statistical difference between patients with HIV disease and controls (438 +/- 34 vs 436 +/- 36 milliseconds, P = .336). Multiple linear regression revealed that both HIV and hepatitis C infection predicted QTc prolongation, as did age, female sex, history of hypertension, use of opiates, low serum K+ and albumin, and high AST. Hepatitis C coinfection nearly doubled the risk of QTc of 470 milliseconds or greater in patients with HIV disease (29.6% vs 15.8%, P < .001).

CONCLUSIONS

Human immunodeficiency virus and hepatitis C infections both independently prolong QTc. Coinfection with hepatitis C greatly increases the likelihood of clinically significant QTc prolongation in patients with HIV disease.

Effect of E. coli heat-stable enterotoxin on colonic transport in guanylyl cyclase C receptor-deficient mice

We studied the functional importance of the colonic guanylyl cyclase C (GCC) receptor in GCC receptor-deficient mice. Mice were anesthetized with pentobarbital sodium, and colon segments were studied in Ussing chambers in HCO3- Ringer under short-circuit conditions. Receptor-deficient mouse proximal colon exhibited similar net Na+ absorption, lower net Cl- absorption, and a negative residual ion flux (J(R)), indicating net HCO3- absorption compared with that in normal mice. In normal mouse proximal colon, mucosal addition of 50 nM Escherichia coli heat-stable enterotoxin (STa) increased the serosal-to-mucosal flux of Cl- (J(s-->m)(Cl)) and decreased net Cl- flux (J(net)(Cl)) accompanied by increases in short-circuit current (I(sc)), potential difference (PD), and tissue conductance (G). Serosal STa had no effect. In distal colon neither mucosal nor serosal STa affected ion transport. In receptor-deficient mice, neither mucosal nor serosal 500 nM STa affected electrolyte transport in proximal or distal colon. In these mice, 1 mM 8-bromo-cGMP produced changes in proximal colon J(s-->m)(Cl) and J(net)(Cl), I(sc), PD, G, and J(R) similar to mucosal STa addition in normal mice. We conclude that the GCC receptor is necessary in the mouse proximal colon for a secretory response to mucosal STa.

Effects of short chain fatty acids on colonic Na+ absorption and enzyme activity

Short chain fatty acids (SCFA) stimulate colonic Na+ absorption and inhibit cAMP and cGMP-mediated Cl- secretion. It is uncertain whether SCFA have equivalent effects on absorption and whether SCFA inhibition of Cl- secretion involves effects on mucosal enzymes. Unidirectional Na+ fluxes were measured across stripped colonic segments in the Ussing chamber. Enzyme activity was measured in cell fractions of scraped colonic mucosa. Mucosal 50 mM acetate, propionate, butyrate and poorly metabolized isobutyrate stimulated proximal colon Na+ absorption equally (300%). Neither 2-bromo-octanoate, an inhibitor of beta-oxidation, nor carbonic anhydrase inhibition affected this stimulation. All SCFA except acetate stimulated distal colon Na+ absorption 200%. Only one SCFA affected proximal colon cGMP phosphodiesterase (PDE) (18% inhibition by 50 mM butyrate). All SCFA at 50 mM stimulated distal colon cAMP PDE (24-43%) and decreased forskolin-stimulated mucosal cAMP content. None of the SCFA affected forskolin-stimulated adenylyl cyclase in distal colon or ST(a)-stimulated guanylyl cyclase in proximal colon. Na+-K+-ATPase in distal colon was inhibited 23-51% by the SCFA at 50 mM. We conclude that all SCFA (except acetate in distal colon) stimulate colonic Na+ absorption equally, and the mechanism does not involve mucosal SCFA metabolism or carbonic anhydrase. SCFA inhibition of cAMP-mediated secretion may involve SCFA stimulation of PDE and inhibition of Na+-K+-ATPase.

Up-regulation of extracellular matrix proteoglycans and collagen type I in human crescentic glomerulonephritis

BACKGROUND

The pathogenesis of crescentic glomerulonephritis (CGN) involves cellular migration and proliferation in the urinary space, frequently followed by fibrous organization. Extracellular matrix proteoglycans (PGs) may regulate these events via effects on cellular migration, interactions with growth factors, including transforming growth factor-beta (TGF-beta), and control of collagen fibrillogenesis. The expression of PG in human CGN is unknown.

METHODS

Renal tissues from 18 patients with CGN were examined immunohistochemically for versican, decorin, biglycan and collagen type I, and were compared with morphologically normal tissues from six tumor nephrectomies. Synthesis of decorin, biglycan, and procollagen type I mRNAs was evaluated by in situ hybridization.

RESULTS

Versican was strongly expressed in cellular crescents and periglomerular areas, whereas decorin and biglycan accumulated in collagen type I-enriched regions, including fibrocellular and fibrous crescents, and interstitial fibrosis. PG and collagen type I accumulation colocalized with myofibroblasts in crescents, periglomerular areas, and interstitium.

CONCLUSIONS

The temporal and spatial patterns of expression demonstrated in this study provide evidence to support pathogenic roles for PG in the evolution of CGN. Based on known biological properties of this molecule, versican may facilitate migration of cells in developing crescents. Decorin and biglycan may contribute to progression of CGN, perhaps via interactions with collagen type I in the remodeled extracellular matrix.