Bicyclic Basic Merbarone Analogues as Antiproliferative Agents.

Pyrimido-pyrimidine derivatives have been developed as rigid merbarone analogues. In a previous study, these compounds showed potent antiproliferative activity and efficiently inhibited topoisomerase IIα. To further extend the structure-activity relationships on pyrimido-pyrimidines, a novel series of analogues was synthesized by a two-step procedure. Analogues 3-6 bear small alky groups at positions 1 and 3 of the pyrimido-pyrimidine scaffold whereas at position 6a (4-chloro)phenyl substituent was inserted. The basic side chains introduced at position 7 were selected on the basis of the previously developed structure-activity relationships. The antiproliferative activity of the novel compounds proved to be affected by both the nature of the basic side chain and the substituents on the pyrimido-pyrimidine moiety. Derivatives 5d and 5e were identified as the most promising molecules still showing reduced antiproliferative activity in comparison with the previously prepared pyrimido-pyrimidine analogues. In topoisomerase IIα-5d docking complex, the ligand would poorly interact with the enzyme and assume a different orientation in comparison with 1d bioactive conformation.

New 1,2,3-triazole-(thio)barbituric acid hybrids as urease inhibitors: Design, synthesis, in vitro urease inhibition, docking study, and molecular dynamic simulation.

A new series of 1,2,3-triazole-(thio)barbituric acid hybrids 8a-n was designed and synthesized on the basis of potent pharmacophores with urease inhibitory activity. Therefore, these compounds were evaluated against Helicobacter pylori urease. The obtained result demonstrated that all the synthesized compounds, 8a-n, were more potent than the standard urease inhibitor, hydroxyurea. Moreover, among them, compounds 8a, 8c-e, 8g,h, and 8k,l exhibited higher urease inhibitory activities than the other standard inhibitor used: thiourea. Docking studies were performed with the synthesized compounds. Furthermore, molecular dynamic simulation of the most potent compounds, 8e and 8l, showed that these compounds interacted with the conserved residues Cys592 and His593, which belong to the active site flap and are essential for enzymatic activity. These interactions have two consequences: (a) blocking the movement of a flap at the entrance of the active site channel and (b) stabilizing the closed active site flap conformation, which significantly reduces the catalytic activity of urease. Calculation of the physicochemical and topological properties of the synthesized compounds 8a-n predicted that all these compounds can be orally active. The ADME prediction of compounds 8a-n was also performed.

Synthesis and characterisation of thiobarbituric acid enamine derivatives, and evaluation of their α-glucosidase inhibitory and anti-glycation activity.

A new series of thiobarbituric (thiopyrimidine trione) enamine derivatives and its analogues barbituric acid derivatives was synthesised, characterised, and screen for in vitro evaluation of α-glucosidase enzyme inhibition and anti-glycation activity. This series of compounds were found to inhibit α-glucosidase activity in a reversible mixed-type manner with IC50 between 264.07 ± 1.87 and 448.63 ± 2.46 µM. Molecular docking studies indicated that compounds of 3g, 3i, 3j, and 5 are located close to the active site of α-glucosidase, which may cover the active pocket, thereby inhibiting the binding of the substrate to the enzyme. Thiopyrimidine trione derivatives also inhibited the generation of advanced glycation end-products (AGEs), which cause long-term complications in diabetes. While, compounds 3a-k, 5, and 6 showed significant to moderate anti-glycation activity (IC50 = 31.5 ± 0.81 to 554.76 ± 9.1 µM).

Barbiturate derived amphiphilic homopolymers: synthesis, characterization, self-assembly and anticancer drug delivery.

Aim: Our aim was to synthesis and characterization of amphiphilic norbornene-derived thiobarbiturate homopolymers (NDTH 1-4) for drug delivery. Methods: Ring-opening metathesis polymerization technique was used to prepare a series of homopolymers. The hydrophobicity is introduced by increasing the number of carbon chains ([-CH2-]n; n = 1, 2, 3 & 4) in between norbornene backbone and thiobarbiturate species. Results: These vesicular aggregates have been used as anticancer Doxorubicin drug delivery vehicles at the acidic (5.5) and physiological (7.4) pHs. Confocal laser-scanning microscopy has demonstrated that the drug-loaded vesicles are easily internalized into living cells. Conclusion: Amphiphilic norbornene-derived thiobarbiturate homopolymer assemblies showed efficient nanocarrier for effective anticancer drug delivery.

New thiobarbituric acid scaffold-based small molecules: Synthesis, cytotoxicity, 2D-QSAR, pharmacophore modelling and in-silico ADME screening.

A series of twenty five new thiobarbituric acid derivatives, viz. 3a-h, 4-7, 8a-c, 9, 10a-c, 11 and 12a-d, were designed and synthesized as potential cytotoxic agents. In-vitro screening of the new compounds against the three human cancer cell lines Caco-2, HepG-2 and MCF-7 was performed to assess their intrinsic activity. Compound 12d exhibited potent sub-micromolar activity against HepG-2 and MCF-7 (IC50 = 0.07 and 0.08 µM, respectively). In-silico pharmacophore modelling of this chemotype compounds disclosed a five features' pharmacophore model representing essential steric and electronic fingerprints essential for activity. Finally, a 2D-QSAR model was devised to quantitatively correlate the 2D molecular feature descriptors of this series of thiobarbiturates with their cytotoxic activity against MCF-7. Finally, in silico evaluation of the physicochemical and ADME properties of these derivatives was performed.

Docking- and pharmacophore-based virtual screening for the identification of novel Mycobacterium tuberculosis protein tyrosine phosphatase B (MptpB) inhibitor with a thiobarbiturate scaffold.

Mycobacterium tuberculosis (Mtb) protein tyrosine phosphatase B (MptpB) is an important virulence factor for Mtb that contributes to survival of the bacteria in macrophages. The absence of a human ortholog makes MptpB an attractive target for new therapeutics to treat tuberculosis. MptpB inhibitors could be an effective treatment to overcome emerging TB drug resistance. Adopting a structure-based virtual screening strategy, we successfully identified thiobarbiturate-based drug-like MptpB inhibitor 15 with an IC50 of 22.4 µM, and as a non-competitive inhibitor with a Ki of 24.7 µM. Importantly, not only did it exhibit moderate cell membrane permeability, compound 15 also displayed potent inhibition of intracellular TB growth in the macrophage, making it an excellent lead compound for anti-TB drug discovery. To the best of our knowledge, this novel thiobarbiturate is the first class of MptpB inhibitor reported so far that leveraged docking- and pharmacophore-based virtual screening approaches. The results of preliminary structure-activity relationship demonstrated that compound 15 identified herein was not a singleton and may inspire the design of novel selective and drug-like MptpB inhibitors.

Synthesis, Molecular Modeling and Biological Evaluation of 5-arylidene-N,N-diethylthiobarbiturates as Potential α-glucosidase Inhibitors.

BACKGROUND: Barbituric acid derivatives are a versatile group of compounds which are identified as potential pharmacophores for the treatment of anxiety, epilepsy and other psychiatric disorders. They are also used as anesthetics and have sound effects on the motor and sensory functions. Barbiturates are malonylurea derivatives with a variety of substituents at C-5 position showing resemblance with nitrogen and sulfur containing compounds like thiouracil which exhibited potent anticancer and antiviral activities. Recently, barbituric acid derivatives have also received great interest for applications in nanoscience. OBJECTIVE: Synthesis of 5-arylidene-N,N-diethylthiobarbiturates, biological evaluation as potential α-glucosidase inhibitors and molecular modeling. METHODS: In the present study, N,N-Diethylthiobarbituric acid derivatives were synthesized by refluxing of N,N-diethylthiobarbituric acid and different aromatic aldehydes in distilled water. In a typical reaction; a mixture of N,N-diethylthiobarbituric acid 0.20 g (1 mmol) and 5-bromo-2- hydroxybenzaldehyde 0.199 g (1 mmol) mixed in 10 mL distilled water and reflux for 30 minutes. After completion of the reaction, the corresponding product 1 was filtered and dried and yield calculated. It was crystallized from ethanol. The structures of synthesized compounds 1-25 were carried out by using 1H, 13C NMR, EI spectroscopy and CHN analysis used for the determination of their structures. The α-glucosidase inhibition assay was performed as given by Chapdelaine et al., with slight modifications and optimization. RESULTS: Our newly synthesized compounds showed a varying degree of α-glucosidase inhibition and at least four of them were found as potent inhibitors. Compounds 6, 5, 17, 11 exhibited IC50 values (Mean±SEM) of 0.0006 ± 0.0002, 18.91 ± 0.005, 19.18 ± 0.002, 36.91 ± 0.003 µM, respectively, as compared to standard acarbose (IC50, 38.25 ± 0.12 µM). CONCLUSION: Our present study has shown that compounds 6, 5, 17, 11 exhibited IC50 values of 0.0006 ± 0.0002, 18.91 ± 0.005, 19.18 ± 0.002, 36.91 ± 0.003 µM, respectively. The studies were supported by in silico data analysis.

Exploiting the Thiobarbituric Acid Scaffold for Antibacterial Activity.

Thiobarbituric acid (TBA) has been considered a privileged structure for developing antimicrobial agents. Diversity was obtained at positions N and at C5 through acylation, Schiff base formation, Knoevenagel condensation, and thioamide and enamine formation. The present work describes the synthesis of small libraries based on the TBA moiety and above-mentioned reactions. Preliminary antimicrobial activity screening of the prepared compounds against selected bacteria (both Gram-positive and -negative) showed the best results for the Boc-Phe-TBA derivative. These results could be useful for designing and building libraries based on other amino acids with distinct protecting groups.

Taurine as a green bio-organic catalyst for the preparation of bio-active barbituric and thiobarbituric acid derivatives in water media.

Taurine, a ß-amino acid that is abundantly available in the tissues of human and animals, is efficiently used as a green bio-organic catalyst in the preparation of some of the biologically active barbituric and thiobarbituric acid derivatives. In the presence of taurine, 5-Arylidene (thio) barbituric acid derivatives were prepared via Knovenagel reaction between aldehydes and (thio)barbituric acid. Using this reagent also pyrano[2,3-d]pyrimidinone(thione) derivatives were synthesized through a three-component reaction between aldehydes, (thio)barbituric and malononitrile. Both reactions are performed in water with good to excellent yields during acceptable reaction times. No organic solvent was used during reaction or separation steps and no extra-purification was exerted. Meanwhile, reusability of taurine was easy and noticeably high.

Design and synthesis of novel thiobarbituric acid derivatives targeting both wild-type and BRAF-mutated melanoma cells.

A series of novel thio- and seleno-barbituric acid derivatives were synthesized by varying the substituents at N1 and N3 (ethyl, methyl, allyl, and phenyl), and C5 tethered with dienyl and trienyl moieties attached to substituents such as phenyl, 2-furanyl, 2-thiophenyl, 1-naphthyl, and 3-pyridyl. The cytotoxic potential of these derivatives was evaluated by using MTT assay against melanoma cell lines expressing either wild-type (CHL-1) or mutant (UACC 903) BRAF gene. Among all, 2b and 8b were identified as the most potent compounds. Both 2b and 8b inhibited viability of various melanoma cells and induced cell death as evidenced by Live and Dead assay. Western blot analysis showed that they induce PARP cleavage and inhibit anti-apoptotic Bcl-2, Bcl-xL and Survivin in a dose-dependent manner within 24 h of the treatment. Novel thiobarbituric acid analogs also inhibited viability of various other solid tumor cell lines, such as pancreatic, breast, and colon. Overall, 2b, 2d, and 8b emerged as the most effective compounds and make good leads for the development of future therapeutic agents.

Synthesis of thiobarbituric acid derivatives: In vitro α-glucosidase inhibition and molecular docking studies.

Synthesis, structure, and evaluation of in vitro α-glucosidase enzyme inhibition of a new class of diethylammonium salts of aryl substituted thiobarbituric acid is described. This protocol is straight, environmentally benign and efficient, involving Aldol-Michael addition reaction in one pot fashion. The 3D chemical structures of the synthesized compounds were assigned based on spectroscopic methods and X-ray single crystal diffraction analyses. All synthesized compounds 3a-3n were evaluated for their in vitro α-glucosidase enzyme inhibitory activity, whereas acarbose was used as the standard drug (IC50=840±1.73µM). All tested compounds were found to possess varying degree of α-glucosidase enzyme inhibition activity with (IC50=19.46±1.84-415.8±4.0µM). Compound3i(IC50=19.4±1.84µM) exhibited the highest activity. To the best of knowledge this is the first report of the in vitro α-glucosidase enzyme inhibition by the diethylamonium salts of aryl substituted thiobarbituric acid. Furthermore, molecular docking studies of selected compounds were also performed to see interactions between active compounds and binding sites.

Synthesis of Pyrazole-Thiobarbituric Acid Derivatives: Antimicrobial Activity and Docking Studies.

A one-pot reaction was described that results in various pyrazole-thiobarbituric acid derivatives as new pharmacophore agents. These new heterocycles were synthesized in high yields with a broad substrate scope under mild reaction conditions in water mediated by NHEt2. The molecular structures of the synthesized compounds were assigned based on different spectroscopic techniques. The new compounds were evaluated for their antibacterial and antifungal activity. Compounds 4h and 4l were the most active compounds against C. albicans with MIC = 4 µg/L. Compound 4c exhibited the best activity against S. aureus and E. faecalis with MIC = 16 µg/L. However, compounds 4l and 4o were the most active against B. subtilis with MIC = 16 µg/L. Molecular docking studies for the final compounds and standard drugs were performed using the OpenEye program.

Design and synthesis of new barbituric- and thiobarbituric acid derivatives as potent urease inhibitors: Structure activity relationship and molecular modeling studies.

In this study 36 new compounds were synthesized by condensing barbituric acid or thiobarbituric acid and respective anilines (bearing different substituents) in the presence of triethyl orthoformate in good yields. In vitro urease inhibition studies against jack bean urease revealed that barbituric acid derived compounds (1-9 and 19-27) were found to exhibit low to moderate activity however thiobarbituric acid derived compounds (10-18 and 28-36) showed significant inhibition activity at low micro-molar concentrations. Among the synthesized compounds, compounds (15), (12), (10), (36), (16) and (35) showed excellent urease inhibition with IC50 values 8.53 ± 0.027, 8.93 ± 0.027, 12.96 ± 0.13, 15 ± 0.098, 18.9 ± 0.027 and 19.7 ± 0.63 µM, respectively, even better than the reference compound thiourea (IC50 = 21 ± 0.011). The compound (11) exhibited comparable activity to the standard with IC50 value 21.83 ± 0.19 µM. In silico molecular docking studies for most active compounds (10), (12), (15), (16), (35) and (36) and two inactive compounds (3) and (6) were performed to predict the binding patterns.

New barbiturates and thiobarbiturates as potential enzyme inhibitors.

A series of 27 new barbiturates and thiobarbiturates have been synthesized by a convenient multi-component reaction in overall excellent yields (87-96%). All the synthesized compounds were characterized by 1H, 13C NMR, EIMS and elemental analysis (C, H, N and S). Furthermore, all compounds were screened for in vitro antioxidant (DPPH radical scavenging), lipoxygenase, chymotrypsin, α-glucosidase and anti-urease activities. Out of the series, 23 in DPPH, 14 in lipoxygenase, 2 in chymotrypsin have shown appreciable IC50 values.

Synthesis and structure-activity relationship of thiobarbituric acid derivatives as potent inhibitors of urease.

A series of thiobarbituric acid derivatives 1-27 were synthesized and evaluated for their urease inhibitory potential. Exciting results were obtained from the screening of these compounds 1-27. Compounds 5, 7, 8, 11, 16, 17, 22, 23 and 24 showed excellent urease inhibition with IC50 values 18.1 ± 0.52, 16.0 ± 0.45, 16.0 ± 0.22, 14.3 ± 0.27, 6.7 ± 0.27, 10.6 ± 0.17, 19.2 ± 0.29, 18.2 ± 0.76 and 1.61 ± 0.18 µM, respectively, much better than the standard urease inhibitor thiourea (IC50=21 ± 0.11 µM). Compound 3, 4, 10, and 26 exhibited comparable activities to the standard with IC50 values 21.4 ± 1.04 and 21.5 ± 0.61 µM, 22.8 ± 0.32, 25.2 ± 0.63, respectively. However the remaining compounds also showed prominent inhibitory potential The structure-activity relationship was established for these compounds. This study identified a novel class of urease inhibitors. The structures of all compounds were confirmed through spectroscopic techniques such as EI-MS and (1)H NMR.

Antibacterial, antiurease, and antioxidant activities of some arylidene barbiturates.

Some series of arylidene barbiturates and thiobarbiturates were evaluated for their antibacterial, antioxidant, and urease inhibition activities. The arylidene barbiturates and thiobarbiturates were tested for antimicrobial activity using the agar well diffusion technique against 13 bacteria. The synthesized compounds (1a-g) were screened for antiurease and antioxidant activities. The results showed that the synthesized compounds (1a-g) had effective antiurease, antioxidant, and antibacterial activities.

Further SAR studies on bicyclic basic merbarone analogues as potent antiproliferative agents.

Pyrimidopyrimidine derivatives 1 were prepared as rigid thioanalogues of merbarone (a catalytic topoisomerase II inhibitor) and screened as antiproliferative agents against different tumor cell lines. A number of the synthesized compounds emerged as cytotoxic in cell-based assays (MT-4, HeLa and MCF-7 cells) at low micromolar concentrations. In a National Cancer Institute screening, selected member of the series showed a broad spectrum of antiproliferative activity against various tumours (melanoma, renal, CNS, colon and breast cancers). The acid-base and steric properties of the substituent at position 7 of the pyrimidopyrimidine scaffold deeply affected potency. Enzymatic assays evidenced that a subset of tested derivatives efficiently inhibit topoisomerase IIα accordingly to merbarone mechanism of action. However this property does not fully rationalize the cytotoxicity data of the full ligand panel, suggesting that different target(s) should be additionally involved.

New methodology for the synthesis of thiobarbiturates mediated by manganese(III) acetate.

A three step synthesis of various thiobarbiturate derivatives 17-24 was established. The first step is mediated by Mn(OAc)3, in order to generate a carbon-carbon bond between a terminal alkene and malonate. Derivatives 1-8 were obtained in moderate to good yields under mild conditions. This key step allows synthesis of a wide variety of lipophilic thiobarbiturates, which could be tested for their anticonvulsive or anesthesic potential.

Synthesis and evaluation of chromenyl barbiturates and thiobarbiturates as potential antitubercular agents.

A novel series of barbiturate and thiobarbiturate analogs of 2-benzoyl-3-methyl-5-oxo-5H-furo[3,2-g]chromene-6-carbaldehydes (3a-g and 4a-d, respectively) and 6-methyl-4,8-dioxo-4,8-dihydropyrano[3,2-g]chromenes (7a-c), were synthesized and evaluated for their antitubercular activities against Mycobacterium tuberculosis H37RV, and cytotoxicity (CC(50)) in the VERO cell MABA assay. The results indicate that the furanochromene series of compounds (3a-g and 4a-d) showed only weak to moderate antitubercular activity. However, the pyranochromene analog 7b showed good antitubercular activity (IC(90): 5.9µg/mL) and cytotoxicity (CC(50): 14.27µg/mL). The antitubercular activity of 7b was superior to the antituberculosis drug, pyrazinamide (PZA; IC(90): >20µg/mL). Analog 7b was considered to be a lead compound for subsequent structural optimization.

Synthesis and biological activity of novel barbituric and thiobarbituric acid derivatives against non-alcoholic fatty liver disease.

Forty-four barbituric acid or thiobarbituric acid derivatives were synthesized and evaluated for their effects on adipogenesis of 3T3-L1 adipocytes by measuring the expression of adiponectin in vitro. Four compounds (3a, 3o, 3s, 4t) were found to increase the expression of adiponectin and lower the leptin level in 3T3-L1 adipocytes at respective concentration of 10 µM. Among them, 3s showed the most efficacious. Oral administration of 3s effectively reduced body weight, liver weight, and visceral fat and regulated serum levels of biochemical markers in the high-fat/diet-induced Wistar rats. Histopathological evaluation of liver sections by Oil Red O and H&E staining confirmed 3s as a potent, orally active molecule for reducing fat deposition against non-alcoholic fatty liver disease.