Synthesis, antimicrobial activity and structure-activity relationship study of N,N-dibenzyl-cyclohexane-1,2-diamine derivatives

We report herein synthesis and antimicrobial activity of a series of N,N-dibenzyl-cyclohexane-1,2-diamine derivatives. In order to study the structure-activity relationship of substituted dibenzyl-cyclohexane-1,2-diamine derivatives, 44 structurally diverse compounds were synthesized and tested against Gram-positive and Gram-negative bacterial strains. Among them, compounds 17-20, 26, 37, 38 were found to be more active than tetracycline with MIC value ranging 0.0005-0.032 μg/mL and no hemolysis upto 1024 μg/mL in mammalian erythrocytes was observed. Some of the compounds have also shown very promising antifungal activity against Candida albicans, Candida glabrata and Geotrichum candidium.     

Synthesis, stereochemistry, antimicrobial evaluation and QSAR studies of 2,6-diaryltetrahydropyran-4-one thiosemicarbazones

A series of 2,6-diaryltetrahydropyran-4-one thiosemicarbazones (11-27) were synthesized and characterized for evaluation of potential antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Bacillus subtilis and Klebsiella pneumonia and antifungal activity against Cryptococcus neoformans, Candida albicans, Rhizopus sp., Aspergillus niger and Aspergillus flavus were evaluated. Compounds 21 and 22 showed maximum inhibition potency at low concentration (6.25 μg/ml) against P. aeruginosa. For antifungal activity, 20 and 21 were effective against C. neoformans and 22-24 against C. albicans at minimum concentration. Further, the results of QSAR studies of these synthesized compounds indicated the importance of weakly polar component of surface area, hydrophobicity and ionization potential parameters in defining their antimicrobial activity.     

Mycobacterium tuberculosis and cholinesterase inhibitors from Voacanga globosa

Globospiramine (1), a new spirobisindole alkaloid possessing an Aspidosperma-Aspidosperma skeleton, together with deoxyvobtusine (2), deoxyvobtusine lactone (3), vobtusine lactone (4) and lupeol (5), were isolated and identified from Voacanga globosa through a bioassay-guided purification. The gross structure and absolute stereochemistry of 1 were established by circular dichroism spectroscopy, HR-MS and unambiguous NMR spectroscopic experiments. In addition, a new biogenetic pathway for the formation of the spiro-Aspidosperma-Aspidosperma skeleton is proposed. Alkaloid 1 showed potent antituberculosis activity against Mycobacterium tuberculosis H₃₇Rv as evidenced in microplate Alamar blue assay (MIC = 4 μg/mL) and low-oxygen recovery assay (LORA (MIC = 5.2 μg/mL). The bisindole alkaloids also exhibited promising activity against acetylcholinesterase and, especially butyrylcholinesterase, with deoxyvobtusine (2) (IC₅₀ = 6.2 μM) as the most strongly inhibiting compound. This study extends the variety of alkaloid structural platforms which exhibit antimycobacterial and anticholinesterase activity.     

Synthesis, evaluation against Leishmania amazonensis and cytotoxicity assays in macrophages of sixteen new congeners Morita-Baylis-Hillman adducts

We report the design, synthesis, in vitro evaluation against Leishmania amazonensis (IC₅₀), cytotoxicity assays in macrophages (CC₅₀), and selectivity index (SICC₅₀/IC₅₀) of sixteen new congeners aromatic Morita-Baylis-Hillman adducts 1-16. The 1-16 were prepared in good to excellent yields (58%-97%) from the “one pot” Morita-Baylis-Hillman Reaction between the aldehydes 29-36 and the acrylates 27 or 28 under DABCO as promoter. The MBHA 2-[Hydroxy(2-nitrophenyl)propyl] propanoate (1, IC₅₀ = 7.52 μg/mL or 28.38 μM; CC₅₀ = 35.77 μg/mL or 134.98 μM; SI = 4.75) and 2-[Hydroxy(2-nitrophenyl)hydroxyethyl] propanoate (9, IC₅₀ = 5.48 μg/mL or 20.52 μM; CC₅₀ = 29.81 μg/mL or 111.64c μM and, SI = 5.43) were the most effective and safe evaluated compounds.     

Synthesis and antimicrobial activities of hexahydroimidazo[1,5-a]pyridinium bromides with varying benzyl substituents

Variously substituted benzyl bromides were employed to quaternize hexahydrobenzylimidazo[1,5-a]pyridine (A) and the resulting bromides (1-11) were evaluated for their in vitro antimicrobial activity against 10 pathogenic microorganisms: Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Micrococcus luteus, Proteus vulgaris, Escherichia coli, Salmonella typhimurium, Klebsiella pneumonia, Candida albicans and Candida krusei. Antimicrobial activities were surprisingly high (MIC: 0.78-400 μg/mL) and the sensitivity of the salts tested has been found to depend strongly both on the benzyl substituents and the microorganisms used. However, the correlation observed between antimicrobial activity and calculated partition coefficient (ClogP) was poor. Acute toxicity assessment of these salts showed LD₅₀ of 757-2000 mg/kg, after oral administration in mice in 24 h.     

Design, synthesis and antifungal activities of novel 1,2,4-triazole derivatives

A series of novel 1,2,4-triazole derivatives with a 4-(4-substitutedphenyl) piperazine side chain were designed and synthesized based on the structure of lanosterol 14α-demethylase (CYP51). Their antifungal activities against eight human pathogenic fungi were evaluated in vitro by measuring the minimal inhibitory concentrations. Nearly all tested compounds were found to be more potent against Candida albicans than control drug fluconazole. Noticeably, the MIC₈₀ value of compounds 6,7,9,14 and 29 is 16 times lower than that of voriconazole against C. albicans. The activities of compounds 7 and 21 against Cryptococcus neoformans in vitro are comparable to that of voriconazole with a MIC₈₀ value of 0.0156 μg/mL. Moreover, the molecular model for the binding between compound 7 and the active site of CACYP51 was provided based on the computational docking results.     

Synthesis of new chalcone derivatives bearing 2,4-thiazolidinedione and benzoic acid moieties as potential anti-bacterial agents

A series of chalcone derivatives bearing the 2,4-thiazolidinedione and benzoic acid moieties (8a-s) were synthesized, characterized, and evaluated for their anti-bacterial activity. Among the tested compounds, the most effective were 8a, 8h, 8k, 8n and 8q with MIC value in the range of 0.5-4 μg/mL against six Gram-positive bacteria (including multidrug-resistant clinical isolates). None of the compounds exhibited any activity against the Gram-negative bacteria Escherichia coli 1356 and E. coli 1682 at 64 μg/mL.     

Synthesis and cytotoxic activity of the heptaphylline and 7-methoxyheptaphylline series

Nineteen carbazole alkaloids modified from heptaphylline (I) and 7-methoxyheptaphylline (II) isolated from Clausena harmandiana were synthesized. Among these derivatives, Ih and IIi showed cytotoxicity against the NCI-H187 cell line with IC₅₀ values of 0.02 and 0.66 μM, respectively, which are about 138 and 4 fold stronger than the ellipticine standard. In addition, oxime Ih displayed cytotoxicity against KB cells with an IC₅₀ value of 0.17 μM which is about 10 times stronger than the ellipticine. This compound demonstrated weak cytotoxicity against Vero cells (IC₅₀ = 66.01 μM). The results show convincingly that Ih may be a promising lead for the development of cytotoxic agents.     

Synthesis and antimicrobial properties of some new thiazolyl coumarin derivatives

Two novel series of hydrazinyl thiazolyl coumarin derivatives have been synthesized and fully characterized by IR, ¹H NMR, ¹³C NMR, elemental analysis and mass spectral data. The structures of some compounds were further confirmed by X-ray crystallography. All of these derivatives, 10a-d and 15a-h, were screened in vitro for antimicrobial activity against various bacteria species including Mycobacterium tuberculosis and Candida albicans. The compounds 10c, 10d and 15e exhibited very good activities against all of the tested microbial strains.     

Tyrosyl-tRNA synthetase inhibitors as antibacterial agents: synthesis, molecular docking and structure-activity relationship analysis of 3-aryl-4-arylaminofuran-2(5H)-ones

Thirty-five 3-aryl-4-arylaminofuran-2(5H)-one derivatives were designed, prepared and tested for their inhibitory activity against tyrosyl-tRNA synthetase. Out of these compounds, 3-(3-bromophenyl)-4-(3,5-dichlorophenylamino)furan-2(5H)-one (35) was the most active with IC₅₀ of 0.09 ± 0.02 μM. The structure-activity relationship revealed that introduction of chlorine atoms at both meta positions of aniline moiety significantly increased the enzyme inhibitory activity. The results of antibacterial assay revealed that the tested compounds showed good activity against Gram-positive bacteria, with 35 being the most potent with MIC₅₀ of 0.06 μg/mL against Staphylococcus aureus ATCC 25923. Molecular docking of 35 into S. aureus tyrosyl-tRNA synthetase active site was also performed. The inhibitor snugly fitting the active site may well explain its excellent inhibitory activity.     

A novel class of trans-methylpyrazoline analogs of combretastatins: synthesis and in-vitro biological testing

Thirteen methylpyrazoline analogs (1a-m) of combretastatin A-4 (CA-4, 2) were synthesized. The trans-geometry of the two substituted phenyl moieties was ascertained by a single crystal X-ray diffraction study of compound 1d. The cytotoxicities of the analogs against the growth of murine B16 melanoma and L1210 lymphoma cells in culture were measured using the MTT assay. One of the derivatives, 1j, which has the same substituents as CA-4 was the most active in the series with IC₅₀ values of 3.3 μM and 6.8 μM against the growth of L1210 and B16 cells, respectively. The activity of this analog against human cancer cell lines was confirmed in the NCI 60 panel. The other active analogs against L1210 were 1b and 1f, which gave IC₅₀ values in the 6-8 μM range. Compound 1j caused microtubule depolymerization with an EC₅₀ value of 4.1 μM. This compound has good water solubility of 372 μM. Molecular modeling studies using DFT showed that compound 1j adopts a “twisted” conformation mimicking CA-4 that is optimal for binding to the colchicine site of tubulin.     

Synthesis and biological evaluation of 1-(4'-Indolyl and 6'-Quinolinyl) indoles as a new class of potent anticancer agents

A novel series of the biheterocycles-based compounds with core structure distinguished from combretastatin A-4 (1) and colchicine (5) have been synthesized and evaluated as potent anti-mitotic agents. Compound 1-(4′-Indolyl and 6′-quinolinyl)-4,5,6-trimethoxyindoles 13 and 19 showed substantial anti-proliferative activity against various human cancer cell lines, regardless to the tissue origin and the expression of multiple-drug resistance MDR1, with a mean IC₅₀ value of 38 and 24 nM respectively. Compound 13 (IC₅₀ = 1.7 μM) also exhibited similar anti-tubulin activities to 1 (IC₅₀ = 1.8 μM) and displayed strong binding property to the colchicine binding site on the microtubules. Computational modeling analysis revealed that the binding mechanism of compound 13 is similar to that of CA4.     

Design, synthesis and biological evaluation of novel 4-thiazolidinones containing indolin-2-one moiety as potential antitumor agent

A series of novel 4-thiazolidinone and indolin-2-one hybrid derivatives 5a-5s and 10a-10s have been designed and synthesized and their cytotoxic activities were evaluated in vitro against three human cancer cell lines including HT-29 (human colon cancer), H460 (human lung cancer), MDA-MB-231 (human breast cancer) by MTT assay. Several potent target compounds (5m, 5p, 5s, 10a, 10c-10g, 10m, 10p) were further evaluated against one cancer cell line SMMC-7721 (human liver cancer) and one normal cell line WI-38 (human fetal lung fibroblasts). Most of the prepared compounds exhibited significant antitumor activities against different human cancer cell lines. Compound 10c (IC₅₀ = 0.025 μM, 0.075 μM, 0.77 μM, 1.95 μM) was 52, 36, 4.8 and 3.3 times more active than Sunitinib (IC₅₀ = 1.3 μM, 2.7 μM, 3.7 μM, 6.47 μM) against HT-29, H460, MDA-MB-231 and SMMC-7721 cancer cell line, respectively.     

Synthesis and evaluation of monoamidoxime derivatives: toward new antileishmanial compounds

A new series of monoamidoxime derivatives was synthesized using manganese(III) acetate by microwave irradiation. Several amidoximes (27-31, 33, 38) showed valuable in vitro activities toward Leishmania donovani promastigotes, exhibiting IC₅₀ values between 5.21 and 7.89 μM. In parallel, the cytotoxicity of these compounds was evaluated on murine J774A.1 cells, revealing the corresponding selectivity index (SI). Among the 13 tested compounds, 4 monoamidoximes (27-30) exhibited an SI more than 20 times better than pentamidine. Moreover, monoamidoxime 28 (4-[5-Benzyl-3-(4-fluorophenylsulfonyl)-5-methyl-4,5-dihydrofuran-2-yl]-N′-hydroxybenzimidamide) is 40 times more selective than pentamidine, and 1.6 times more than amphotericin B, used as reference drug compounds.     

Design, synthesis and antimicrobial activity of chiral 2-(substituted-hydroxyl)-3-(benzo[d]oxazol-5-yl)propanoic acid derivatives

Chiral 2-(substituted-hydroxyl)-3-(benzo[d]oxazol-5-yl)propanoic acid derivatives were synthesized and their antibacterial activities were evaluated against fungus, Gram-negative and Gram-positive bacteria. In general, these compounds showed in vitro activities against all screened Gram-negative and Gram-positive bacteria, but poor MIC values for fungus Candida albicans. Remarkably, the (S)-configuration-substituted phenoxyl side chain on position 2 of propanoic acid exerted excellent antibacterial activity against all screened bacteria. Preliminary structure-activity studies revealed that the hydrophobic substitutes, para-tert-butyl (11r), para-phenyl (11s) and para-benzyloxy (11t) on the phenoxyl side chain displayed best activities against all Gram-negative and Gram-positive bacteria with MIC values between 1.56 and 6.25 μg/mL.     

Synthesis and in vitro anti-tumor activity of new oxadiazole thioglycosides

A facile, convenient and high yielding synthesis of novel thioglycosides incorporating 1,3,4-oxadiazole, triazole and or triazine moieties from readily available starting materials has been described. The key step of this protocol is the formation of 3-isobutyl-1-phenyl-1H-pyrazole-4-carbaldehyde (3) via condensation between methyl iso-butyl ketone and phenylhydrazine followed by application of Vilsmeier-Haack reaction. 3 was converted either to 1,3,4-oxadiazole derivative or condensed with O-aminothiols to give the bases 8, 19 and 20 in good yields, respectively. The aglycons 8, 19, and 20 were coupled with different activated halosugars in the presence of basic medium. Pharmacological evaluation of compounds 8, 14, 16 and 22 in vitro against 2-cell lines MCF-7 (breast) and HEPG2 (liver) revealed them to possess high anti-tumor activities with IC₅₀ values ranging from 2.67-20.25 (μg/mL) for breast cell line (MCF-7) and 4.62-43.6 (μg/mL) for liver cell line (HEPG2). None of the tested compounds exhibited any toxicity in doses up to 500 mg kg⁻¹ of the animal body weight.     

New fluorine-containing hydrazones active against MDR-tuberculosis

Several new fluorine-containing hydrazones were synthesized and screened for their in vitro antimycobacterial activity. Nine of these derivatives have shown a remarkable activity against MDR-TB strain with MIC 0.5 μg/mL and high value of selectivity index (SI). Compound 3h with the highest SI (1268.58) was used for stability evaluation with putative metabolites (ciprofloxacin and formylciprofloxacin) detection. Compound 3h was stable at pH 7.4 of aqueous buffer and rat plasma, in acidic buffers (at pH 3 and 5) slow decomposition was observed. Interestingly, no formylciprofloxacin was detected in the solution, and only slightly increased concentration of ciprofloxacin was observed instead. Trifluoromethyl hydrazones 3f and 3g exhibited the best activity also against two strains of Mycobacterium kansasii (MIC 1-4 μmol/L). All evaluated compounds were found to be non-cytotoxic.     

Cyathane diterpenes from Chinese mushroom Sarcodon scabrosus and their neurite outgrowth-promoting activity

Two novel cyathane diterpenoids, designated scabronines K (1) and L (2), were isolated from the fruiting bodies of the basidiomycete Sarcodon scabrosus together with four known analogues, sarcodonins G (3), A (5), M (6), and scabronine H (4). Their structures were elucidated on the basis of extensive spectroscopic analysis including 2D-NMR (HMBC, HSQC, ROESY, ¹H,¹H-COSY) and MS experiments. The isolated compounds were evaluated for nerve growth factor (NGF)-mediated neurite outgrowth using rat pheochromocytoma (PC12) cells as a model system of neuronal differentiation. Among these compounds, only sarcodonins G and A (3 and 5) at 25 μM showed significant neurite outgrowth (neuritegenesis)-promoting activity in the presence of 20 ng/mL NGF after 24 h treatment. Their structure-neurite inducing activity relationship was also discussed.     

Synthesis and anticancer effects of some novel pyrazolo[3,4-d]pyrimidine derivatives by generating reactive oxygen species in human breast adenocarcinoma cells

A series of novel substituted pyrazolo[3,4-d]pyrimidines (compounds 2-12) were synthesized starting with pyrimidinone derivative 1. Their in vitro cytotoxicity against human breast adenocarcinoma (MCF-7) cell lines has been investigated and most of the tested compounds exploited potent cytotoxic activity against MCF-7 cell lines comparable to the activity of the commonly used anticancer drug cisplatin. Treatment of MCF-7 cells with increased doses (2, 5, 10, 20 μg/ml) of the tested compounds revealed that the activity of superoxide dismutase and the level of hydrogen peroxide were significantly increased, while the activities of catalase and glutathione peroxidase and the levels of reduced glutathione were significantly lowered compared with control MCF-7 cells. In general, acyclic nucleoside derivative 4 revealed the highest anticancer activity among the other tested compounds.     

4-anilinoquinoline triazines: a novel class of hybrid antimalarial agents

A novel class of hybrid 4-anilinoquinoline triazines have been synthesized and evaluated in vitro for their antimalarial activity against CQ-sensitive 3D7 strain of P. falciparum as well as for their cytotoxicity toward VERO cell line. Five compounds (19, 20, 23, 41 and 45) exhibited the antimalarial potency superior to CQ. Compounds 14 and 16 were found to be orally active at a dose of 100 mg/kg × 4 days against CQ-resistant strain of P. yoelii. Inhibition of β-hematin formation assay and molecular docking study has been conducted in order to gain insight into the mechanism of action of proposed targets for the 4-anilinoquinoline and triazine moiety of the hybrid compounds.