Development of 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and their salts as potent cytotoxic agents and topoisomerase I/IIα inhibitors

A novel series of 35 angularly fused pentacyclic 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridin-5-ium chlorides were designed and synthesized. Their cytotoxic activities were investigated against six human cancer cell lines (NCIH23, HCT15, NUGC-3, ACHN, PC-3, and MDA-MB-231). Among all screened compounds; 28, 30, 34, 35, 46, 48, 52, and 53 compounds exhibited potent cytotoxic activities against all tested human cancer cell lines. Further, these potent lead cytotoxic agents were evaluated against human Topoisomerase I and IIα inhibition. Among them, the compound 48 exhibited dual Topoisomerase I and IIα inhibition especially at 20?μM concentrations the compound 48 exhibited 1.25?times more potent Topoisomerase IIα inhibitory activity (38.3%) than the reference drug etoposide (30.6%). The compound 52 also exhibited excellent (88.4%) topoisomerase I inhibition than the reference drug camptothecin (66.7%) at 100?μM concentrations. Molecular docking studies of the compounds 48 and 52 with topo I discovered that they both intercalated into the DNA single-strand cleavage site where the compound 48 have van der Waals interactions with residues Arg364, Pro431, and Asn722 whilst the compound 52 have with Arg364, Thr718, and Asn722 residues. Both the compounds 48 and 52 have π–π stacking interactions with the stacked DNA bases. The docking studies of the compound 48 with topo IIα explored that it was bound to the topo IIα DNA cleavage site where etoposide was situated. The benzo[f]chromeno[4,3-b][1,7]naphthyridine ring of the compound 48 was stacked between the DNA bases of the cleavage site with π–π stacking interactions and there were no hydrogen bond interactions with topo IIα.     

Synthesis, in vitro and in vivo evaluation of 2-aryl-4H-chromene and 3-aryl-1H-benzo[f]chromene derivatives as novel α-glucosidase inhibitors

Herein we report a study of novel arylchromene derivatives as analogs of naturally occurring flavonoids with prominent α-glucosidase inhibitory properties. Novel inhibitors were identified via simple stepwise in silico screening, efficient synthesis, and biological evaluation. It is shown that 2-aryl-4H-chromene core retains pharmacophore properties while being readily available synthetically. A lead compound identified through screening inhibits yeast α-glucosidase with IC₅₀ of 62.26?µM and prevents postprandial hyperglycemia in rats at 2.2?mg/kg dose.     

Novel (S)-1,3,4,12a-tetrahydropyrazino[2,1-c][1,4]benzodiazepine-6,12(2H,11H)-dione derivatives: Selective inhibition of MV-4-11 biphenotypic B myelomonocytic leukemia cells’ growth is accompanied by reactive oxygen species overproduction and apoptosis

A series of optically pure (R)- and (S)-1,3,4,12a-tetrahydropyrazino[2,1-c][1,4]benzodiazepine-6,12(2H,11H)-dione derivatives was designed and synthesized as novel anthramycin analogues in a three-step, one-pot procedure, and tested for their antiproliferative activity on nine following cell lines: MV-4-11, UMUC-3, MDA-MB-231, MCF7, LoVo, HT-29, A-549, A2780 and BALB/3T3. The key structural features responsible for exhibition of cytotoxic effect were determined: the (S)-configuration of chiral center and the presence of hydrophobic 4-biphenyl substituent in the side chain. Introduction of bromine atom into the 8 position (8g) or substitution of dilactam ring with benzyl group (8m) further improved the activity and selectivity of investigated compounds. Among others, compound 8g exhibited selective cytotoxic effect against MV-4-11 (IC₅₀?=?8.7?μM) and HT-29 (IC₅₀?=?17.8?μM) cell lines, while 8m showed noticeable anticancer activity against MV-4-11 (IC₅₀?=?10.8?μM) and LoVo (IC₅₀?=?11.0?μM) cell lines. The cell cycle arrest in G₁/S checkpoint and apoptosis associated with overproduction of reactive oxygen species was also observed for 8e and 8m.     

Design,synthesis, and structure-activity relationships of novel 4,7,12,12a-tetrahydro-5H-thieno[3′,2′:3,4]pyrido[1,2-b]isoquinoline and 5,8,12,12a-tetrahydro-6H-thieno[2′,3′:4,5]pyrido[2,1-a]isoquinoline derivatives as cellular activators of adenosine 5′-monophosphate-activated protein kinase (AMPK)

To discover more derivatives with better glucose-lowering efficacy compared with berberine, twenty-three novel compounds with 4,7,12,12a-tetrahydro-5H-thieno[3′,2′:3,4]pyrido[1,2-b]isoquinoline or 5,8,12,12a-tetrahydro-6H-thieno[2′,3′:4,5]pyrido[2,1-a]isoquinoline cores were designed, synthesized, and biologically evaluated in vitro in continuation of our previous work on indirect activators of adenosine 5′-monophosphate-activated protein kinase (AMPK). Nine compounds effectively stimulated glucose consumption (>2.3-fold at 10 μM) in L6 myotube cells, and two compounds (4d and 4s) exhibited superior inhibitory activity (<57.6% at 5 μM) compared with berberine on gluconeogenesis in rat primary hepatocytes. Additionally, these compounds significantly up-regulated the phosphorylation of AMPK and its substrate, acetyl-CoA carboxylase (ACC) and slightly decreased the mitochondrial membrane potential in L6 myotube cells.     

Design and synthesis of 1,4-substituted 1H-1,2,3-triazolo-quinazolin-4(3H)-ones by Huisgen 1,3-dipolar cycloaddition with PI3Kγ isoform selective activity

A strategy for construction of medicinally important 1,4-substituted 1H-1,2,3-triazolo-quinazolin-4(3H)-ones has been devised and presented here. The compounds have been synthesized using one-pot multicomponent strategy under microwave assisted conditions. Triazolyl-quinazolinone based D-ring modified analogs are designed based on IC87114 scaffold, which is first known isoform selective inhibitor of PI3Kδ. Herein, we identified two triazolyl-quinazolinone compounds (5a and 5l) based on same scaffold with PI3Kγ specific inhibitory potential, the selectivity towards this isoform is well supported by in silico results, wherein, these compounds show better interaction and affinity and inhibitory activity for PI3Kγ rather than PI3Kδ. This repositioning of scaffold from PI3Kδ to PI3Kγ isoform can be very useful from medicinal chemistry and drug discovery perspective to unravel molecular interactions of this new scaffold in different cellular pathways.     

The light-harvesting chlorophyll a/b · protein complex of the green alga Acetabularia mediterranea isolation and characterization of two subunits

In the green alga Acetabularia mediterranea a light-harvesting chlorophyll a/b · protein complex of 67 000 daltons has been found which contains two polypeptide chains of 21 500 and 23 000 daltons. These two polypeptides were isolated on a preparative scale and were further characterized by several different methods. Both polypeptides proved to be very similar. While their amino acid and sugar compositions as well as their immunochemical properties were almost identical the tryptic peptides and the cyanogen bromide fragments of the two polypeptides revealed minor but significant differences. The 67 000-dalton chlorophyll a/b · protein complex and its two polypeptide components were compared to the light-harvesting chlorophyll a/b · protein of higher plants.     

Discovery of the imidazo[1,5-a][1,2,4]-triazolo[1,5-d][1,4]benzodiazepine scaffold as a novel,potent and selective GABAA α5 inverse agonist series

Through iterative design cycles we have discovered a number of novel new classes where the imidazo[1,5-a][1,2,4]-triazolo[1,5-d][1,4]benzodiazepine was deemed the most promising GABA_A α5 inverse agonist class with potential for cognitive enhancement. This class combines a modest subtype binding selectivity with inverse agonism and has the most favourable molecular properties for further lead optimisation towards a central nervous system (CNS) acting medicine.     

Synthesis and SAR study of new hydroxy and chloro-substituted 2,4-diphenyl 5H-chromeno[4,3-b]pyridines as selective topoisomerase IIα-targeting anticancer agents

As part of our effort to develop potential topoisomerase IIα (topo IIα) targeting anticancer agents, we systematically designed a new series of hydroxy and chloro-substituted 2,4-diphenyl 5H-chromeno[4,3-b]pyridines. Total eighteen compounds were synthesized and tested for their ability to inhibit the function of topo I and IIα, and proliferation of human breast (T47D), colorectal (HCT15), and cervix (HeLa) cancer cells. Except compound 11, all of the tested compounds displayed selective topo IIα inhibitory activity. Compounds 8–18, 22, 24, and 25 showed excellent topo IIα inhibitory activity than a positive control, etoposide. Most of the compounds appeared to be superior to reference compounds in their antiproliferative activity. Structure-activity relationship (SAR) study has shown that it is better to place the hydroxyphenyl group at the 4-position of the central pyridine for superior topo IIα inhibition and antiproliferative activity. Similarly, the 3′-, or 4′-hydroxyphenyl substitution at the 2- and 4-positon of pyridine ring is important for better activity than 2′-substitution.     

Imidazo[1,5-a][1,2,4]-triazolo[1,5-d][1,4]benzodiazepines as potent and highly selective GABAA α5 inverse agonists with potential for the treatment of cognitive dysfunction

In a search for GABA_A α5 ligands that combine high subtype binding selectivity with a marked inverse agonism imidazo[1,5-a][1,2,4]-triazolo[1,5-d][1,4]benzodiazepines were identified as a promising class. A short tandem reaction allowed rapid access to this chemical series, thereby facilitating rapid SAR generation which guided the optimization process. Two compounds (10e and 11f) were found to be active in an in vivo paradigm for cognitive improvement.     

Multifunctional 5,6-dimethoxybenzo[d]isothiazol-3(2H)-one-N-alkylbenzylamine derivatives with acetylcholinesterase,monoamine oxidases and β-amyloid aggregation inhibitory activities as potential agents against Alzheimer’s disease

A series of 5,6-dimethoxybenzo[d]isothiazol-3(2H)-one-N-alkylbenzylamine derivatives were designed, synthesized and evaluated as potential multifunctional agents for the treatment of Alzheimer’s disease (AD). The in vitro assays indicated that most of these derivatives were selective AChE inhibitors with good multifunctional properties. Among them, compounds 11b and 11d displayed comprehensive advantages, with good AChE (IC₅₀?=?0.29?±?0.01?μM and 0.46?±?0.02?μM, respectively), MAO-A (IC₅₀?=?8.2?±?0.08?μM and 7.9?±?0.07?μM, respectively) and MAO-B (IC₅₀?=?20.1?±?0.16?μM and 43.8?±?2.0% at 10?μM, respectively) inhibitory activities, moderate self-induced Aβ_1–42 aggregation inhibitory potency (35.4?±?0.42% and 48.0?±?1.53% at 25?μM, respectively) and potential antioxidant activity. In addition, the two representative compounds displayed high BBB permeability in vitro. Taken together, these multifunctional properties make 11b and 11d as a promising candidate for the development of efficient drugs against AD.     

Design and synthesis of benzofuro[3,2-b]pyridin-2(1H)-one derivatives as anti-leukemia agents by inhibiting Btk and PI3Kδ

Btk inhibitors and PI3Kδ inhibitors play crucial roles in the treatment of leukemia, and studies confirmed that the synergetic inhibition against Btk and PI3Kδ could gain an optimal response. Herein, a series of novel benzofuro[3,2-b]pyridin-2(1H)-one derivatives were designed and synthesized as dual Btk/PI3Kδ kinases inhibitors for the treatment of leukemia. Studies indicated that most compounds could suppress the proliferation of multiple leukemia or lymphoma cells (Raji, HL60 and K562 cells) at low micromolar concentrations in vitro. Further kinase assays identified several compounds could simultaneously inhibit Btk kinase and PI3Kδ kinase. Thereinto, compound 16b exhibited the best inhibitory activity (Btk: IC₅₀?=?139?nM; PI3Kδ: IC₅₀?=?275?nM) and showed some selectivity against PI3Kδ compared to PI3Kβ/γ. Finally, the SAR of target compounds was preliminarily discussed combined with docking results. In brief, 16b possessed of the potency for the further optimization as anti-leukemia drugs by inhibiting simultaneously Btk kinase and PI3Kδ kinase.     

Design,synthesis, and biological activity of substituted 2-amino-5-oxo-5H-chromeno[2,3-b]pyridine-3-carboxylic acid derivatives as inhibitors of the inflammatory kinases TBK1 and IKKε for the treatment of obesity

The non-canonical IκB kinases TANK-binding kinase 1 (TBK1) and inhibitor of nuclear factor kappa-B kinase ε (IKKε) play a key role in insulin-independent pathways that promote energy storage and block adaptive energy expenditure during obesity. Utilizing docking calculations and the x-ray structure of TBK1 bound to amlexanox, an inhibitor of these kinases with modest potency, a series of analogues was synthesized to develop a structure activity relationship (SAR) around the A- and C-rings of the core scaffold. A strategy was developed wherein R₇ and R₈ A-ring substituents were incorporated late in the synthetic sequence by utilizing palladium-catalyzed cross-coupling reactions on appropriate bromo precursors. Analogues display IC₅₀ values as low as 210?nM and reveal A-ring substituents that enhance selectivity toward either kinase. In cell assays, selected analogues display enhanced phosphorylation of p38 or TBK1 and elicited IL-6 secretion in 3T3-L1 adipocytes better than amlexanox. An analogue bearing a R₇ cyclohexyl modification demonstrated robust IL-6 production in 3T3-L1 cells as well as a phosphorylation marker of efficacy and was tested in obese mice where it promoted serum IL-6 response, weight loss, and insulin sensitizing effects comparable to amlexanox. These studies provide impetus to expand the SAR around the amlexanox core toward uncovering analogues with development potential.     

Lipase-catalyzed asymmetric synthesis of naphtho[2,3-c]furan-1(3H)-one derivatives by a one-pot dynamic kinetic resolution/intramolecular Diels–Alder reaction: Total synthesis of (−)-himbacine

One-pot sequential reactions using the acyl moieties installed by enzymatic dynamic kinetic resolution of alcohols have been little investigated. In this work, the acryloyl moiety installed via the lipase/oxovanadium combo-catalyzed dynamic kinetic resolution of a racemic dienol [4-(cyclohex-1-en-1-yl)but-3-en-2-ol or 1-(cyclohex-1-en-1-yl)but-2-en-1-ol] with a (Z)-3-(phenylsulfonyl)acrylate underwent an intramolecular Diels–Alder reaction in a one-pot procedure to produce an optically active naphtho[2,3-c]furan-1(3H)-one derivative (98% ee). This method was successfully applied to the asymmetric total synthesis of (?)-himbacine.     

八肋游仆虫大核基因组中组蛋白基因 H4A和H4B的克隆及分析

组蛋白作为核小体的基本组分,是染色质的结构和功能必需的。组蛋白的变体和修饰共同参与染色质修饰及基因的表达调控。真核生物细胞中的5种组蛋白在进化中高度保守,然而纤毛虫的组蛋白H4与其他真核生物相比有较大的差异。本实验应用PCR技术从八肋游仆虫(Euplotes octocarinatus)中获得了2种组蛋白H4基因,分别为H4A和H4B,GenBank登录号为:JN715068和JN715069。序列分析表明,H4A基因开放阅读框324 bp,预测编码107个氨基酸,分子量为11.6 ku,等电点为10.99。而H4B基因编码框384 bp,编码127个氨基酸,分子量为14.4 ku,等电点为9.93。Blast结果显示,H4A序列与其他生物中H4的一致性相对较高,达81%～94%,而H4B的一致性为36%～70%。H4A和H4B的一致性仅为44.7%。实时荧光定量PCR表明,H4A的转录本高于H4B。结果提示:在进化过程中八肋游仆虫可能进化出特殊的组蛋白H4基因,不同的组蛋白H4可能发挥不同的功能。     

In vitro metabolism of a mixture of [4-C]pregnenolone and [17α-H]pregnenolone by polycystic ovary: Pathways of testosterone biosynthesis

When minced polycystic ovarian tissue was incubated with a mixture of [4-¹⁴C]-pregnenolone and [17α-³H]pregnenolone² and added cofactors for 25, 40 and 60 min, the following metabolites were isolated and characterized: progesterone, 17-hydroxyprogesterone, 17-hydroxypregnenolone, dehydroepiandrosterone, 4-androstenedione, and testosterone; unmetabolized substrates were also recovered. There were increased amounts of progesterone, 17-hydroxyprogesterone, dehydroepiandrosterone, and 4-androstenedione formed as the incubation time increased.     

Synthesis and in vitro evaluations of 6-(hetero)-aryl-imidazo[1,2-b]pyridazine-3-sulfonamide’s as an inhibitor of TNF-α production

Tumor necrosis factor-α is an important pro-inflammatory cytokine having a key role in hosts defensive process of immune systems and its over expression led to a diverse range of inflammatory diseases such as Rheumatoid arthritis, Cronh’s disease, psoriasis, etc. This paper describes our medicinal chemistry efforts on imidazo[1,2-b]pyridazine scaffold: design, synthesis and biological evaluation. By the introducing sulfonamide functionality at 3 positions and substituting 6 positions with (hetero)-aryl groups’, a small library of compounds was prepared. All synthesized compounds were screened for lipopolysaccharide (LPS) mediated TNF-α production inhibitory activity. Biological data revealed that the majority of the compounds of this series showed moderate to potent TNF-α production inhibitory activity. Compound 5u and 5v are the most potent compounds from the series with activity of IC₅₀?=?0.5?µM and 0.3?µM respectively. A short SAR demonstrates that 3-sulfonyl-4-arylpiperidine-4-carbonitrile moiety on imidazo[1,2-b]pyridazine showed better activity compared to the 3-(4-aryllpiperazin-1-yl) sulfonyl) in hPBMC assay. The molecular modeling studies revealed that the potent TNF-α production inhibitory activity 5v due to the extra stability of complex because of an extra pi-pi (π-π) stacking, hydrogen-bonding interactions.     

Effects of N,N′-dicyclohexylcarbodiimide on isolated and reconstituted cytochrome b-c1 complex from bovine heart mitochondria

N,N′-Dicyclohexylcarbodiimide (DCCD) inhibits the activity of ubiquinol-cytochrome c reductase in the isolated and reconstitued mitochondrial cytochrome b-c₁ complex. DCCD inhibits equally electron flow and proton translocation (i.e., the $\text{H}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}$ ratio is not affected) catalysed by the enzyme reconstituted into phospholipid vesicles. The inhibitory effects are accompanied by structural alterations in the polypeptide pattern of both isolated and reconstituted enzyme. Cross-linking was observed between subunits V (iron-sulfur protein) and VII, indicating that these polypeptides are in close proximity. A clear correlation was found between the kinetics of inhibition of enzymic activity and the cross-linking, suggesting that the two phenomena may be coupled. Binding of [¹⁴C]DCCD was also observed, to all subunits with the isolated enzyme and preferentially to cytochrome b with the reconstituted vesicles; in both cases, however, it was not correlated kinetically with the inhibition of the enzymic activity.     

6β-[2-Methylbutanoyloxy]tropan-3α-ol,a new alkaloid from Datura ceratocaula structure and biosynthesis

6β-[2-methylbutanoyloxy]tropan-3α-ol, a new alkaloid, has been isolated from the aerial parts of Datura ceratocaula (Solanaceae). Its chemotaxonomic significance within the genus is discussed. Biosynthetically, the 2-methylbutanoyl moiety is derived from L-isoleucine.     

Covalent binding of benzo[a]pyrene to cytochrome P-450βNF-B2 and other proteins in reconstituted mixed-function oxidase systems

A reconstituted mixed-function oxidase system, containing the major β-naphthoflavone-induced isozyme of rat liver cytochrome P-450 bound benzo[a]pyrene covalently in the presence of NADPH. NADPH-cytochrome P-450 reductase was required for binding and a maximum rate of adduct formation was obtained at 8 units of reductase per nmol cytochrome P-450. Phosphatidylcholine inhibited this reaction. Benzo[a]pyrene was bound to the cytochrome, but not to the reductase, as shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Approximately 6 molecules of benzo[a]pyrene bound to each molecule cytochrome P-450 during prolonged incubations. No binding occurred when the β-naphthoflavone-induced isozyme of cytochrome P-450 was replaced by the major isozyme induced by phenobarbital, but both cytochromes incorporated benzo[a]pyrene to approximately the same extent when they were incubated together in the presence of the reductase and NADPH. Metabolically activated benzo[a]pyrene also bound covalently to purified epoxide hydrodrolase, when this enzyme was added to the reconstituted mixed-function oxidase system.