Synthesis,biological evaluation and 3D-QSAR studies of new chalcone derivatives as inhibitors of human P-glycoprotein

P-glycoprotein (P-gp) is an ATP-dependent multidrug resistance efflux transporter that plays an important role in anticancer drug resistance and in pharmacokinetics of medicines. Despite a large number of structurally and functionally diverse compounds, also flavonoids and chalcones have been reported as inhibitors of P-gp. The latter share some similarity with the well studied class of propafenones, but do not contain a basic nitrogen atom. Furthermore, due to their rigidity, they are suitable candidates for 3D-QSAR studies. In this study, a set of 22 new chalcone derivatives were synthesized and evaluated in a daunomycin efflux inhibition assay using the CCRF.CEM.VCR1000 cell line. The compound 10 showed the highest activity (IC₅₀ = 42 nM), which is one order of magnitude higher than the activity for an equilipohillic propafenone analogue. 2D- and 3D-QSAR studies indicate the importance of H-bond acceptors, methoxy groups, hydrophobic groups as well as the number of rotatable bonds as pharmacophoric features influencing P-gp inhibitory activity.     

Synthesis and biological evaluation of new bisindole-imidazopyridine hybrids as apoptosis inducers

A series of diindolylmethanes (5a-t) were designed, synthesized, and examined for their cytotoxicity against four human cancer cell lines like prostate (DU-145), lung (A549), breast (MCF-7) and cervical cancer (HeLa). These results revealed that among all the hybrids, two (5k and 5r) were identified and exhibited significant cytotoxic effect against A549 cancer cells with IC₅₀ values of 1.65 ± 0.3 and 1.80 ± 0.8 µM respectively. To investigate the reasons for the cytotoxic activity, the conventional biological assays were carried out with 5k and 5r on the A549 cancer cells. Both hybrids led to the arrest of A549 cell lines at the G2/M phase of the cell cycle and strongly induced apoptosis. Further the apoptotic effects of 5k and 5r were confirmed by ROS, annexin-V FITC, and mitochondrial membrane potential. Moreover, structure–activity relationships were elucidated with various substitutions on these hybrids.     

Synthesis and biological evaluation of novel oxadiazole derivatives: A new class of thymidine phosphorylase inhibitors as potential anti-tumor agents

Based on the fact that the thymidine phosphorylase inhibitors are considered potential anti-tumor agents, a range of novel oxadiazole derivatives 3a–3u was designed and synthesized by a simple and facile synthetic route. The biological assay revealed that majority of compounds displayed modest inhibitory activity against thymidine phosphorylase at low micromolar concentrations (IC₅₀ 173.23 ± 3.04 to 14.40 ± 2.45 μM). In the current study the most active compounds were 3h and 3q with IC₅₀ values 14.40 ± 2.45 and 17.60 ± 1.07 μM, respectively. Molecular docking studies were performed on the most active compounds (3h, 3k, 3o–3q) to show their binding mode.     

Synthesis and biological evaluation of naphthoquinone analogs as a novel class of proteasome inhibitors

Screening of the NCI Diversity Set-1 identified PI-083 (NSC-45382) a proteasome inhibitor selective for cancer over normal cells. Focused libraries of novel compounds based on PI-083 chloronaphthoquinone and sulfonamide moieties were synthesized to gain a better understanding of the structure–activity relationship responsible for chymotrypsin-like proteasome inhibitory activity. This led to the demonstration that the chloronaphthoquinone and the sulfonamide moieties are critical for inhibitory activity. The pyridyl group in PI-083 can be replaced with other heterocyclic groups without significant loss of activity. Molecular modeling studies were also performed to explore the detailed interactions of PI-083 and its derivatives with the β5 and β6 subunits of the 20S proteasome. The refined model showed an H-bond interaction between the Asp-114 and the sulfonamide moiety of the PI-083 in the β6 subunit.     

Synthesis and biological evaluation of nimesulide based new class of triazole derivatives as potential PDE4B inhibitors against cancer cells

A new class of 1,2,3-triazol derivatives derived from nimesulide was designed as potential inhibitors of PDE4B. Synthesis of these compounds was carried out via a multi-step sequence consisting of copper-catalyzed azide–alkyne cycloaddition (CuAAC) as a key step in aqueous media. The required azide was prepared via the reaction of aryl amine (obtained from nimesulide) with α-chloroacetyl chloride followed by displacing the α-chloro group by an azide. Some of the synthesized compounds showed encouraging PDE4B inhibitory properties in vitro that is >50% inhibition at 30 μM that were supported by the docking studies of these compounds at the active site of PDE4B enzyme (dock scores ～ ?28.6 for a representative compound). Two of these PDE4 inhibitors showed promising cytotoxic properties against HCT-15 human colon cancer cells in vitro with IC₅₀ ～ 21–22 μg/mL.     

Synthesis and biological evaluation of new donepezil-like Thiaindanones as AChE inhibitors

Pharmacomodulations of previously reported thiaindanones related to donepezil were achieved with the aim to enhance their AChE inhibitory activity. Condensation of the cyclopentane carbonyl group into hydrazone or cyanolefine derivatives, as well as its hydrogenation and the subsequent substitution of the resulting hydroxyl group led to new 2-(4-benzylpiperazin-1-yl)-N-(1,3-dibromo-6-hydroxy-5,6-dihydro-4H-cyclopenta[c]thien-4-yl) acetamides. The in vitro evaluation of this new series, according to the method of Ellman, shows however that it conserved only partially the biological activity. The best compound remains the alcohol 11 (IC(50) = 0.40 microM, against 0.02 microM for donepezil).     

Synthesis and biological evaluation of new Donepezil-like Thiaindanones as AChE inhibitors

Pharmacomodulations of previously reported thiaindanones related to donepezil were achieved with the aim to enhance their AChE inhibitory activity. Condensation of the cyclopentane carbonyl group into hydrazone or cyanolefine derivatives, as well as its hydrogenation and the subsequent substitution of the resulting hydroxyl group led to new 2-(4-benzylpiperazin-1-yl)-N-(1,3-dibromo-6-hydroxy-5,6-dihydro-4H-cyclopenta[c]thien-4-yl) acetamides. The in vitro evaluation of this new series, according to the method of Ellman, shows however that it conserved only partially the biological activity. The best compound remains the alcohol 11 (IC₅₀ = 0.40 μM, against 0.02 μM for donepezil).     

Synthesis and biological evaluation of salicylate-based compounds as a novel class of methionine aminopeptidase inhibitors

A series of salicylate-based compounds were designed and synthesized based on the simple function group replacement from our previously reported catechol-containing inhibitors of methionine aminopeptidase (MetAP). Some of these salicylate derivatives showed similar potency and metalloform selectivity, and some showed considerable antibacterial activity. These findings are consistent with our previous conclusion that Fe(II) is the likely metal used by MetAP in bacterial cells and provide new lead structures that can be further developed as novel antibacterial agents.     

Synthesis and biological evaluation of new potential inhibitors of N-acylethanolamine hydrolyzing acid amidase

N-Acylethanolamines, including N-palmitoyl-ethanolamine (PEA), are hydrolyzed to the corresponding fatty acids and ethanolamine by fatty acid amide hydrolase (FAAH). Recently, N-acylethanolamine-hydrolyzing acid amidase (NAAA) was identified as being able to specifically hydrolyze PEA. In order to find selective and effective inhibitors of this enzyme, we synthesized and screened several amides, retroamides, esters, retroesters and carbamates of palmitic acid (1–21) and esters with C15 and C17 alkyl chains (22–27). Cyclopentylhexadecanoate (13) exhibited the highest inhibitory activity on NAAA (IC₅₀ = 10.0 μM), without inhibiting FAAH up to 50 μM. Compound 13 may become a useful template to design new NAAA inhibitors.     

Synthesis and biological evaluation of bergenin-1,2,3-triazole hybrids as novel class of anti-mitotic agents

In continuation of our investigation of pharmacologically-motivated natural products, we have isolated bergenin (1) as a major compound from Mallotus philippensis, which is deployed in different Indian traditional systems of medicine. Here, a series of bergenin-1,2,3-triazole hybrids were synthesized and evaluated for their potentials against a panel of cancer cell lines. Several of the hybrid derivatives were found more potent in comparison to parent compound bergenin (1). Among them, 4j demonstrated potent activity against A-549 and HeLa cell lines with IC₅₀ values of 1.86 µM and 1.33 μM, respectively, and was equipotent to doxorubicin. Cell cycle analysis showed that 4j arrested HeLa cells at G2/M phase and lead to accumulation of Cyclin B1 protein. Cell based tubulin polymerization assays and docking studies demonstrated that 4j disrupts tubulin assembly by occupying colchicine binding pocket of tubulin.     

Synthesis and biological evaluation of a new series of N-ylides as protein farnesyltransferase inhibitors

A new family of 30 benzoylated N-ylides 4 and 5 was synthesized and evaluated for the inhibitory activity on human protein farnesyltransferase. Most of these novel compounds possessed in vitro inhibition potencies in the micromolar range. The nature of the substituents on the pyridine and phenyl units proved to be important in determining inhibitory activity and generally, the replacement of the cyanoacrylonitrile function by a cyanoethylacrylate group decreased the biological potential on farnesyltransferase. These results completed our SAR study on this original class of N-ylides.     

Synthesis and biological evaluation of indolyl glyoxylamides as a new class of antileishmanial agents

A series of indolylglyoxylamide derivatives have been synthesized and evaluated in vitro against amastigote form of Leishmania donovani. Compound 8c has been identified as the most active analog of the series with IC₅₀ value of 5.17 μM and SI value of 31.48, and is several folds more potent than the standard drugs sodium stilbogluconate and pentamidine.     

Synthesis and biological evaluation of some thiazole derivatives as new cholinesterase inhibitors

In the present study, some thiazole derivatives were synthesized via the ring closure reaction of 1-[2-(2-oxobenzo[d]thiazol-3(2H)-yl)acetyl]thiosemicarbazide with various phenacyl bromides. The chemical structures of the compounds were elucidated by ¹H NMR, ¹³C NMR and mass spectral data and elemental analyses. Each derivative was evaluated for its ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) using a modification of Ellman’s spectrophotometric method. The compounds were also investigated for their cytotoxic properties using MTT assay. The most potent AChE inhibitor was found as compound 4e (IC₅₀?=?25.5?±?2.12 µg/mL) followed by compounds 4i (IC₅₀?=?38.50?±?2.12 µg/mL), 4c (IC₅₀?=?58.42?±?3.14 µg/mL) and 4g (IC₅₀?=?68?±?2.12 µg/mL) when compared with eserine (IC₅₀?=?0.025?±?0.01 µg/mL). Effective compounds on AChE exhibited weak inhibition on BuChE (IC₅₀ > 80 µg/mL). MTT assay indicated that the cytotoxic dose (IC₅₀?=?71.67?±?7.63 µg/mL) of compound 4e was higher than its effective dose.     

Synthesis and biological evaluation of a new class of glycoconjugated disulfides that exhibit potential anticancer properties

A synthetic strategy, based on the in situ generation of sulfenic acids and their thermolysis in the presence of thiols, was developed for obtaining a collection of polyvalent disulfides in which a benzene scaffold accommodates two or three flexible arms connecting saccharide moieties. Targeting carbohydrate metabolism or carbohydrate-binding proteins may constitute important approaches in the discovery process of new therapeutic anticancer agents. Therefore, a preliminary screening to ascertain the cytostatic/cytotoxic potential of this new class of enantiopure glycoconjugated disulfides has been conducted. Among them, products with two disulfide arms, harbouring galactose rings, induced high levels of apoptosis on U937 histiocytic lymphoma cells, but lower levels of cell death on peripheral blood mononuclear cells from healthy donors. Further experiments indicated that apoptosis induced by these glycoconjugated bis(disulfides) in U937 cells corresponds to the Bcl-2-sensitive, intrinsic form of apoptotic cell death. The bioinvestigation was extended to a panel of human cancer cell lines with different levels of malignancy and resistance to chemotherapeutic agents. Compounds under study proved to induce detectable levels of cell death towards all the tested cancer cell lines.     

Synthesis and evaluation of naphthoflavones as a new class of non purine xanthine oxidase inhibitors

In view of reported xanthine oxidase inhibitory potential of naphthopyrans and flavones, naphthoflavones as hybrids of the two were designed, synthesized and evaluated for in vitro xanthine oxidase inhibitory activity in the present study. The results of the assay revealed that the naphthoflavones possess promising inhibitory potential against the enzyme with IC₅₀ values ranging from 0.62 to 41.2 μM. Structure activity relationship indicated that the nature and placement of substituents on the phenyl ring at 2nd position remarkably influences the inhibitory activity. Substitution of halo and nitro groups at ortho and para position of the phenyl ring (2nd position) remarkably favored the activity. NF-4 with p-fluoro phenyl ring was the most potent inhibitor with IC₅₀ value of 0.62 μM. Enzyme kinetics study was also performed to investigate the inhibition mechanism and it was found that the naphthoflavones displayed mixed type inhibition. The basis of significant inhibition of xanthine oxidase by NF-4 was rationalized by molecular modeling studies.     

Synthesis and biological evaluation of N-alkyl-N-(4-methoxyphenyl)pyridin-2-amines as a new class of tubulin polymerization inhibitors

Based on our prior antitumor hits, 32 novel N-alkyl-N-substituted phenylpyridin-2-amine derivatives were designed, synthesized and evaluated for cytotoxic activity against A549, KB, KB_VIN, and DU145 human tumor cell lines (HTCL). Subsequently, three new leads (6a, 7g, and 8c) with submicromolar GI₅₀ values of 0.19–0.41 μM in the cellular assays were discovered, and these compounds also significantly inhibited tubulin assembly (IC₅₀ 1.4–1.7 μM) and competitively inhibited colchicine binding to tubulin with effects similar to those of the clinical candidate CA-4 in the same assays. These promising results indicate that these tertiary diarylamine derivatives represent a novel class of tubulin polymerization inhibitors targeting the colchicine binding site and showing significant anti-proliferative activity.     

Synthesis and biological evaluation of cinnamido linked benzophenone hybrids as tubulin polymerization inhibitors and apoptosis inducing agents

A new class of hybrid molecules containing cinnamide subunit linked to benzophenone as inhibitors of tubulin polymerization were synthesized and evaluated for their anticancer potential. These hybrids exhibit anticancer activity with IC₅₀ values ranging from 0.06 to 16.3 μM. Compounds 4f and 4g possessing fluoro and trifluoromethyl on the cinnamido subunit showed significant cytotoxic activity with IC₅₀ values 0.06 and 0.09 μM against HeLa cell line, respectively. These compounds showed cell cycle arrest at G2/M phase of the cell cycle and inhibited tubulin polymerization followed by activation of caspase-3 activity and apoptotic cell death. Further in vitro tubulin polymerization assay showed that the level of tubulin inhibition was comparable to that of 2a for the compounds 4f and 4g. Moreover, Hoechst 33258 staining and DNA fragmentation assay suggested that these compounds induce cell death by apoptosis. Overall, the current study demonstrates that the synthesis of benzophenone linked cinnamide subunit conjugates as promising anticancer agents with G2/M arrest and apoptotic-inducing ability via targeting tubulin.     

Design,synthesis, biological evaluation and molecular modelling studies of indole glyoxylamides as a new class of potential pancreatic lipase inhibitors

A series of eighteen indole glyoxylamide analogues were synthesized, characterized and evaluated for their pancreatic lipase inhibitory activity. Porcine pancreatic lipase (Type II) was used with 4-nitrophenyl butyrate (as substrate) for the in vitro assay. Compound 8f exhibited competitive inhibition against pancreatic lipase with IC₅₀ value of 4.92 µM, comparable to that of the standard drug, orlistat (IC₅₀ = 0.99 µM). Compounds 7a-i and 8a-i were subjected to molecular docking into the active site of human PL (PDB ID: 1LPB) wherein compound 8f possessed a potential MolDock score of −153.037 kcal/mol. Molecular dynamics simulation of 8f complexed with pancreatic lipase, confirmed the role of aromatic substitution in stabilizing the ligand through hydrophobic interactions (maximum observed RMSD = 3.5 Å).     

Synthesis and biological evaluation of novel indole-pyrazoline hybrid derivatives as potential topoisomerase 1 inhibitors

A series of novel indole-pyrazoline hybrid derivatives were designed, synthesized, and evaluated for topoisomerase 1 (Top1) inhibitory activity. Top1-mediated relaxation assays showed that our synthesized compounds had variable Top1 inhibitory activity. Among these compounds, 3-(5-(naphthalen-1-yl)-1-phenyl-4,5-dihydro-1H-pyrazol-3-yl)-1-(phenylsulfonyl)-1H-indole (6n) was found to be a strong Top1 inhibitor with better inhibitory activity than CPT and hit compounds. Our further experiments rationalized the mode of action for this new type of inhibitors, which showed no significant binding to supercoiled DNA.     

Synthesis and biological evaluation of novobiocin analogues as potential heat shock protein 90 inhibitors

Recent studies have shown that novobiocin (NB), a member of the coumermycin (CA) family of antibiotics with demonstrated DNA gyrase inhibitory activity, inhibits Heat shock protein 90 (HSP90) by binding weakly to a putative ATP-binding site within its C-terminus. To develop more potent HSP90 inhibitors that target this site and to define structure–activity relationships (SARs) for this class of compounds, we have synthesized twenty seven 3-amido-7-noviosylcoumarin analogues starting from NB and CA. These were evaluated for evidence of HSP90 inhibition using several biological assays including inhibition of cell proliferation and cell cycle arrest, induction of the heat shock response, inhibition of luciferase-refolding in vitro, and depletion of the HSP90 client protein c-erbB-2/HER-2/neu (HER2). This SAR study revealed that a substantial increase in biological activity can be achieved by introduction of an indole-2-carboxamide group in place of 4-hydroxy-isopentylbenzamido group at C-3 of NB in addition to removal/derivatization of the 4-hydroxyl group from the coumarin ring. Methylation of the 4-hydroxyl group in the coumarin moiety moderately increased biological activity as shown by compounds 11 and 13. Our most potent new analogue 19 demonstrated biological activities consistent with known HSP90-binding agents, but with greater potency than NB.