Synthesis and evaluation of Strychnos alkaloids as MDR reversal agents for cancer cell eradication

Natural products represent the fourth generation of multidrug resistance (MDR) reversal agents that resensitize MDR cancer cells overexpressing P-glycoprotein (Pgp) to cytotoxic agents. We have developed an effective synthetic route to prepare various Strychnos alkaloids and their derivatives. Molecular modeling of these alkaloids docked to a homology model of Pgp was employed to optimize ligand–protein interactions and design analogues with increased affinity to Pgp. Moreover, the compounds were evaluated for their (1) binding affinity to Pgp by fluorescence quenching, and (2) MDR reversal activity using a panel of in vitro and cell-based assays and compared to verapamil, a known inhibitor of Pgp activity. Compound 7 revealed the highest affinity to Pgp of all Strychnos congeners (K_d = 4.4 μM), the strongest inhibition of Pgp ATPase activity, and the strongest MDR reversal effect in two Pgp-expressing cell lines. Altogether, our findings suggest the clinical potential of these synthesized compounds as viable Pgp modulators justifies further investigation.     

Design and synthesis of tetrahydroisoquinoline derivatives as potential multidrug resistance reversal agents in cancer

Exploration for new MDR-modulator utilizing tetrahydroisoquinoline as scaffold disclosed 6,7-dimethoxy-1-(3,4-dimethoxy)benzyl-2-(N-n-octyl-N'-cyano)guanyl-1,2,3,4-tetrahydroisoquinoline (7) as a readily accessible medicinal lead. Compound 7 possessed potent MDR reversal activity in the range of the reference compound verapamil, and had not cardiovascular activity compared to verapamil.     

Monoterpene indole alkaloid azine derivatives as MDR reversal agents

Aiming at generating a library of bioactive indole alkaloid derivatives as multidrug resistance (MDR) reversers, two epimeric indole alkaloids (1 and 2) were submitted to chemical transformations, giving rise to twenty-four derivatives (5-28), bearing new aromatic or aliphatic azine moieties. The structure of the compounds was established by 1D and 2D NMR (COSY, HMBC, HMQC and NOESY) experiments. Two different strategies were employed for assessing their anti-MDR potential, namely through the evaluation of their activity as inhibitors of typical MDR ABC transporters overexpressed by cell transfection, such as ABCB1 (P-gp), ABCC1 (MRP1), and ABCG2 (BCRP), or by evaluating their ability as collateral sensitivity (CS) agents in cells overexpressing MRP1. A considerable MDR reversing activity was observed for compounds bearing the aromatic azine moiety. The strongest and most selective P-gp inhibition was found for the epimeric azines 5 and 6, bearing a para-methylbenzylidene moiety. Instead, compounds 17 and 18 that possess a di-substituted benzylidene portion with methoxy and hydroxyl groups, selectively inhibited MRP1 drug-efflux. None of these compounds inhibited BCRP. Compounds 5, 6 and 18 were further investigated in drug combination experiments, which corroborated their anti-MDR potential. Moreover, it was observed that compound 12, with an aromatic azine moiety, and compounds 23-26, sharing a new aliphatic substituent, displayed a CS activity, selectively killing MRP1-overexpressing cells. Among these last compounds, it could be established that addition of 19, 23 and 25 to MRP1-overexpressing cells led to glutathione depletion triggering cell death through apoptosis.     

Design and synthesis of 4-quinolinone 2-carboxamides as calpain inhibitors

Calpains are involved in a variety of calcium-regulated cellular processes, such as signal transduction, cell proliferation, differentiation, and apoptosis. Excessive calpain activation contributes to serious cellular damage and has been reported in many pathological conditions. 4-Quinolinone 2-carboxamide derivatives were prepared and evaluated for mu-calpain inhibitory activities. Of the compounds synthesized, 3a and 3k, which possess a primary amide and 4-methoxyphenethyl amide at P1' region, were found to most potently inhibit mu-calpain with IC50 values of 0.71+/-0.07 and 0.73+/-0.23 microM, respectively. On the other hand, the incorporation of pyridine-containing amides decreased inhibitory activity.     

Design,synthesis and evaluation of novel triazole core based P-glycoprotein-mediated multidrug resistance reversal agents

A novel series of triazol-N-ethyl-tetrahydroisoquinoline based compounds were designed and synthesized via click chemistry. Most of the synthesized compounds showed P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) reversal activities. Among them, compound 7 with little cytotoxicity towards GES-1 cells (IC₅₀ >80 μM) and K562/A02 cells (IC₅₀ >80 μM) exhibited more potency than verapamil (VRP) on increasing anticancer drug accumulation in K562/A02 cells. Moreover, compound 7 could significantly reverse MDR in a dose-dependent manner and also persist longer chemo-sensitizing effect than VRP with reversibility. Further mechanism studies revealed that compound 7 in reversing MDR revealed that it could remarkably increase the intracellular accumulation of both rhodamine-123 (Rh123) and adriamycin (ADM) in K562/A02 cells as well as inhibit their efflux from the cells. These results suggested that compound 7 showed more potency than the classical P-gp inhibitor VRP under the same conditions, which may be a promising P-gp-mediated MDR modulator for further development.     

Design, synthesis, and evaluation of estradiol-linked genotoxicants as anti-cancer agents

A series of bifunctional compounds was prepared consisting of 17beta estradiol linked to a DNA damaging N,N-bis-(2-chloroethyl)aniline. The objective of our studies was to determine the characteristics of the linker that permitted both reaction with DNA and binding of the resultant covalent adducts to the estrogen receptor. Linker characteristics were pivotal determinants underlying the ability of the compounds to kill selectively breast cancer cells that express the estrogen receptor.     

Design,synthesis and in vitro anticancer evaluation of 4,6-diamino-1,3,5-triazine-2-carbohydrazides and -carboxamides

Series of substituted 4,6-diamino-1,3,5-triazine-2-carbohydrazides and -carboxamides have been synthesised, based on molecular modelling of candidate structures related to the previously reported Rad6B-inhibitory diamino-triazinylmethyl benzoate anticancer agents TZ8 and TZ9. Synthesis of the target compounds was readily accomplished in two steps from aryl biguanides via reaction of phenylhydrazine or benzylamines with key 4-amino-6-(arylamino)-1,3,5-triazine-2-carboxylate intermediates. These new triazine derivatives were tested for in vitro anticancer activity against the Rad6B expressing human breast cancer cell lines MDA-MB-231 and MCF-7. Active compounds, such as the triazinyl-carbohydrazides 3a–e, were found to exhibit low micromolar IC₅₀ values particularly in the Rad6B-overexpressing MDA-MB-231 cell line.     

Design,synthesis, and evaluation of novel coumarin-dithiocarbamate derivatives (IDs) as anti-colorectal cancer agents

Colorectal cancer (CRC) is a common malignant tumour of human digestive tract. The high mortality rate of CRC is closely related to the limitations of existing treatments. Thus, there is an urgent need to search for new anti-CRC agents. In this work, twenty novel coumarin-dithiocarbamate derivatives (IDs) were designed, synthesized and evaluated in vitro. The results suggest that the most active compound ID-11 effectively inhibited the proliferation of CRC cell lines while shown little impact on normal colon epithelial cells. Mechanism studies revealed that ID-11 displayed bromodomain-containing protein 4 inhibitory activity, and induced G2/M phase arrest, apoptosis as well as decreased the expression levels of the key genes such as c-Myc and Bcl-2 in CRC cell lines. Moreover, the ADMET properties prediction results shown that ID-11 possess well metabolic characteristics without obvious toxicities. Our data demonstrated that compound ID-11 may be a promising anti-CRC agent and deserved for further development.     

Design,synthesis and evaluation of carbazole derivatives as potential antimicrobial agents

Five series of novel carbazole derivatives containing an aminoguanidine, dihydrotriazine, thiosemicarbazide, semicarbazide or isonicotinic moiety were designed, synthesised and evaluated for their antimicrobial activities. Most of the compounds exhibited potent inhibitory activities towards different bacterial strains (including one multidrug-resistant clinical isolate) and one fungal strain with minimum inhibitory concentrations (MICs) between 0.5 and 16 µg/ml. Compounds 8f and 9d showed the most potent inhibitory activities (MICs of 0.5–2 µg/ml). Furthermore, compounds 8b, 8d, 8f, 8k, 9b and 9e with antimicrobial activities were not cytotoxic to human gastric cancer cell lines (SGC-7901 and AGS) or a normal human liver cell line (L-02). Structure–activity relationship analyses and docking studies implicated the dihydrotriazine group in increasing the antimicrobial potency and reducing the toxicity of the carbazole compounds. In vitro enzyme activity assays suggested that compound 8f binding to dihydrofolate reductase might account for the antimicrobial effect.     

Design,synthesis and evaluation of oxime-functionalized nitrofuranylamides as novel antitubercular agents

A series of oxime-functionalized nitrofuranylamides were designed, synthesized and evaluated for their in vitro anti-mycobacterial activities against MTB H37Rv and drug-resistant clinical isolates. Among them, two compounds 7a and 7b exhibited excellent activity against the three tested strains. Both of them were comparable to the first-line anti-TB agents INH and RIF against MTB H37Rv, and were far more potent than INH and RIF against MDR-TB 16833 and 16995 strains. Thus, both of them could act as leads for further optimization.     

Design,synthesis, and evaluation of novel 2-phenylpropionic acid derivatives as dual COX inhibitory-antibacterial agents

A series of 2-(4-substitutedmethylphenyl)propionic acid derivatives (6a–6m) were synthesized, characterized and evaluated for cyclooxygenase (COX) enzyme inhibitory and antimicrobial activity. Test compounds that exhibited good COX inhibition and antibacterial activity were further screened for their cytotoxicity and genotoxicity. Compounds 6h and 6l showed better COX-1 and COX-2 inhibition when compared to ibuprofen. Inhibition potency of these compounds against COX-2 was very close to that of nimesulide. The compounds 6d, 6h, 6l and 6m displayed promising antibacterial property when compared to chloramphenicol. However, the compound 6l was emerged as the best dual COX inhibitory-antibacterial agent in this study. The ADME prediction of the compounds revealed that they may have a good pharmacokinetic profile. Docking results of the compounds 6h and 6l with COX-1 (PDB ID: 1EQG) also exhibited a strong binding profile.

     

Design, synthesis and evaluation of new 6-substituted-5-benzyloxy-4-oxo-4H-pyran-2-carboxamides as potential Src inhibitors

Src family kinases (SFKs) are nonreceptor tyrosine kinases that are reported to be critical for cancer progression. Inhibiting the catalytic activity of these proteins has become one of the major therapeutic concepts in contemporary drug discovery. We report here the design and the synthesis of novel 6-substituted-5-benzyloxy-4-oxo-4H-pyran-2-carboxamides as potential inhibitors of Src kinase. The synthesis of these derivatives and the preliminary results of biological activity will be discussed.     

Pyridazinone hybrids: Design,synthesis and evaluation as potential anticonvulsant agents

A series of new hybrid benzothiazole containing pyridazinones derivatives were designed and synthesized fulfilling all the pharmacophoric requirements essential for the anticonvulsant activity. In-silico and in vitro studies revealed that some of these hybrid derivatives demonstrated admirable GABA AT inhibitory activity. An attempt has also been made to validate the results of in vitro GABA AT inhibition of the most potent compound SPS-5F (IC₅₀ 9.10 μM) through in vivo anticonvulsant screening. Compound SPS-5F administration significantly increases the whole brain GABA level, might be through the inhibition of GABA AT enzyme.     

New terpenoids from Maytenus apurimacensis as MDR reversal agents in the parasite Leishmania

Two new sesquiterpenes (1-2) and one new lupane triterpene (3) have been isolated from the roots of Maytenus apurimacensis. The novel beta-dihydroagarofurans are the first sesquiterpenes with a basic polyhydroxy skeleton of 15-deoxyalatol and 4,15-dideoxyalatol that show high MDR reversing activity in the protozoan parasite Leishmania tropica.     

Design,synthesis and biological evaluation of coumarin-3-carboxamides as selective carbonic anhydrase IX and XII inhibitors

A series of novel 7-hydroxycoumarin-3-carboxamides was synthesized by the reaction of 7-hydroxy-2-oxo-2H-chromene-3-carboxylic acid with various substituted aromatic amines. The newly synthesized compounds were evaluated for their inhibitory activity against the four physiologically relevant human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms CA I, CA II, CA IX and CA XII. The CA inhibition results show that the newly synthesized 7-hydroxycoumarin-3-carboxamides (4a-n) exhibited selective inhibition of the tumor associated isoforms, CA IX and CA XII over CA I and II isoforms. The inhibition constants ranged from sub micromolar to low micromolar. Amongst all the compounds tested, compound 4m was the most effective inhibitor exhibiting sub micromolar potency against both hCA IX and hCA XII, with a K_i of 0.2 µM. Therefore, it can be anticipated that compound 4m can serve as a lead for development of anticancer therapy by exhibiting a novel mechanism of action. The binding modes of the most potent compounds within hCA IX and XII catalytic clefts were investigated by docking studies.     

Design,synthesis and evaluation of new 6-substituted-5-benzyloxy-4-oxo-4H-pyran-2-carboxamides as potential Src inhibitors

Src family kinases (SFKs) are nonreceptor tyrosine kinases that are reported to be critical for cancer progression. Inhibiting the catalytic activity of these proteins has become one of the major therapeutic concepts in contemporary drug discovery. We report here the design and the synthesis of novel 6-substituted-5-benzyloxy-4-oxo-4H-pyran-2-carboxamides as potential inhibitors of Src kinase. The synthesis of these derivatives and the preliminary results of biological activity will be discussed.     

Synthesis and evaluation of nitric oxide-releasing DDB derivatives as potential Pgp-mediated MDR reversal agents in MCF-7/Adr cells

Novel furoxan-based nitric oxide (NO)-releasing DDB derivatives (7a-j) were synthesized. Compounds 7i and 7j significantly reversed the resistance of MCF-7/Adr cells to doxorubicin in the combination treatment, and markedly increased the intracellular accumulation of doxorubicin probably via inhibiting Pgp-mediated intracellular drug efflux as well as down-regulating doxorubicin-induced Pgp expression. It was demonstrated that NO released by 7i and 7j played an important role in increasing intracellular doxorubicin accumulation and chemo-sensitizing MCF-7/Adr cells to doxorubicin, and the synergic effects of DDB and NO-donor moieties in 7i and 7j may contribute to reversing Pgp-mediated MDR in MCF-7/Adr cells to doxorubicin.     

Design, solid-phase synthesis, and biological evaluation of novel 1,5-diarylpyrrole-3-carboxamides as carbonic anhydrase IX inhibitors

Following previous studies we herein report the synthesis and the pharmacological evaluation of a new class of human carbonic anhydrase (hCA) inhibitors, 1,5-diarylpyrrole-3-carboxamides prepared by a solid-phase strategy involving a PS(HOBt) resin. A molecular modeling study was conducted in order to simulate the binding mode of this new family of enzyme inhibitors within the active site of hCA IX. This study revealed that the 3-position of the pyrrole was opened to the solvent, so we introduced an amino side-chain, protonated at physiological pH both to enhance the aqueous solubility and to decrease the cell membrane penetration. This strategy consisted of preparing membrane-impermeant inhibitors that may selectively target the tumor-associated hCA IX. Physico-chemical characterizations including aqueous solubility and lipophilic parameters are described. Pharmacological studies revealed high hCA IX inhibitory potency in the nanomolar range. Some compounds are selective for hCA IX displaying hCA I/hCA IX and hCA II/hCA IX ratios higher than 20 and 5, respectively.     

Design,synthesis and evaluation of structurally diverse chrysin-chromene-spirooxindole hybrids as anticancer agents

A series of structurally diverse chrysin-chromene-spirooxindole hybrids were designed, synthesized via a Knoevenagel/Michael/cyclization of chrysin and isatylidene malononitrile derivatives through utilizing a hybrid pharmacophore approach. The newly synthesized compounds were evaluated for their in vitro anticancer activity, and most of the compounds showed stronger anti-proliferative activity than parent compound chrysin. In particular, compound 3e had the highest cytotoxicity towards A549 cells (IC₅₀ = 3.15 ± 0.51 μM), and had better selectivity in A549 cells and normal MRC-5 cells. Furthermore, compound 3e could significantly inhibit the proliferation and migration of A549 cells in a dose-dependent manner, as well as induce the apoptosis possibly through mitochondria-mediated caspase-3/8/9 activation and multi-target co-regulation of the p53 signaling pathway. Thus, our results provide in vitro evidence that compound 3e may be a potential candidate for the development of new anti-tumour drugs.     

Design, synthesis and biological evaluation of some pyrazole derivatives as anti-inflammatory-antimicrobial agents

The synthesis of novel series of structurally related 1H-pyrazolyl derivatives is described. All the newly synthesized compounds were tested for their in vivo anti-inflammatory activity by two different bioassays namely; cotton pellet-induced granuloma and sponge implantation model of inflammation in rats. In addition, COX-1 and COX-2 inhibitory activities, ulcerogenic effects and acute toxicity were determined. The same compounds were evaluated for their in vitro antimicrobial activity against Escherichia coli, as an example of Gram negative bacteria, Staphylococcus aureus as an example of Gram positive bacteria, and Candida albicans as a representative of fungi. The combined anti-inflammatory data from local and systemic in vivo animal models showed that compounds 4, 5, 8, 9, 11 and 12a exhibited anti-inflammatory activity comparable to that of indomethacin with no or minimal ulcerogenic effects and high safety margin (LD(50)>500 mg/Kg). In addition, compounds 4, 7, 10, 12a and 12b displayed appreciable antibacterial activities when compared with ampicillin, especially against S. aureus. Compounds 4 and 12a are the most distinctive derivatives identified in the present study because of their remarkable in vivo and in vitro anti-inflammatory potency and their pronounced antibacterial activities comparable to ampicillin against Gram positive. On the other hand, compound 12a exhibited good selective inhibitory activity against COX-2 enzyme. Therefore, such compound would represent a fruitful matrix for the development of anti-inflammatory-antimicrobial candidates.