Design and Synthesis of Novel Betulin Derivatives Containing Thio-/Semicarbazone Moieties as Apoptotic Inducers through Mitochindria-Related Pathways.

Two new series of betulin derivatives with semicarbazone (7a-g) or thiosemicarbazone (8a-g) groups at the C-28 position were synthesized. All compounds were evaluated for their in vitro cytotoxicities in human hepatocellular carcinoma cells (HepG2), human breast carcinoma cells (MCF-7), human lung carcinoma cells (A549), human colorectal cells (HCT-116) and normal human gastric epithelial cells (GES-1). Among these compounds, 8f displayed the most potent cytotoxicity with an IC50 value of 5.86 ± 0.61 µM against MCF-7 cells. Furthermore, the preliminary mechanism studies in MCF-7 cells showed that compound 8f could trigger the intracellular mitochondrial-mediated apoptosis pathway by losing MMP level, which was related with the upregulation of Bax, P53 and cytochrome c expression; the downregulation of Bcl-2 expression; activation of the expression levels of caspase-3, caspase-9, cleaved caspase-3 and cleaved caspase-9; and an increase in the amounts of intracellular reactive oxygen species. These results indicated that compound 8f may be used as a valuable skeleton structure for developing novel antitumor agents.

Complex formation of an estrone-salicylaldehyde semicarbazone hybrid with copper(II) and gallium(III): Solution equilibria and biological activity.

The solution chemical properties such as proton dissociation, complex formation with copper(II) and gallium(III) ions in addition to antibacterial and antitumor activity of a novel tridentate salicyaldehyde semicarbazone-estrone hybrid (estrone-SC) and a related bicyclic compound (thn-SC) were investigated. The crystal structure of complex [Cu(thn-SCH-1)Cl] was studied by single crystal X-ray diffraction method. Estrone-SC and thn-SC form mono-ligand complexes with Cu(II) characterized by relatively high stability, however, they are much less stable than their thiosemicarbazone analogues. The neutral Cu(II) complexes with (O-,N,O-)(H2O) coordination mode predominate at physiological pH. Estrone-SC and thn-SC are more efficient Ga(III) binders in comparison with thiosemicarbazones, although the complexes also suffer dissociation at pH 7.4. The Cu(II) complex of estrone-SC displayed significant cytotoxicity in A549, SW480 and CH1/PA cancer cells, and moderate apoptosis induction and ROS formation. The semicarbazone compounds did not exhibit antibacterial effect; unlike the related Cu(II)-thiosemicarbazone complexes represented by the fairly low MIC values (3-50 µM) obtained on the Gram-positive Staphylococcus aureus and Enterococcus faecalis bacteria.

Synthesis, cytotoxicity, and in vivo antitumor activity study of parthenolide semicarbazones and thiosemicarbazones.

Parthenolide is an important sesquiterpene lactone with potent anticancer activities. In order to further improve its biological activity, a series of parthenolide semicarbazone or thiosemicarbazone derivatives was synthesized and evaluated for their anticancer activity. Derivatives were tested in vitro against 5 human tumor cell lines, and many of these showed higher cytotoxicity than parthenolide. Five compounds were further studied for their antitumor activity in mice. The in vivo result indicated that compound 4d showed both promising antitumor activity against mice colon tumor and small side effects on immune systems. The cell apoptosis and cell cycle distribution of compound 4d were also studied. Molecular docking studies revealed multiple interactions between 4d and NF-κB. Our findings demonstrate the potential of semicarbazones as a promising type of compounds with anticancer activity.

Novel Steroidal 5α,8α-Endoperoxide Derivatives with Semicarbazone/Thiosemicarbazone Side-chain as Apoptotic Inducers through an Intrinsic Apoptosis Pathway: Design, Synthesis and Biological Studies.

A series of novel steroidal 5α,8α-endoperoxide derivatives bearing semicarbazone (7a-g) or thiosemicarbazone (7h-k) side chain were designed, synthesized and evaluated for their cytotoxicities in four human cancer cell lines (HepG2, HCT-116, MCF-7, and A549) using the MTT assay in vitro. The results showed that compound 7j exhibited significant cytotoxic activity against HepG2 cells (IC50 = 3.52 µM), being more potent than ergosterol peroxide. Further cellular mechanism studies in HepG2 cells indicated that compound 7j triggered the mitochondrial-mediated apoptosis by decreasing mitochondrial membrane potential (MMP), which was associated with up-regulation of Bax, down-regulation of Bcl-2, activation levels of the caspase cascade, and formation of reactive oxygen species (ROS). The above findings indicated that compound 7j may be used as a promising skeleton for antitumor agents with improved efficacy.

Synthesis and preliminary screening for the biological activity of some steroidal Δ4-unsaturated semicarbazone derivatives.

Eleven new steroidal mono- and bis(semicarbazones) 2a-e, 4d and 3a-e have been prepared starting from various 3-oxo-α,ß-unsaturated steroids. Mono-semicarbazones 2a-e were further subjected to ethyl chloroacetate in boiling absolute ethanol but, instead of expected intramolecular cyclocondensation reaction products, the new carbazate esters 5a-e were obtained. The structures of all synthesized compounds and identification of each E/Z isomer were deduced by elemental analysis, HRMS, NMR, and IR spectroscopy. Preliminary screening for the cytotoxic activity in vitro of the new compounds has been conducted against three cancer cell lines, K562, Jurkat and HeLa cells. HeLa cells were the most sensitive while K562 cells were the least sensitive to the cytotoxic action of the novel steroid derivatives. Compounds 2e, 3c and 5e were found to have the best but still moderate cytotoxic effects. All tested compounds showed very weak antimicrobial activities. These results demonstrate that the replacement of thioxo group with carbonyl group in steroidal hydrazone derivatives resulted in decrease in their biological activity.

Rhenium and Technetium-oxo Complexes with Thioamide Derivatives of Pyridylhydrazine Bifunctional Chelators Conjugated to the Tumour Targeting Peptides Octreotate and Cyclic-RGDfK.

This research aimed to develop new tumor targeted theranostic agents taking advantage of the similarities in coordination chemistry between technetium and rhenium. A γ-emitting radioactive isotope of technetium is commonly used in diagnostic imaging, and there are two ß- emitting radioactive isotopes of rhenium that have the potential to be of use in radiotherapy. Variants of the 6-hydrazinonicotinamide (HYNIC) bifunctional ligands have been prepared by appending thioamide functional groups to 6-hydrazinonicotinamide to form pyridylthiosemicarbazide ligands (SHYNIC). The new bidentate ligands were conjugated to the tumor targeting peptides Tyr3-octreotate and cyclic-RGD. The new ligands and conjugates were used to prepare well-defined {M═O}3+ complexes (where M = 99mTc or natRe or 188Re) that feature two targeting peptides attached to the single metal ion. These new SHYNIC ligands are capable of forming well-defined rhenium and technetium complexes and offer the possibility of using the 99mTc imaging and 188/186Re therapeutic matched pairs.

Synthesis, characterization and biological activities of semicarbazones and their copper complexes.

Substituted semicarbazones/thiosemicarbazones and their copper complexes have been prepared and several single crystal structures examined. The copper complexes of these semicarbazone/thiosemicarbazones were prepared and several crystal structures examined. The single crystal X-ray structure of the pyridyl-substituted semicarbazone showed two types of copper complexes, a monomer and a dimer. We also found that the p-nitrophenyl semicarbazone formed a conventional 'magic lantern' acetate-bridged dimer. Electron Paramagnetic Resonance (EPR) of several of the copper complexes was consistent with the results of single crystal X-ray crystallography. The EPR spectra of the p-nitrophenyl semicarbazone copper complex in dimethylsulfoxide (DMSO) showed the presence of two species, confirming the structural information. Since thiosemicarbazones and semicarbazones have been reported to exhibit anticancer activity, we examined the anticancer activity of several of the derivatives reported in the present study and interestingly only the thiosemicarbazone showed activity while the semicarbazones were not active indicating that introduction of sulphur atom alters the biological profile of these thiosemicarbazones.

Design, Synthesis and Antiproliferative Activity of Novel Benzothiazole Derivatives Conjugated with Semicarbazone Scaffold.

Two series of novel benzothiazole derivatives conjugated with semicarbazone scaffold were designed and synthesized through a structure-based molecular hybridization strategy. All the target compounds were evaluated for their cytotoxicity in vitro against three cancer cell lines (HT-29, MKN-45 and H460) by standard MTT assay. The pharmacological results indicated that seven compounds (17h-n) exhibited comparable or even better antiproliferative activity in comparison with reference drugs Sorafenib and PAC-1. Particularly, compound 17i displayed remarkable cytotoxicity against tested three cancer cell lines with IC50 values of 0.84, 0.06 and 0.52 µM, which were 4.3-, 36.6-, 4.2-folds more potent than Sorafenib and 1.2-, 13.7-, 6.9-times more active than PAC-1, respectively.

Novel Mechanism of Cytotoxicity for the Selective Selenosemicarbazone, 2-Acetylpyridine 4,4-Dimethyl-3-selenosemicarbazone (Ap44mSe): Lysosomal Membrane Permeabilization.

Selenosemicarbazones show marked antitumor activity. However, their mechanism of action remains unknown. We examined the medicinal chemistry of the selenosemicarbazone, 2-acetylpyridine 4,4-dimethyl-3-selenosemicarbazone (Ap44mSe), and its iron and copper complexes to elucidate its mechanisms of action. Ap44mSe demonstrated a pronounced improvement in selectivity toward neoplastic relative to normal cells compared to its parent thiosemicarbazone. It also effectively depleted cellular Fe, resulting in transferrin receptor-1 up-regulation, ferritin down-regulation, and increased expression of the potent metastasis suppressor, N-myc downstream regulated gene-1. Significantly, Ap44mSe limited deleterious methemoglobin formation, highlighting its usefulness in overcoming toxicities of clinically relevant thiosemicarbazones. Furthermore, Cu-Ap44mSe mediated intracellular reactive oxygen species generation, which was attenuated by the antioxidant, N-acetyl-L-cysteine, or Cu sequestration. Notably, Ap44mSe forms redox active Cu complexes that target the lysosome to induce lysosomal membrane permeabilization. This investigation highlights novel structure-activity relationships for future chemotherapeutic design and underlines the potential of Ap44mSe as a selective anticancer/antimetastatic agent.

Semicarbazone analogs as anticonvulsant agents: a review.

Semicarbazones are synthesized by the condensation of semicarbazide and aldehyde/ketone. The literature survey revealed that semicarbazones had been emerged as compounds with diverse biological activities including anticonvulsant, antitubercular, anticancer, and antimicrobial activities. The anticonvulsant activity of semicarbazones is mainly attributed due to the presence of an aryl binding site with aryl/alkyl hydrophobic group, a hydrogen bonding domain and an electron donor group and they are suggested to act by inhibiting sodium ion (Na(+)) channel. Dimmock et al., reported an extensive series of semicarbazones and reported 4-(4-fluorophenoxy) benzaldehyde semicarbazone (C0102862, V102862) as lead molecule. In MES (oral) screening C0102862 showed protective index (PI > 315) more than carbamazepine (PI 101), phenytoin (PI > 21.6) and valproate (PI > 2.17). This review briefly describes the information available about semicarbazone analogs and their anticonvulsant activity.

Synthesis and biological evaluation of novel 4-(2-fluorophenoxy)-2-(1H-tetrazol-1-yl)pyridines bearing semicarbazone moieties as potent antitumor agents.

A series of 4-(2-fluorophenoxy)-2-(1H-tetrazol-1-yl)pyridines bearing semicarbazone moieties were synthesized and evaluated for their in vitro antitumor potency. Some of the compounds (10b, 10c, 10e-10h, 10m-10p, 10r, and 11b) exhibited moderate to excellent antitumor activity as compared to sorafenib and PAC-1, as well as low levels of toxicity toward the human fetal lung fibroblast cell line WI-38. The most promising compound 10p (IC50 = 0.08, 0.36, 0.97 µM) was 45.1-, 6.1-, and 2.4-fold more active than sorafenib (IC50 = 3.61, 2.19, 2.32 µM), and 17, 3.2, and 2.9 times better than PAC-1 (IC50 = 1.36, 1.17, 2.83 µM) against three cancer cell lines (HT-29, H460, and MKN-45), respectively. In addition, further studies examining enzymatic activity suggested that the marked pharmacological activity observed might be ascribed to an inhibitory action against CRAf kinase.

Discovery and optimization of novel 4-phenoxy-6,7-disubstituted quinolines possessing semicarbazones as c-Met kinase inhibitors.

A novel series of N(1)-(3-fluoro-4-(6,7-disubstituted-quinolin-4-yloxy)phenyl)-N(4)-arylidenesemicarbazide derivatives were synthesized and evaluated for their c-Met kinase inhibition and cytotoxicity against A549, HT-29, MKN-45 and MDA-MB-231 cancer cell lines in vitro. Several potent compounds were further evaluated against three other cancer cell lines (U87MG, NCI-H460 and SMMC7721). Most of compounds tested exhibited moderate to excellent activity. The studies of SARs identified the most promising compound 28 (c-Met IC50=1.4nM) as a c-Met kinase inhibitor. In this study, a promising compound 28 was identified, which displayed 2.1-, 3.3-, 48.4- and 3.6-fold increase against A549, HT-29, U87MG and NCI-H460 cell lines, respectively, compared with that of Foretinib.

Synthesis and spectroscopic characterization of 3,4-difluoroacetophenone-thiosemicarbazone and its palladium(II) complex: evaluation of antimicrobial and antitumour activity.

A new cis-palladium(II)diaqua(3,4-difluoroacetophenonethiosemicarbazone complex (Pd(II) complex) is synthesized using 3,4-difluoroacetophenonethiosemicarbazone(L). The L and its Pd(II) complex are characterized and confirmed by elemental analyses, electrochemical analyses, FT-IR, FT-Raman, UV-Vis, HRMS and LC-MS techniques. Ligand L is further characterized by (1)H, (13)C and (19)F NMR spectroscopy. The crystal structure of L is unambiguously characterized by single X-ray crystallography. The ligand (L) belongs to monoclinic system with P2(1)/C space group and the unit cell parameters are a(Å)=9.1144(7), b(Å)=13.7928(7), c(Å)=8.4174(5), α(°)=90, ß(°)=100.715, γ(°)=90 and volume V(A(3))=1039.73(11). The Raman bands observed for the L and its Pd(II) complex are in good agreement with the FT-IR spectral data. The Pd(II) complex is found to be highly efficient in inhibiting the growth of human pathogens like Salmonella typhimurium and Klebsiella pneumonia with MIC value 10.0µg/mL whose inhibition zones are almost comparable with the standard antibiotic. The synthesized compounds have shown antiproliferative activity against the human breast cancer cell lines MDA-MB231 by intermitting the regular pathway of ribonucleotidereductase.

Synthesis and biological evaluation of 4-phenoxy-6,7-disubstituted quinolines possessing semicarbazone scaffolds as selective c-Met inhibitors.

Novel quinoline derivatives bearing acyclic semicarbazones were prepared and their chemical structures as well as the relative stereochemistry were confirmed. All the synthesized compounds were evaluated for their c-Met kinase inhibitory activity and their cytotoxicity against the cell lines HT-29, MKN-45, and MDA-MB-231 in vitro. Several potent compounds were further evaluated against A549 cells. Most compounds displayed moderate to excellent activity, and the structure-activity relationship studies identified the most promising compound 35 as a selective c-Met kinase inhibitor (IC50 = 4.3 nM). Compound 35 showed a 3.5- and 18.8-fold increase in cytotoxicity in vitro against HT-29 and A549 cells, respectively, compared to that of foretinib. Poor off-target effects of compound 35 were further confirmed by the antiproliferative activity against the c-Met inhibition less sensitive MDA-MB-231 cell line (IC50 = 0.77 µM).

Prochelator BHAPI protects cells against paraquat-induced damage by ROS-triggered iron chelation.

A prochelator named BHAPI (N'-(1-(2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyloxy)phenyl)ethylidene)isonicotinohydrazide) based on the structure of experimental metal chelator HAPI (N'-[1-(2-hydroxyphenyl)ethyliden]isonicotinoylhydrazide) has been synthesized. The prochelator, which shows limited affinity for metal ions, is converted efficiently upon reaction with hydrogen peroxide into its chelator form, which binds di- and trivalent metal ions, including Zn(2+), Cu(2+) and Fe(3+). This work shows that the prochelator has a protective effect on cells under oxidative stress induced by either hydrogen peroxide or the cytotoxic herbicide paraquat. The effect of BHAPI and HAPI on cellular iron status was assessed by monitoring the mRNA level of the transferrin receptor. Whereas the chelator HAPI induces iron deficiency in cultured retinal pigment epithelial cells, the prochelator does not, providing evidence that the differential metal-binding capacity of these compounds observed in vitro is replicated in the cellular context.

Effect of N(4)-phenyl substitution in 2-oxo-1,2-dihydroquinoline-3-carbaldehyde semicarbazones on the structure, DNA/protein interaction, and antioxidative and cytotoxic activity of Cu(II) complexes.

A new ligand, 2-oxo-1,2-dihydroquinoline-3-carbaldehyde semicarbazone (OQsc-H) (1);, its N(4)-phenyl derivative (OQsc-Ph) (2); and their corresponding copper(II) complexes [CuCl(2)(OQsc-H)]·H(2)O·CH(3)OH (3), [CuCl(2)(OQsc-Ph)(H(2)O)]·CH(3)OH (4), and [CuNO(3)(OQsc-Ph)(H(2)O)]NO(3)·H(2)O·C(2)H(5)OH (5) have been synthesized and characterized by structural, analytical, and spectral methods, in order to investigate the influence of N(4)-phenyl substitution on structure and pharmacological properties. In all of the complexes, the ligands coordinated to the Cu(II) ion in a neutral fashion via ONO donor atoms. The single-crystal X-ray structures of neutral complex (3) and cationic complex (5) exhibit a slightly distorted square-pyramidal structure, while neutral complex (4) revealed an octahedral structure. The interaction of the compounds with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that compounds 1-5 could interact with CT-DNA through intercalation. A gel electrophoresis pictogram demonstrated the ability of the complexes (3-5) to cleave the pBR322 plasmid DNA through a hydrolytic process. The interactions of the compounds with bovine serum albumin (BSA) were also investigated using UV-visible, fluorescence, and synchronous fluorescence spectroscopic methods. The results indicated that all of the compounds could quench the intrinsic fluorescence of BSA in a static quenching process. Investigations of antioxidative properties showed that all of the compounds have strong radical scavenging potencies against hydroxyl radicals, 2,2-diphenyl-1-picrylhydrazyl radicals, nitric oxide, and superoxide anion radicals. Further, the cytotoxic effect of the compounds examined on cancerous cell lines such as human cervical cancer cells (HeLa), human laryngeal epithelial carcinoma cells (HEp-2), human liver carcinoma cells (Hep G2), human skin cancer cells (A431), and noncancerous NIH 3T3 mouse embryonic fibroblasts cell lines showed that all three complexes exhibited substantial cytotoxic activity. Further, all of the pharmacological investigations support the fact that there exists a strong influence of N(4)-phenyl substitution in semicarbazone.

Microwave assisted synthesis, spectroscopic, electrochemical and DNA cleavage studies of lanthanide(III) complexes with coumarin based imines.

The present work stems from our interest in the synthesis, characterization and biological evaluation of lanthanide(III) complexes of a class of coumarin based imines which have been prepared by the interaction of hydrated lanthanide(III) chloride with the sodium salts of 3-acetylcoumarin thiosemicarbazone (ACTSZH) and 3-acetylcoumarin semicarbazone (ACSZH) in 1:3 molar ratio using thermal as well as microwave method. Characterization of the ligands as well as the metal complexes have been carried out by elemental analysis, melting point determinations, molecular weight determinations, magnetic moment, molar conductance, IR, (1)H NMR, (13)C NMR, electronic, EPR, X-ray powder diffraction and mass spectral studies. Spectral studies confirm ligands to be monofunctional bidentate and octahedral environment around metal ions. The redox behavior of one of the synthesized metal complex was investigated by cyclic voltammetry. Further, free ligands and their metal complexes have been screened for their antimicrobial as well as DNA cleavage activity. The results of these findings have been presented and discussed.

Proteasome inhibition by peptide-semicarbazones.

Peptide-semicarbazones derived from Z-Trp-Trp-Phe-aldehyde inhibit the chymotryptic activity of the human proteasome at nanomolar concentrations, but are less active in a NFkappaB reporter gene assay. Cyclic semicarbazones, in contrast, combine a strong inhibitory effect on the enzyme with an inhibition of NFkappaB signaling in the nanomolar range. In addition, a practical synthesis for scale-up of such compounds was developed.

Design of selective peptidomimetic agonists for the human orphan receptor BRS-3.

New tool substances may help to unravel the physiological role of the human orphan receptor BRS-3 and its possible use as a drug target for the treatment of obesity and cancer. In continuation of our work on BRS-3, the solid- and solution-phase synthesis of a library of low molecular weight peptidomimetic agonists based on the recently developed short peptide agonist 4 is described. Functional potencies of the compounds were determined measuring calcium mobilization in a fluorometric imaging plate reader (FLIPR) assay. Focusing on the N-terminus, the d-Phe-Gln moiety of 4 was modified in a combinatorial SAR-oriented medicinal chemistry approach. With the incorporation of N-arylated glycine and alanine building blocks azaglycine, piperazine, or piperidine and the synthesis of semicarbazides and semicarbazones, a number of highly potent and selective compounds with a reduced number of peptide bonds were obtained, which also should have enhanced metabolic stability.

Synthesis and antitumour evaluation of 4-bromophenyl semicarbazones.

4-Bromophenyl semicarbazone derivatives have been synthesized and their chemical structures have been confirmed by means of their IR, 1H-NMR data and by elemental analyses. The in vitro evaluation in the 3-cell line, one dose primary anticancer assay is described. The 4-bromo substituted p-nitrobenzylidene phenyl semicarbazone (5) showed significant activity against breast MCF7 cell line and was further evaluated for potential anticancer activity in an in vitro human disease-oriented tumour cell line screening panel that consisted of 59 human tumour cell lines arranged in nine subpanels, representing diverse histologies. Melanoma UACC-62 cell line was relatively more sensitive to compounds 5 (growth inhibitions: GI50 = 15.3 mumol/l).