Bis[3,5-bis(benzylidene)-4-oxo-1-piperidinyl]amides: a novel class of potent cytotoxins

Dimeric 3,5-Bis(benzylidene)-4-piperidones: Tumor-Selective Cytotoxicity and Structure-Activity Relationships

Background: The objective of this study is to find novel antineoplastic agents that display greater toxicity to malignant cells than to neoplasms. In addition, the mechanisms of action of representative compounds are sought. This report describes the cytotoxicity of a number of dimers of 3,5-bis(benzylidene)-4-piperidones against human malignant cells (promyelocytic leukemia HL-60 and squamous cell carcinoma HSC-2, HSC-3, and HSC-4). Methods: Tumor specificity was evaluated by the selectivity index (SI), that is the ratio of the mean CC50 for human non-malignant oral cells (gingival fibroblasts, pulp cells, periodontal ligament fibroblasts) to that for malignant cells. Results: The compounds were highly toxic to human malignant cells. On the other hand, these molecules were less toxic to human non-malignant cells. In particular, a potent lead molecule, 3b, was identified. A QSAR study revealed that the placement of electron-releasing and hydrophilic substituents into the aryl rings led to increases in cytotoxic potencies. The modes of action of a lead compound discovered in this study designated 3b were the activation of caspases-3 and -7, as well as causing PARP1 cleavage and G2 arrest, followed by sub-G1 accumulation in the cell cycle. This compound also depolarized the mitochondrial membrane and generated reactive oxygen species in human colon carcinoma HCT116 cells. In conclusion, this study has revealed that, in general, the compounds described in this report are tumor-selective cytotoxins.

In Situ Stabilisation of Silver Nanoparticles at Chitosan-Functionalised Graphene Oxide for Reduction of 2,4-Dinitrophenol in Water

This investigation reports the in situ growth of silver nanoparticles onto covalently bonded graphene oxide-chitosan, which serve as supported nanocatalysts for the NaBH4 reduction of 2,4-dinitrophenol in aqueous systems. Fumaryl chloride reacted with chitosan in an acidic environment to yield a tailored polymeric material. The latter was, in turn, treated with the pre-synthesised graphene oxide sheets under acidic conditions to generate the GO-functionalised membrane (GO-FL-CS). The adsorption of Ag+ from aqueous media by GO-FL-CS yielded a set of membranes that were decorated with silver nanoparticles (Ag NPs@GO-FL-CS) without any reducing agent. Various analytical tools were used to characterise these composites, including Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area analysis, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray analysis, inductively coupled plasma-mass spectrometry, and transmission electron microscopy. The silver-loaded materials were further used for the remediation of 2,4-dinitrophenol from aqueous solutions under batch operation. The BET analysis revealed that the functionalisation of GO with chitosan and Ag NPs (average size 20-60 nm) resulted in a three-fold increased surface area. The optimised catalyst (Ag mass loading 16.95%) displayed remarkable activity with an apparent pseudo-first-order rate constant of 13.5 × 10-3 min-1. The cyclic voltammetry experiment was conducted to determine the nitro-conversion pathway. The reusability/stability test showed no significant reduction efficiency of this metal-laden composite over six cycles. Findings from the study revealed that Ag NPs@GO-FL-CS could be employed as a low-cost and recyclable catalyst to convert toxic nitroaromatics in wastewater.

Investigation of anti-cancer and migrastatic properties of novel curcumin derivatives on breast and ovarian cancer cell lines

Background

Curcumin is known for its multitude of medicinal properties, including anti-cancer and migrastatic activity. Efforts to overcome poor bioavailability, stability, and side effects associated with the higher dose of curcumin has led to the development of newer derivatives of curcumin. Thus, the focus of this study is to screen novel curcumin derivatives, namely ST03 and ST08, which have not been reported before, for their cytotoxicity and migrastatic property on cancer cells.

Methods

Anti-cancer activity of ST03 and ST08 was carried out using standard cytotoxicity assays viz., LDH, MTT, and Trypan blue on both solid and liquid cancer types. Flow cytometric assays and western blotting was used to investigate the cell death mechanisms. Transwell migration assay was carried out to check for migrastatic properties of the compounds.

Results

Both the compounds, ST03 and ST08, showed ~ 100 fold higher potency on liquid and solid tumour cell lines compared to its parent compound curcumin. They induced cytotoxicity by activating the intrinsic pathway of apoptosis in the breast (MDA-MB-231) and ovarian cancer cell lines (PA-1) bearing metastatic and stem cell properties, respectively. Moreover, ST08 also showed inhibition on breast cancer cell migration by inhibiting MMP1 (matrix metalloproteinase 1).

Conclusion

Both ST03 and ST08 exhibit anti-cancer activity at nanomolar concentration. They induce cell death by activating the intrinsic pathway of apoptosis. Also, they inhibit migration of the cancer cells by inhibiting MMP1 in breast cancer cells.

Effects of green synthesised silver nanoparticles (ST06-AgNPs) using curcumin derivative (ST06) on human cervical cancer cells (HeLa) in vitro and EAC tumor bearing mice models

Background

In recent years, green synthesized silver nanoparticles have been increasingly investigated for their anti-cancer potential. In the present study, we aimed at the biosynthesis of silver nanoparticles (AgNPs) using a curcumin derivative, ST06. Although, the individual efficacies of silver nanoparticles or curcumin derivatives have been studied previously, the synergistic cytotoxic effects of curcumin derivative and silver nanoparticles in a single nanoparticulate formulation have not been studied earlier specifically on animal models. This makes this study novel compared to the earlier synthesized curcumin derivative or silver nanoparticles studies. The aim of the study was to synthesize ST06 coated silver nanoparticles (ST06-AgNPs) using ST06 as both reducing and coating agent.

Methods

The synthesized nanoparticles AgNPs and ST06-AgNPs were characterised for the particle size distribution, morphology, optical properties and surface charge by using UV-visible spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Elemental composition and structural properties were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The presence of ST06 as capping agent was demonstrated by Fourier transform infrared spectroscopy (FTIR).

Results

The synthesized nanoparticles (ST06-AgNPs) were spherical and had a size distribution in the range of 50–100 nm. UV-Vis spectroscopy displayed a specific silver plasmon peak at 410 nm. The in vitro cytotoxicity effects of ST06 and ST06-AgNPs, as assessed by MTT assay, showed significant growth inhibition of human cervical cancer cell line (HeLa). In addition, studies carried out in EAC tumor-induced mouse model (Ehrlich Ascites carcinoma) using ST06-AgNPs, revealed that treatment of the animals with these nanoparticles resulted in a significant reduction in the tumor growth, compared to the control group animals.

Conclusion

In conclusion, green synthesized ST06-AgNPs exhibited superior anti-tumor efficacy than the free ST06 or AgNPs with no acute toxicity under both in vitro and in vivo conditions. The tumor suppression is associated with the intrinsic apoptotic pathway. Together, the results of this study suggest that ST06-AgNPs could be considered as a potential option for the treatment of solid tumors.

A Computational Study of Structure and Reactivity of N-Substitued-4-Piperidones Curcumin Analogues and Their Radical Anions

In this work, a computational study of a series of N-substitued-4-piperidones curcumin analogues is presented. The molecular structure of the neutral molecules and their radical anions, as well as their reactivity, are investigated. N-substituents include methyl and benzyl groups, while substituents on the aromatic rings cover electron-donor and electron-acceptor groups. Substitutions at the nitrogen atom do not significantly affect the geometry and frontier molecular orbitals (FMO) energies of these molecules. On the other hand, substituents on the aromatic rings modify the distribution of FMO. In addition, they influence the capability of these molecules to attach an additional electron, which was studied through adiabatic (AEA) and vertical electron affinities (VEA), as well as vertical detachment energy (VDE). To study electrophilic properties of these structures, local reactivity indices, such as Fukui (f⁺) and Parr (P⁺) functions, were calculated, and show the influence of the aromatic rings substituents on the reactivity of α,β-unsaturated ketones towards nucleophilic attack. This study has potential implications for the design of curcumin analogues based on a 4-piperidone core with desired reactivity.

Tumor-selective cytotoxicity of a novel pentadiene analogue on human leukemia/ lymphoma cells

BACKGROUND

A novel series of structurally divergent 1,5-diaryl-3-oxo-1,4-pentadiene analogues 1-10 displayed marked cytotoxic potencies towards a number of human leukemia/lymphoma cells.

OBJECTIVE

To identify novel selective cytotoxic compounds that induce apoptosis.

METHODS

The Differential Nuclear Staining (DNS) screening protocol was utilized to measure the cytotoxicity of all experimental dienones on several cancerous cells. Additionally, the selective cytotoxicity index was calculated by comparing the dienone's cytotoxicity between leukemia/lymphoma cells vs. non-cancerous cells. Furthermore, to discern whether a selected dienone induced cell death via apoptosis or necrosis on T-lymphocyte leukemia cells, diverse approaches were utilized to detect individual biochemical facets of apoptosis.

RESULTS

The dienones were tested for their anti-neoplastic efficiency on human leukemia/lymphoma-derived cell lines. Special emphasis was applied on dienone 1, on the basis of its sub-micromolar cytotoxicity (CC₅₀=0.43+0.02 μM) and high selective cytotoxicity index (11.1) exerted on T-leukemia cells. In general, dienone 1 showed the most potent cytotoxic properties as compared to other dienones and a related reference cytotoxin curcumin as well as the EF-24 curcumin analogue. Dienone 1 caused cell death by apoptosis in Jurkat cells as evidenced by inducing phosphatidylserine externalization, mitochondrial depolarization and caspase-3/7. These effects were mainly attributed to the induction of apoptotic pathways.

CONCLUSION

The novel dienone 1 was found to exhibit potent anti-leukemia activity by inducing programmed cell death/apoptosis. Consequently, dionone 1 should be developed further to examine its potential efficacy to combat malignancies in a pre-clinical animal model.

Evaluation of α,β-unsaturated ketones as antileishmanial agents

In this study, we assessed the antileishmanial activity of 126 α,β-unsaturated ketones. The compounds NC901, NC884, and NC2459 showed high leishmanicidal activity for both the extracellular (50% effective concentration [EC50], 456 nM, 1,122 nM, and 20 nM, respectively) and intracellular (EC50, 1,870 nM, 937 nM, and 625 nM, respectively) forms of Leishmania major propagated in macrophages, with little or no toxicity to mammalian cells. Bioluminescent imaging of parasite replication showed that all three compounds reduced the parasite burden in the murine model, with no apparent toxicity.

Novel 3,5-bis(arylidene)-4-oxo-1-piperidinyl dimers: structure-activity relationships and potent antileukemic and antilymphoma cytotoxicity

Novel clusters of 3,5-bis(benzylidene)-4-oxo-1-piperidinyl dimers 3-5 were evaluated against human Molt4/C8 and CEM T-lymphocytes and human HeLa cervix adenocarcinoma cells as well as murine L1210 leukemia neoplasms. Several of these compounds demonstrated IC50 values in the submicromolar and low micromolar range and compounds possessing 4-fluoro, 4-chloro and 3,4,5-trimethoxy substituents in the series 3 and 4 were identified as potent molecules. A heat map revealed the very high cytotoxic potencies of representative compounds against a number of additional leukemic and lymphoma cell lines and displayed greater toxicity to these cells than nonmalignant MCF10A and Hs-27 neoplasms. These dienones are more refractory to breast and prostate cancers. The evaluation of representative compounds in series 3-5 against a panel of human cancer cell lines revealed them to be potent cytotoxins with average IC50 values ranging from 0.05 to 8.51 μM. In particular, the most potent compound 4g demonstrated over 382-fold and 590-fold greater average cytotoxic potencies in this screen than the reference drugs, melphalan and 5-fluorouracil, respectively. A mode of action investigation of two representative compounds 3f and 4f indicated that they induce apoptosis which is due, at least in part, to the activation of caspase-3 and depolarization of the mitochondrial membrane potential.

Pronounced toxicity differences between homobifunctional protein cross-linkers and analogous monofunctional electrophiles

Bifunctional electrophiles have been used in various chemopreventive, chemotherapeutic, and bioconjugate applications. Many of their effects in biological systems are traceable to their reactive properties, whereby they can modify nucleophilic sites in DNA, proteins, and other cellular molecules. Previously, we found that two different bifunctional electrophiles--diethyl acetylenedicarboxylate and divinyl sulfone--exhibited a strong enhancement of toxicity when compared with analogous monofunctional electrophiles in both human colorectal carcinoma cells and baker's yeast. Here, we have compared the toxicities for a broader panel of homobifunctional electrophiles bearing diverse electrophilic centers (e.g., isothiocyanate, isocyanate, epoxide, nitrogen mustard, and aldehyde groups) to their monofunctional analogues. Each bifunctional electrophile showed at least a 3-fold enhancement of toxicity over its monofunctional counterpart, although in most cases, the differences were even more pronounced. To explain their enhanced toxicity, we tested the ability of each bifunctional electrophile to cross-link recombinant yeast thioredoxin 2 (Trx2), a known intracellular target of electrophiles. The bifunctional electrophiles were capable of cross-linking Trx2 to itself in vitro and to other proteins in cells exposed to toxic concentrations. Moreover, most cross-linkers were preferentially reactive with thiols in these experiments. Collectively, our results indicate that thiol-reactive protein cross-linkers in general are much more potent cytotoxins than analogous monofunctional electrophiles, irrespective of the electrophilic group studied.

Novel 3,5-bis(arylidene)-4-piperidone dimers: potent cytotoxins against colon cancer cells

Two novel series of dimeric 3,5-bis(arylidene)-4-piperidones 7 and 8 were prepared as cytotoxic agents. A specific objective of this study was the discovery of novel compounds displaying potent anti-proliferative activities against colon cancers. Most of the compounds demonstrate potent cytotoxicity against HCT116 and HT29 colon cancer cell lines in which the IC50 values range from low micromolar to nanomolar values. In general, the majority of the compounds showed greater cytotoxicity and some degree of selectivity toward HCT116 cells compared to HT29 cells. Compound 9 in which the amidic carbonyl groups were excised was substantially less potent than 8a in both cell lines suggested that the amide groups are important components of the molecules for exhibiting cytotoxicity. Virtually all the compounds were more potent than a reference drug 5-fluorouracil which is used in treating colon cancers as well as a related enone curcumin. QSAR studies were undertaken and some guidelines for amplification of the project have been formulated. Flow cytometry analysis of a representative potent compound 7f revealed that it induces apoptosis in HCT116 cells.

Bifunctional electrophiles cross-link thioredoxins with redox relay partners in cells

Thioredoxin protects cells against oxidative damage by reducing disulfide bonds in improperly oxidized proteins. Previously, we found that the baker's yeast cytosolic thioredoxin Trx2 undergoes cross-linking to form several protein-protein complexes in cells treated with the bifunctional electrophile divinyl sulfone (DVSF). Here, we report that the peroxiredoxin Tsa1 and the thioredoxin reductase Trr1, both of which function in a redox relay network with thioredoxin, become cross-linked in complexes with Trx2 upon DVSF treatment. Treatment of yeast with other bifunctional electrophiles, including diethyl acetylenedicarboxylate (DAD), mechlorethamine (HN2), and 1,2,3,4-diepoxybutane (DEB), resulted in the formation of similar cross-linked complexes. Cross-linking of Trx2 and Tsa1 to other proteins by DVSF and DAD is dependent on modification of the active site Cys residues within these proteins. In addition, the human cytosolic thioredoxin, cytosolic thioredoxin reductase, and peroxiredoxin 2 form cross-linked complexes to other proteins in the presence of DVSF, although each protein shows different susceptibilities to modification by DAD, HN2, and DEB. Taken together, our results indicate that bifunctional electrophiles potentially disrupt redox homeostasis in yeast and human cells by forming cross-linked complexes between thioredoxins and their redox partners.