The cytotoxic effect of 2-acylated-1,4-naphthohydroquinones on leukemia/lymphoma cells

Design, Synthesis, and Antibacterial Activities of Multi-Functional C2-Functionalized 1,4-Naphthoquinonyl Organoseleniums

A practical and efficient reaction for C2-selenylation of 1,4-naphthoquinones has been explored. This coupling reaction of two redox structural motifs, such as 2-bromo-1,4-naphthoquinone with diaryldiselenide/ebselen has been achieved by using sodium borohydride reducing agent at room temperature. Using this approach, several 2-selenylated-1,4-naphthoquinones were obtained in moderate to good yields and thoroughly characterized by multinuclear (1H, 13C, and 77Se) NMR, cyclic voltammetry, and mass spectrometry. Further, light-irradiated thiolation of the synthesized selenazinone was also performed to show the utility of the synthesized compound for post-functionalization. Several 2-selenylated-1,4-naphthoquinones were studied by SC-XRD in which intramolecular Se⋅⋅⋅N (from quinolinyl ligand) non-bonded interactions were observed. Photophysical studies (UV-visible, emission, solvatochromism, and quantum yield) were also performed on selected C2-selenylated naphthoquinones. The naphthoquinonyl organoseleniums were also screened for their antibacterial properties and quinonyl organoselenium 5 d shows good antibacterial potential against S. aureus ATCC 29213 with MIC 0.5 μg/mL and a Selectivity Index of >200. Moreover, it also exhibited equipotent activity against various strains of S. aureus and Enterococcus faecium, including strains resistant to vancomycin and meropenem. From structure-activity correlation, it seems that nice blend of oxidant properties from quinone and antioxidant properties from selenium moiety makes it better candidate for antibacterial activity.

Podophyllotoxin: Recent Advances in the Development of Hybridization Strategies to Enhance Its Antitumoral Profile

Podophyllotoxin is a naturally occurring cyclolignan isolated from rhizomes of Podophyllum sp. In the clinic, it is used mainly as an antiviral; however, its antitumor activity is even more interesting. While podophyllotoxin possesses severe side effects that limit its development as an anticancer agent, nevertheless, it has become a good lead compound for the synthesis of derivatives with fewer side effects and better selectivity. Several examples, such as etoposide, highlight the potential of this natural product for chemomodulation in the search for new antitumor agents. This review focuses on the recent chemical modifications (2017-mid-2023) of the podophyllotoxin skeleton performed mainly at the C-ring (but also at the lactone D-ring and at the trimethoxyphenyl E-ring) together with their biological properties. Special emphasis is placed on hybrids or conjugates with other natural products (either primary or secondary metabolites) and other molecules (heterocycles, benzoheterocycles, synthetic drugs, and other moieties) that contribute to improved podophyllotoxin bioactivity. In fact, hybridization has been a good strategy to design podophyllotoxin derivatives with enhanced bioactivity. The way in which the two components are joined (directly or through spacers) was also considered for the organization of this review. This comprehensive perspective is presented with the aim of guiding the medicinal chemistry community in the design of new podophyllotoxin-based drugs with improved anticancer properties.

Light-Driven Carbon-Carbon Coupling of α-sp3-CH of Aliphatic Alcohols with sp2-CH Bond of 1,4-Naphthoquinones

Here, an α-selective C_sp3-H bond functionalization of primary aliphatic alcohols with 1,4-naphthoquinones yielded C_sp²-C_sp² coupled products driven by blue-LED light under catalyst, metal, base, and reagent-free conditions. In this transformation, cleavage of three C-H bonds (two sp³-C-H, one sp²-C-H, and one O-H) and four new bonds formed, leading to fluorescent 2-acylated-1,4-naphthohydroquinones.

Radical Hydroalkylation and Hydroacylation of Alkenes by the Use of Benzothiazoline under Thermal Conditions

The hydroalkylation and hydroacylation of electron-deficient alkenes proceeded smoothly by using benzothiazoline derivatives as radical-transfer reagents under thermal conditions without light irradiation or any additive. Both benzyl and benzoyl moieties were transferred efficiently.

An acylhydroquinone derivative produces OXPHOS uncoupling and sensitization to BH3 mimetic ABT-199 (Venetoclax) in human promyelocytic leukemia cells

Since cancer cells have different mitochondrial bioenergetic requirements than non-cancerous cells, therapeutic inhibition of its mitochondrial functionality continues to be an important target for anticancer drug discovery. In this study, a series of acylhydroquinones with different acyl-chain length, and their chlorinated derivatives, in the aromatic ring, synthesized by Fries rearrangement under microwave irradiation, were evaluated for their anticancer activity in two leukemia cell lines. Findings from the primary and secondary screening of the 18 acylhydroquinones, tested at 5 µM on acute promyelocytic leukemia HL-60 and acute lymphoblastic leukemia CEM cells lines, identified an acylchlorohydroquinone (12) with a highly selective anti-proliferative effect toward HL-60 cells. This compound induced S-phase arrest in the cell cycle progression of HL-60 cells with insignificant toxicity on leukemic CEM cells and non-cancerous Hs27 cells. In HL-60 leukemic cells, 12 triggered increased mitochondrial NADH oxidation, increased respiration in presence of oligomycin (state 4o), mitochondrial depolarization, and ROS production, suggesting an uncoupling of OXPHOS. This provoked a metabolic adaptation dependent on AMPK/ACC/autophagy axis, having the mitochondrial β-oxidation a pro-survival role since the combination of 12 and etomoxir, a carnitine palmitoyl-transferase (CPT) inhibitor promoted extensive HL-60 cell death. Finally, 12-induced metabolic stress sensitized to HL-60 cells to cell death by the FDA-approved anti-leukemic drug ABT-199, a BH3 mimetic. Therefore, our results suggest that acylchlorohydroquinone is a promising scaffold in anti-promyelocytic leukemia drug research.

Continuous-Flow Photochemical Transformations of 1,4-Naphthoquinones and Phthalimides in a Concentrating Solar Trough Reactor

A series of photochemical transformations has been successfully conducted under continuous-flow conditions in a concentrating solar trough reactor. Photoacylations and [2+2]-photocycloadditions involving 1,4-naphthoquinones gave the corresponding photoproducts in moderate to high yields with residence times of 70min. Likewise, acetone-sensitized photodecarboxylations involving phthalimides furnished the corresponding benzylated hydroxy phthalimidines in good to excellent yields and purity with residence times of 40min. Compared with corresponding exposures to direct sunlight conducted in a solar float, flow operation generally gave superior conversions and subsequent yields.

Assessing Parameter Suitability for the Strength Evaluation of Intramolecular Resonance Assisted Hydrogen Bonding in o-Carbonyl Hydroquinones

Intramolecular hydrogen bond (IMHB) interactions have attracted considerable attention due to their central role in molecular structure, chemical reactivity, and interactions of biologically active molecules. Precise correlations of the strength of IMHB's with experimental parameters are a key goal in order to model compounds for drug discovery. In this work, we carry out an experimental (NMR) and theoretical (DFT) study of the IMHB in a series of structurally similar o-carbonyl hydroquinones. Geometrical parameters, as well as Natural Bond Orbital (NBO) and Quantum Theory of Atoms in Molecules (QTAIM) parameters for IMHB were compared with experimental NMR data. Three DFT functionals were employed to calculated theoretical parameters: B3LYP, M06-2X, and ωB97XD. O…H distance is the most suitable geometrical parameter to distinguish among similar IMHBs. Second order stabilization energies ΔEij(2) from NBO analysis and hydrogen bond energy (EHB) obtained from QTAIM analysis also properly distinguishes the order in strength of the studied IMHB. ΔEij(2) from NBO give values for the IMHB below 30 kcal/mol, while EHB from QTAIM analysis give values above 30 kcal/mol. In all cases, the calculated parameters using ωB97XD give the best correlations with experimental ¹H-NMR chemical shifts for the IMHB, with R² values around 0.89. Although the results show that these parameters correctly reflect the strength of the IMHB, when the weakest one is removed from the analysis, arguing experimental considerations, correlations improve significantly to values around 0.95 for R².

A Study about Regioisomeric Hydroquinones with Multiple Intramolecular Hydrogen Bonding

A theoretical exploration about hydrogen bonding in a series of synthetic regioisomeric antitumor tricyclic hydroquinones is presented. The stabilization energy for the intramolecular hydrogen bond (IHB) formation in four structurally different situations were evaluated: (a) IHB between the proton of a phenolic hydroxyl group and an ortho-carbonyl group (forming a six-membered ring); (b) between the oxygen atom of a phenolic hydroxyl group and the proton of an hydroxyalkyl group (seven membered ring); (c) between the proton of a phenolic hydroxyl group with the oxygen atom of the hydroxyl group of a hydroxyalkyl moiety (seven-membered ring); and (d) between the proton of a phenolic hydroxyl group and an oxygen atom directly bonded to the aromatic ring in ortho position (five-membered ring). A conformational analysis for the rotation around the hydroxyalkyl substituent is also performed. It is observed that there is a correspondence between the conformational energies and the IHB. The strongest intramolecular hydrogen bonds are those involving a phenolic proton and a carbonyl oxygen atom, forming a six-membered ring, and the weakest are those involving a phenolic proton with the oxygen atom of the chromenone, forming five-membered rings. Additionally, the synthesis and structural assignment of two pairs of regioisomeric hydroquinones, by 2D-NMR experiments, are reported. These results can be useful in the design of biologically-active molecules.

A novel class of piperidones exhibit potent, selective and pro-apoptotic anti-leukemia properties

In the present pre-clinical study, a series of 1-[3-(2-methoxyethylthio)-propionyl]-3,5- bis(benzylidene)-4 piperidones and structurally-related compounds were observed to be cytotoxic in vitro to three human leukemia cell lines, namely Nalm-6, CEM and Jurkat. The 50% cytotoxic concentration (CC₅₀) values of the three cell lines ranged between 0.9-126.4 µM and 0.3-11.7 µM at 24 and 48 h subsequent to exposure, respectively. The two lead compounds with sub-micromolar CC₅₀ concentrations, 1-(2-methoxyethylthio-propionyl)-3,5-bis(benzylidene)-4 piperidone (2a) and 3,5-bis(4-fluorobenzylidene)-1-[3-(2-methoxyethyl sulfinyl)-propionyl]-4-piperidone (3e), were selected for additional analyses. Several strategies were undertaken to determine whether the above piperidones caused cell death via apoptosis or necrosis on T-lymphocyte leukemia Jurkat cells. The results revealed that the two piperidones caused phosphatidylserine externalization, mitochondrial depolarization and activation of caspase-3, which are all biochemical hallmarks of apoptosis. In addition, the selected piperidones displayed selective cytotoxicity towards leukemia cells, and were less toxic in non-cancerous control cells. Therefore, the findings of the present study revealed that the novel piperidones 2a and 3e exert a selective cytotoxic effect on lymphocyte leukemia cells by favoring the activation of the intrinsic/mitochondrial apoptotic pathway.

A novel curcumin-like dienone induces apoptosis in triple-negative breast cancer cells

PURPOSE

According to the World Health Organization (WHO), breast cancer is the most common cancer affecting women worldwide. In the USA ~12.3 % of all women are expected to be diagnosed with various types of breast cancer, exhibiting varying degrees of therapeutic response rates. Therefore, the identification of novel anti-breast cancer drugs is of paramount importance.

METHODS

The 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore was incorporated into a number of cytotoxins. Three of the resulting dienones, 2a, 2b and 2c, were tested for their anti-neoplastic potencies in a variety of human breast cancer-derived cell lines, including the triple negative MDA-MB-231 cell line and its metastatic variant, using a live-cell bio-imaging method. Special emphasis was put on dienone 2c, since its anti-cancer activity and its mode of inflicting cell death have so far not been reported.

RESULTS

We found that all three dienones exhibited potent cytotoxicities towards the breast cancer-derived cell lines tested, whereas significantly lower toxicities were observed towards the non-cancerous human breast cell line MCF-10A. The dienones 2b and 2c exhibited the greatest selective cytotoxicity at submicromolar concentration levels. We found that these two dienones induced phosphatidylserine externalization in MDA-MB-231 cells in a concentration-dependent manner, suggesting that their cytotoxic effect might be mediated by apoptosis. This possibility was confirmed by our observation that the dienone 2c can induce mitochondrial depolarization, caspase-3 activation, cell cycle disruption and DNA fragmentation in MDA-MB-231 cells.

CONCLUSION

Our findings indicate that dienone 2c uses the mitochondrial/intrinsic pathway to inflict apoptosis in triple negative MDA-MB-231 breast cancer-derived cells. This observation warrants further assessment of dienone 2c as a potential anti-breast cancer drug.

Small structural changes on a hydroquinone scaffold determine the complex I inhibition or uncoupling of tumoral oxidative phosphorylation

Mitochondria participate in several distinctiveness of cancer cell, being a promising target for the design of anti-cancer compounds. Previously, we described that ortho-carbonyl hydroquinone scaffold 14 inhibits the complex I-dependent respiration with selective anti-proliferative effect on mouse mammary adenocarcinoma TA3/Ha cancer cells; however, the structural requirements of this hydroquinone scaffold to affect the oxidative phosphorylation (OXPHOS) of cancer cells have not been studied in detail. Here, we characterize the mitochondrial metabolism of TA3/Ha cancer cells, which exhibit a high oxidative metabolism, and evaluate the effect of small structural changes of the hydroquinone scaffold 14 on the respiration of this cell line. Our results indicate that these structural changes modify the effect on OXPHOS, obtaining compounds with three alternative actions: inhibitors of complex I-dependent respiration, uncoupler of OXPHOS and compounds with both actions. To confirm this, the effect of a bicyclic hydroquinone (9) was evaluated in isolated mitochondria. Hydroquinone 9 increased mitochondrial respiration in state 4o without effects on the ADP-stimulated respiration (state 3ADP), decreasing the complexes I and II-dependent respiratory control ratio. The effect on mitochondrial respiration was reversed by 6-ketocholestanol addition, indicating that this hydroquinone is a protonophoric uncoupling agent. In intact TA3/Ha cells, hydroquinone 9 caused mitochondrial depolarization, decreasing intracellular ATP and NAD(P)H levels and GSH/GSSG ratio, and slightly increasing the ROS levels. Moreover, it exhibited selective NAD(P)H availability-dependent anti-proliferative effect on cancer cells. Therefore, our results indicate that the ortho-carbonyl hydroquinone scaffold offers the possibility to design compounds with specific actions on OXPHOS of cancer cells.