David Ríos

Biological Evaluation of 3-Acyl-2-Arylamino-1,4-Naphthoquinones as Inhibitors of Hsp90 Chaperoning Function

Hsp90 is a chaperone that plays a key function in cancer cells by stabilizing proteins responsible of cell growth and survival. Disruption of the Hsp90 chaperone machinery leads to the proteasomal degradation of its client proteins. Hsp90 appears then as an attractive target for the development of new anticancer molecules. We have shown that ascorbate- driven menadione-redox cycling inhibits Hsp90 activity by provoking an N-terminal cleavage of the protein, inducing the degradation of several of its client proteins. Since the mechanism involves an oxidative stress, we explored the effect of a series of diverse donor-acceptor 3-acyl-2-phenylamino 1,4-naphthoquinones on Hsp90 integrity, in the presence of ascorbate. Results show that quinone-derivatives that bear two electroactive groups (namely quinone and nitro) exhibit the highest inhibitory activity (Hsp90 cleavage and cell death). The biological activity of the series mainly relies on their redox capacity and their lipophilicity, which both modulate the ability of these compounds to induce a cytotoxic effect in K562 cells. As observed with other redox cycling quinones, the protein cleavage is blocked in the presence of N-terminal Hsp90 inhibitors suggesting that the availability or occupancy of nucleotide binding site in the N-terminal pocket of Hsp90 plays a critical role. In addition the survival of cancer cells and their metabolic and redox homeostasis were strongly impaired by the presence of ascorbate. Since these effects were similar to that obtained by ascorbate/menadione and they were blocked by the antioxidant N-acetylcyteine (NAC), it appears that oxidative stress is a major component of this cytotoxicity.

DNA Damage and Inhibition of Akt Pathway in MCF-7 Cells and Ehrlich Tumor in Mice Treated with 1,4-Naphthoquinones in Combination with Ascorbate

The aim of this study was to enhance the understanding of the antitumor mechanism of 1,4-naphthoquinones and ascorbate. Juglone, phenylaminonaphthoquinone-7, and 9 (Q7/Q9) were evaluated for effects on CT-DNA and DNA of cancer cells. Evaluations in MCF-7 cells are DNA damage, ROS levels, viability, and proliferation. Proteins from MCF-7 lysates were immunoblotted for verifying PARP integrity, γH2AX, and pAkt. Antitumor activity was measured in Ehrlich ascites carcinoma-bearing mice. The same markers of molecular toxicity were assessed in vivo. The naphthoquinones intercalate into CT-DNA and caused oxidative cleavage, which is increased in the presence of ascorbate. Treatments caused DNA damage and reduced viability and proliferation of MCF-7 cells. Effects were potentiated by ascorbate. No PARP cleavage was observed. Naphthoquinones, combined with ascorbate, caused phosphorylation of H2AX and inhibited pAkt. ROS were enhanced in MCF-7 cells, particularly by the juglone and Q7 plus ascorbate. Ehrlich carcinoma was inhibited by juglone, Q7, or Q9, but the potentiating effect of ascorbate was reproduced in vivo only in the cases of juglone and Q7, which caused up to 60% inhibition of tumor and the largest extension of survival. Juglone and Q7 plus ascorbate caused enhanced ROS and DNA damage and inhibited pAkt also in Ehrlich carcinoma cells.

Eco-Friendly Synthesis and Antiproliferative Evaluation of Some Oxygen Substituted Diaryl Ketones

A broad variety of oxygen-substituted diaryl ketones has been synthesized by solar energy-induced Friedel Crafts acylations of 1,4-benzo- and 1,4-naphthoquinones with benzaldehydes. The in vitro antiproliferative properties of the photoproducts were assessed on prostate (DU-145), bladder (T24) and breast (MCF7) human-derived tumor cell lines and compared to non-tumor mouse fibroblasts (Balb/3T3). Among the tested compounds, it was found that those containing a 3,4,5-trimethoxyphenyl A-ring, such as 12 and 22 are more active on DU-145, with EC50 values of 1.2 and 5.9 μM, respectively. By comparing their effects on the three cancer cell lines, the analogue 22 has the best mean selective index (2.4).

Synthesis and antitumor evaluation of 6-aryl-substituted benzo[j]phenanthridine- and benzo[g]pyrimido[4,5-c]isoquinolinequinones.

A variety of novel 6-arylsubstituted benzo[j]phenanthridine- and benzo[g]-pyrimido[4,5-c]isoquinolinequinones were synthesized from 1,4-naphthoquinone, aryl-aldehydes and enaminones via a two-step synthetic approach. The cytotoxic activity of the aminoquinone derivatives was evaluated in vitro against one normal cell line (MRC-5 lung fibroblasts) and three human cancer cell lines (AGS human gastric adenocarcinoma; SK-MES-1 human lung cancer cells, and J82 human bladder carcinoma) in 72-h drug exposure assays using the MTT colorimetric method. Structure–activity relationships within the series of angular quinones reveal that the insertion of pyrrol-2-yl and furan-2-yl groups at the 6-position is more significant for the increase of the potency and selectivity index of the pharmacophores.

Synthesis and in vitro antiproliferative evaluation of 3-acyl-2-arylamino-1,4-naphthoquinones

A variety of 3-acyl-2-arylamino-1,4-naphthoquinones were synthesized and evaluated for their antiproliferative activities on a panel of three cancer cells. The designed compounds were prepared from their respective acylhydroquinones by oxidation with silver (I) oxide, followed by amination of the resulting 2-acyl-1,4-naphthoquinones, under aerobic conditions. The donor–acceptor properties of the 2,3-disubstituted 1,4-naphthoquinones were evaluated by means of their first half-wave potentials. The biological screening of the 1,4-quinones showed that the antiproliferative activity depends upon the nature of the substituents at the quinone nucleus. The effect of the substituents on the antiproliferative activity is discussed in terms of their donor–acceptor interactions and lipophilicity.

Modulatory Effect of 2-(4-Hydroxyphenyl)amino-1,4-naphthoquinone on Endothelial Vasodilation in Rat Aorta

The vascular endothelium plays an essential role in the control of the blood flow. Pharmacological agents like quinone (menadione) at various doses modulate this process in a variety of ways. In this study, Q7, a 2-phenylamino-1,4-naphthoquinone derivative, significantly increased oxidative stress and induced vascular dysfunction at concentrations that were not cytotoxic to endothelial or vascular smooth muscle cells. Q7 reduced nitric oxide (NO) levels and endothelial vasodilation to acetylcholine in rat aorta. It also blunted the calcium release from intracellular stores by increasing the phenylephrine-induced vasoconstriction when CaCl2 was added to a calcium-free medium but did not affect the influx of calcium from extracellular space. Q7 increased the vasoconstriction to BaCl2 (10−3 M), an inward rectifying K+ channels blocker, and blocked the vasodilation to KCl (10−2 M) in aortic rings precontracted with BaCl2. This was recovered with sodium nitroprusside (10−8 M), a NO donor. In conclusion, Q7 induced vasoconstriction was through a modulation of cellular mechanisms involving calcium fluxes through K+ channels, and oxidative stress induced endothelium damage. These findings contribute to the characterization of new quinone derivatives with low cytotoxicity able to pharmacologically modulate vasodilation.

Synthetic approaches and in vitro cytotoxic evaluation of 2-acyl-3-(3,4,5-trimethoxyanilino)-1,4-naphthoquinones

2-Acyl-1,4-naphthoquinones react with 3,4,5-trimethoxyaniline, under aerobic conditions, to give benzophenanthridinequinone, benzocarbazole and 2-acyl-3-(3,4,5-trimethoxyanilino)-1,4-naphthoquinone derivatives. The formation of the heterocyclic compounds is discussed in terms of the ring closure of C–C Michael type adduct intermediates through two alternative N–C-bond formations. The propensity of the substrates to undergo preferential C–C instead of C–N bond formation and the further heterocyclization of the C–C Michael type adduct intermediates is rationalized by using product stability parameters assessed by DFT calculations. Preliminary results are reported on a convenient access towards 2-acyl-3-(3,4,5-trimethoxyanilino)-1,4-naphthoquinones from 2-acylnaphthoquinones and their cytotoxic activities on cancer cells.

Inhibition of cancer cell growth and migration by dihydroxynaphthyl aryl ketones

Dihydroxynaphthyl aryl ketones 1-5 exhibit activity as tubulin polymerization inhibitors by targeting the colchicine binding site of microtubules making them potential anticancer drugs. Therefore, analogues 1-5 have been evaluated for their cytotoxic activity against the cancer cell lines DU-145 (prostate), T24 (bladder) and MCF-7 (breast). Notable differences in biological activity were observed for compounds 1-5, most likely related to the nature of the aryl substituent bonded to the carbonyl group. Among the tested compounds, only compound 5 showed selectivity for cancer cells over healthy, non-transformed cells. T24 cancer cells treated with compound 5 presented a concentration-dependent decrease in cell proliferation and a loss of migration ability. The cytotoxicity of compounds 1-5 on the selected cell-based assays is discussed in terms of it lipophilicity and polarizability parameters.

Oxidative phenylamination of 5-substituted 1-hydroxynaphthalenes to N-phenyl-1,4-naphthoquinone monoimines by air and light "on water".

Summary A number of N-phenyl-1,4-naphthoquinone monoimines 6–10 were prepared by on-water oxidative phenylamination of 1,5-dihydroxynaphthalene (1) and 5-acetylamino-1-hydroxynaphthalene (5) with oxygen-substituted phenylamines under aerobic conditions and either solar or green LED radiation, in the presence of rose bengal as singlet oxygen sensitizer. As compared to the conventional oxidative phenylamination procedures, this novel synthetic method offers the advantage of aerobic conditions “on water” instead of hazardous oxidant reagents currently employed in aqueous alcoholic media.

In Vitro Inhibition of Helicobacter pylori Growth by Redox Cycling Phenylaminojuglones

Infection by Helicobacter pylori increases 10 times the risk of developing gastric cancer. Juglone, a natural occurring 1,4-naphthoquinone, prevents H. pylori growth by interfering with some of its critical metabolic pathways. Here, we report the design, synthesis, and in vitro evaluation of a series of juglone derivatives, namely, 2/3-phenylaminojuglones, as potential H. pylori growth inhibitors. Results show that 5 out of 12 phenylaminojuglones (at 1.5 μg/mL) were 1.5–2.2-fold more active than juglone. Interestingly, most of the phenylaminojuglones (10 out of 12) were 1.1–2.8 fold more active than metronidazole, a known H. pylori growth inhibitor. The most active compound, namely, 2-((3,4,5-trimethoxyphenyl)amino)-5-hydroxynaphthalene-1,4-dione 7, showed significant higher halo of growth inhibitions (HGI = 32.25 mm) to that of juglone and metronidazole (HGI = 14.50 and 11.67 mm). Structural activity relationships of the series suggest that the nature and location of the nitrogen substituents in the juglone scaffold, likely due in part to their redox potential, may influence the antibacterial activity of the series.