Anticancer and superoxide scavenging activities of p-alkylaminophenols having various length alkyl chains

[Prevention and Treatment of Cancer with Vitamin A and Its Derivatives: Cell Differentiation and Proliferation]

Normal differentiation and proliferation of cells are essential for maintaining homeostasis. Following the successful completion of whole genome sequencing, protein modification has been attracted increasing attention in order to understand the roles of protein diversification in protein function and to elucidate molecular targets in mechanisms of signal transduction. Vitamin A is an essential nutrient for health maintenance. It is present as β-carotene in green and yellow vegetables and retinyl ester in animal products and absorbed into the body from the intestines. After ingestion, it is converted to retinol and oxidized in target cells to retinal, which plays critical roles in vision. It is then further oxidized to retinoic acid (RA), which exhibits a number of effects prior to being metabolized by cytochrome P450 and excreted from the body. Since RA exhibits cell differentiation-inducing actions, it is used as a therapeutic agent for patients with acute promyelocytic leukemia. The current paper describes: (1) HL60 cell differentiation and cell differentiation induction therapy by RA; (2) roles played by RA and retinal and their mechanisms of action; (3) retinoylation, post-translational protein-modified by RA, a novel non-genomic RA mechanism of action without RA receptor; (4) new actions of β-carotene and retinol in vivo and (5) potent anticancer effects of p-dodecylaminophenol (p-DDAP), a novel vitamin A derivative created from the RA derivative fenretinide. We propose that nutritional management of vitamin A can be effective at preventing and treating diseases, and that p-DDAP is a promising anticancer drug.

Are Zn(II) pincer complexes efficient apoptosis inducers? a deep insight into their activity against A549 lung cancer cells

To expand the array of chemotherapeutic drugs, earth-abundant metal complexes are found to be the future direction. In this regard, new zinc(II) complexes 1-3 of 8-aminoquinoline-based pincer ligands were synthesized, characterized and tested for their anticancer activity. The IC50 values of these complexes were estimated by an MTT assay to be 16.35-17.95 μM and 33.35-40 μM against A549 lung and MCF-7 breast cancer cells respectively. Among them, 3 was slightly better than the other complexes and, thus, subjected to detailed studies. Moreover, the ligand corresponding to 3 was less active against both the cell lines than the complex. Further, 3 showed no toxicity against normal fibroblast cell line L929, which instantly elevated the drug characteristic of our complex. An AO-EB staining assay revealed that 3 can induce apoptosis in A549, and it was quantified by flow cytometry as 22.77%. Moreover, the depolarization of the mitochondrial membrane potential determined by JC-1 staining indicated excess ROS production sites in the mitochondria, which was confirmed by carboxy-H2DCFDA staining. Interestingly, the present complexes show better activity than that of the standard drug cisplatin against A549 cells. Overall, the studies provided promising results that can be extended for clinical applications.

Examination of aminophenol-containing compounds designed as antiproliferative agents and potential atypical retinoids

Retinoic acid (RA, 1), an oxidized form of vitamin A, binds to retinoic acid receptors (RAR) and retinoid X receptors (RXR) to regulate gene expression and has important functions such as cell proliferation and differentiation. Synthetic ligands regarding RAR and RXR have been devised for the treatment of various diseases, particularly promyelocytic leukemia, but their side effects have led to the development of new, less toxic therapeutic agents. Fenretinide (4-HPR, 2), an aminophenol derivative of RA, exhibits potent antiproliferative activity without binding to RAR/RXR, but its clinical trial was discontinued due to side effects of impaired dark adaptation. Assuming that the cyclohexene ring of 4-HPR is the cause of the side effects, methylaminophenol was discovered through structure-activity relationship research, and p-dodecylaminophenol (p-DDAP, 3), which has no side effects or toxicity and is effective against a wide range of cancers, was developed. Therefore, we thought that introducing the motif carboxylic acid found in retinoids, could potentially enhance the anti-proliferative effects. Introducing chain terminal carboxylic functionality into potent p-alkylaminophenols significantly attenuated antiproliferative potencies, while a similar structural modification of weakly potent p-acylaminophenols enhanced growth inhibitory potencies. However, conversion of the carboxylic acid moieties to their methyl esters completely abolished the cell growth inhibitory effects of both series. Insertion of a carboxylic acid moiety, which is important for binding to RA receptors, abolishes the action of p-alkylaminophenols, but enhances the action of p-acylaminophenols. This suggests that the amido functionality may be important for the growth inhibitory effects of the carboxylic acids.

Precursor-Directed Synthesis of Apoptosis-Initiating N-Hydroxyalkyl Phenylbenzoisoquinolindione Alkaloids

A precursor-directed approach to access N-hydroxyalkyl phenylbenzoisoquinolindiones (PBIQs) has been developed. Incubation of plant material of Xiphidium caeruleum with hydroxylamines of various chain lengths (C₂ , C₄ , C₆ , C₈ , C₁₀ and C₁₂ ) resulted in 11 new 5-hydroxy- and 5-methoxy PBIQs with different N-hydroxyalkyl side chain lengths. The antiproliferative effect and the cytotoxicity against HUVEC, K-562, and HeLa cell lines of 26 previously reported PBIQs and the 11 newly synthesized N-hydroxyalkyl PBIQs was determined for the first time. The results revealed that introducing long-chain N-aliphatic amine moieties improved the antiproliferative effect and cytotoxicity of PBIQs when compared to derivatives with N-amino acids as side chains.

Catalyst-free Synthesis of Aminomethylphenol Derivatives in Cyclopentyl Methyl Ether via Petasis Borono-Mannich Reaction

OBJECTIVE

Aminomethylphenol molecules have wider applications in pharmaceuticals, agrochemicals, plant protection and promising functional materials. The development of an efficient and practical method to prepare this class of compound is highly desirable from both environmental and economical points of view.

MATERIALS AND METHODS

In order to establish an effective synthetic method for preparing aminomethylphenol derivatives, the Petasis borono-Mannich reaction of salicylaldehyde, phenylboronic acid and 1,2,3,4- tetrahydroisoquinoline was selected as a model reaction. A variety of reaction conditions are investigated, including solvent and temperature. The generality and limitation of the established method were also evaluated.

RESULTS AND DISCUSSION

It was found that model reaction can be carried out in cyclopentyl methyl ether at 80 oC under catalyst-free conditions. This protocol, with broad substrate applicability, the reaction of various arylboronic acid, secondary amine and salicylaldehyde proceeded smoothly under optimal reaction conditions to afford various aminomethylphenol derivatives in high yields. A practical, scalable, and high-yielding synthesis of aminomethylphenol derivatives was successfully accomplished.

CONCLUSION

A catalyst-free practical method for the synthesis of minomethylphenol derivatives based on Petasis borono-Mannich (PBM) reaction of various arylboronic acid, secondary amine and salicylaldehyde in cyclopentyl methyl ether has been developed. The salient features of this protocol are avoidance of any additive/catalyst and toxic organic solvents, use of cyclopentyl methyl ether as the reaction medium, clean reaction profiles, easy operation, and high to excellent yield.

Vitamin A in health care: Suppression of growth and induction of differentiation in cancer cells by vitamin A and its derivatives and their mechanisms of action

Vitamin A is an important micro-essential nutrient, whose primary dietary source is retinyl esters. In addition, β-carotene (pro-vitamin A) is a precursor of vitamin A contained in green and yellow vegetables that is converted to retinol in the body after ingestion. Retinol is oxidized to produce visual retinal, which is further oxidized to retinoic acid (RA), which is used as a therapeutic agent for patients with promyelocytic leukemia. Thus, the effects of retinal and RA are well known. In this paper, we will introduce (1) vitamin A circulation in the body, (2) the actions and mechanisms of retinal and RA, (3) retinoylation: another RA mechanism not depending on RA receptors, (4) the relationship between cancer and actions of retinol or β-carotene, whose roles in vivo are still unknown, and (5) anti-cancer actions of vitamin A derivatives derived from fenretinide (4-HPR). We propose that vitamin A nutritional management is effective in the prevention of cancer.

Sulfur and selenium derivatives of quinazoline and pyrido[2,3-d]pyrimidine: synthesis and study of their potential cytotoxic activity in vitro

The synthesis, cytotoxic activities and selectivities of 35 derivatives related to quinazoline and pyrido[2,3-d]pyrimidine are described. The synthesized compounds were screened in vitro against four tumoral cell lines - leukemia (CCRF-CEM), colon (HT-29), lung (HTB-54) and breast (MCF-7) - and two cell lines derived from non-malignant cell lines, one mammary (184B5) and one from bronchial epithelium (BEAS-2B). MCF-7 and HTB-54 were the most sensitive cell lines with GI(50) values below 10μM for eleven and ten compounds, respectively. Two compounds (2o and 3a) were identified that evoked a marked cytotoxic effect in all cell lines tested and one compound, 7h, was potent and selective against MCF-7. A preliminary study into the mechanism of the potent derivatives 2o, 3a and 7h indicated that the cytotoxic activities of these compounds might be mediated by inducing cell death without affecting cell cycle phases.

p-Dodecylaminophenol derived from the synthetic retinoid, fenretinide: antitumor efficacy in vitro and in vivo against human prostate cancer and mechanism of action

Fenretinide, N-(4-hydroxyphenyl)retinamide (4-HPR) is an aminophenol-containing synthetic retinoid derivative of all-trans-retinoic acid, which is a potent chemopreventive and antiproliferative agent against various cancers. Clinical studies of 4-HPR have shown side effects consisting of night blindness and ocular toxicity. To maintain potent anticancer activity without side effects, p-dodecylaminophenol (p-DDAP) was designed based on structure-activity relationships of 4-HPR. In our study, we investigate whether p-DDAP shows anticancer activity against human prostate cancer cell line PC-3 when compared with 4-HPR. p-DDAP inhibited PC-3 cell growth progressively from low to high concentration in a dose-dependent manner. p-DDAP was the most potent antiproliferative agent in vitro among 6 p-alkylaminophenols and 3 4-hydroxyphenyl analogs examined including 4-HPR. Cells treated with p-DDAP were shown to undergo apoptosis, based on condensation nuclei, cytofluorimetric analysis, propidium iodide staining and the expression of bcl-2 and caspase 3. p-DDAP arrested the S phase of the cell cycle, while 4-HPR arrested the G(0)/G(1) phase. In addition, both the i.v. and i.p. administration of p-DDAP suppressed tumor growth in PC-3-implanted mice in vivo. p-DDAP showed no effects on blood retinol concentrations, in contrast to reductions after 4-HPR administration. These results indicate that p-DDAP exhibits excellent anticancer efficacy against hormonal independent prostate cancer in vitro and in vivo, and it may have great potential for clinical use in the treatment of prostate cancer with reduced side effects.

Potent anticancer activities of novel aminophenol analogues against various cancer cell lines

Novel aminophenol analogues were synthesized based on the structure of fenretinide (N-(4-hydroxyphenyl)retinamide, 5), which is a potent anticancer agent. Our findings showed that the anticancer activities of 5 were due to the side chain attached to the aminophenol moiety. A p-octylaminophenol (p-OAP) provided the most potent anticancer activity among p-alkylaminophenols examined. In this study, we investigated anticancer activities against various cancer cell lines by the new aminophenols, p-dodecylaminophenol (1), p-decylaminophenol (2), N-(4-hydroxyphenyl)dodecananamide (3), and N-(4-hydroxyphenyl)decananamide (4), which exhibits a side chain as long as 5. Cell growth of breast cancer (MCF-7, MCF-7/Adr(R)), prostate cancer (DU-145), and leukemia (HL60) cells was suppressed by 1 and 2 in a fashion dependent on the length of the alkyl chain attached to the aminophenol. In contrast, 3 and 4 were extremely weak. Compound 5 was less potent than 1. Cell growth of liver cancer (HepG2) was not markedly affected by these compounds. In addition, apoptosis of HL60 cells was induced by 1 and 2 in a chain length-dependent manner, but not by 3 and 4. Incorporation of compounds into HL60 cells was in the order 1>2=3>4. These results indicated that anticancer activities for 1 and 2 are correlated with their incorporation into cancer cells and their capability to induce apoptosis, but not for 3 and 4. Compound 1, a potent anticancer agent with potency strikingly greater than 5, may potentially be useful in clinic.

Antioxidant and anticancer activities of novel p-alkylaminophenols and p-acylaminophenols (aminophenol analogues)

Novel compounds were designed based on fenretinide, N-(4-hydroxyphenyl)retinamide (2), which is a synthetic amide of all-trans-retinoic acid (1) that is a potent antioxidant and anticancer agent. Our recent findings indicated that antioxidant and anticancer activities were due to p-methylaminophenol moiety (8) in 2, and that p-octylaminophenol (7), which has an elongated alkyl chain, was more potent than 8. This finding lets us to investigate whether compounds containing alkyl or acyl chains linked to an aminophenol residue as long as 2 and 1, would show activities greater than 2. For this purpose, we prepared p-dodecanoylaminophenol (3), p-decanoylaminophenol (4), p-dodecylaminophenol (5), and p-decylaminophenol (6). The p-alkylaminophenols, 5 and 6, exhibited superoxide scavenging activities, but not p-acylaminophenols, 3 and 4. Elongation of the alkyl chain length reduced superoxide trapping capability (8>7>6>5). In contrast, lipid peroxidation in rat liver microsomes was reduced by 5 and 6 in dose-dependent manner. Compounds 3 and 4 were poor lipid peroxidation inhibitors, being approximately 400- to 1300-fold lower than 5 and 6. In addition, all compounds inhibited cell growth of human leukemia cell lines, HL60 and HL60R, in dose-dependent manners (5>6>3=4). The HL60R cell line is resistant against 1. Growth of both cell lines was suppressed by 5 and 6 in a fashion dependent on the length of the aminophenol alkyl chain, but not by 3 and 4. These results indicate that 5, a potent anticancer agent greater than 2, may potentially have clinical utility, and that its anticancer activity is correlated with inhibitory potency against lipid peroxidation, but not with superoxide scavenging activity.