Synthesis and biological evaluation of new C-10 substituted dithranol pleiotropic hybrids.

Selective alkylation of the antipsoriatic drug dithranol (DTR) at C-10 with tert-butyl bromoacetate, followed by acid-mediated deprotection, produced the corresponding carboxylic acid 4 which was coupled with selectively protected polyamines (PAs), such as putrescine (PUT), spermidine (SPD) and spermine (SPM), dopamine and aliphatic amines and substituted benzylamines producing a series of DTR-PA hybrids, after acid-mediated deprotection, as well as simple amides. The compounds were tested as antioxidants and inhibitors of lipoxygenase (LOX). The amides 4,4'-dimethoxybenzhydrylamide 13 (86% and 95%), 2,4-dimethoxybenzylamide 12 (87% and 81%) and dodecylamide 9 (98% and 74%), and the hybrid DTR-SPM (7) (93% and 87%), showed the highest antioxidant activity in the DPPH and AAPH assays, whereas the most potent inhibitors of LOX were amide 13 (IC50=7 µM), the benzylamide 10 (IC50=7.9 µM) and the butylamide 8 (IC50=10 µM). Molecular binding studies showed that binding of these derivatives into the hydrophobic domain blocks approach of substrate to the active site, inhibiting soybean LOX. Amide 13 presented the highest anti-inflammatory activity (79.7%). The DTR moiety was absolutely necessary for securing high anti-inflammatory potency. Ethyl ester 3 (IC50=0.357 µM) and the amides 9 (IC50=0.022 µM) and 13 (IC50=0.56 µM) exhibited higher antiproliferative activity than DTR (IC50=0.945 µM) on HaCaT keratinocytes whereas amide 13 generally presented better cytocompatibility. Amide 13 is a very promising lead compound for further development as an anti-inflammatory and antiproliferative agent.

Em08red, a dual functional antiproliferative emodin analogue, is a downregulator of ErbB2 expression and inducer of intracellular oxidative stress.

Expression of ErbB2 protein is inversely correlated with the prognosis in cancer patients. Consequently, strategies targeting ErbB2 remain an attractive option in treating several types of malignancies, including oral cancer. In addition, many studies have shown that emodin and emodin derivatives are able to inhibit growth of ErbB2-overexpressing tumor cells. In this study, a series of computer modeling-generated emodin analogues were synthesized and tested for their antiproliferative activity against oral cancer cell lines overexpressing ErbB2. Among these analogues, em08red (1,8-dihydroxy-9(10H)-anthracenone) demonstrated potent antiproliferative activity against all three tested ErbB2-overexpressing cell lines, ie, FaDu, HSC3, and OECM1. Treatment with em08red significantly downregulated activation of ErbB2 as well as the ErbB2 protein expression level in the tested cell lines and induced G2 arrest. Antiapoptosis protein (Bcl-xl and Bcl-2) expression levels were also downregulated, and active caspase-3 and caspase-9 was detected in cells after treatment with em08red. Moreover, treatment with em08red stimulated production of cytotoxic reactive oxygen species in treated cells, and this could be partially reversed by pretreatment with N-acetylcysteine. Overall, we demonstrated inhibition of ErbB2 function and induction of reactive oxygen species in tumor cells by em08red, which prevented proliferation of tumor cells and induced apoptotic cell death.

Therapeutic and cytotoxic effects of the novel antipsoriasis codrug, naproxyl-dithranol, on HaCaT cells.

A novel topical codrug, naproxyl-dithranol (Nap-DTH), in which dithranol and naproxen are linked via an ester in a 1:1 ratio to form a single chemical entity, was synthesized. The antiproliferative, anti-inflammatory and toxic effects of Nap-DTH were assessed, at the cellular level, using various in vitro methods. Cultured HaCaT keratinocytes were treated with Nap-DTH, and the cellular effects were compared with those of the parent compounds, individually and as a 1:1 mixture of naproxen:dithranol to mimic 1:1 in situ liberation from Nap-DTH. The results demonstrate that Nap-DTH did not modify proliferation and only exhibited slight toxic effects after 24 h at concentrations >21 µM. At a lower concentration (3.4 µM), Nap-DTH did not alter cell proliferation or inflammation, which suggests that the codrug is therapeutically inert. Relating to this, the 1:1 mixture of naproxen:dithranol exhibited the lowest toxic effect and the highest antiproliferative effect on HaCaT keratinocytes compared to dithranol at the same concentration. Moreover, the 1:1 mixture exhibited a reduced inflammatory effect compared to dithranol alone, as reflected by the upregulation of cyclooxygenase-2 by 45% and 136%, respectively. In spite of the 1:1 mixture showing a greater downregulation of Ki-67 and a 2-fold reduction of proliferating cell nuclear antigen (both cellular markers of proliferation) than dithranol, dithranol showed a much greater induction of cleaved caspase-3 protein expression (upregulated by 287%, compared to 85% for the 1:1 mixture). This suggests that when dithranol was administered with naproxen, inhibition of cell growth plays a more important role in the antiproliferation effects than the induction of apoptotic cell death. These results confirm that the codrug would lead to a better therapeutic profile and fewer adverse effects compared to its parent compounds.

Cornified envelope formation by anthralin, simple analogues, and related anthracenones.

The ability of the antipsoriatic anthralin to induce HaCaT keratinocyte differentiation was investigated and correlated with its potency to inhibit proliferation of keratinocytes. To determine the structural requirements for this effect, anthralin and seventeen simple analogues or related anthracenones were examined for their ability to induce the formation of cornified envelope as a marker of terminal differentiation. Covalently cross-linked protein was measured as a key feature of this process. Induction of keratinocyte differentiation was significant at a concentration of 0.5 microM anthralin after 48 h exposure. The presence of the 1,8-dihydroxy groups is a critical determinant of cross-linking activity, since removing or exchanging these groups prevented the induction of keratinocyte differentiation. Furthermore, at least one hydrogen atom at the 10-position of anthralin is required. Moreover, anthralin, anthralin dimer, and anthralin triacetate exhibited antiproliferative and antirespiratory activity at concentrations required to induce keratinocyte differentiation, suggesting a causality between these effects. In addition, cornified envelope formation was observed for a number of related anthracenones at concentrations as low as 1-5 microM. In general, compounds containing benzoyl substituents, independent of the position in the anthralin nucleus, were more potent than those having benzyl substituents. Only marginal differences in cross-linking potency were observed within a number of phenylpropionyl substituted analogues, suggesting that the ability to induce keratinocyte differentiation is independent of the nature of substituents at the side chain.

Heterocyclic substituted anthralin derivatives as inhibitors of keratinocyte growth and inducers of differentiation.

Heterocyclic substituted derivatives of the antipsoriatic anthralin were synthesized and evaluated in vitro for their antiproliferative action against keratinocytes and their ability to induce keratinocyte differentiation. The indole-2-carboxylic acid analogue 2e exhibited the same excellent antiproliferative activity as anthralin and also induced terminal differentiation of keratinocytes. As a benefit of its strongly diminished potential to generate oxygen radicals, 2e did not induce damage of keratinocyte membranes.

Characterization of novel 10-substituted 1,8-dihydroxy-9(10H)-anthracenone derivatives by mass spectrometry.

Anthralin and its derivatives containing a variety of simple or functionalized aliphatic and aromatic substituents are of special interest in research on psoriasis. In this connection, 10-arylthio-1,8-dihydroxy-9(10H)-anthracenones were synthesized and examined by means of mass spectrometry. In general, the molecules in question fragmented upon electron impact into ions at m/z 225 (C-S bond cleavage and charge retention at the anthralin component) and into ions of unknown structure at m/z 226, requiring H-migration from the S-bound substituent R into the anthralin moiety. Since mass spectrometry methods furnished us elegant, matchless means of tracing the amounts of material in the analysis, especially in the case of physiologically active compounds, we decided to use mass spectrometry procedures for unequivocal identification and purity determination of 10-arylthio-anthralins.

Simple analogues of anthralin: unusual specificity of structure and antiproliferative activity.

Fifty-nine simple analogues of the antipsoriatic agent, anthralin, have been prepared by modifying the positions of the 1,8-hydroxyl groups, replacement of the hydroxyl groups, substitution at the oxygen functions, introduction of additional functional groups into various positions of the anthracenone nucleus, or removal of particular structural elements. The compounds were evaluated for their antiproliferative action against human keratinocytes and inhibition of the generation of leukotriene B4 in polymorphonuclear leukocytes, which may be useful to resolve the proliferative and inflammatory aspects of psoriasis, respectively. Even though many anthracenones were more potent inhibitors of leukotriene biosynthesis than anthralin, none of the compounds was substantially more effective as this drug in suppressing keratinocyte cell growth. There is an absolute requirement for two hydroxyl groups peri to a hydrogen bond acceptor such as a keto or an imino group for high potency. In addition to further delineating the nature of the pharmacophore for this class of compounds, also naphthalenedione with a peri hydroxyl group was identified as a pharmacophore with antiproliferative activity against keratinocyte growth.

Anthralin derivatives--inhibition of 5-lipoxygenase--antipsoriatic efficacy.

Inhibition of 5-lipoxygenase by anthralin (1) and 41 derivatives is determined: the acids 38 and 39, the lactones 40-42 and 9-anthrone (8) are the most potent inhibitors, the lactone 41 reaching the efficacy of nordihydroguaiaretic acid (NDGA). The results were correlated with the hydrophilic/lipophilic balance of the test compounds and their clinical efficacy as far as known. There is no correlation between the "minimum structure" of Krebs and Schaltegger concerning antipsoriatic activity and the inhibitory effects against 5-lipoxygenase.

[10-Acyldithranol dimers; new derivatives of the antipsoriatic dithranol; synthesis, characterization and biochemical properties]. / 10-Acyldithranol-Dimere; Neue Derivate des Antipsoriatikums Dithranol; Syntheseversuche, Charakterisierung und biochemische Eigenschaften.

With regard to the synthesis of 10-(omega-carboxyacyl)-derivatives dithranol 1 was reacted with the carboxylic acid dichlorides of succinic acid, glutaric acid, adipic acid and pimelic acid in toluene and collidin as a base. Instead of the expected derivatives the 10-acyldithranol dimers 5-7 were isolated as main products except for the reaction of succinyl chloride where only lactone 2 was formed. Moreover the 6-ring lactone 3 as a side product and traces of the 7-ring lactone 4 could also be isolated and characterized. All compounds revealed to be inhibitors of the enzyme glucose-6-phosphate dehydrogenase, indicating antipsoriatic activity.

[Synthesis and biochemical properties of new 10-acyl derivatives of dithranols: acetylsalicyldithranol and 1-acetyllactyldithranol]. / Synthese und biochemische Eigenschaften von weiteren 10-Acylderivaten des Dithranols: Acetylsalicyldithranol und L-Acetyllaktyldithranol.

By reaction of the corresponding acid chlorides of acetylsalicylic acid (8) and L-acetyllactic acid (5) with dithranol (1) in toluene and collidin or pyridine as a base two new 10-acylderivatives of (1) were prepared: L-acetyllactyldithranol (2) and acetylsalicyldithranol (3). Both derivatives strongly inhibited the enzyme glucose-6-phosphate dehydrogenase, indicating possible antipsoriatic activity.

Structure and tumor-promoting activity of analogues of anthralin (1,8-dihydroxy-9-anthrone).

Seventeen analogues of the tumor-promoting agent anthralin were tested for the same biological property by repeated skin application on mouse skin using female ICR/Ha Swiss mice, after a single application of a subcarcinogenic dose of 7,12-dimethylbenz[a]anthracene. Seven of the compounds tested are new compounds. They are 1,8-diacetoxy-9-anthrone, 1,8-dimyristoyloxy-9-anthrone, 1,8-dihydroxy-10-acetyl-9-anthrone, 1,8-dihydroxy-10-myristoyl-9-anthrone, 1,8,10-trihydroxy-9-anthrone, 1,8-dihydroxy-9,10-dihydroanthracene, and myristoyljuglone. All compounds were used in pure form for the bioassays. Of the 17 test compounds four showed notable tumor-promoting activity. They are 1,8-dihydroxy-10-acetyl-9-anthrone, 1,8-dihydroxy-10-myristoyl-9-anthrone, 1-hydroxy-9-anthrone, and juglone. In order to determine whether there is any relationship between tumor-promoting activity and metal chelation in this series, the chelating abilities of anthralin and of its inactive analogue 1,8-dihydroxyanthraquinone were examined using the bivalent metal ions Cu(II), Zn(II), Mn(II), Mg(II), and Ca(II). No relationship between chelation and tumor-promoting ability was found.