Novel Tetracyclic Azaphenothiazines with the Quinoline Ring as New Anticancer and Antibacterial Derivatives of Chlorpromazine

Phenothiazine derivatives are widely studied in various fields such as biology, chemistry, and medicine research because of their pharmaceutical effects. The first compound used successfully in the treatment of psychosis was a phenthiazine derivative, chlorpromazine. Apart from its activity in neurons, chlorpromazine has also been reported to display anticancer and antibacterial properties. In this study, we present the synthesis and research on the activity of A549, MDA, MiaPaCa, PC3, and HCT116 cancer cell lines and of S. aureus, S. epidermidis, E. coli, and P. aeruginosa bacterial strains against a series of new tetracyclic chlorpromazine analogues containing a quinoline scaffold in their structure instead of the benzene ring and various substituents at the thiazine nitrogen. The structure of these novel molecules has been determined by 1H NMR, 13C NMR, and HRMS spectral techniques. The seven most active of the twenty-four new chlorpromazine analogues tested were selected to study the mechanism of cytotoxic action. Their ability to induce apoptosis or necrosis in cancer cells was assessed by flow cytometry analysis. The results obtained confirmed the proapoptotic activity of selected compounds, especially in terms of inducing late apoptosis or necrosis in cancer cell lines A549, MiaPaCa-2, and HCT-116. Furthermore, studies on the induction of cell cycle arrest suggest that the new chlorpromazine analogues exert antiproliferative effects by inducing cell cycle arrest in the S phase and, consequently, apoptosis.

Evaluation of the Lipophilicity of Angularly Condensed Diquino- and Quinonaphthothiazines as Potential Candidates for New Drugs

Lipophilicity is one of the most important properties of compounds required to estimate the absorption, distribution, and transport in biological systems, in addition to solubility, stability, and acid-base nature. It is crucial in predicting the ADME profile of bioactive compounds. The study assessed the usefulness of computational and chromatographic methods (thin-layer chromatography in a reversed-phase system, RP-TLC) for estimating the lipophilicity of 21 newly synthesized compounds belonging to diquinothiazines and quinonaphthiazines. In order to obtain reliable values of the relative lipophilicities of diquinothiazines and quinonaphthiazines, the partition coefficients obtained using different algorithms such as AlogPs, AClogP, AlogP, MLOGP, XLOGP2, XLOGP3, logP, and ClogP were compared with the chromatographic RM0 values of all the tested compounds measured by the experimental RP-TLC method (logPTLC). Additionally, logPTLC values were also correlated with other descriptors, as well as the predicted ADME and drug safety profiling parameters. The linear correlations of logPTLC values of the tested compounds with other calculated molecular descriptors such as molar refractivity, as well as ADME parameters (Caco-2 substrates, P-gp inhibitors, CYP2C19, and CYP3A4) generally show poor predictive power. Therefore, in silico ADME profiling can only be helpful at the initial step of designing these new candidates for drugs. The compliance of all discussed diquinothiazines and naphthoquinothiazines with the rules of Lipiński, Veber, and Egan suggests that the tested pentacyclic phenothiazine analogs have a chance to become therapeutic drugs, especially orally active drugs.

Synthesis and Structural Characterization of Novel Dimers of Dipyridothiazine as Promising Antiproliferative Agents

Many new isomeric dipyridothiazine dimers have been presented as molecules with anticancer potential. These compounds were obtained in efficient syntheses of 1,6-, 1,8-, 2,7- and 3,6-diazaphenothiazines with selected alkylaromatic linkers. The structures of these compounds has been proven with two-dimensional spectroscopic techniques (COSY, NOESY, HSQC and HMBC) and high-resolution mass spectrometry (HRMS). In silico analyses of probable molecular targets were performed using the Way2Drug server. All new dimers were tested for anticancer activity against breast cancer line MCF7 and colon cancer line SW480. Cytotoxicity was assessed on normal L6 muscle cells. The tested dimers had high anticancer potential expressed as IC50 and the selectivity index SI. The most active derivative, 4c, showed an IC50 activity of less than 1 µM and an SI selectivity index higher than 100. Moreover, the compounds were characterized by low toxicity towards normal cells, simultaneously indicating a high cytostatic potential.

Study of Lipophilicity and ADME Properties of 1,9-Diazaphenothiazines with Anticancer Action

Lipophilicity is one of the key properties of a potential drug that determines the solubility, the ability to penetrate through cell barriers, and transport to the molecular target. It affects pharmacokinetic processes such as adsorption, distribution, metabolism, excretion (ADME). The 10-substituted 1,9-diazaphenothiazines show promising if not impressive in vitro anticancer potential, which is associated with the activation of the mitochondrial apoptosis pathway connected with to induction BAX, forming a channel in MOMP and releasing cytochrome c for the activation of caspases 9 and 3. In this publication, the lipophilicity of previously obtained 1,9-diazaphenothiazines was determined theoretically using various computer programs and experimentally using reverse-phase thin-layer chromatography (RP-TLC) and a standard curve. The study presents other physicochemical, pharmacokinetic, and toxicological properties affecting the bioavailability of the test compounds. ADME analysis was determined in silico using the SwissADME server. Molecular targets studies were identified in silico using the SwissTargetPrediction server. Lipinski's rule of five, Ghose's, and Veber's rules were checked for the tested compounds, confirming their bioavailability.

14-Substituted Diquinothiazines as a New Group of Anticancer Agents

A series of novel double-angularly condensed diquinothiazines with aminoalkyl, amidoalkyl, sulfonamidoalkyl, and substituted phenyl groups was designed, synthesized, and evaluated for their anticancer activity against four selected human tumor cell lines (HTC116, SH-SY5Y, A549, and H1299). The cytotoxicity of the novel diquinothiazines was investigated against BEAS-2B cells. The activities of the compounds were compared to etoposide. Among them, compounds with aminoalkyl and phenyl groups showed excellent broad-spectrum anticancer activity. The most active 14-(methylthiophenyl)diquinothiazine, 3c, showed low cytotoxicity against BEAS-2B cells and high activity against tumor cell lines HTC116, SH-SY5Y, A549, and H1299, with IC50 values of 2.3 µM, 2.7 µM, 17.2 µM, and 2.7 µM, respectively (etopiside 8.6 µM, 3.9 µM, 44.8 µM, and 0.6, respectively). Live long-term microscopic observations of cell survival using the starting molecule M0 were also performed. Flow cytometry showed the proapoptotic effects of the studied diquinothiazines. Inhibition of the cell cycle in the S phase was observed, which is associated with damage to nucleic acids and connected to DNA replication arrest.

Lipophilicity and Pharmacokinetic Properties of New Anticancer Dipyridothiazine with 1,2,3-Triazole Substituents

The lipophilicity parameters (logP_calcd, R_M0 and logP_TLC) of 10 new active anticancer dipirydothiazines with a 1,2,3-triazole ring were determined theoretically using computational methods and experimentally by reversed-phase TLC. Experimental lipophilicity was assessed using mobile phases (a mixture of TRIS buffer and acetone) using a linear correlation between the R_M retention parameter and the volume of acetone. The R_M0 parameter was correlated with the specific hydrophobic surface b, revealing two congenerative subgroups: 1,2,3-triazole-1,6-diazaphenothiazines and 1,2,3-triazole-1,8-diazaphenothiazines hybrids. The R_M0 parameter was converted into the logP_TLC lipophilicity parameter using a calibration curve. The investigated compounds appeared to be moderately lipophilic. Lipophilicity has been compared with molecular descriptors and ADME properties. The new derivatives followed Lipinski’s, Ghose’s and Veber’s rules.

Interaction of new tri-, tetra-, and pentacyclic azaphenothiazine derivatives with calf thymus DNA: Spectroscopic and molecular docking studies

Azaphenothiazines (AZA), modified phenothiazine derivatives, have been reported to exhibit a wide spectrum of biological activities, including anticancer activities, but the mechanisms of their interactions with biomolecules are not fully recognized. In this work, the mode of interaction of selected AZA with calf thymus DNA was investigated using UV-Vis absorption, fluorescence spectroscopy (competition experiment with ethidium bromide, quenching of fluorescence) and molecular docking. The investigated AZA represent dipyrido[3,4-b;3'4'-e][1,4]thiazine, quino[3,2-b]benzo[1,4]thiazine and diquino[3,2-b;2',3'-e][1,4]thiazine possessing tricyclic, tetracyclic and pentacyclic ring system with the additional N,N-dimethylaminopropyl group at the nitrogen atom in the 1,4 thiazine ring. The results obtained from spectroscopic studies showed that AZA bind to DNA by insertion of a fragment of the fused rings system between the base pair stack in the double helix of DNA. In addition, the number of rings in the AZA structures seemed to be related to the strength of the interaction, because pentacyclic AZA (binding constant K^b = 6.31 × 10⁶ L/mol) demonstrated 10-fold higher affinity towards DNA than the tetracyclic AZA and about 100-fold higher affinity than that of tricyclic AZA. The molecular docking results showed that the binding mode of AZA to DNA helix was an intercalation mode with the partial insertion of one planar part of the AZA structure (the pyridine or quinoline ring) into the neighboring bases of one of the DNA chains with additional hydrogen bonding with the minor groove through the positively charged N,N-dimethylaminopropyl group. Chemical potential (μ), chemical hardness (ƞ), electronegativity (χ) and the value of electrons transferred from one system to another (ΔN) calculated from the HOMO and LUMO energies by the density functional theory method indicated that AZA acted as the electron acceptors to the DNA bases.

Phenothiazines Modified with the Pyridine Ring as Promising Anticancer Agents

Azaphenothiazines are the largest and most perspective group of modified phenothiazines, and they exhibit variety of biological activities. The review sums up the current knowledge on the anticancer activity of isomeric pyridobenzothiazines and dipyridothiazines, which are modified azaphenothiazines with one and two pyridine rings, respectively, against 10 types of cancer cell lines. Some 10-substituted dipyridothiazines and even 10-unsubstituted parent compounds, such as 10H-1,9-diazaphenothiazine and 10H-3,6-diazaphenothiazine, exhibited very potent action with the IC50 values less than 1 µg/mL and 1 µM against selected cancer cell lines. The strength of the anticancer action depends both on the tricyclic ring scaffolds and the substituents at the thiazine nitrogen atom. The review discusses the kind of the substituents, nature of tricyclic ring scaffolds with the location of the azine nitrogen atoms, the types of the cancer cell lines, and the mechanism of action.

Dual Action of Dipyridothiazine and Quinobenzothiazine Derivatives-Anticancer and Cholinesterase-Inhibiting Activity

The inverse correlation observed between Alzheimer’s disease (AD) and cancer has prompted us to look for cholinesterase-inhibiting activity in phenothiazine derivatives that possess anticancer properties. With the use of in silico and in vitro screening methods, our study found a new biological activity in anticancer polycyclic, tricyclic, and tetracyclic compounds. The virtual screening of a library of 120 ligands, which are the derivatives of azaphenothiazine, led to the identification of 25 compounds that can act as potential inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Biological assays revealed the presence of selective inhibitors of eeAChE (electric eel AChE) or eqBuChE (equine serum BuChE) and nonselective inhibitors of both enzymes among the tested compounds. Their potencies against eeAChE were in a submicromolar-to-micromolar range with IC₅₀ values from 0.78 to 19.32 μM, while their IC₅₀ values against eqBuChE ranged from 0.46 to 10.38 μM. The most potent among the compounds tested was the tetracyclic derivative, 6-(4-diethylaminobut-2-ynyl)-9-methylthioquinobenzothiazine 24, which was capable of inhibiting both enzymes. 9-Fluoro-6-(1-piperidylethyl)quinobenzothiazine 23 was found to act as a selective inhibitor of eqBuChE with an IC₅₀ value of 0.46 μM. Compounds with such a dual antitumor and cholinesterase-inhibitory activity can be considered as a valuable combination for the treatment of both cancer and AD prevention. The results presented in this study might open new directions of research on the group of tricyclic phenothiazine derivatives.

Therapeutic effects of an azaphenothiazine derivative in mouse experimental colitis

Phenothiazines represent a class of compounds of potential therapeutic utility. In this report we evaluated therapeutic value of an azaphenothiazine derivative, 6-acetylaminobutyl-9-chloroquino[3,2-b]benzo[1,4]thiazine (QBT), given intragastrically, in the model of dextran sodium sulfate-induced colitis in C57BL/6 mice using 5-aminosalicylic acid (5-ASA) as a reference drug. Colitis symptoms such as body weight loss, diarrhea and hematochezia (blood in stool) were observed and registered and disease activity index (DAI) was calculated. In addition, weight and cell numbers in the lymphatic organs and histological parameters of the colon wall were analyzed. The effects of QBT on viability of colon epithelial cell lines were also determined. We showed that weight and cell number of draining mesenteric lymph nodes were lower in mice treated with QBT in comparison to their control counterparts. The number of thymocytes, drastically reduced in control mice, was elevated in mice treated with the compounds with a significant effect of 5-ASA. In addition, an abnormal composition of blood cell types was partially corrected in these groups. Histological analysis of the colon revealed that the pathological changes were partially normalized by QBT and even to a higher degree by 5-ASA. In conclusion we demonstrated a therapeutic efficacy of the compound in amelioration of local and systemic pathological changes associated with chemically-induced colitis in mice. A possible mechanism of action of the compound is discussed.

10H-1,9-diazaphenothiazine and its 10-derivatives: synthesis, characterisation and biological evaluation as potential anticancer agents

10H-1,9-diazaphenothiazine was obtained in the sulphurisation reaction of diphenylamine with elemental sulphur and transformed into new 10-substituted derivatives, containing alkyl and dialkylaminoalkyl groups at the thiazine nitrogen atom. The 1,9-diazaphenothiazine ring system was identified with advanced 1H and 13C NMR techniques (COSY, NOESY, HSQC and HMBC) and confirmed by X-ray diffraction analysis of the methyl derivative. The compounds exhibited significant anticancer activities against the human glioblastoma SNB-19, melanoma C-32 and breast cancer MDA-MB-231 cell lines. The most active 1,9-diazaphenothiazines were the derivatives with the propynyl and N, N-diethylaminoethyl groups being more potent than cisplatin. For those two compounds, the expression of H3, TP53, CDKN1A, BCL-2 and BAX genes was detected by the RT-QPCR method. The proteome profiling study showed the most probable compound action on SNB-19 cells through the intrinsic mitochondrial pathway of apoptosis. The 1,9-diazaphenotiazine system seems to be more potent than known isomeric ones (1,6-diaza-, 1,8-diaza-, 2,7-diaza- and 3,6-diazaphenothiazine).

Design, Synthesis, and Structural Characterization of Novel Diazaphenothiazines with 1,2,3-Triazole Substituents as Promising Antiproliferative Agents

A series of novel 1,2,3-triazole-diazphenothiazine hybrids was designed, synthesized, and evaluated for anticancer activity against four selected human tumor cell lines (SNB-19, Caco-2, A549, and MDA-MB231). The majority of the synthesized compounds exhibited significant potent activity against the investigated cell lines. Among them, compounds 1d and 4c showed excellent broad spectrum anticancer activity, with IC₅₀ values ranging from 0.25 to 4.66 μM and 0.25 to 6.25 μM, respectively. The most promising compound 1d, possessing low cytotoxicity against normal human fibroblasts NHFF, was used for gene expression analysis using reverse transcription–quantitative real-time PCR (RT–qPCR). The expression of H3, TP53, CDKN1A, BCL-2, and BAX genes revealed that these compounds inhibited the proliferation in all cells (H3) and activated mitochondrial events of apoptosis (BAX/BCL-2).

Prolongation of skin graft survival in mice by an azaphenothiazine derivative

Azaphenothiazines are predominantly immunosuppressive compounds. We evaluated the efficacy of an azaphenothiazine derivative, 6-chloroethylureidoethyldiquino[3,2-b;2',3'-e][1,4]thiazine (DQT) in prolongation of survival of skin allografts between BALB/c and C57Bl/6 mice. The mice were treated intraperitoneally (i.p.) with 100 μg of DQT on alternate days, on days 1-13 of the experiment (7 doses). The effect of DQT on a two-way mixed lymphocyte reaction (MLR) in the human model, as well as its effect on production of TNF α and IL-10 in a whole blood cell culture, stimulated by lipopolysaccharide (LPS), were evaluated. In addition, DQT effects were investigated regarding the proportion of T cell subsets in human peripheral blood lymphocytes (PBMC) by flow cytometry. Lastly, the effect of DQT on expression of signaling molecules involved in pro apoptotic pathways was determined by RT PCR. The results showed that DQT significantly extended skin graft survival. The compound also strongly suppressed two-way MLR in the human model at a concentration range of 2.5-5.0 μM. In addition, DQT inhibited LPS-inducible TNF α, but not IL-10 production. The compound preferentially caused a loss of the CD3-CD8+CD11b + PBMC cell subset, and transformed CD3+CD8+^high into CD3+CD8+^low cells. Lastly, we demonstrated significant increases in expression of caspases (in particular caspase 8) and of p53 in a culture of Jurkat T cells. We conclude that the immunosuppressive actions of the compound in allograft rejection may be predominantly associated with induction of cell apoptosis and inhibition of TNF α production. The apoptosis could be predominantly selective for the CD3-CD8+CD11b + cell phenotype.

Synthesis, Anticancer Activity, and Apoptosis Induction of Novel 3,6-Diazaphenothiazines

New 10-substituted derivatives of 3,6-diazaphenothiazine, containing the triple bond linker terminated with tertiary cyclic and acyclic amine groups, were synthesized and screened for their anticancer action. The compounds exhibited varied anticancer activities against human glioblastoma SNB-19, melanoma C-32, and breast cancer MDA-MB231 cell lines, depending on the nature of the substituents. The most active 3,6-diazaphenothiazine, 4, was the derivative with the N,N-diethylamino-2-butynyl substituent against glioblastoma SNB-19, and was ten times more potent than cisplatin. For this compound, the expression of H3, TP53, CDKN1A, BCL-2, and BAX genes was detected by the RT-qPCR method. The gene expression ratio BAX/BCL-2 indicated the induction of mitochondrial apoptosis in cancer cell lines. The transformation of the propynyl substituent into amino-2-butynyl can be a method applicable to the search for more anticancer-active azaphenothiazines.

Topically applied azaphenothiazines inhibit experimental psoriasis in mice

The therapeutic efficacy of topically applied azaphenothiazine derivatives: 9-chloro-6-acetylaminobutylquinobenzo[3,2-b][1,4]thiazine (compound 4) and 6-chloroethylureidoethyldiquino[3,2-b;2';3'-e][1,4]thiazine (compound 5) in the amelioration of inflammatory symptoms of imiquimod-induced psoriasis in mice was investigated. Clobederm®, containing clobetasol propioniate, served as a reference drug. The application of the compounds led to thinning of the epidermis and reduction of the cell layers. The suppressive actions of the compounds were even stronger with regard to pathological changes of the dermis. The compounds also exerted generalized, anti-inflammatory effects by decreasing the number of circulating leukocytes, lowering subiliac lymph node weight and partially normalizing an altered blood cell composition. The changes in the composition of main cell types in the epidermis and dermis were less affected by the compounds. In addition, both compounds inhibited to a similar degree production of tumor necrosis factor α (TNF α) in human whole blood cell culture. Whereas compound 5 strongly inhibited IL-8 and CXCL10 chemokines in human keratinocytes - KERTr cell line, transfected with poly(I:C), the suppressive action of compound 4 in this model was weak. In addition, compound 5, but not compound 4, exhibited at low doses proapoptotic properties with regard to colonic cell lines. In summary, we demonstrated the therapeutic potential of two selected azaphenotiazines in the amelioration of the skin pathology elicited in a mouse experimental model of psoriasis.

10H-3,6-Diazaphenothiazine induces G2/M phase cell cycle arrest and caspase-dependent apoptosis and inhibits cell invasion of A2780 ovarian carcinoma cells through the regulation of NF-κB and (BIRC6-XIAP) complexes

The asymptomatic properties and high treatment resistance of ovarian cancer result in poor treatment outcomes and high mortality rates. Although the fundamental chemotherapy provides promising anticancer activities, it is associated with severe side effects. The derivative of phenothiazine, namely, 10H-3,6-diazaphenothiazine (PTZ), was synthesized and reported with ideal anticancer effects in a previous paper. In this study, detailed anticancer properties of PTZ was examined on A2780 ovarian cancer cells by investigating the cytotoxicity profiles, mechanism of apoptosis, and cell invasion. Research outcomes revealed PTZ-induced dose-dependent inhibition on A2780 cancer cells (IC₅₀ =0.62 µM), with significant less cytotoxicity toward HEK293 normal kidney cells and H9C2 normal heart cells. Generation of reactive oxygen species (ROS) and polarization of mitochondrial membrane potential (ΔΨm) suggests PTZ-induced cell death through oxidative damage. The RT² Profiler PCR Array on apoptosis pathway demonstrated PTZ-induced apoptosis via intrinsic (mitochondria-dependent) and extrinsic (cell death receptor-dependent) pathway. Inhibition of NF-κB and subsequent inhibition of (BIRC6-XIAP) complex activities reduced the invasion rate of A2780 cancer cells penetrating through the Matrigel™ Invasion Chamber. Lastly, the cell cycle analysis hypothesizes that the compound is cytostatic and significantly arrests cell proliferation at G₂/M phase. Hence, the exploration of the underlying anticancer mechanism of PTZ suggested its usage as promising chemotherapeutic agent.

Topically applied azaphenothiazines inhibit contact sensitivity to oxazolone in mice

In this work we investigated the efficacy of two topically applied azaphenothiazine derivatives, 9-chloro-6-acetylaminobutylquinobenzo[3,2-b][1,4]thiazine (compound 4) and 6-chloroethylureidoethyldiquino[3,2-b;2';3'-e][1,4]thiazine (compound 5), in the amelioration of inflammatory symptoms of contact sensitivity (CS) to oxazolone in mice, in relation to the commercial ointment Protopic® (tacrolimus), the reference drug. The compounds were administered 24 h following elicitation of CS and, 24 h later, the parameters of inflammation, such as ear edema, blood composition, leukocyte level, numbers of cells in the draining lymph nodes, histological picture of the inflamed tissue, and the morphometric analysis, were analyzed. The study showed that the effectiveness of the studied azaphenothiazines applied as a 0.1% ointment was comparable to the reference drug regarding suppression of the inflammatory process, when all the investigated histological parameters are taken into account.

Azaphenothiazines - promising phenothiazine derivatives. An insight into nomenclature, synthesis, structure elucidation and biological properties

For the last two decades, classical phenothiazines have attracted attention of researchers, as the hitherto investigations have revealed many significant biological activities within this class of compounds, other than originally discovered neuroleptic ones. Important, new pharmaceutical results on phenothiazines, as 10-substituted dibenzothiazines, were recently highlighted in several reviews. Azaphenothiazines are structurally modified phenothiazines by substitution of one or both benzene rings in the phenothiazine ring system with the azine rings, such as: pyridine, pyridazine, pyrimidine, pyrazine, 1,2,4-triazine, quinoline, quinoxaline, benzoxazine and benzothiazine. They form over 50 different heterocyclic systems, of tri-, tetra-, penta- and hexacyclic structures, and contain from one to even four azine nitrogen atoms. This review summarizes the methodical knowledge on azaphenothiazines, referring to their nomenclature, synthesis, structure analysis and above all significant varied biological activities, examined in vitro and in vivo. It describes, in addition, current trends in the synthesis of azaphenothiazines. The influence of the azaphenothiazine ring system, the nature of the substituents, predominantly at the thiazine nitrogen atom, as well as at the azine nitrogen atom and carbon atom, on the biological activities, were also discussed.

Synthesis and biological evaluation of novel propargylquinobenzothiazines and their derivatives as potential antiproliferative, anti-inflammatory, and anticancer agents

Azaphenothiazines containing the quinoline ring, 8-10-substituted 6H-quinobenzothiazines and 6H-diquinothiazine were transformed into new 6-propargyl and 6-dialkylaminobutynyl derivatives containing the triple bond. Most of them displayed strong antiproliferative actions against human peripheral blood mononuclear cells (PBMC) stimulated with phytohemagglutinin A (PHA), strongly suppressed lipopolysaccharide (LPS)-induced TNF-α production by whole blood human cell cultures, and exhibited low cytotoxicity. Three propargylquinobenzothiazines with the bromine, trifluoromethyl, and methylthio groups at position 9 and propargyldiquinothiazine exhibited comparable actions to cisplatin against the L-1210 and SW-948 tumor lines. 6-Propargyl-9-trifluoromethylquinobenzothiazine was shown to block caspase 3 expression and inhibit expression of caspase 8 and 9 in Jurkat cells indicating its possible mechanism of action. These derivatives could be promising, potential therapeutics for treatment of neoplastic diseases and autoimmune disorders.

3,6-Diazaphenothiazines as potential lead molecules - synthesis, characterization and anticancer activity

3,6-Diazaphenothiazines were obtained in cyclization of 3-amino-3'-nitro-2,4'-dipyridinyl sulfide and the reaction of sodium 3-amino-2-pyridinethiolate with 4-chloro-3-nitropyridine followed by alkylation and heteroarylation. The thiazine ring formation ran via the Smiles rearrangement. The structure elucidation was based on 2D NMR and X-ray analysis of N-methylated product. 3,6-Diazaphenothiazines were investigated for antitumor activity using glioblastoma SNB-19, melanoma C-32 and breast cancer MCF-7 cells. 10H-3,6-diazaphenothiazine was 10 times more active (IC50 < 0.72 μg/mL) than cisplatin. Two diazaphenothiazines with the 2-pyrimidinyl and dimethylaminopropyl substituents were selectively active against MCF-7 and C-32 cells. The expressions of H3 (proliferation marker), TP53, CDKN1A (cell cycle regulators), BAX and BCL-2 (proapoptopic and antiapoptopic genes) were detected by RT-QPCR method. The expression analysis suggests the cell cycle arrest and the mitochondrial apoptosis pathway activation in MCF-7 and SNB-19 cells.

Synthesis and anticancer and lipophilic properties of 10-dialkylaminobutynyl derivatives of 1,8- and 2,7-diazaphenothiazines

New derivatives of two isomeric types of azaphenothiazines, 1,8- and 2,7-diazaphenothiazine, containing the triple bond substituents and additionally tertiary cyclic and acyclic amine groups, were synthesized and tested for their anticancer activity. The compounds exhibited differential inhibitory activities. Better results were obtained when the acetylenic group was transformed via the Mannich reaction to the dialkylaminobutynyl groups. The most active was 2,7-diazaphenothiazine with the N-methylpiperazine-2-butynyl substituent against the human ductal breast epithelial tumor cell line T47D, more potent than cisplatin. The 2,7-diazaphenothiazine system turned out to be more active than isomeric 1,8-diaza one. For the most active compound, the expression of TP53, CDKN1A, BCL-2 and BAX genes was detected by the RT-QPCR method. The gene expression ratio BACL-2/BAX suggests the mitochondrial apoptosis in T47D cells. The synthesis makes possible to obtain many new bioactive phenothiazines with the dialkylaminoalkynyl substituents inserting various tertiary cyclic and acyclic amine moieties to the substituents.

6-Substituted 9-fluoroquino[3,2-b]benzo[1,4]thiazines display strong antiproliferative and antitumor properties

6-Substituted 9-fluoroquino[3,2-b]benzo[1,4]thiazines - a new type of tetracyclic azaphenothiazines-were obtained from of 6H-9-fluoroquinobenzothiazine by the introduction of appropriate substituents to the thiazine nitrogen atom (alkyl, aminoalkyl, amidoalkyl, sulfonamidoalkyl and nitrogen half-mustard groups). The compounds displayed differential cytotoxic as well as antiproliferative actions against human peripheral blood mononuclear cells (PBMC) stimulated with phytohemagglutinin A (PHA). In addition, they suppressed lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-α) production by whole blood human cell cultures. Two compounds (4 and 15, with the propargyl and methanesulfonamidopropyl groups) were selected for further experiments because of lack of cytotoxicity and strong antiproliferative actions. Compound 4 showed strong suppressive actions on growth of L1210, SW948, A-431 and CX-1 tumor cell lines which were close to those of cisplatin, the reference drug (e.g. GI50 of 2.28 μg/mL vs. 1.86 μg/mL for L1210 cells). Further, the compound appeared to be equally effective as cyclosporine A (CsA) in the inhibition of human two-way mixed lymphocyte reaction (MLR). The compound did not significantly inhibit interleukin 2 (IL-2)-induced growth of CTLL-2 cell line. In addition, inhibition of prostaglandin (PG) synthesis by indomethacin or block of PG receptors did not interfere with the inhibitory effect of the compound on PHA-induced cell proliferation. Therefore, it is likely that the compound acts by inhibiting cell cycle as proposed for other phenothiazines. Further studies are required for the elucidation of the mechanism of action and therapeutic utility of these compounds in more advanced in vivo models.

Synthesis of quinoline/naphthalene-containing azaphenothiazines and their potent in vitro antioxidant properties

New tetracyclic and pentacyclic azaphenothiazines containing one or two quinoline rings instead of benzene rings were obtained in the original reactions of isomeric diquinodithiins, dichlorodiquinolinyl sulfides, and disulfide with aromatic amines. The type of ring fusion in the azaphenothiazine system was concluded from the ¹H NMR spectra. The obtained azaphenothiazines were evaluated in vitro for their antioxidant activity on rat hepatic microsomal membranes for protection of non-enzymatic lipid peroxidation promoted by the Fe²⁺/ascorbic acid redox system. Most compounds exhibited a very significant antioxidant activity with IC₅₀ values between 1 and 23 μM. The degree of antioxidant activity depends on the lipophilicity and molecular size as well as the (non)substitution of the thiazine nitrogen atom and type of ring system fusion. It is the first time to our knowledge that azaphenothiazines are shown to exhibit such potent antioxidant activity.

Synthesis and selected immunological properties of 10-substituted 1,8-diazaphenothiazines

A new type of tricyclic azaphenothiazines-1,8-diazaphenothiazines-was obtained in the reaction of 2,3- and 3,4-disubstituted pyridines. The reaction ran as the Smiles rearrangement. The 1,8-diazaphenothiazine system was determined using NOE experiment and 2D NMR spectra (COSY, HSQC, HMBC). 10H-1,8-diazaphenothiazine was transformed into 10-derivatives with alkyl, aminoalkyl, amidoalkyl, sulfonamidoalkyl, and nitrogen half-mustard groups. The compounds were tested for their effects on phytohemagglutinin A-induced proliferative response of human peripheral blood mononuclear cells (PBMC) and lipopolysaccharide-induced tumor necrosis factor alpha production by human whole blood cultures. The compounds exhibited differential, dose-dependent inhibitory activities in these tests. All the compounds were low toxic against PBMC. The compounds showing the highest antiproliferative activity strongly inhibited the growth of leukemia L-1210 and colon cancer SW-948 cell lines, similarly as cisplatin, a reference drug.

Estimation of the lipophilicity of new anticancer and immunosuppressive 1,8-diazaphenothiazine derivatives

The lipophilicity of anticancer and immunosuppressant active 1,8-diazaphenothiazine derivatives ( 1: - 16: ) has been investigated. Their lipophilicity (RM0 and log PTLC) was determined by reversed-phase thin-layer chromatography with mixtures of acetone and TRIS buffer as mobile phases. The parameter RM0 and specific hydrophobic surface area b were significantly intercorrelated showing congeneric classes of dipyridothiazines. The parameter RM0 was discussed in the terms of the structure-lipophilicity relationships and transformed into parameter log PTLC by use of the calibration curve. The lipophilicity was correlated with molecular and biomolecular descriptors (human intestinal absorption, blood-brain barrier, plasma protein binding, MDCK) and in vitro tumor necrosis factor alpha inhibition and antiproliferative activity.

Antimicrobial properties of substituted quino[3,2-b]benzo[1,4]thiazines

Our previous studies demonstrated that among phenothiazines several derivatives could be found showing strong antiproliferative actions and the property of inhibiting inducible tumor necrosis factor alpha (TNF a) production in human blood cultures. The aim of this investigation was to determine potential antimicrobial actions of forty four new phenothiazine derivatives with the quinobenzothiazine structure. The compounds showed differential antibacterial and antifungal activities against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans depending on the compound structures, concentrations and bacterial strains. More specifically, 6-(1-methyl- 2-piperidylethyl) quinobenzothiazine displayed strongest actions against S. aureus and E. coli whereas 6-methanesulfonylaminobutyl-9-methylthioquinobenzothiazine exhibited the most universal antimicrobial properties. The correlation between antimicrobial activity and the chemical structure of quinobenzothiazines was discussed.

6-[3-(p-Tolyl-sulfonyl-amino)-prop-yl]diquino-thia-zine

In the title mol-ecule {systematic name: N-[3-(diquino[3,2-b;2',3'-e][1,4]thia-zin-6-yl)prop-yl]-4-methyl-benzene-sulfon-amide}, C28H24N4O2S2, the penta-cyclic system is relatively planar [maximum deviation from the mean plane = 0.242 (1) Å]. The dihedral angle between two quinoline ring systems is 8.23 (2)° and that between the two halves of the 1,4-thia-zine ring is 5.68 (3)°. The conformation adopted by the 3-(p-tolyl-sulfonyl-amino)-propyl substituent allows for the formation of an intra-molecular N-H⋯N hydrogen bond and places the benzene ring of this substituent above one of the quinoline fragments of the penta-cyclic system. In the crystal, mol-ecules are arranged via π-π stacking inter-actions into (0-11) layers [centroid-centroid distances = 3.981 (1)-4.320 (1) Å for the rings in the penta-cyclic system and 3.645 (1) Å for the tolyl benzene rings]. In addition, mol-ecules are involved in weak C-H⋯O, which connect the layers, and C-H⋯S hydrogen bonds. The title compound shows promising anti-cancer activity against renal cancer cell line UO-31.

Synthesis and selected immunological properties of substituted quino[3,2-b]benzo[1,4]thiazines

A new type of azaphenothiazines - tetracyclic quino[3,2-b]benzo[1,4]thiazines, possessing common substituents (H, CH3, Cl, Br, F, CF3, SCH3) in positions 8-10 and pharmacophoric aminoalkyl substituents in position 6, were obtained from diquinodithiin and 2,2'-dichloro-3,3'-diquinolinyl disulfide in several-step syntheses. Sixty one compounds, grouped as the 6H, 6-dialkylaminoalkyl, 6-acylaminoalkyl and sulfonylaminoalkyl derivatives, were tested for cytotoxicity, their effects on phytohemagglutin A (PHA)-induced proliferative response of human peripheral blood mononuclear cells (PBMC) and lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-α) production by these cells. The compounds exhibited differential inhibitory activities in these tests and significantly varied in terms of cytotoxicity. The most promising compounds were tested for growth inhibition of leukemia L-1210 cells, colon cancer SV-948 cells and epidermal carcinoma A-341 cells. The most active compounds exhibited anticancer activity against these cell lines comparable to that of cisplatin. The structure-activity relationship of the compounds were discussed.

N-[4-(9-Chloro-quino[3,2-b]benzo[1,4]thia-zin-6-yl)but-yl]acetamide

In the title mol­ecule, C₂₁H₂₀ClN₃OS, the tetra­cyclic system is close to planar [r.m.s. deviation = 0.110 (4) Å]. The dihedral angle between the quinoline ring system and the benzene ring is 178.3 (1)° and the angle between two (S—C=C—N) halves of the thia­zine ring is 173.4 (1)°. In the crystal, mol­ecules are arranged via π–π inter­actions [centroid–centroid distances = 3.603 (2)–3.739 (2) Å] into slipped stacks extending along [010]. Inter­molecular N—H⋯O hydrogen bonds link the amide groups of neighbouring mol­ecules along the stack, generating a C(4) motif. The title compound shows promising anti­proliferative and anti­cancer activity.

10-(Prop-2-yn-1-yl)-2,7-diaza-phenothia-zine

In the title mol-ecule [systematic name: 10-(prop-2-yn-1-yl)dipyrido[3,4-b:3',4'-e][1,4]thia-zine], C(13)H(9)N(3)S, the dihedral angle between the two pyridine rings is 146.33 (7)° and the angle between two halves of the thia-zine ring is 138.84 (8)°, resulting in a butterfly shape for the tricyclic system. The central thia-zine ring adopts a boat conformation, with the 2-propynyl substituent at the thia-zine N atom located in a pseudo-equatorial position and oriented to the concave side of the diaza-phenothia-zine system. In the crystal, mol-ecules are arranged via π-π inter-actions between the pyridine rings [centroid-centroid distances = 3.838 (1) and 3.845 (1) Å] into stacks extending along [001]. There are C-H⋯C and C-H⋯N inter-actions between mol-ecules of neighbouring stacks.

Recent progress in biological activities of synthesized phenothiazines

This review summarizes recent medicinal chemistry investigations in vitro and in vivo in search for new phenothiazines of promising biological activities. New phenothiazine derivatives (over 50 main structures) contain dialkylaminoalkyl, cycloaminoalkyl and aminoalkyl substituents and their acyl and sulfonyl derivatives, and other substituents with varied the monocyclic (pyrazole, thiazole, oxadiazole, thiadiazole, tetrazole) and bicyclic (quinolizine, pyrazolopyrimidine, thiazolopyridine, azabicyclononane and spiro[chromanpyrimidine] heterocycles linked directly or via the alkyl chain with the thiazine nitrogen atom or with the benzene ring. The modifications of the tricyclic ring system with the bicyclic homoaromatic ring (naphthalene) and monocyclic and bicyclic azine rings (pyridine, pyrimidine, pyrazine and quinoline) led to compounds of significant biological activities. Recently obtained phenothiazines exhibit promising antibacterial, antifungal, anticancer, antiviral, anti-inflammatory, antimalarial, antifilarial, trypanocidal, anticonvulsant, analgesic, immunosuppressive and multidrug resistance reversal properties. These activities were the results of the actions of phenothiazines on biological systems via the interaction of the pharmacophoric substituent (in some cases of strict length), via the interaction of the multicyclic ring system (π-π interaction, intercalation in DNA) and via the lipophilic character allowing the penetration through the biological membranes. The activities were examined by using various biological systems such as cell lines, bacteria, viruses, parasites, laboratory mice, rats and rabbits, and monolayer and bilayer membranes. Some mechanisms of the actions are discussed. This review shows current tendency in the phenothiazine synthesis (without synthetic routes) and reveals the phenothiazine core to be very potent pharmacophoric moiety which can be a rich source of new compounds having desirable biological activities.

Anticancer activity of newly synthesized azaphenothiazines from NCI's anticancer screening bank

The activity of the newly synthesized azaphenothiazines: tricyclic 10-substituted dipyridothiazines 1-9, pentacyclic 6-substituted diquinothiazines 10-22 and hexacyclic diquinothiazinium salt 23 was tested on 55-60 in vitro cell lines. The cell lines included nine types of cancer: leukemia, non-small cell lung cancer, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, prostate cancer and breast cancer (National Cancer Institute, Bethesda, MD, USA). The features of the chemical substituent at the thiazine nitrogen atom confer the anticancer activity of diquinothiazines 10-23. Unexpectedly, the most active of the dipyridothiazines 1-9 was the unsubstituted compound 1 (the substituent is a hydrogen atom). The most cytotoxic compound was the half-mustard derivative 18. The GI(50) value of this compound was -7.06 (corresponding to 40 ng/ml) when tested on the melanoma cell line SK-MEL-5 and -6.0 - -6.62 using cell lines from various cancers including: leukemia (CCRF-CEM), the MOLT-4 cell line, colon cancer (HCT-116), central nervous system cancer (SNB-75 and SF-295), prostate cancer (PC-3), non-small cell lung cancer (NCI-H460 and HOP-92), ovarian cancer (IGROV1 and OVCAR-4) and breast cancer (MDA-MB-460). The ethylene group in the aminoalkylazaphenothiazines is as a good linker and is similar to the propylene and butylene linkers in aminoalkylphenothiazines. To our knowledge, this is the first demonstration of significant azaphenothiazine anticancer activity.

Antioxidant activity of newly synthesized 2,7-diazaphenothiazines

A series of 19 derivatives of 2,7-diazaphenothiazine was synthesized and evaluated for their antioxidant activity bearing in mind the structural similarity with "classical" phenothiazines several of which are considered powerful antioxidants. Among the new derivatives that inhibited in vitro Fe(2+)/ascorbate-induced lipid peroxidation of rat liver microsomal membranes, several exhibited significant antioxidant activity with IC(50 )values in the range of 64-125 microM. Although N-substitution led to a variable degree of antioxidant activity, the latter appears to correlate with the lipophilicity (expressed as clogP values) of the substituted derivatives. Reduced lipophilicity may also explain the relatively lower protection offered by these derivatives against lipid peroxidation when compared to their "classical" phenothiazine counterparts. Thus, modification of the phenothiazine structure by a substitution of two benzene rings with pyridine rings to form this new type of azaphenothiazines does not enhance antioxidant activity, although it retains it.

[New derivatives of phenothiazines with anticancer activities]

Phenothiazines belong to the oldest group of neuroleptic drugs. These compounds exhibit neuroleptic, antipsychotic and sedative properties. Recently, syntheses and promising biological activities of new phenothiazine derivatives have been reported. This review surveys the research on the anticancer phenothiazine derivatives.