Bioactive Phenothiazines and Benzo[a]phenothiazines: Spectroscopic Studies, and Biological and Biomedical Properties and Applications

Host-guest systems for the SAMPL9 blinded prediction challenge: phenothiazine as a privileged scaffold for binding to cyclodextrins

Model systems are widely used in biology and chemistry to gain insight into more complex systems. In the field of computational chemistry, researchers use host-guest systems, relatively simple exemplars of noncovalent binding, to train and test the computational methods used in drug discovery. Indeed, host-guest systems have been developed to support the community-wide blinded SAMPL prediction challenges for over a decade. While seeking new host-guest systems for the recent SAMPL9 binding prediction challenge, which is the focus of the present PCCP Themed Collection, we identified phenothiazine as a privileged scaffold for guests of β cyclodextrin (βCD) and its derivatives. Building on this observation, we used calorimetry and NMR spectroscopy to characterize the noncovalent association of native βCD and three methylated derivatives of βCD with five phenothiazine drugs. The strongest association observed, that of thioridazine and one of the methyl derivatives, exceeds the well-known high affinity of rimantidine with βCD. Intriguingly, however, methylation of βCD at the 3 position abolished detectible binding for all of the drugs studied. The dataset has a clear pattern of entropy-enthalpy compensation. The NMR data show that all of the drugs position at least one aromatic proton at the secondary face of the CD, and most also show evidence of deep penetration of the binding site. The results of this study were used in the SAMPL9 blinded binding affinity-prediction challenge, which are detailed in accompanying papers of the present Themed Collection. These data also open the phenothiazines and, potentially, chemically similar drugs, such as the tricyclic antidepressants, as relatively potent binders of βCD, setting the stage for future SAMPL challenge datasets and for possible applications as drug reversal agents.

Design, Synthesis and Antimicrobial Properties of New Tetracyclic Quinobenzothiazine Derivatives

A new method for modifying the structure of tetracyclic quinobenzothiazinium derivatives has been developed, allowing introduction of various substituents at different positions of the benzene ring. The method consists of reacting appropriate aniline derivatives with 5,12-(dimethyl)thioquinantrenediinium bis-chloride. A series of new quinobenzothiazine derivatives was obtained with propyl, allyl, propargyl and benzyl substituents in 9, 10 and 11 positions, respectively. The structure of the obtained compounds was analyzed by 1H and 13C NMR (HSQC, HMBC) and X-ray analysis. All the compounds were tested against reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212, and representatives of multidrug-resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis (VRE). In addition, all the compounds were evaluated in vitro against Mycobacterium smegmatis ATCC 700084 and M. marinum CAMP 5644. 9-Benzyloxy-5-methyl-12H-quino [3,4-b][1,4]benzothiazinium chloride (6j), 9-propoxy-5-methyl-12H-quino[3,4-b][1,4]benzothiazinium chloride (6a) and 9-allyloxy-5-methyl-12H-quino[3,4-b][1,4]benzothiazinium chloride (6d) demonstrated high activity against the entire tested microbial spectrum. The activities of the compounds were comparable with oxacillin, tetracycline and ciprofloxacinagainst staphylococcal strains and with rifampicin against both mycobacterial strains. Compound 6j had a significant effect on the inhibition of bacterial respiration as demonstrated by the MTT assay. The compounds showed not only bacteriostatic activity, but also bactericidal activity. Preliminary in vitro cytotoxicity screening of the compounds performed using normal human dermal fibroblasts (NHDF) proved that the tested compounds showed an insignificant cytotoxic effect on human cells (IC50 > 37 µM), making these compounds interesting for further investigation. Moreover, the intermolecular similarity of novel compounds was analyzed in the multidimensional space (mDS) of the structure/property-related in silico descriptors by means of principal component analysis (PCA) and hierarchical clustering analysis (HCA), respectively. The distance-oriented structure/property distribution was related with the experimental lipophilic data.

The evolution of clinical guidelines for antimicrobial photodynamic therapy of skin

Antimicrobial photodynamic therapy has become an important component in the treatment of human infection. This review considers historical guidelines, and the scientific literature to envisage what future clinical guidelines for treating skin infection might include. Antibiotic resistance, vertical and horizontal infection control strategies and a range of technologies effective in eradicating microbes without building up new resistance are described. The mechanism of action of these treatments and examples of their clinical use are also included. The research recommendations of NICE Guidelines on the dermatological manifestations of microbial infection were also reviewed to identify potential applications for PDT. The resistance of some microbes to antibiotics can be halted, or even reversed through the use of supplementary drugs, and so they are likely to persist as a treatment of infection. Conventional PDT will undoubtedly continue to be used for a range of skin conditions given existing healthcare infrastructure and a large evidence base. Daylight PDT may find broader antimicrobial applications than just Acne and Cutaneous Leishmaniasis, and Ambulatory PDT devices could become popular in regions where resources are limited or daylight exposure is not possible or inappropriate. Nanotheranostics were found to be highly relevant, and often include PDT, however, new treatments and novel applications and combinations of existing treatments will be subject to Clinical Trials.

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.

Anti-staphylococcal activity and mode of action of thioridazine photoproducts

Antibiotic resistance became an increasing risk for population health threatening our ability to fight infectious diseases. The objective of this study was to evaluate the activity of laser irradiated thioridazine (TZ) against clinically-relevant bacteria in view to fight antibiotic resistance. TZ in ultrapure water solutions was irradiated (1–240 min) with 266 nm pulsed laser radiation. Irradiated solutions were characterized by UV–Vis and FTIR absorption spectroscopy, thin layer chromatography, laser-induced fluorescence, and dynamic surface tension measurements. Molecular docking studies were made to evaluate the molecular mechanisms of photoproducts action against Staphylococcus aureus and MRSA. More general, solutions were evaluated for their antimicrobial and efflux inhibitory activity against a panel of bacteria of clinical relevance. We observed an enhanced antimicrobial activity of TZ photoproducts against Gram-positive bacteria. This was higher than ciprofloxacin effects for methicillin- and ciprofloxacin-resistant Staphylococcus aureus. Molecular docking showed the Penicillin-binding proteins PBP3 and PBP2a inhibition by sulforidazine as a possible mechanism of action against Staphylococcus aureus and MRSA strains, respectively. Irradiated TZ reveals possible advantages in the treatment of infectious diseases produced by antibiotic-resistant Gram-positive bacteria. TZ repurposing and its photoproducts, obtained by laser irradiation, show accelerated and low-costs of development if compared to chemical synthesis.

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).

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.

Lipophilicity of New Anticancer 1,6- and 3,6-diazaphenothiazines by of Use RP TLC and Different Computational Methods

The lipophilicity of new two series of anticancer active 10-substituted 1,6- and 3,6-diazaphenothiazines has been investigated using reversed-phase thin-layer chromatography. Their lipophilicity (RM0 and log PTLC) was determined with mixtures of acetone and Tris buffer as mobile phases. The relative lipophilicity parameter RM0 and specific hydrophobic surface area b were significantly intercorrelated showing congeneric classes of diazaphenothiazines. The parameter RM0 was transformed into parameter log PTLC by use of the calibration curve. The parameter log PTLC was compared with computationally calculated lipophilic parameters log Pcalcd. The lipophilicity was discussed with the structure elements and was correlated with molecular descriptors, ADME properties and in vitro anticancer activities.

Linear and circular dichroism characterization of thionine binding mode with DNA polynucleotides

The binding mode of thionine (3,7-diamino-5-phenothiazinium) with alternating and non-alternating DNA polynucleotides at low binding ratios was conclusively determined using linear and circular dichroism spectroscopies. The binding to [poly(dG-dC)]₂ and poly(dG)·poly(dC) was purely intercalative and was insensitive to ionic strength. Intercalative binding to [poly(dA-dT)]₂ is observed at low ionic strength, but a shift of some dye to an non-intercalative mode is observed as the background salt concentration increases. With poly(dA)·poly(dT), intercalative binding is unfavourable, although some dye molecules may intercalate at low ionic strength, and groove binding is strongly promoted with increasing concentration of background salt. However, stacking with bases is observed with single-stranded poly(dA) and with triplex poly(dT)_⁎poly(dA)·poly(dT) which suggests that the unusual structure of poly(dA)·poly(dT) precludes intercalation. Thionine behaves similarly to the related dye methylene blue, and small differences may be attributed either to the ability of thionine to form H-bonds that stabilize intercalation or to its improved stacking interactions in the basepair pocket on steric grounds.

Selected azaphenothiazines inhibit delayed type hypersensitivity and carrageenan reaction in mice

Several, previously selected azaphenothiazines, as strongly antiproliferative agents in in vitro models, were subjected to evaluation for their potential immunosuppressive effects in the model of delayed type hypersensitivity (DTH) to ovalbumin (OVA) in BALB/c mice and in foot pad inflammation induced by carrageenan in CBA mice. In the DTH model the compounds were given to mice intraperitoneally (i.p.) in 50μg or 250μg doses, 1h before the elicitation of the response. In the carrageenan-induced foot pad inflammation the compounds were given i.p. in 50μg or 250μg doses, 24h and 2h before administration of carrageenan. Among the compounds, the significantly suppressive activities in both models were exhibited only by compound 5 (6-chloroethylureidoethyldiquino[3,2-b;2',3'-e][1,4]thiazine) and compound 4 (6-acetylaminobutyl-9-chloroquino[3,2-b]benzo[1,4]thiazine). Structure-activity relationship, plausible mechanism of action and potential application in therapy of the compounds are 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.

Novel aminoalkylated azaphenothiazines as potential inhibitors of T98G, H460 and SNU80 cancer cell lines in vitro

A set of twenty-one novel aminoalkylated azaphenothiazines is synthesized using a two-step methodology starting from azaphenothiazines. The key step was the selective monoalkylation at position 10 of azaphenothiazines. In all, twenty-five molecules, including intermediates, were investigated for their in vitro anticancer activity, of which fourteen azaphenothiazines (2b, 3a, 3c, 3d, 3e-h, 3j, 3n, 3o, 3p, 3s, and 3u) were found to decrease the metabolic viability and growth of the T98G, H460 and SNU80 cancer cells effectively in a dose-dependent manner. In silico, pharmacokinetic studies suggest that these molecules have good bioavailability, water solubility and other drug-like parameters. Compounds 3a, 3c and 3g were identified as the leading molecules for future investigation due to their (a) high activity against T98G brain, H460 lung and SNU80 thyroid cancer cells; (b) low cytotoxicity with regard to non-malignant HEK293 and MRC5 cells; (c) low toxic risk levels based on in vitro and in silico evaluations; (d) good theoretical oral bioavailability according to Lipinski 'rule of five' pharmacokinetic parameters; and (e) better drug-likeness and drug-score values.

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.

Iodine-mediated synthesis of benzopyridothiazines via tandem C–H thiolation and amination

Tandem C–H thiolation/amination for benzopyridothiazines.

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 and antibacterial activity of some novel 4-oxopyrido[2,3-a]phenothiazines

A series of substituted 4-oxopyrido[2,3-a]phenothiazine-3-carboxylic acids (6a-d) were prepared via cyclization of the corresponding ethyl 7-(arylthioxy)-8-nitro(or azido)-4-oxoquinoline-3-carboxylates (3a-d/4a-d), followed by hydrolysis of the resultant esters (5a-d). Among these tetracyclics, compound 6a with unsubstituted terminal benzo-ring D was the most active against representative Gram-positive and Gram-negative bacterial strains. These compounds were also active against methicillin-resistant Staphylococcus aureus (MRSA), with very low toxicity to normal cells. Virtual screening using ligand-protein docking modeling predicted that the compounds 6a-d are potential inhibitors of the topoisomerase IV enzyme and that hydrophobic interactions and hydrogen bonds are the major molecular interactions between these compounds and the residues of the active site of topoisomerase IV.

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.

Retarded photooxidation of cyamemazine in biomimetic microenvironments

Cyamemazine (CMZ) is a neuroleptic drug that mediates cutaneous phototoxicity in humans. Here, the photobehavior of CMZ has been examined within α1 -acid glycoproteins, β- and γ-cyclodextrins and SDS micelles. In all these microenvironments, CMZ emission was enhanced and blue-shifted, and its lifetime was longer. Irradiation of the entrapped drug at 355 nm, under air; led to the N,S-dioxide. Within glycoproteins or SDS micelles the reaction was clearly slower than in phosphate buffered solution (PBS); protection by cyclodextrins was less marked. Transient absorption spectroscopy in PBS revealed formation of the triplet state ((3)CMZ*) and the radical cation (CMZ(+•)). Upon addition of glycoprotein, the contribution of CMZ(+•) became negligible, whereas (3)CMZ* dominated the spectra; in addition, the triplet lifetime became considerably longer. In cyclodextrins, this occurred to a lower extent. In all microheterogeneous systems, quenching by oxygen was slower than in solution; this was most remarkable inside glycoproteins. The highest protection from photooxidation was achieved inside SDS micelles. The results are consistent with photooxidation of CMZ through photoionization and subsequent trapping of the resulting radical cation by oxygen. This reaction is extremely sensitive to the medium and constitutes an appropriate probe for localization of the drug within a variety of biological compartments.

UV-light effects on cytochrome c modulated by the aggregation state of phenothiazines

The present study shows the factors that modulate the photodamage promoted by phenothiazines. Cytochrome c was irradiated with UV light for 120 min, over a pH range from 4.0 to 8.0, in the absence and in the presence of different concentrations of thioridazine (TR) and fluphenazine (FP). In the absence of phenothiazines, the maximal rate of a Soret band blue shift (nm/min) from 409 to 406 nm was obtained at pH 4.0 (0.028 nm/min). The presence of phenothiazines at the concentration range 10-25 µmol/L amplified and accelerated a cytochrome c blue shift (409 to 405 nm, at a rate = 0.041 nm/min). Above 25 µmol/L, crescent concentrations of phenothiazines contributed to cytochrome c protection with (maximal at 2500 µmol/L). Scanning electronic microscopy revealed the formation of nanostructures. The pH also influenced the effect of low phenothiazine concentrations on cytochrome c. Thus, the predominance of phenothiazine-promoted cytochrome c damage or protection depends on a balance of the following factors: the yield of photo-generated drug cation radicals, which is favored by acidic pH; the stability of the cation radicals, which is favored by the drug aggregation; and the cytochrome c structure, modulated by the pH.

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.

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.