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.

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.

Lipophilicity is an essential parameter of a compound that determines the solubility and pharmacokinetic properties that determine the transport of the drug to the molecular target. Dimers of dipyridothiazines are diazaphenothiazine derivatives exhibiting diverse anticancer potential in vitro, which is related to their affinity for histone deacetylase. In this study, the lipophilicity of 16 isomeric dipyridothiazine dimers was investigated theoretically and experimentally by reversed-phase thin-layer chromatography (RP-TLC) in an acetone–TRIS buffer (pH = 7.4). The relative lipophilicity parameter R_M0 and specific hydrophobic surface area b were significantly intercorrelated, showing congeneric classes of dimers. The parameter R_M0 was transformed into parameter logP_TLC by use of the calibration curve. Molecular descriptors, ADMET parameters and probable molecular targets were determined in silico for analysis of the pharmacokinetic profile of the tested compounds showing anticancer activity. The analyzed compounds were tested in the context of Lipinski’s rule of five, Ghose’s rule and Veber’s rule, confirming their bioavailability.

Dimers of dipyridothiazines with an m-xylene moiety are presented in terms of a comparative analysis with anticancer active structural analogs containing a lutidine system. The synthesis of new isomeric dimers was described, the structure of which was confirmed by ¹H, ¹³C and 2D NMR, and HR MS spectroscopic methods. The preliminary prediction of the pharmacological profile using the Way2Drug server indicated the anticancer potential of the tested derivatives. In vitro biological activity tests were performed on a normal skin cell line (HaCaT) and five cancer cell lines, including human primary colon cancer (SW480), human metastatic colon cancer (SW620), human breast adenocarcinoma (MDA-MB-231), human lung carcinoma (A-549), and human glioblastoma (LN-229), which indicated low cytotoxic activity. In order to explain the surprisingly low activity, a comparative structural analysis of the tested analogs compared to the dimers with the lutidine system was performed using quantum mechanics and molecular docking in relation to histone deacetylase. Molecular docking indicated the different binding sites of the analyzed dimers, which explained the differences in the activity.

Pyridine derivatives are widely distributed in nature and have valuable pharmacological properties. The pyridine core can be found in drugs such as sorafenib, zapiclone or prothipendyl. Dipyridothiazines are derivatives of phenothiazines that exhibit valuable anticancer, antioxidant and immunomodulatory activities. In this study, we present the synthesis and preliminary in vitro analysis of anticancer activity towards melanotic (COLO829, G361) and amelanotic (A375, C32) melanoma cells and normal human fibroblasts (HDF) of a series of new tricyclic diazaphenothiazines containing a pyridine scaffold in their structure. The structures of these new molecules was confirmed using spectral techniques, including ¹H NMR, ¹³C NMR, 2D NMR and HRMS. An in vitro panel of experiments was assessed using the WST-1 assay and cytometric techniques. The two most promising compounds were analyzed for their effect on intracellular GSH levels, mitochondrial membrane potential and their ability to initiate DNA fragmentation to determine the potential mechanism of both cytotoxic and proapoptotic activity. The conducted studies confirmed the ability of the new 3-methyl-1,6-diazaphenothiazines to induce apoptosis in cancer cells, especially in terms of inducing initial as well as late-phase apoptosis. Moreover, the studied compounds were found to induce redox imbalance (evidenced by GSH depletion) in the analyzed melanoma cells, which may be an important factor that directs melanoma cells towards cell death signaling pathways.

New dimers of selected dipyridothiazines with an m-xylene linker have been designed, synthesized and characterized. Their structure was identified using 1H and 13C NMR as well as 2D NMR techniques (COSY, ROESY, HSQC and HMBC experiments) and HR MS spectrometry. The compounds were subjected to preliminary in silico biological profile tests using the Way2Drug server and analysis of the probable cytotoxic effect on various cancer cell lines. Preliminary in vitro cytotoxicity tests were performed against normal cell lines (HaCaT) and five cancer cell lines (SW480, SW620, MDA-MB-231, A-549, LN-229) showing moderate activity. An analysis of the structure-activity relationship was performed.