Phenothiazine derivatives and their impact on the necroptosis and necrosis processes. A review

Milligram scale enantioresolution of promethazine and its main metabolites, determination of their absolute configuration and assessment of enantioselective effects on human SY-SY5Y cells

The misuse of pharmaceuticals has significantly increased in recent decades, becoming a major public health concern. The risks associated with medication misuse are particularly high in cases of overdose, especially when the active substances are chiral, as enantioselectivity plays an important role in toxicity. Promethazine (PMZ) is a chiral antihistamine marketed as a racemate and it is misused in "Purple Drank", a recreational drug beverage, that combines codeine and/or PMZ, with soda or alcohol leading to serious health consequences and fatalities in consumers around the world, particularly among teenagers. Information regarding the enantioselectivity in the toxicity of (R,S)-PMZ and its main metabolites, namely promethazine sulfoxide (PMZSO) and desmonomethyl promethazine (DMPMZ), is unknown. This work reported, for the first time, the enantioseparation, in milligram scale, of (R,S)-PMZ, (R,S)-DMPMZ, (R,S)- PMZSO and the determination of their absolute configurations by electronic circular dichroism (ECD). The enantioseparation of all the six enantiomers was accomplished in a homemade semi-preparative column with amylose tris-3,5-dimethylphenylcarbamate (AD) coated with aminopropyl Nucleosil silica. The enantiomeric purity was evaluated using the analytical Lux® 3 µm i-Amylose-3 column, yielding enantiomeric purity values ranging between 94.4% and 99.7%. The elution order of all the enantiomers was accomplished combining the ECD results with an optical rotation detector. The elution order of the enantiomers was influenced only by the chiral selector, rather than the mobile phase. The cytotoxicity of the racemates and the isolated enantiomers towards differentiated SH-SY5Y cells was evaluated. (R,S)-DMPMZ exhibited a significantly higher cytotoxicity than (R,S)-PMZ, suggesting the metabolic bioactivation of (R,S)-PMZ. Conversely, no significant cytotoxicity was found for (R,S)-PMZSO, underscoring a metabolic detoxification pathway. Remarkably, enantioselectivity was observed for the cytotoxicity of PMZ; (R)-PMZ was significantly more cytotoxic than (S)-PMZ. The results underscore the importance to isolate the enantiomers in their enantiomerically form and their correct identification for toxicity enantioselectivity studies, which are vital to understand the drug's behaviour and safety, especially in case of overdoses.

Synthesis of Phenothiazine Embedded Heteroporphyrins

A series of phenothiazine embedded heteroporphyrins containing one phenothiazine unit, two pyrrole rings and one heterocycle such as furan, thiophene, selenophene and tellurophene connected via four meso carbons were synthesized. The macrocycles were synthesized by condensing the phenothiazine based tripyrrane with corresponding 2,5-bis(hydroxymethyl)heterocycle under BF3  ⋅ OEt2 catalyzed conditions and compared the structural, spectral, and electrochemical properties with the reported phenothiazinophyrins. The studies showed that the phenothiazine embedded heteroporphyrins were nonaromatic and electronic properties were significantly altered by replacing the pyrrole ring from phenothiazinophyrin with different heterocycles. The X-ray structure of phenothiazine embedded thiaporphyrin revealed that the macrocycle was distorted with an inverted thiophene ring. Both mono-protonated and diprotonated derivatives of macrocycles were generated by the controlled addition of trifluoroacetic acid to the macrocycles. The macrocyclic protons experienced upfield/downfield shifts in protonated derivatives compared to their corresponding neutral phenothiazine embedded heteroporphyrins. However, the heterocyclic ring in both mono- and diprotonated derivatives retained its inverted conformation. The macrocycles in their neutral and protonated form exhibit nonaromatic absorption features. The studies indicated the electron rich nature of macrocycles and DFT/TD-DFT studies were carried out to justify the experimental observations.

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.