Antitubercular polyhalogenated phenothiazines and phenoselenazine with reduced binding to CNS receptors

Halogenated Antimicrobial Agents to Combat Drug-Resistant Pathogens

Antimicrobial resistance presents us with a potential global crisis as it undermines the abilities of conventional antibiotics to combat pathogenic microbes. The history of antimicrobial agents is replete with examples of scaffolds containing halogens. In this review, we discuss the impacts of halogen atoms in various antibiotic types and antimicrobial scaffolds and their modes of action, structure-activity relationships, and the contributions of halogen atoms in antimicrobial activity and drug resistance. Other halogenated molecules, including carbohydrates, peptides, lipids, and polymeric complexes, are also reviewed, and the effects of halogenated scaffolds on pharmacokinetics, pharmacodynamics, and factors affecting antimicrobial and antivirulence activities are presented. Furthermore, the potential of halogenation to circumvent antimicrobial resistance and rejuvenate impotent antibiotics is addressed. This review provides an overview of the significance of halogenation, the abilities of halogens to interact in biomolecular settings and enhance pharmacological properties, and their potential therapeutic usages in preventing a postantibiotic era. SIGNIFICANCE STATEMENT: Antimicrobial resistance and the increasing impotence of antibiotics are critical threats to global health. The roles and importance of halogen atoms in antimicrobial drug scaffolds have been established, but comparatively little is known of their pharmacological impacts on drug resistance and antivirulence activities. This review is the first to extensively evaluate the roles of halogen atoms in various antibiotic classes and pharmacological scaffolds and to provide an overview of their ability to overcome antimicrobial resistance.

A Dual Functional Fluorescent Probe Based on Phenothiazine for Detecting Hg2+ and ClO- and its Applications

For the efficient detection of Hg2+ and ClO-, a double-analyte-responsive fluorescent probe PTB was successfully synthesized by combining N-butyl-3-formyl phenothiazine with hydrazine benzothiazole, and designing a specific reaction site for recognizing two analytes (Hg2+ and ClO-) in a compound. It was shown that probe PTB successfully formed a stable complex with Hg2+ in the coordination ratio of 2:1 by using the strong sulfur affinity of Hg2+, which resulted in a remarkable "turn-off" effect, with a quenching efficiency of 92.5% and four reversible cycles of Hg2+ fluorescence detection. For the fluorescence detection of Hg2+, the response time is fast (≤ 2 min) and the detection limit is low (7.8 nM), showing extremely high sensitivity, and the performance is obviously better than that of the reported fluorescent probes for detecting Hg2+. In particular, probe PTB has low toxicity and good biocompatibility, and has been successfully used for imaging of Hg2+ in living cells. Moreover, probe PTB uses thioether bond and carbon-nitrogen double bond as reaction sites to detect ClO-, which has large Stokes Shift (149 nm), good selectivity, high quenching efficiency (96.5%) and fast time response (about 10 s), and successfully detects ClO- in actual water samples. The dual functional fluorescent probe PTB is sensitive for Hg2+ and ClO-. It has been successfully used for making pH fluorescent test paper and imaging detection of exogenous Hg2+ in VSMC cells with low toxicity.

Antioxidant Properties of New Phenothiazine Derivatives

Phenothiazine and its derivatives have a number of properties that contribute to their wider practical use in the production of biologically active substances, drugs, dyes, etc. Therefore, the synthesis and study of new compounds is of great relevance. The aim of this work was to investigate the antioxidant activity of a number of new phenothiazine derivatives. The patterns of electroreduction of oxygen and its radicals in the presence of phenothiazine derivatives in aqueous ethanol media were studied by voltammetry. The influence of various factors on antioxidant activity was considered by the methods of experiment planning. The optimal conditions for the manifestation of the antioxidant activity of phenothiazine derivatives have been found, which seems to be relevant since it opens up new possibilities for their further use as complex preparations with antioxidant activity, including in psychiatric practice.

Towards Asymmetrical Methylene Blue Analogues: Synthesis and Reactivity of 3-N′-Arylaminophenothiazines

The search for new ways to obtain analogues of the well-known Methylene Blue dye is an important synthetic task. Herein, we proposed and developed an approach to the synthesis of 3-N′-arylaminophenothiazines and asymmetrical 3,7-di(N′-arylamino)phenothiazines. This approach included the optimization of synthetic strategy by quantification analysis of the positive charge distribution in the cation of 3-N′-arylaminophenothiazine derivative. The obtained experimental data are confirmed by DFT studies. Two synthetic routes for asymmetrical phenothiazine diarylamino derivatives were suggested and verified. The developed convenient and versatile synthetic approach makes it easy to obtain aromatic Methylene Blue isostructural analogues with various substituents. As a result, a series of novel 3-N′-arylaminophenothiazines and asymmetrical 3,7-di(N′-arylamino)phenothiazines containing ester, tert-butoxycarbonyl, sulfonic acid, hydroxyl and amine groups were obtained in high yields.

Selenium as an emerging versatile player in heterocycles and natural products modification

The diverse pharmacological activities of organoselenium compounds are closely correlated to their ability to scavenge and induce reactive oxygen species (ROS), their intrinsic oxidative properties, and their Se(0) release property. The incorporation of selenium into small molecules, and particularly into heterocycles and natural products, has shown great potential in altering the potency and selectivity of these molecules. Therefore, selenium will play an important role in drug discovery in the near future. We summarize how different organoselenium species affect cellular oxidative stress levels, and try to correlate the structural properties of selenium-containing heterocycles and natural product derivatives to their biological activities and therapeutic applications. We also provide some information to guide the rational design of selenium-containing drugs.

Novel Functionalized Amino Acids as Inhibitors of GABA Transporters with Analgesic Activity

Neuropathic pain resistance to pharmacotherapy has encouraged researchers to develop effective therapies for its treatment. γ-Aminobutyric acid (GABA) transporters 1 and 4 (mGAT1 and mGAT4) have been increasingly recognized as promising drug targets for neuropathic pain (NP) associated with imbalances in inhibitory neurotransmission. In this context, we designed and synthesized new functionalized amino acids as inhibitors of GABA uptake and assessed their activities toward all four mouse GAT subtypes (mGAT1–4). According to the obtained results, compounds 2RS,4RS-39c (pIC₅₀ (mGAT4) = 5.36), 50a (pIC₅₀ (mGAT2) = 5.43), and 56a (with moderate subtype selectivity that favored mGAT4, pIC₅₀ (mGAT4) = 5.04) were of particular interest and were therefore evaluated for their cytotoxic and hepatotoxic effects. In a set of in vivo experiments, both compounds 50a and 56a showed antinociceptive properties in three rodent models of NP, namely, chemotherapy-induced neuropathic pain models (the oxaliplatin model and the paclitaxel model) and the diabetic neuropathic pain model induced by streptozotocin; however compound 56a demonstrated predominant activity. Since impaired motor coordination is also observed in neuropathic pain conditions, we have pointed out that none of the test compounds induced motor deficits in the rotarod test.

Small molecule selenium-containing compounds: Recent development and therapeutic applications

Selenium (Se) is an essential micronutrient of organism and has important function. It participates in the functions of selenoprotein in several manners. In recent years, Se has attracted much attention because of its therapeutic potential against several diseases. Many natural and synthetic organic Se-containing compounds were studied and explored for the treatment of cancer and other diseases. Studies have showed that incorporation of Se atom into small molecules significantly enhanced their bioactivities. In this paper, according to different applications and structural characteristics, the research progress and therapeutic application of Se-containing compounds are reviewed, and more than 110 Se-containing compounds were selected as representatives which showed potent activities such as anticancer, antioxidant, antifibrolytic, antiparasitic, antibacterial, antiviral, antifungal and central nervous system related effects. This review is expected to provide a basis for further study of new promising Se-containing compounds.

Small organic molecules targeting the energy metabolism of Mycobacterium tuberculosis

Causing approximately 10 million incident cases and 1.3-1.5 million deaths every year, Mycobacterium tuberculosis remains a global health problem. The risk is further exacerbated with latent tuberculosis (TB) infection, the HIV pandemic, and increasing anti-TB drug resistance. Therefore, unexplored chemical scaffolds directed towards new molecular targets are increasingly desired. In this context, mycobacterial energy metabolism, particularly the oxidative phosphorylation (OP) pathway, is gaining importance. Mycobacteria possess primary dehydrogenases to fuel electron transport; aa₃-type cytochrome c oxidase and bd-type menaquinol oxidase to generate a protonmotive force; and ATP synthase, which is essential for both growing mycobacteria as well as dormant mycobacteria because ATP is produced under both aerobic and hypoxic conditions. Small organic molecules targeting OP are active against latent TB as well as resistant TB strains. FDA approval of the ATP synthase inhibitor bedaquiline and the discovery of clinical candidate Q203, which both interfere with the cytochrome bc₁ complex, have already confirmed mycobacterial energy metabolism to be a valuable anti-TB drug target. This review highlights both preferable molecular targets within mycobacterial OP and promising small organic molecules targeting OP. Progressive research in the area of mycobacterial OP revealed several highly potent anti-TB compounds with nanomolar-range MICs as low as 0.004 μM against Mtb H37Rv. Therefore, we are convinced that targeting the OP pathway can combat resistant TB and latent TB, leading to more efficient anti-TB chemotherapy.