Comparison in practical applications of crown ether sensor molecules containing an acridone or an acridine unit – a study on protonation and complex formation

Novel Crown Ether-Functionalized Fusidic Acid Butyl Ester: Synthesis, Biological Evaluation, In Silico ADMET, and Molecular Docking Studies

Crown ethers have gained importance in the field of medicine because of their resemblance to natural ionophores like valinomycin. With the goal of developing new pharmacologically important crown ethers, a novel series of crown ethers linked with Fusidic acid butyl ester 10a-d were synthesized and characterized by means of their 1H NMR, 13C NMR DEPT-135, FT-IR, and mass spectrometry. In vitro antioxidant and α-glucosidase inhibition activities of all crown ethers along with the precursor Fusidic acid butyl ester were examined and compared to the standard butylated hydroxyanisole and acarbose, respectively. Compounds (FABE-16-crown-4) 10b and (FABE-19-crown-5) 10c showed high antioxidant potential with the IC50 = 22.5 ± 0.2 μM and 32.1 ± 0.3 μM, respectively, when compared to the standard BHA (IC50 = 44.2 ± 0.34 μM). To understand the binding mode of the compounds, molecular docking investigations were performed using human antioxidant protein, peroxiredoxin 5. Molecular docking studies revealed higher docking scores (-6.5 and -6.7 kcal/mol) for the highly active compounds 10c and 10b, respectively, than standard BHA (-5.3 kcal/mol). Synthesized crown ethers exhibited moderate α-glucosidase inhibition with (IC50 = 23.5 ± 0.2 to 76.5 ± 0.1 μM) when compared to acarbose as standard (IC50 = 5.2 ± 0.8 μM). The in silico ADMET predictions indicated that the prepared compounds obeyed (bRO5) and Veber's rule for the acceptance as orally administered drugs and indicated that all the prepared crown ethers exhibited calculated values of drug likeness parameters in acceptable ranges that showed good potential of these molecules for further drug development investigations.

Recent Advances in the Synthesis and Optical Applications of Acridine-based Hybrid Fluorescent Dyes

Acridine-based hybrid fluorescent dyes represent a category of dyes that integrate the acridine chromophore with other functional groups or materials to enhance their fluorescence properties. These dyes have garnered substantial attention across various domains, encompassing bioimaging, sensing, and optoelectronics. In recent years, researchers have directed their efforts toward fabricating acridine-based hybrid fluorescent dyes with improved water solubility, biocompatibility, and targeting capabilities. These advancements have facilitated their utilization in biological imaging applications, such as monitoring cellular processes, investigating protein-protein interactions, and detecting specific biomolecules. This review delineates the recent progress in synthesizing acridine-based hybrid fluorescent dyes and their applications in optical properties over the past decade. This review is anticipated to catalyze the development of innovative fluorescent materials featuring heightened properties and functionalities.

Unprecedented 100% conversion from pyridinic to pyrrolic nitrogen configuration for electrochemically active nitrogen-doped carbon materials

Nitrogen-doped carbons with promising electrochemical performance exhibit a strong dependence on nitrogen configuration. Therefore, accurate control of nitrogen configurations is crucial to clarify their influence. Unfortunately, there is still no well-defined conversion route to finely control nitrogen configuration. Herein, we proposed the concept of 100% conversion from pyridinic to pyrrolic nitrogen in carbon materials through low-temperature pyrolysis and alkali activation of hydroxypyridine-3-halophenol-formaldehyde resins. Their dehalogenation pyrolysis promotes formation of carbon intermediates and conversion of tautomeric pyridone and hydroxypyridine into pyrrolic and pyridinic nitrogen through eliminating carbonyl and hydroxyl functionalities, respectively. Continuous thermal alkali activation introduces hydroxyl groups into carbon materials, converting pyridinic species to intermediate hydroxypyridine and pyridone; subsequently, these configurations transform to pyridinic and pyrrolic nitrogen, respectively, and finally, an excessive alkali ensures 100% conversion from pyridinic to pyrrolic nitrogen. NaOH activation for pyrrolic and pyridinic nitrogen co-doped carbon and KOH activation for model nitrogen-containing compounds including acridine, phenanthridine, and acridone further confirm that alkali activation plays an indispensable role in 100% conversion from pyridinic to pyrrolic units through the tautomeric hydroxypyridine and pyridone intermediates. Low-temperature alkali-induced controllable conversion of nitrogen configuration in carbon materials is suitable modulating nitrogen configurations for almost all nitrogen-doped carbon materials in electrochemical applications.

Crown ether decorated silicon photonics for safeguarding against lead poisoning

Lead (Pb2+) toxification is a concerning, unaddressed global public health crisis that leads to 1 million deaths annually. Yet, public policies to address this issue have fallen short. This work harnesses the unique abilities of crown ethers, which selectively bind to specific ions. This study demonstrates the synergistic integration of highly-scalable silicon photonics, with crown ether amine conjugation via Fischer esterification in an environmentally-friendly fashion. This realizes an integrated photonic platform that enables the in-operando, highly-selective and quantitative detection of various ions. The development dispels the existing notion that Fischer esterification is restricted to organic compounds, facilitating the subsequent amine conjugation for various crown ethers. The presented platform is specifically engineered for selective Pb2+ detection, demonstrating a large dynamic detection range, and applicability to field samples. The compatibility of this platform with cost-effective manufacturing indicates the potential for pervasive implementation of the integrated photonic sensor technology to safeguard against societal Pb2+ poisoning.

A novel fluorescent sensor for diammonium and metal ions based on a supramolecular charge-transfer complex of bis(aza-18-crown-6)-containing dienone

A bis(aza-18-crown-6)-containing 2,5-di(benzylidene)cyclopentanone and a bis(ammoniopropyl) derivative of 1,2-di(4-pyridyl)ethylene in MeCN were found to form a supramolecular charge-transfer complex, which can act as an "off-on" fluorescent sensor for the Ca2+ and 1,12-dodecanediammonium ions. The molecular structure of this complex in solution was studied by density functional theory calculations.

Entropy Effects in Intermolecular Associations of Crown-Ethers and Cyclodextrins with Amino Acids in Aqueous and in Non-Aqueous Media

The analysis of the ratios of entropy and enthalpy characteristics and their contributions to the change in the Gibbs energy of intermolecular interactions of crown ethers and cyclodextrins with amino acids is carried out. Two different types of macrocycles were chosen for examination: crown ethers with a hydrophilic interior and cyclodextrins with a hydrophobic inner cavity and a hydrophilic exterior. The thermodynamics of complex formation of crown ethers and cyclodextrins with amino acids in water and aqueous-organic solvents of variable composition was examined. The contributions of the entropy solvation of complexes of 18-crown-6 with glycine, alanine, phenylalanine to the change in the entropy of complexation in water-ethanol and water-dimethyl sulfoxide solvents was calculated and analyzed. It was found that the ratios of the entropy and enthalpy solvation of the reagents for these systems have similar trends when moving from water to aqueous-organic mixtures. The relationship between the thermodynamic characteristics and structural features of the complexation processes between cyclodextrins and amino acids has been established. The thermodynamic enthalpy–entropy compensation effect was revealed, and its features for complexation of cyclodextrins and 18-crown-6 were considered. It was concluded that, based on the thermodynamic parameters of molecular complexation, one could judge the mode of the formation of complexes, the main driving forces of the interactions, and the degree of desolvation.