2,3-unsubstituted chromones and their enaminone precursors as versatile reagents for the synthesis of fused pyridines

A divergent and regioselective approach to fused pyridines was developed through formal [3 + 3] cyclocondensations from simple 2,3-unsubstituted chromones or their enaminone precursors.     

Calix[4]arene N-chalconeamides: synthesis and influence on Mg2+,ATP-dependent Ca2+ accumulation in the smooth muscle subcellular structures

The cone-shaped calixarene N-chalconeamides were synthesized by the reaction of calix[4]arene carboxylic acids or acid chlorides with aminochalcones. It was found, that calixarene chalconeamides influence the Mg²⁺, ATP-dependent Ca²⁺ accumulation in mitochondria and sarcoplasmatic reticulum of the smooth muscle cells.     

First Trifluoromethylated Phenanthrolinediamides: Synthesis,Structure, Stereodynamics and Complexation with Ln(III)

The first examples of 1,10-phenanthroline-2,9-diamides bearing CF₃-groups on the side amide substituents were synthesized. Due to stereoisomerism and amide rotation, such complexes have complicated behavior in solutions. Using advanced NMR techniques and X-ray analysis, their structures were completely elucidated. The possibility of the formation of complex compounds with lanthanoids nitrates was shown, and the constants of their stability are quantified. The results obtained are explained in terms of quantum-chemical calculations.     

Chemical Variability and Pharmacological Potential of Propolis as a Source for the Development of New Pharmaceutical Products

This review aims to analyze propolis as a potential raw material for the development and manufacture of new health-promoting products. Many scientific publications were retrieved from the Scopus, PubMed, and Google Scholar databases via searching the word "propolis". The different extraction procedures, key biologically active compounds, biological properties, and therapeutic potential of propolis were analyzed. It was concluded that propolis possesses a variety of biological properties because of a very complex chemical composition that mainly depends on the plant species visited by bees and species of bees. Numerous studies found versatile pharmacological activities of propolis: antimicrobial, antifungal, antiviral, antioxidant, anticancer, anti-inflammatory, immunomodulatory, etc. In this review, the composition and biological activities of propolis are presented from a point of view of the origin and standardization of propolis for the purpose of the development of new pharmaceutical products on its base. It was revealed that some types of propolis, especially European propolis, contain flavonoids and phenolic acids, which could be markers for the standardization and quality evaluation of propolis and its preparations. One more focus of this paper was the overview of microorganisms’ sensitivity to propolis for further development of antimicrobial and antioxidant products for the treatment of various infectious diseases with an emphasis on the illnesses of the oral cavity. It was established that the antimicrobial activity of different types of propolis is quite significant, especially to Gram-negative bacteria and lipophilic viruses. The present study could be also of interest to the pharmaceutical industry as a review for the appropriate design of standardized propolis preparations such as mouthwashes, toothpastes, oral drops, sprays, creams, ointments, suppositories, tablets, and capsules, etc. Moreover, propolis could be regarded as a source for the isolation of biologically active substances. Furthermore, this review can facilitate partially overcoming the problem of the standardization of propolis preparations, which is a principal obstacle to the broader use of propolis in the pharmaceutical industry. Finally, this study could be of interest in the area of the food industry for the development of nutritionally well-balanced products. The results of this review indicate that propolis deserves to be better studied for its promising therapeutic effects from the point of view of the connection of its chemical composition with the locality of its collection, vegetation, appropriate extraction methods, and standardization.     

Natural Dietary Compounds in the Treatment of Arsenic Toxicity

Chronic exposure to arsenic (As) compounds leads to its accumulation in the body, with skin lesions and cancer being the most typical outcomes. Treating As-induced diseases continues to be challenging as there is no specific, safe, and efficacious therapeutic management. Therapeutic and preventive measures available to combat As toxicity refer to chelation therapy, antioxidant therapy, and the intake of natural dietary compounds. Although chelation therapy is the most commonly used method for detoxifying As, it has several side effects resulting in various toxicities such as hepatotoxicity, neurotoxicity, and other adverse consequences. Drugs of plant origin and natural dietary compounds show efficient and progressive relief from As-mediated toxicity without any particular side effects. These natural compounds have also been found to aid the elimination of As from the body and, therefore, can be more effective than conventional therapeutic agents in ameliorating As toxicity. This review provides an overview of the recently updated knowledge on treating As poisoning through natural dietary compounds. This updated information may serve as a basis for defining novel prophylactic and therapeutic formulations.     

Selenium: An Antioxidant with a Critical Role in Anti-Aging

Aging is characterized by an imbalance between damage inflicted by reactive oxygen species (ROS) and the antioxidative defenses of the organism. As a significant nutritional factor, the trace element selenium (Se) may remodel gradual and spontaneous physiological changes caused by oxidative stress, potentially leading to disease prevention and healthy aging. Se is involved in improving antioxidant defense, immune functions, and metabolic homeostasis. An inadequate Se status may reduce human life expectancy by accelerating the aging process or increasing vulnerability to various disorders, including immunity dysfunction, and cancer risk. This review highlights the available studies on the effective role of Se in aging mechanisms and shows the potential clinical implications related to its consumption. The main sources of organic Se and the advantages of its nanoformulations were also discussed.     

QSAR models for analgesic activity prediction of terpenes and their derivatives

Structural Chemistry - In the present study, quantitative structure-activity relationship (QSAR) models were developed to predict analgesic activity of some mono-/bicyclic terpenoids and their...     

Tetrodotoxin: History,Biology, and Synthesis

This review provides a comprehensive coverage of the history, biology and chemistry of tetrodotoxin (TTX). It traces the origin of this remarkable molecule all the way back to the ancient Chinese medicine records. The discovery of biological activity, isolation, and a brief overview of structure elucidation are summarized. Next, the biology of TTX is discussed, primarily in the context of its activity in the sodium channels, its anesthetic properties, and its potential use in cancer treatment or drug addiction. Biosynthesis of TTX is covered before the discussion of the total syntheses. All total, formal or partial syntheses are covered but those total syntheses that have been discussed in previous reviews are only briefly summarized. Finally, the synthesis of natural and unnatural derivatives is surveyed, and a conclusion and outlook are provided for this very extensive field of endeavor. To the best of our knowledge the literature coverage is complete up to December 2018.     

Terpenoid Hydrazones as Biomembrane Penetration Enhancers: FT-IR Spectroscopy and Fluorescence Probe Studies

Hydrazones based on mono- and bicyclic terpenoids (verbenone, menthone and carvone) have been investigated in vitro as potential biomembrane penetration enhancers. In this regard, liposomes composed of lecithin or cardiolipin as phospholipid phase components with incorporated fluorescence probes have been prepared using the thin-film ultrasonic dispersion method. The mean particle size of the obtained liposomes, established using laser diffraction, was found to be 583 ± 0.95 nm, allowing us to categorize them as multilamellar vesicles (MLVs) according to their morphology. Pursuant to fluorescence analysis, we may assume a reduction in microviscosity and, consequently, a decrease in the packing density of lecithin and cardiolipin lipids to be the major mechanism of action for terpenoid hydrazones 1–15. In order to determine the molecular organization of the lipid matrix, lipids were isolated from rat strata cornea (SCs) and their interaction with tested compounds was studied by means of Fourier transform infrared spectroscopy. FT-IR examination suggested that these hydrazones fluidized the SC lipids via the disruption of the hydrogen-bonded network formed by polar groups of SC constituents. The relationship between the structure of terpenoid hydrazones and their ability to enhance biomembrane penetration is discussed.     

Γ-flatness and Bishop–Phelps–Bollobás type theorems for operators

The Bishop–Phelps–Bollobás property deals with simultaneous approximation of an operator T and a vector x at which T nearly attains its norm by an operator $T_0$ and a vector $x_0$, respectively, such that $T_0$ attains its norm at $x_0$. In this note we extend the already known results about the Bishop–Phelps–Bollobás property for Asplund operators to a wider class of Banach spaces and to a wider class of operators. Instead of proving a BPB-type theorem for each space separately we isolate two main notions: Γ-flat operators and Banach spaces with ${\mathrm{ACK}}_{\rho }$ structure. In particular, we prove a general BPB-type theorem for Γ-flat operators acting to a space with ${\mathrm{ACK}}_{\rho }$ structure and show that uniform algebras and spaces with the property β have ${\mathrm{ACK}}_{\rho }$ structure. We also study the stability of the ${\mathrm{ACK}}_{\rho }$ structure under some natural Banach space theory operations. As a consequence, we discover many new examples of spaces Y such that the Bishop–Phelps–Bollobás property for Asplund operators is valid for all pairs of the form ($X,Y$).