Towards Antibacterial Agents: Synthesis and Biological Activity of Multivalent Amide Derivatives of Thiacalix[4]arene with Hydroxyl and Amine Groups.

Antimicrobial resistance to modern antibiotics stimulates the search for new ways to synthesize and modify antimicrobial drugs. The development of synthetic approaches that can easily change different fragments of the molecule is a promising solution to this problem. In this work, a synthetic approach was developed to obtain multivalent thiacalix[4]arene derivatives containing different number of amine and hydroxyl groups. A series of macrocyclic compounds in cone, partial cone, and 1,3-alternate stereoisomeric forms containing -NHCH2CH2R (R = NH2, N(CH3)2, and OH) and -N(CH2CH2OH)2 terminal fragments, and their model non-macrocyclic analogues were obtained. The antibacterial activity against Gram-positive (Staphylococcus aureus, Bacillus cereus, and Enterococcus faecalis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains and cytotoxicity of the obtained compounds were studied. Structure-activity relationships were established: (1) the macrocyclic compounds had high antibacterial activity, while the monomeric compounds had low activity; (2) the compounds in cone and partial cone conformations had better antibacterial activity compared to the compounds in 1,3-alternate stereoisomeric form; (3) the macrocyclic compounds containing -NHCH2CH2N(CH3)2 terminal fragments had the highest antibacterial activity; (4) introduction of additional terminal hydroxyl groups led to a significant decrease in antibacterial activity; (5) the compounds in partial cone conformation had significant bactericidal activity against all studied cell strains; the best selectivity was observed for the compounds in cone conformation. The mechanism of antibacterial activity of lead compounds with terminal fragments -NHCH2CH2N(CH3)2 was proved using model negatively charged POPG vesicles, i.e., the addition of these compounds led to an increase in the size and zeta potential of the vesicles. The obtained results open up the possibility of using the synthesized macrocyclic compounds as promising antibacterial agents.

Towards potential antifungal agents: synthesis, supramolecular self-assembly and in vitro activity of azole mono-, sesqui- and diterpenoids.

Terpenes and their derivatives are natural antifungal and antimicrobial agents. In this paper, potential antifungal agents were developed on the basis of farnesol, geraniol, myrtenol, perillyl alcohol, cedrol and phytol. The synthesized compounds exist in aqueous solutions as stable associates (D = 142-216 nm, PDI 0.04-0.16, Z = +0.9-+46 mV). Formation of stable associates of the compounds in solution promotes compaction and dosed release of the drug. The membranotropic activity of the compounds was also investigated to open up their possible application in the treatment of skin diseases. The relationship between membranotropism and lipophilicity coefficient (log P) has been established. The antifungal and antimicrobial activities of the obtained compounds were studied in vitro on the clinical isolate of Candida sp., Candida albicans, yeast Saccharomyces cerevisiae, Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus, Bifidobacterium bifidum) bacteria. Candida sp. (0.0781 mg mL-1) and Saccharomyces cerevisiae (0.0049 mg mL-1) showed the highest sensitivity to the agents.

Fluorescein-Labeled Thiacalix[4]arenes as Potential Theranostic Molecules: Synthesis, Self-Association, and Antitumor Activity.

In this paper, a series of thiacalix[4]arenes were synthesized as potential theranostic molecules for antitumor therapy. We propose an original strategy for the regioselective functionalization of thiacalix[4]arene with a fluorescent label to obtain antiangiogenic agent mimetics. The aggregation properties of the synthesized compounds were determined using the dynamic light scattering. The average hydrodynamic diameter of self-associates formed by the macrocycles in 1,3-alternate conformation is larger (277-323 nm) than that of the similar macrocycle in cone conformation (185-262 nm). The cytotoxic action mechanism of the obtained compounds and their ability to penetrate into of human lung adenocarcinoma and human duodenal adenocarcinoma cells were established using the MTT-test and flow cytometry. Thiacalix[4]arenes in 1,3-alternate conformation did not have a strong toxic effect. The toxicity of macrocycles in cone conformations on HuTu-80 and A549 cells (IC50 = 21.83-49.11 µg/mL) is shown. The resulting macrocycles are potential theranostic molecules that combine both the pharmacophore fragment for neoplasmas treatment and the fluorescent fragment for monitoring the delivery and biodistribution of nanomedicines.

Supramolecular Amphiphiles Based on Pillar[5]arene and Meroterpenoids: Synthesis, Self-Association and Interaction with Floxuridine.

In recent years, meroterpenoids have found wide biomedical application due to their synthetic availability, low toxicity, and biocompatibility. However, these compounds are not used in targeted drug delivery systems due to their high affinity for cell membranes, both healthy and in cancer cells. Using the approach of creating supramolecular amphiphiles, we have developed self-assembling systems based on water-soluble pillar[5]arene and synthetic meroterpenoids containing geraniol, myrtenol, farnesol, and phytol fragments. The resulting systems can be used as universal drug delivery systems. It was shown by turbidimetry that the obtained pillar[5]arene/synthetic meroterpenoid systems do not interact with the model cell membrane at pH = 7.4, but the associates are destroyed at pH = 4.1. In this case, the synthetic meroterpenoid is incorporated into the lipid bilayer of the model membrane. The characteristics of supramolecular self-assembly, association constants and stoichiometry of the most stable pillar[5]arene/synthetic meroterpenoid complexes were established by UV-vis spectroscopy and dynamic light scattering (DLS). It was shown that supramolecular amphiphiles based on pillar[5]arene/synthetic meroterpenoid systems form monodisperse associates in a wide range of concentrations. The inclusion of the antitumor drug 5-fluoro-2'-deoxyuridine (floxuridine) into the structure of the supramolecular associate was demonstrated by DLS, 19F, 2D DOSY NMR spectroscopy.

Progress in the Chemistry of Macrocyclic Meroterpenoids.

In the last decade, the chemistry of meroterpenoids-conjugated molecules formed from isoprenyl fragments through biosynthetic pathways-has developed rapidly. The class includes some natural metabolites and fully synthetic fragments formed through nonbiological synthesis. In the field of synthetic receptors, a range of structures can be achieved by combining fragments of different classes of organic compounds into one hybrid macrocyclic platform which retains the properties of these fragments. This review discusses the successes in the synthesis and practical application of both natural and synthetic macrocycles. Among the natural macrocyclic meroterpenoids, special attention is paid to isoprenylated flavonoids and phenols, isoprenoid lipids, prenylated amino acids and alkaloids, and isoprenylpolyketides. Among the synthetic macrocyclic meroterpenoids obtained by combining the "classical" macrocyclic platforms, those based on cyclodextrins, together with meta- and paracyclophanes incorporating terpenoid fragments, and meroterpenoids obtained by macrocyclization of several terpene derivatives are considered. In addition, issues related to biomedical activity, processes of self-association and aggregation, and the formation of host-guest complexes of various classes of macrocyclic merotenoids are discussed in detail.