Kata Mlinarić-Majerski

We prepared a so far unknown class of hexaaza crown ethers substituted with six adamantyl side-arms and used them for extraction of alkali metal cations from an aqueous medium. These host molecules were designed to take advantage of intramolecular Lo...

The adamantane derived diaza-crown ether ZG613 was assessed as a potential breast cancer cells and breast epithelial to mesenchymal transition (EMT)-model cells targeting agent. We postulated that ZG613 activity relies on its plasma/mitochondria membrane disruption ability based on adamantane hydrophobicity and/or crown ether related ionophoric properties. We performed molecular dynamics (MD) simulations and next generation sequencing, followed by in vitro study of cell death, membrane perturbations and ionophoric ability, as well as in vivo study of effects on the tumour growth. MD simulation and RNA sequencing pointed toward physical disruption of plasma membrane by ZG613, corroborated by measured increase in membrane permeability leading to cell death. Measurements of ion fluxes confirmed ZG613 inability to transport Na ⁺ and K ⁺ , as predicted by MD simulation. EMT-model cells exhibit changes in mitochondrial morphology and ATP levels, successfully targeted by ZG613. ZG613 caused mild retardation of tumour growth in vivo. In conclusion, ZG613 kills breast cancer cells and breast EMT-model cells by physical disruption of plasma membrane and impairments of mitochondrial functions. Breast EMT cells represent good potential targets within the breast tumour, due to their plasma membrane and mitochondrial instability.

In this report, we extend the SAR analysis of a number of lipophilic guanylhydrazone analogues with respect to in vitro growth inhibition of Trypanosoma brucei and Trypanosoma cruzi. Sleeping sickness and Chagas disease, caused by the tropical parasites T. brucei and T. cruzi, constitute a significant socioeconomic burden in low-income countries of sub-Saharan Africa and Latin America, respectively. Drug development is under-funded. Moreover, current treatments are outdated and difficult to administer, while drug resistance is an emerging concern. The synthesis of adamantane-based compounds that have potential as antitrypanosomal agents, is extensively reviewed. The critical role of the adamantane ring was further investigated by synthesizing and testing a number of novel lipophilic guanylhydrazones. Introduction of hydrophobic bulky substituents onto the adamantane ring generated the most active analogues, illustrating the synergistic effect of the lipophilic character of the C1 side chain and guanylhydrazone moiety on trypanocidal activity. The n-decyl C1-substituted compound G8 (R = C₁₀H₂₁) proved to be the most potent adamantane derivative against T. brucei with activity in nanomolar range (EC₅₀=90 nM). Molecular simulations were also performed as an effort to understand the structure-activity relationships between the studied guanylhydrazone analogues and their suggested enzyme target.

In this study, three groups of adamantylphthalimides, bearing different substituents at the phthalimide moiety, N‐(4′‐R²)phthalimidoadamantanes (1–7), 3‐[N‐(4′‐R²)phthalimido]‐1‐adamantanols (8–10), and 3‐[N‐(4′‐R²)phthalimido]adamantane‐1‐carboxylic acids (11–15), were synthesized and screened against tumor cells and viruses. The most potent compounds are not substituted at the adamantane and bear an OH or NH₂ substituent at the phthalimide (compounds 3 and 5). The antiproliferative activities of compounds 3 and 5 are in the micromolar range, much higher than the one of thalidomide. A minor antiviral activity against cytomegalovirus and varicella‐zoster virus was found for compounds 3 and 5, but these compounds lacked selectivity. The results presented are important for the rational design of the next‐generation compounds with anticancer and antiviral activities.

A series of tetrapeptides and pentapeptides was synthesized bearing a phthalimide chromophore at the N-terminus. The C-terminus of the peptides was strategically substituted with an amino acid, Phe, Phe(OMe) or Phe(OMe)2 characterized by different oxidation potential. The photochemical reactivity of the peptides was investigated by preparative irradiations and isolation of photoproducts, as well as with laser flash photolysis. Upon photoexcitation, the peptides undergo photoinduced electron transfer (PET) and decarboxylation, followed by diastereoselective cyclization with the retention of configuration for tetrapeptides, or inversion of configuration for pentapeptides. Molecular dynamics (MD) simulations and NOE experiments enabled assignment of the stereochemistry of the cyclic peptides. MD simulations of the linear peptides disclosed conformational reasons for the observed diastereoselectivity, being due to the peptide backbone spatial orientation imposed by the Phe amino acids. The photochemical efficiency for the decarboxylation and cyclization is not dependant on the peptide length, but it depends on the oxidation potential of the amino acid at the C-terminus. The results described herein are particularly important for the rational design of efficient photochemical reactions for the preparation of cyclic peptides with the desired selectivity.

A prodrug is encapsulated in CB[7] and is photochemically transformed into an active drug inside this supramolecular complex.

The photochemical reactivity of 2‐hydroxymethylphenol (1) was investigated experimentally by photochemistry under cryogenic conditions, by detecting reactive intermediates by IR spectroscopy, and by using nanosecond and femtosecond transient absorption spectroscopic methods in solution at room temperature. In addition, theoretical studies were performed to facilitate the interpretation of the experimental results and also to simulate the reaction pathway to obtain a better understanding of the reaction mechanism. The main finding of this work is that photodehydration of 1 takes place in an ultrafast adiabatic photochemical reaction without any clear intermediate, delivering quinone methide (QM) in the excited state. Upon photoexcitation to a higher vibrational level of the singlet excited state, 1 undergoes vibrational relaxation leading to two photochemical pathways, one by which synchronous elimination of H₂O gives QM 2 in its S₁ state and the other by which homolytic cleavage of the phenolic O−H bond produces a phenoxyl radical (S₀). Both are ultrafast processes that occur within a picosecond. The excited state of QM 2 (S₁) probably deactivates to S₀ through a conical intersection to give QM 2 (S₀), which subsequently delivers benzoxete 4. Elucidation of the reaction mechanisms for the photodehydration of phenols by which QMs are formed is important to tune the reactivity of QMs with DNA and proteins for the potential application of QMs in medicine as therapeutic agents.

Anthrols 2–7 were synthesized and their photochemical reactivity investigated by irradiations in aq CH₃OH. Upon excitation with visible light (λ > 400 nm) in methanolic solutions, they undergo photodehydration or photodeamination and deliver methyl ethers, most probably via quinone methides (QMs), with methanolysis quantum efficiencies Φ_R = 0.02–0.3. Photophysical properties of 2–7 were determined by steady-state fluorescence and time-correlated single photon counting. Generally, anthrols 2–7 are highly fluorescent in aprotic solvents (Φ_F = 0.5–0.9), whereas in aqueous solutions the fluorescence is quenched due to excited-state proton transfer (ESPT) to solvent. The exception is amine 4 that undergoes excited-state intramolecular proton transfer (ESIPT) in neat CH₃CN where photodeamination is probably coupled to ESIPT. Photodehydration may take place via ESIPT (or ESPT) that is coupled to dehydration or via a hitherto undisclosed pathway that involves photoionization and deprotonation of radical cation, followed by homolytic cleavage of the alcohol OH group from the phenoxyl radical. QMs were detected by laser flash photolysis and their reactivity with nucleophiles investigated. Biological investigation of 2–5 on human cancer cell lines showed enhancement of antiproliferative effect upon exposure of cells to irradiation by visible light, probably due to formation of electrophilic species such as QMs.