Optically active iodohelicene derivatives exhibit histamine N-methyl transferase inhibitory activity

Chiral helical scaffolds: Unlocking their potential in biomolecular interactions and biomedical applications

In nature, various molecules possess spiral geometry. Such helical structures are even prevalent within the human body, represented classically by DNA and three-dimensional (secondary structure) protein folding. In this review, we chose helicenes and helicene-like structures -synthetically accessible carbon-rich molecules- as a compelling example of helically chiral scaffolds. Helicene chemistry, traditionally anchored in materials science, has been a subject of increasing interest in the biomedical field due to the unique optical and chiral properties of these helical structures. This review explores the diverse applications of helicenes in biomedicine, focusing on their role in cell imaging, protective coatings for implants, drug delivery systems, biosensors, and drug discovery. We discuss the unique properties of helicenes and helicene-like structures, highlighting their ability to form complex interactions with various biomolecules and their potential in the development of candidates for therapeutic agents. Recent advances in helicene derivatives with enhanced circularly polarized luminescence and other photochemical properties are also reviewed, underlining their utility in precise bio-imaging and diagnostic techniques. The review consolidates the current literature and emphasizes the growing importance of helicenes in bridging chemistry, materials science, and biology for innovative technological and biomedical applications.

Hexahelicene DNA-binding: Minor groove selectivity, semi-intercalation and chiral recognition

In this contribution, we focused on a fundamental study targeting the interaction of water-soluble [6]helicene derivative 1 (1-butyl-3-(2-methyl[6]helicenyl)-imidazolium bromide) with double-stranded (ds) DNA. A synthetic 30-base pair duplex, plasmid, chromosomal calf thymus and salmon DNA were investigated using electrochemistry, electrophoresis and spectroscopic tools supported by molecular dynamics (MD) and quantum mechanical approaches. Both experimental and theoretical work revealed the minor groove binding of 1 to the dsDNA. Both the positively charged imidazole ring and hydrophobic part of the side chain contributed to the accommodation of 1 into the dsDNA structure. Neither intercalation into the duplex DNA nor the stable binding of 1 to single-stranded DNA were found in topoisomerase relaxation experiments with structural components of 1, i.e. [6]helicene (2) and 1-butyl-3-methylimidazolium bromide (3), nor by theoretical calculations. Finally, the binding of optically pure enantiomers (P)-1 and (M)-1 was studied using circular dichroism spectroscopy, isothermal titration calorimetry and UV Resonance Raman (UVRR) methods. Using MD and quantum mechanical methods, minor groove and semi-intercalation were proposed for compound 1 as the predominant binding modes. From the UVRR findings, we also can conclude that 1 tends to preferentially interact with adenine and guanine residues in the structure of dsDNA.

Inhibition of Astrocytic Histamine N-Methyltransferase as a Possible Target for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) represents the principal cause of dementia among the elderly. Great efforts have been established to understand the physiopathology of AD. Changes in neurotransmitter systems in patients with AD, including cholinergic, GABAergic, serotoninergic, noradrenergic, and histaminergic changes have been reported. Interestingly, changes in the histaminergic system have been related to cognitive impairment in AD patients. The principal pathological changes in the brains of AD patients, related to the histaminergic system, are neurofibrillary degeneration of the tuberomammillary nucleus, the main source of histamine in the brain, low histamine levels, and altered signaling of its receptors. The increase of histamine levels can be achieved by inhibiting its degrading enzyme, histamine N-methyltransferase (HNMT), a cytoplasmatic enzyme located in astrocytes. Thus, increasing histamine levels could be employed in AD patients as co-therapy due to their effects on cognitive functions, neuroplasticity, neuronal survival, neurogenesis, and the degradation of amyloid beta (Aβ) peptides. In this sense, the evaluation of the impact of HNMT inhibitors on animal models of AD would be interesting, consequently highlighting its relevance.