Drug likeness prediction of 5-hydroxy-substituted coumarins with high affinity to 5-HT1A and 5-HT2A receptors

Advances in drug design and therapeutic potential of selective or multitarget 5-HT1A receptor ligands

5-HT1A receptor (5-HT1A-R) is a serotoninergic G-protein coupled receptor subtype which contributes to several physiological processes in both central nervous system and periphery. Despite being the first 5-HT-R identified, cloned and studied, it still represents a very attractive target in drug discovery and continues to be the focus of a myriad of drug discovery campaigns due to its involvement in numerous neuropsychiatric disorders. The structure-activity relationship studies (SAR) performed over the last years have been devoted to three main goals: (i) design and synthesis of 5-HT1A-R selective/preferential ligands; (ii) identification of 5-HT1A-R biased agonists, differentiating pre- versus post-synaptic agonism and signaling cellular mechanisms; (iii) development of multitarget compounds endowed with well-defined poly-pharmacological profiles targeting 5-HT1A-R along with other serotonin receptors, serotonin transporter (SERT), D2-like receptors and/or enzymes, such as acetylcholinesterase and phosphodiesterase, as a promising strategy for the management of complex psychiatric and neurodegenerative disorders. In this review, medicinal chemistry aspects of ligands acting as selective/preferential or multitarget 5-HT1A-R agonists and antagonists belonging to different chemotypes and developed in the last 7 years (2017-2023) have been discussed. The development of chemical and pharmacological 5-HT1A-R tools for molecular imaging have also been described. Finally, the pharmacological interest of 5-HT1A-R and the therapeutic potential of ligands targeting this receptor have been considered.

New Piperazine Derivatives of 6-Acetyl-7-hydroxy-4-methylcoumarin as 5-HT1A Receptor Agents

A series of 15 new derivatives of 6-acetyl-7-hydroxy-4-methylcoumarin containing a piperazine group were designed with the help of computational methods and were synthesized to study their affinity for the serotonin 5-HT_1A and 5-HT_2A receptors. Among them, 6-acetyl-7-{4-[4-(3-bromophenyl)piperazin-1-yl]butoxy}-4-methylchromen-2-one (4) and 6-acetyl-7-{4-[4-(2-chlorophenyl)piperazin-1-yl]butoxy}-4-methylchromen-2-one (7) exhibited excellent activity for 5-HT_1A receptors with Ki values 0.78 (0.4-1.4) nM and 0.57 (0.2-1.3) nM, respectively, comparable to the Ki values of 8-OH-DPAT (0.25 (0.097-0.66) nM). The equilibrium dissociation constant values of the tested compounds showed differential intrinsic activities of the agonist and antagonist modes.

Deposition of pentamidine analogues in the human body - spectroscopic and computational approaches

Bis-benzamidines are a diverse group of compounds with high potential in pharmacotherapy, and among them, pentamidine is a drug of great therapeutic significance in Pneumocystis jiroveci pneumonia (PJP) prophylaxis and therapy. Pharmacokinetic properties of these cationic species such as transport, acid/base equilibria, and interactions with potential target molecules are still of interest, especially for recently designed compounds. To broaden our knowledge drug-likeness, human serum albumin binding, and acidity constants (K_a) were experimentally and theoretically examined for five pentamidine analogues 1 - 5 with -NH-CO-chain-CO-NH-bridges of increasing length and O, N, and S atoms in the chain. The studied analogues display very marked activity against Pneumocystis carinii without cytotoxicity that inspired us to perform an in silico analysis of their mode of action based on the hypothesis that the small DNA groove of rich in adenine-thymine pairs is their molecular target. These studies allowed us to classify them as very promising lead molecules.

Design, Synthesis, and Biological Evaluation of a Series of 5- and 7-Hydroxycoumarin Derivatives as 5-HT1A Serotonin Receptor Antagonists

We have designed and synthesized a series of 60 new 5- and 7-hydroxycoumarin derivatives bearing the piperazine moiety with the expected binding to 5-HT_1A and 5-HT_2A receptors. Molecular docking of all investigated compounds revealed subnanomolar estimates of 5-HT_1AR K_i for three ligands and 5-HT_2AR Ki for one ligand as well as numerous low nanomolar estimates of K_i for both receptors. Intrigued by these results we synthesized all 60 new derivatives using microwave-assisted protocols. We show that three new compounds show a relatively high antagonistic activity against the 5HT_1A receptor, although lower than the reference compound WAY-100635. These compounds also showed relatively low binding affinities to the 5-HT_2A receptor. We also provide a detailed structure-activity analysis of this series of compounds and compare it with previously obtained results for an exhaustive series of coumarin derivatives.

Coumarin-piperazine derivatives as biologically active compounds

A number of psychiatric disorders, including anxiety, schizophrenia, Parkinson's disease, depression and others CNS diseases are known to induce defects in the function of neural pathways sustained by the neurotransmitters, like dopamine and serotonin. N-arylpiperazine moiety is important for CNS-activity, particularly for serotonergic and dopaminergic activity. In the scientific literature there are many examples of coumarin-piperazine derivatives, particularly with arylpiperazines linked to a coumarin system via an alkyl liner, which can modulate serotonin, dopamine and adrenergic receptors. Numerous studies have revealed that the inclusion of a piperazine moiety could occasionally provide unexpected improvements in the bioactivity of various biologically active compounds. The piperazine analogs have been shown to have a potent antimicrobial activity and they can also act as BACE-1 inhibitors. On the other hand, arylpiperazines linked to coumarin derivatives have been shown to have antiproliferative activity against leukemia, lung, colon, breast, and prostate tumors. Recently, it has been reported that coumarin-piperazine derivatives exhibit a Fneuroprotective effect by their antioxidant and anti-inflammatory activities and they also show activity as acetylcholinesterase inhibitors and antifilarial activity. In this work we provide a summary of the latest advances in coumarin-related chemistry relevant for biological activity.

Evaluation of blood-brain barrier penetration and examination of binding to human serum albumin of 7-O-arylpiperazinylcoumarins as potential antipsychotic agents

The delivery of drugs to the brain is complicated by the multiple factors including low blood-brain barrier (BBB) passive permeability, active BBB efflux systems, and plasma protein binding. Thus, a detailed understanding of the transport of the new potent substances through the membranes is vitally important and their physico-chemical characteristics should be analyzed at first. This work presents an evaluation of drug likeness of eight 7-O-arylpiperazinylcoumarin derivatives with high affinity towards serotoninergic receptors 5-HT_1A and 5-HT_2A with particular analysis of the requirements for the CNS chemotherapeutics. The binding constants to human serum albumin (HSA) were determined at physiological pH using fluorescence spectroscopy, and then their mode of action was explained by analysis of theoretical HSA complexes. Dynamic simulation of systems allowed for reliable evaluation of the interaction strength. The analyzed coumarins were able to pass BBB, and they present good drug likeness properties. They showed high affinities to HSA (log K_Q = 5.3-6.0 which corresponds to -8.12 to -7.15 kcalmol^-1 of Gibbs free energy). The changes of the emission intensity upon binding to HSA were scrutinized showing the different mode of action for 4-phenylpiperazinylcoumarins. The values of computed Gibbs free energy and determined on the basis of experimentally obtained binding constants log K_Q coincide suggesting a good quality of the theoretical model. Overall the 8-acetyl-7-O-arylpiperazinyl-4-methylcoumarin derivatives represent valuable lead compounds to be further tested in various preclinical assays as a possible chemotherapeutics against CNS diseases. Studied coumarins can be metabolized by cytochrome P450 to aldehydes and hydroxy derivatives. The existence of other binding sites inside HSA than Sudlow's site 1 was postulated. The longer aliphatic linker between coumarin and piperazine moieties favored binding to HSA in other than Sudlow site 1 pocket.