Rafael Dolezal

Tacrine–Trolox Hybrids: A Novel Class of Centrally Active, Nonhepatotoxic Multi-Target-Directed Ligands Exerting Anticholinesterase and Antioxidant Activities with Low In Vivo Toxicity

Coupling of two distinct pharmacophores, tacrine and trolox, endowed with different biological properties, afforded 21 hybrid compounds as novel multifunctional candidates against Alzheimers disease. Several of them showed improved inhibitory properties toward acetylcholinesterase (AChE) in relation to tacrine. These hybrids also scavenged free radicals. Molecular modeling studies in tandem with kinetic analysis exhibited that these hybrids target both catalytic active site as well as peripheral anionic site of AChE. In addition, incorporation of the moiety bearing antioxidant abilities displayed negligible toxicity on human hepatic cells. This striking effect was explained by formation of nontoxic metabolites after 1 h incubation in human liver microsomes system. Finally, tacrine-trolox hybrids exhibited low in vivo toxicity after im administration in rats and potential to penetrate across blood-brain barrier. All of these outstanding in vitro results in combination with promising in vivo outcomes highlighted derivative 7u as the lead structure worthy of further investigation.

7-MEOTA–donepezil like compounds as cholinesterase inhibitors: Synthesis, pharmacological evaluation, molecular modeling and QSAR studies

A novel series of 7-methoxytacrine (7-MEOTA)-donepezil like compounds was synthesized and tested for their ability to inhibit electric eel acetylcholinesterase (EeAChE), human recombinant AChE (hAChE), equine serum butyrylcholinesterase (eqBChE) and human plasmatic BChE (hBChE). New hybrids consist of a 7-MEOTA unit, representing less toxic tacrine (THA) derivative, connected with analogues of N-benzylpiperazine moieties mimicking N-benzylpiperidine fragment from donepezil. 7-MEOTA-donepezil like compounds exerted mostly non-selective profile in inhibiting cholinesterases of different origin with IC50 ranging from micromolar to sub-micromolar concentration scale. Kinetic analysis confirmed mixed-type inhibition presuming that these inhibitors are capable to simultaneously bind peripheral anionic site (PAS) as well as catalytic anionic site (CAS) of AChE. Molecular modeling studies and QSAR studies were performed to rationalize studies from in vitro. Overall, 7-MEOTA-donepezil like derivatives can be considered as interesting candidates for Alzheimers disease treatment.

7-Methoxytacrine-p-Anisidine Hybrids as Novel Dual Binding Site Acetylcholinesterase Inhibitors for Alzheimer’s Disease Treatment

Alzheimer’s disease (AD) is a debilitating progressive neurodegenerative disorder that ultimately leads to the patient’s death. Despite the fact that novel pharmacological approaches endeavoring to block the neurodegenerative process are still emerging, none of them have reached use in clinical practice yet. Thus, palliative treatment represented by acetylcholinesterase inhibitors (AChEIs) and memantine are still the only therapeutics used. Following the multi-target directed ligands (MTDLs) strategy, herein we describe the synthesis, biological evaluation and docking studies for novel 7-methoxytacrine-p-anisidine hybrids designed to purposely target both cholinesterases and the amyloid cascade. Indeed, the novel derivatives proved to be effective non-specific cholinesterase inhibitors showing non-competitive AChE inhibition patterns. This compounds’ behavior was confirmed in the subsequent molecular modeling studies.

Multitarget Tacrine Hybrids with Neuroprotective Properties to Confront Alzheimer’s Disease

Alzheimers disease (AD) is a multifactorial neurodegenerative disorder. Several hallmarks such as β-amyloid (Aβ) aggregation underlying amyloid plaque formation, τ-hyperphosphorylation leading to production of neurofibrillary tangles, and decline in the number of cholinergic neurons appear to be fundamental in the pathophysiology of the disease. Other evidence points also to the involvement of oxidative stress, biometal dyshomeostasis, inflammation, and cell cycle regulatory failure. Taking into account such premises, many attractive targets for the development of anti-AD drugs have emerged. Specifically, the multifactorial nature of AD calls for multi-target-directed ligands (MTDLs) which can be beneficial by providing interactions with multiple targets. Tacrine (THA), the first clinically effective acetylcholinesterase inhibitor, was approved for the treatment of mild to moderate AD. Unfortunately, frequent adverse effects including peripheral cholinergic effects and hepatotoxicity limited its therapeutic potential. Based on the numerous biological systems involved in AD progression, this review covers THA-incorporated hybrids possessing a neuroprotective profile. In particular, it focuses on THA hybrids capable of scavenging reactive oxygen species (ROS), and derivatives which reduce the formation of Aβ-plaques either directly by confronting the Aβ1-42 selfaggregation process or indirectly by inhibiting the BACE-1 enzyme or AChE-induced Aβ1-40 aggregation. Particular interest is also addressed to THA hybrids with suppressed hepatotoxicity.

Design, synthesis and in vitro testing of 7-methoxytacrine-amantadine analogues: a novel cholinesterase inhibitors for the treatment of Alzheimer’s disease

Abstract A series of cholinesterase inhibitors acting as dual binding site heterodimers for the management of Alzheimer’s disease were developed. The series of 7-methoxytacrine (7-MEOTA)-amantadine ureas (11–17) was designed, prepared evaluated in vitro towards human acetyl/butyryl cholinesterase (hAChE, hBChE) and compared with the series of 7-MEOTA-amantadine thioureas (4–10). The heterodimers have different length of linkers combining 7-MEOTA and amantadine moieties. In comparison with 7-MEOTA, the newly synthesized compounds were better inhibitors of both cholinesterases. The urea analogues did not have the anticipated benefit of increased inhibitory activity and have comparable IC50 values with thiourea derivatives.

Ligand-based 3D QSAR analysis of reactivation potency of mono- and bis-pyridinium aldoximes toward VX-inhibited rat acetylcholinesterase

To predict unknown reactivation potencies of 12 mono- and bis-pyridinium aldoximes for VX-inhibited rat acetylcholinesterase (rAChE), three-dimensional quantitative structure-activity relationship (3D QSAR) analysis has been carried out. Utilizing molecular interaction fields (MIFs) calculated by molecular mechanical (MMFF94) and quantum chemical (B3LYP/6-31G*) methods, two satisfactory ligand-based CoMFA models have been developed: 1. R(2)=0.9989, Q(LOO)(2)=0.9090, Q(LTO)(2)=0.8921, Q(LMO(20%))(2)=0.8853, R(ext)(2)=0.9259, SDEP(ext)=6.8938; 2. R(2)=0.9962, Q(LOO)(2)=0.9368, Q(LTO)(2)=0.9298, Q(LMO(20%))(2)=0.9248, R(ext)(2)=0.8905, SDEP(ext)=6.6756. High statistical significance of the 3D QSAR models has been achieved through the application of several data noise reduction techniques (i.e. smart region definition SRD, fractional factor design FFD, uninformative/iterative variable elimination UVE/IVE) on the original MIFs. Besides the ligand-based CoMFA models, an alignment molecular set constructed by flexible molecular docking has been also studied. The contour maps as well as the predicted reactivation potencies resulting from 3D QSAR analyses help better understand which structural features are associated with increased reactivation potency of studied compounds.

6-Hydroxyquinolinium salts differing in the length of alkyl side-chain: Synthesis and antimicrobial activity

Quaternary ammonium salts substituted with a long alkyl chain exemplify a trustworthy group of medicinal compounds frequently employed as antifungal and antibacterial agents. A great asset of these surfactants underlying their widespread use is low local and system toxicity in humans. In this Letter, a series of novel quaternary 6-hydroxyquinolinium salts with varying length of N-alkyl chain (from C10 to C18) was synthesized and tested for in vitro activity against pathogenic bacterial and fungal strains. 6-Hydroxyquinolinium salt with C12 alkyl chain seems to be very interesting candidate due to a high antimicrobial efficacy and cytotoxic safety.

HPC Cloud Technologies for Virtual Screening in Drug Discovery

Increasing development in computer technologies, storage capabilities, networking, and multithreading as well as accelerated progression of computational chemistry methods in past decades have allowed performing advanced virtual screening (VS) methods to assist drug discovery. By employing virtualized computer resources and suitable middleware it is possible to support growing computer demands of VS with flexible cloud services adapted for High Performance Computing (HPC). This paper resumes the possibilities of cloud services for VS applications in drug discovery and shows possible track to move VS computing software to cloud environment.

Parallel Flexible Molecular Docking in Computational Chemistry on High Performance Computing Clusters

The main objective in pharmaceutical research is development of novel drugs with improved biological effect in specifically afflicted organisms. A common practice in drug design focuses on systematic organic derivatization of chemical structures exhibiting certain biological activity and subsequent biological in vitro evaluation of the resulted benefits. However, this classical approach can be more or less classified as a chance drug discovery, being very arduous, expensive and time consuming. Nowadays, a lot of enthusiasm is given to rationally oriented drug research techniques like computer-aided drug design, virtual screening, bioinformatics, chemometrics, quantitative structure-activity relationships, etc. In the present article, we deal with designing a high performance computing (HPC) support for flexible molecular docking (FMD) which can be beneficially utilized in structure-based virtual screening (SBVS). The principles of FMD are briefly introduced and a solution combining message passing interface (MPI) with multithreading is proposed. The merits (e.g. availability, scalability, performance) of MPI-HPC enhanced SBVS/FMD are compared with other HPC techniques utilized for novel lead structures discovery in medicinal chemistry.

Novel Tacrine-Scutellarin Hybrids as Multipotent Anti-Alzheimer’s Agents: Design, Synthesis and Biological Evaluation

A novel series of 6-chlorotacrine-scutellarin hybrids was designed, synthesized and the biological activity as potential anti-Alzheimer’s agents was assessed. Their inhibitory activity towards human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBChE), antioxidant activity, ability to cross the blood-brain barrier (BBB) and hepatotoxic profile were evaluated in vitro. Among these compounds, hybrid K1383, bearing two methylene tether between two basic scaffolds, was found to be very potent hAChE inhibitor (IC50 = 1.63 nM). Unfortunately, none of the hybrids displayed any antioxidant activity (EC50 ≥ 500 μM). Preliminary data also suggests a comparable hepatotoxic profile with 6-Cl-THA (established on a HepG2 cell line). Kinetic studies performed on hAChE with the most active compound in the study, K1383, pointed out to a mixed, non-competitive enzyme inhibition. These findings were further corroborated by docking studies.