N-Substituted piperidine-3-carbohydrazide-hydrazones against Alzheimer's disease: Synthesis and evaluation of cholinesterase, beta-amyloid inhibitory activity, and antioxidant capacity.

A series of piperidine-3-carbohydrazide-hydrazones bearing phenylethyl, phenylpropyl, and phenylbutyl substituents on piperidine nitrogen were designed and synthesized as cholinesterase (ChE) inhibitors. The title compounds were screened for acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) inhibitory activities and antioxidant capacities, and the active ones for Aß42 self-aggregation inhibition, in vitro. The chemiluminescence method was used to determine the effect of the selected compounds on the reactive oxygen species (ROS) levels in brain tissue. Physicochemical properties were calculated by the MOE program. Kinetic analysis and molecular modeling studies were also carried out for the most active compounds. Generally, the final compounds exhibited moderate to good AChE or BuChE inhibitory activity. Among them, 3g and 3j showed the most potent activity against AChE (IC50 = 4.32 µM) and BuChE (IC50 = 1.27 µM), respectively. The kinetic results showed that both compounds exhibited mixed-type inhibition. Among the selected compounds, nitro derivatives (3g, 4g, and 5g) provided better Aß42 inhibition. According to the chemiluminescence assay, 4i exhibited the most active superoxide free-radical scavenger activity and 3g, 3j, and 4i showed similar scavenger activity on other ROS. All results suggested that 3g, 3j, and 4i have good AChE/BuChE, Aß42 inhibitory potentials and antioxidant capacities and can therefore be suggested as promising multifunctional agents to combat Alzheimer's disease.

The antibacterial activity of photodynamic agents against multidrug resistant bacteria causing wound infection.

Antimicrobial photodynamic inactivation (aPDI) of multidrug-resistant (MDR) wound pathogens was evaluated with cationic porphyrin derivatives (CPDs). MDR bacterial strains including Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, and Klebsiella pneumoniae were used. The CPDs named PM, PE, PN, and PL were synthesized as a photosensitizer (PS). A diode laser with a wavelength of 655 nm was used as a light source. aPDI of the combinations formed with different energy densities (50, 100, and 150 J/cm²) and PS concentrations (ranging from 3.125 to 600 µM) were evaluated on each bacterial strain. Dark toxicity, cytotoxicity, and phototoxicity were determined on fibroblast cells. In the aPDI groups, survival reductions of up to 5.80 log10 for E. coli, 5.90 log10 for P. aeruginosa, 6.11 log10 for K. pneumoniae, and 6.78 log10 for A. baumannii were obtained. The cytotoxic effect of PL and PM on fibroblast cells was very limited. PN was the type of CPD with the highest dark toxicity on fibroblast cells. In terms of providing broad-spectrum aPDI without or with very limited cytotoxic effect, the best result was observed in aPDI application with PL. The other CPDs need some modifications to show bacterial selectivity for use at 50 µM and above.

Design, synthesis, acetylcholinesterase, butyrylcholinesterase, and amyloid-ß aggregation inhibition studies of substituted 4,4'-diimine/4,4'-diazobiphenyl derivatives.

A series of 4,4'-diimine/4,4'-diazobiphenyl derivatives were designed, synthesized, and evaluated for their ability to inhibit both the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes, as well as Aß1-42 aggregation, in vitro. The AChE and BChE inhibition assays demonstrated that all compounds displayed moderate AChE inhibitory activity in the range of IC50 = 5.77-16.22 µM, while they displayed weak or no BChE inhibition. Among the title compounds, compound 2l, 4,4'-bis(quinolin-8-yldiazenyl)-1,1'-biphenyl, having a diazo-quinoline moiety demonstrated the most potent inhibition against AChE with an IC50 value of 5.77 µM. Furthermore, diazo derivatives 2d, 4,4'-bis[(4-methoxyphenyl)diazenyl]-1,1'-biphenyl, and 2i, 4,4'-bis(pyridin-3-yldiazenyl)-1,1'-biphenyl, provided better potency on Aß1-42 aggregation, with an inhibition value of 74.08% and 78.39% at 100 µM and 55.35% and 61.36% at 25 µM, respectively. Molecular modeling studies were carried out for the most active compound against AChE, compound 2l. All the results suggested that compounds 2d and 2i have better inhibitory potencies on Aß1-42 aggregation and moderate AChE enzyme activity, and therefore can be highlighted as promising compounds.

Antibacterial activity of porphyrin derivatives against multidrug-resistant bacteria.

In this study, it was aimed to investigate the antibacterial activities of the cationic porphyrin derivatives against some multi drug resistant clinical bacterial isolates and standard strains for the development of potential antibacterial agents. In addition to the standard strains, methicillin-resistant Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa clinical isolates were studied. We synthesized eight (P1-P8) cationic porphyrin derivatives. The minimum inhibitory concentrations (MIC) of these substances were determined by micro dilution method. Ciprofloxacin was used for quality control. The study was repeated three times. All porphyrin derivatives exhibited antibacterial activity at different levels according to the studied bacteria. The strongest antibacterial activity was obtained with compounds P6, P7 and P8. These compounds were found to have MIC values of <5-156µg/ml. Because of the low MIC values, it has been concluded that these synthesized porphyrin derivatives may be high-potency agents against bacteria with high resistance profile.

Synthesis, bioactivity and molecular modeling studies on potential anti-Alzheimer piperidinehydrazide-hydrazones.

A group of N-benzylpiperidine-3/4-carbohydrazide-hydrazones were designed, synthesized and evaluated for acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) activities, Aß42 self-aggregation inhibitory potentials, and antioxidant capacities, in vitro. All of the compounds displayed eeAChE and huAChE inhibitory activity in a range of IC50 = 5.68-11.35 µM and IC50 = 8.80-74.40 µM, respectively and most of the compounds exhibited good to moderate inhibitory activity on BuChE enzyme. Kinetic analysis and molecular modeling studies were also performed for the most potent compounds (1g and 1j). Not only the molecular modeling studies but also the kinetic analysis suggested that these compounds might be able to interact with the catalytic active site (CAS) and the peripheral anionic site (PAS) of the enzymes. In the light of the results, compound 1g and compound 1j may be suggested as lead compounds for multifunctional therapy of AD.

Photodynamic antimicrobial activity of new porphyrin derivatives against methicillin resistant Staphylococcus aureus.

Methicillin resistant Staphylococcus aureus (MRSA) with multiple drug resistance patterns is frequently isolated from skin and soft tissue infections that are involved in chronic wounds. Today, difficulties in the treatment of MRSA associated infections have led to the development of alternative approaches such as antimicrobial photodynamic therapy. This study aimed to investigate photoinactivation with cationic porphyrin derivative compounds against MRSA in in-vitro conditions. In the study, MRSA clinical isolates with different antibiotic resistance profiles were used. The newly synthesized cationic porphyrin derivatives (PM, PE, PPN, and PPL) were used as photosensitizer, and 655 nm diode laser was used as light source. Photoinactivation experiments were performed by optimizing energy doses and photosensitizer concentrations. In photoinactivation experiments with different energy densities and photosensitizer concentrations, more than 99% reduction was achieved in bacterial cell viability. No decrease in bacterial survival was observed in control groups. It was determined that there was an increase in photoinactivation efficiency by increasing the energy dose. At the energy dose of 150 J/cm2 a survival reduction of over 6.33 log10 was observed in each photosensitizer type. While 200 µM PM concentration was required for this photoinactivation, 12.50 µM was sufficient for PE, PPN, and PPL. In our study, antimicrobial photodynamic therapy performed with cationic porphyrin derivatives was found to have potent antimicrobial efficacy against multidrug resistant S. aureus which is frequently isolated from wound infections.

Multifunctional cholinesterase inhibitors for Alzheimer's disease: Synthesis, biological evaluations, and docking studies of o/p-propoxyphenylsubstituted-1H-benzimidazole derivatives.

This study indicates the synthesis, cholinesterase (ChE) inhibitory activity, and molecular modeling studies of 48 compounds as o- and p-(3-substitutedethoxyphenyl)-1H-benzimidazole derivatives. According to the ChE inhibitor activity results, generally, para series are more active against acetylcholinesterase (AChE) whereas ortho series are more active against butyrylcholinesterase (BuChE). The most active compounds against AChE and BuChE are compounds A12 and B14 with IC50 values of 0.14 and 0.22 µM, respectively. Additionally, the most active 16 compounds against AChE/BuChE were chosen to investigate the neuroprotective effects, and the results indicated that most of the compounds have free radical scavenging properties and show their effects by reducing free radical production; moreover, some of the compounds significantly increased the viability of SH-SY5Y cells exposed to H2 O2 . Overall, compounds A12 and B14 with potential AChE and BuChE inhibitory activities, high neuroprotection against H2 O2 -induced toxicity, free radical scavenging properties, and metal chelating abilities may be considered as lead molecules for the development of multi-target-directed ligands against Alzheimer's disease.

Synthesis, biological evaluation, and docking studies of some 5-chloro-2(3H)-benzoxazolone Mannich bases derivatives as cholinesterase inhibitors.

A series of N-substituted-5-chloro-2(3H)-benzoxazolone derivatives were synthesized and evaluated for their acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) inhibitory, and antioxidant activities. The structures of the title compounds were confirmed by spectral and elemental analyses. The cholinesterase (ChE) inhibitory activity studies were carried out using Ellman's colorimetric method. The free radical scavenging activity was also determined by in vitro ABTS (2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) assay. The biological activity results revealed that all of the title compounds displayed higher AChE inhibitory activity than the reference compound, rivastigmine, and were selective for AChE. Among the tested compounds, compound 7 exhibited the highest inhibition against AChE (IC50 = 7.53 ± 0.17 µM), while compound 11 was found to be the most active compound against BuChE (IC50 = 17.50 ± 0.29 µM). The molecular docking study of compound 7 showed that this compound can interact with the catalytic active site (CAS) of AChE and also has potential metal chelating ability and a proper log P value. On the other hand, compound 2 bearing a methyl substituent at the ortho position on the phenyl ring showed better radical scavenging activity (IC50 = 1.04 ± 0.04 mM) than Trolox (IC50 = 1.50 ± 0.05 mM).

Synthesis and evaluation of pyridinium-hydrazone derivatives as potential antitumoral agents.

The hydrazones of 4-hydrazinylpyridinium bearing alkylphenyl groups on pyridinium nitrogen were synthesized and evaluated for their cytotoxic activity against MCF-7, PC3, U2OS, and HEK293 cell lines by Wst1 cell proliferation assay. Cytotoxic activity results indicated that d derivatives having butylene chain; 4 and 5 series having naphthalene and anthracene ring systems showed high cytotoxic activity (IC50  = 3.27-8.54 µm) on cancer cells. 3d (4-(2-(4-hydroxybenzylidene)hydrazinyl)-1-(4-phenylbutyl)pyridinium bromide) was the most cytotoxic compound with IC50 value of 3.27 µm against MCF-7. The most active derivatives (1d, 2d, 3d, 4, and 5 series) were selected to investigate for the effects on autophagy by analyzing the expression of autophagy marker proteins. The conversion of LC3-I to its lipidated form LC3-II is essential for autophagy and related to autophagosomes. According to our results, all tested compounds except for 3d induced lipidated form LC3-II accumulation. Then, the effects of the compounds on p62 protein level were also analyzed by the immunoblotting as the autophagy inhibition results in accumulation of p62. Further molecular mechanistic studies including morphological analysis and live-death assays indicated that all tested compounds (1d, 2d, 3d, 4, and 5 series) are potent antitumoral molecules and all except for 3d have potential to inhibit autophagic flux.

Mannich-Benzimidazole Derivatives as Antioxidant and Anticholinesterase Inhibitors: Synthesis, Biological Evaluations, and Molecular Docking Study.

A series of Mannich bases of benzimidazole derivatives having a phenolic group were designed to assess their anticholinesterase and antioxidant activities. The acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activities were evaluated in vitro by using Ellman's method. According to the activity results, all of the compounds exhibited moderate to good AChE inhibitory activity (except for 2a), with IC50 values ranging from 0.93 to 10.85 µM, and generally displayed moderate BuChE inhibitory activity. Also, most of the compounds were selective against BuChE. Compound 4b was the most active molecule on the AChE enzyme and also selective. In addition, we investigated the antioxidant effects of the synthesized compounds against FeCl2 /ascorbic acid-induced oxidative stress in the rat brain in vitro, and the activity results showed that most of the compounds are effective as radical scavengers. Molecular docking studies and molecular dynamics simulations were also carried out.

Synthesis and molecular docking studies of some 4-phthalimidobenzenesulfonamide derivatives as acetylcholinesterase and butyrylcholinesterase inhibitors.

A series of 4-phthalimidobenzenesulfonamide derivatives were designed, synthesized and evaluated for the inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Structures of the title compounds were confirmed by spectral and elemental analyses. The cholinesterase (ChE) inhibitory activity studies were carried out using Ellman's colorimetric method. The biological activity results revealed that all of the title compounds (except for compound 8) displayed high selectivity against AChE. Among the tested compounds, compound 7 was found to be the most potent against AChE (IC50= 1.35 ± 0.08 µM), while compound 3 exhibited the highest inhibition against BuChE (IC50= 13.41 ± 0.62 µM). Molecular docking studies of the most active compound 7 in AChE showed that this compound can interact with both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE.

Synthesis, Biological Evaluation and Molecular Docking Study of Hydrazone-Containing Pyridinium Salts as Cholinesterase Inhibitors.

A series of pyridinium salts bearing alkylphenyl groups at 1 position and hydrazone structure at 4 position of the pyridinium ring were synthesized and evaluated for the inhibition of both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. The cholinesterase (ChE) inhibitory activity studies were carried out by using the Ellman's colorimetric method. All compounds displayed considerable AChE and BuChE inhibitory activity and some of the compounds manifested remarkable anti-AChE activity compared to the reference compound, galantamine. Among the title compounds, the series including benzofuran aromatic ring exhibited the best inhibitory activity both on AChE and BuChE enzymes. Compound 3b, 4-[2-(1-(benzofuran-2-yl)ethylidene)hydrazinyl]-1-(3-phenylpropyl)pyridinium bromide, was the most active compound with IC50 value of 0.23 (0.24) µM against enantiomeric excess (ee)AChE (human (h)AChE) while compound 3a, 4-[2-(1-(benzofuran-2-yl)ethylidene)hydrazinyl]-1-phenethylpyridinium bromide, was the most active compound with IC50 value of 0.95 µM against BuChE. Moreover, 3a and b exhibited higher activity than the reference compound galantamine (eeAChE (hAChE) IC50 0.43 (0.52) µM; BuChE IC50 14.92 µM). Molecular docking studies were carried out on 3b having highest inhibitory activity against AChE.

Synthesis, biological activity and molecular modeling studies on 1H-benzimidazole derivatives as acetylcholinesterase inhibitors.

A series of N-{2-[4-(1H-benzimidazole-2-yl)phenoxy]ethyl}substituted amine derivatives were designed to assess cholinesterase inhibitor activities. Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitor activities were evaluated in vitro by using Ellman's method. It was discovered that most of the compounds displayed AChE and/or BuChE inhibitor activity and few compounds were selective against AChE/BuChE. Compound 3c and 3e were the most active compounds in the series against eeAChE and hAChE, respectively. Molecular docking studies and molecular dynamics simulations were also carried out.

1,4-Substituted 4-(1H)-pyridylene-hydrazone-type inhibitors of AChE, BuChE, and amyloid-ß aggregation crossing the blood-brain barrier.

Given the fundamentally multifactorial character of Alzheimer's disease (AD), addressing more than one target for disease modification or therapy is expected to be highly advantageous. Here, following the cholinergic hypothesis, we aimed to inhibit both acetyl- and butyrylcholinesterase (AChE and BuChE) in order to increase the concentration of acetylcholine in the synaptic cleft. In addition, the formation of the amyloid ß fibrils should be inhibited and already preformed fibrils should be destroyed. Based on a recently identified AChE inhibitor with a 1,4-substituted 4-(1H)-pyridylene-hydrazone skeleton, a substance library has been generated and tested for inhibition of AChE, BuChE, and fibril formation. Blood-brain barrier mobility was ensured by a transwell assay. Whereas the p-nitrosubstituted compound 18C shows an anti-AChE activity in the nanomolar range of concentration (IC50=90 nM), the bisnaphthyl substituted compound 20L was found to be the best overall inhibitor of AChE/BuChE and enhances the fibril destruction.

Synthesis and antimicrobial activity of some pyridinium salts.

Some substituted benzylidenehydrazinylpyridinium derivatives bearing benzyl, ethylphenyl and propylphenyl groups on the pyridinium nitrogen were synthesized and screened for possible antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans using the microdilution method. Antimicrobial test results indicated that compounds containing a 3-phenylpropyl chain displayed the highest antimicrobial activity against Staphylococcus aureus and the compound 3d was the most active in the series against all tested bacteria and fungi strains.