New cyclopentaquinoline and 3,5-dichlorobenzoic acid hybrids with neuroprotection against oxidative stress for the treatment of Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative brain disease. Thus, drugs including donepezil, rivastigmine, and galantamine are not entirely effective in the treatment of this multifactorial disease. The present study evaluates eight derivatives (3a-3h) as candidates with stronger anti-AD potential but with less side effects. Reactive oxygen species (ROS) assays were used to assess oxidative stress which involve in the neurodegeneration. The neuroprotective properties of 3e against oxidative stress were done in three experiments using MTT test. The anti-AD potential was determined based on their anticholinesterase inhibition ability, determined using Ellman's method, Aß aggregation potential according to thioflavin (Th) fluorescence assay, and their antioxidative and anti-inflammatory activities. Compound 3e exhibited moderate cholinesterase inhibition activity (AChE, IC50 = 0.131 µM; BuChE, IC50 = 0.116 µM; SI = 1.13), significant inhibition of Aß(1-42) aggregation (55.7%, at 5 µM) and acceptable neuroprotective activity. Extensive analysis of in vitro and in vivo assays indicates that new cyclopentaquinoline derivatives offer promise as candidates for new anti-AD drugs.

Synthesis and Biological Studies of Novel Aminophosphonates and Their Metal Carbonyl Complexes (Fe, Ru).

The quest to find new inhibitors of biologically relevant targets is considered an important strategy to introduce new drug candidates for the treatment of neurodegenerative diseases. A series of (aminomethyl)benzylphosphonates 8a-c and their metallocarbonyl iron 9a-c and ruthenium 10a-c complexes were designed, synthesized, and evaluated for their inhibitory potentials against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) by determination of IC50. Metallocarbonyl derivatives, in general, did not show significant inhibition activity against these enzymes, the most potent inhibitor was the (aminomethyl)benzylphosphonate 8a (IC50 = 1.215 µM against AChE). Molecular docking analysis of AChE and (aminomethyl)benzylphosphonates 8a-c showed the strongest interactions of 8a and AChE compared to isomers 8b and 8c. Cytotoxicity studies of synthesized compounds towards the V79 cell line were also performed and discussed.

New Tetrahydroacridine Hybrids with Dichlorobenzoic Acid Moiety Demonstrating Multifunctional Potential for the Treatment of Alzheimer's Disease.

A series of new tetrahydroacridine and 3,5-dichlorobenzoic acid hybrids with different spacers were designed, synthesized, and evaluated for their ability to inhibit both cholinesterase enzymes. Compounds 3a, 3b, 3f, and 3g exhibited selective butyrylcholinesterase (EqBuChE) inhibition with IC50 values ranging from 24 to 607 nM. Among them, compound 3b was the most active (IC50 = 24 nM). Additionally, 3c (IC50 for EeAChE = 25 nM and IC50 for EqBuChE = 123 nM) displayed dual cholinesterase inhibitory activity and was the most active compound against acetylcholinesterase (AChE). Active compound 3c was also tested for the ability to inhibit Aß aggregation. Theoretical physicochemical properties of the compounds were calculated using ACD Labs Percepta and Chemaxon. A Lineweaver-Burk plot and docking study showed that 3c targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. Moreover, 3c appears to possess neuroprotective activity and could be considered a free-radical scavenger. In addition, 3c did not cause DNA damage and was found to be less toxic than tacrine after oral administration; it also demonstrated little inhibitory activity towards hyaluronidase (HYAL), which may indicate that it possesses anti-inflammatory properties. The screening for new in vivo interactions between 3c and known receptors was realized by yeast three-hybrid technology (Y3H).

Novel tetrahydroacridine derivatives with iodobenzoic moieties induce G0/G1 cell cycle arrest and apoptosis in A549 non-small lung cancer and HT-29 colorectal cancer cells.

A series of nine tetrahydroacridine derivatives with iodobenzoic moiety were synthesized and evaluated for their cytotoxic activity against cancer cell lines-A549 (human lung adenocarcinoma), HT-29 (human colorectal adenocarcinoma) and somatic cell line-EA.hy926 (human umbilical vein cell line). All compounds displayed high cytotoxicity activity against A549 (IC50 59.12-14.87 µM) and HT-29 (IC50 17.32-5.90 µM) cell lines, higher than control agents-etoposide and 5-fluorouracil. Structure-activity relationship showed that the position of iodine in the substituent in the para position and longer linker most strongly enhanced the cytotoxic effect. Among derivatives, 1i turned out to be the most cytotoxic and displayed IC50 values of 14.87 µM against A549 and 5.90 µM against HT-29 cell lines. In hyaluronidase inhibition assay, all compounds presented anti-inflammatory activity, however, slightly lower than reference compound. ADMET prediction showed that almost all compounds had good pharmacokinetic profiles. 1b, 1c and 1f compounds turned out to act against chemoresistance in cisplatin-resistant 253J B-V cells. Compounds intercalated into DNA and inhibited cell cycle in G0/G1 phase-the strongest inhibition was observed for 1i in A549 and 1c in HT-29. Among compounds, the highest apoptotic effect in both cell lines was observed after treatment with 1i. Compounds caused DNA damage and H2AX phosphorylation, which was detected in A549 and HT-29 cells. All research confirmed anticancer properties of novel tetrahydroacridine derivatives and explained a few pathways of their mechanism of cytotoxic action.

Discovery of New Cyclopentaquinoline Analogues as Multifunctional Agents for the Treatment of Alzheimer's Disease.

Here we report the two-step synthesis of 8 new cyclopentaquinoline derivatives as modifications of the tetrahydroacridine structure. Next, the biological assessment of each of them was performed. Based on the obtained results we identified 6-chloro-N-[2-(2,3-dihydro-1H-cyclopenta[b]quinolin-9-ylamino)-hexyl]]-nicotinamide hydrochloride (3e) as the most promising compound with inhibitory potencies against EeAChE and EqBuChE in the low nanomolar level 67 and 153 nM, respectively. Moreover, 3e compound is non-hepatotoxic, able to inhibit amyloid beta aggregation, and shows a mix-type of cholinesterase's inhibition. The mixed type of inhibition of the compound was confirmed by molecular modeling. Then, yeast three-hybrid (Y3H) technology was used to confirm the known ligand-receptor interactions. New derivatives do not show antioxidant activity (confirmed by the use of two different tests). A pKa assay method was developed to identify the basic physicochemical properties of 3e compound. A LogP assay confirmed that 3e compound fulfills Lipinsky's rule of five.

Tetrahydroacridine derivatives with fluorobenzoic acid moiety as multifunctional agents for Alzheimer's disease treatment.

A novel series of 9-amino-1,2,3,4-tetrahydroacridine derivatives with 2-fluorobenzoic acid or 3-fluorobenzoic acid moiety were designed, synthesized and evaluated as inhibitors of cholinesterases and aggregation of ß-amyloid. In the study target compounds were very potent inhibitors of AChE and BChE. The most promising agents had higher inhibitory potency than the reference drugs which was tacrine. Ultimately, the kinetic assay shows the most active target compound 3c against AChE. Almost all of them were more potent against BChE than AChE. Compound 3c in various concentrations was tested by aggregation experiment. Inhibition of ß-amyloid aggregation was 77.32% and 80.43% at 50µM and 100µM, respectively. Therefore, compound 3c is a promising agent for the treatment of AD.

New cyclopentaquinoline hybrids with multifunctional capacities for the treatment of Alzheimer's disease.

Alzheimer's disease (AD) is the most common progressive form of brain neurodegeneration and the most prevailing cause of dementia. Unfortunately, the aetiology of AD is not completely studied but different factors are associated with the development of AD such as among others low level of acetylcholine, aggregation of ß-amyloid (Aß), hyperphosphorylated tau protein, oxidative stress, and inflammation. The study encompass organic syntheses of 2,3-dihydro-1H-cyclopenta[b]quinoline with 5,6-dichloronicotinic acid and suitable linkers derivatives as multifunctional agents for AD treatment. Afterwards self-induced amyloid beta aggregation, inhibition studies of acetylcholinesterase and butyrylcholinesterase and molecular docking studies were performed. The results showed that 3b compound exhibited the best acetylcholinesterase inhibitory activity, with IC50 value of 0.052 µM which is lower compared to references. Besides, all synthesised compounds showed good butyrylcholinesterase inhibitory activity with IC50 values from 0.071 to 0.797 µM. Compound 3b exhibited strong Aß1-42 aggregation inhibitory effect with 25.7% at 5 µM to 92.8% at 100 µM as well as good anti-inflammatory effect. Thus, new compounds could create new perspectives for further development as a multi-target-directed agent for AD treatment.

Synthesis, biological evaluation and molecular modeling of new tetrahydroacridine derivatives as potential multifunctional agents for the treatment of Alzheimer's disease.

A novel series of 9-amino-1,2,3,4-tetrahydroacridine derivatives with 4-dimethylaminobenzoic acid moiety was synthesized and tested towards inhibition of cholinesterases and amyloid ß aggregation. Target compounds were designed as dual binding site cholinesterase inhibitors able to bind to both the catalytic and the peripheral site of the enzyme and therefore potentially endowed with other properties. The obtained derivatives were very potent inhibitors of both cholinesterases (EeAChE, EqBChE) with IC50 values ranging from sub-nanomolar to nanomolar range, and the inhibitory potency of the most promising agents was higher than that of the reference drugs (rivastigmine and tacrine). The kinetic studies of the most active compound 3a revealed competitive type of AChE inhibition. Moreover, all target compounds were more potent inhibitors of human AChE than tacrine with the most active compound 3b (IC50 = 19 nM). Compound 3a was also tested and displayed inhibitory potency against AChE-induced Aß 1-42 aggregation (80.6% and 91.3% at 50 µM and 100 µM screening concentration, respectively). Moreover, cytotoxicity assay performed on A549 cells did not indicate toxicity of this agent. Compound 3a is a promising candidate for further development of novel multi-functional agents in the therapy of AD.

Biological assessment of new tetrahydroacridine derivatives with fluorobenzoic moiety in vitro on A549 and HT-29 cell lines and in vivo on animal model.

A new series of tetrahydroacridine derivatives with the fluorobenzoyl moiety was synthesized and evaluated for cytotoxic activity against lung cancer cell lines A549 and colorectal cancer HT29. The cytotoxic activity of the compounds was compared on the somatic cell line-EAhy926. Compounds showed high cytotoxic activity on A549 cells (IC50 183.26-68.07 µM) and HT29 cells (IC50 68.41-19.70 µM), higher than controls-etoposide (IC50 451.47 µM) toward A549 and 5-fluorouracil (IC50 1626.85 µM) against HT29. Derivative 4 was the most cytotoxic to A549, whereas for the cell lines HT29 compound 6. Selected compounds showed similar cytotoxicity to the EAhy926 cell line (IC50 about 50 µM). In the hyaluronidase inhibition assay, all compounds exhibited anti-inflammatory activity, including 4 exhibiting the best inhibitory activity-IC50 of 52.27 µM when the IC50 heparin was 56.41 µM. Mathematical modeling was performed to determine LD50 after intraperitoneal, oral, intravenous and subcutaneous administration and to predict potential mutagenicity and carcinogenicity of the compounds analyzed. Obtained results showed that tested derivatives are slightly toxic compounds, and LD50 values (mg/kg) ranged from 680 to 1200 (oral rat model), the analyzed compounds have low mutagenic potential, and differences between derivatives are insignificant and very low probability of carcinogenicity. To confirm mathematical calculations, an in vivo test was carried out on a laboratory mouse model for two selected compounds. It allowed to qualify compounds: 6 to category 4 of the GHS scale, and 4 to category 3 of the GHS scale.

Novel tetrahydroacridine derivatives with iodobenzoic acid moiety as multifunctional acetylcholinesterase inhibitors.

New synthesized series of 9-amino-1,2,3,4-tetrahydroacridine derivatives with iodobenzoic acid moiety were studied for their inhibitory activity toward cholinesterase and against ß-amyloid aggregation. All novel molecules 3a-3i interacted with both cholinesterases-acetylcholinesterase and butyrylcholinesterase-delivered nanomolar IC50 values. The structure-activity relationship showed that N-butyl moiety derivatives are stronger inhibitors toward AChE and BuChE than N-ethyl and N-propyl moieties compounds. The most potent compound toward acetylcholinesterase was inhibitor 3f (IC50  = 31.2 nm), and it was more active than reference drug, tacrine (IC50  = 100.2 nm). Compound 3f showed strong inhibition of butyrylcholinesterase (IC50  = 8.0 nm), also higher than tacrine (IC50  = 16.3 nm). In the kinetic studies, compound 3f revealed mixed type of acetylcholinesterase inhibition. The computer modeling was carried out. The most active compound 3f was confirmed as peripheral anionic site inhibitor of acetylcholinesterase. Moreover, molecule 3f inhibited ß-amyloid aggregation (at the concentration 10 µm-24.96% of inhibition, 25 µm-72%, 50 µm-78.44%, and 100 µm-84.92%). Therefore, among all examined, compound 3f is the most promising molecule for further, more detailed research of novel multifunctional agents in the therapy of Alzheimer's disease.

Tetrahydroacridine derivatives with dichloronicotinic acid moiety as attractive, multipotent agents for Alzheimer's disease treatment.

A novel series of 9-amino-1,2,3,4-tetrahydroacridine and 5,6-dichloronicotinic acid moiety were conjugated with different linkers. Afterwards new derivatives were evaluated as potential multifunctional acetylcholinesterase inhibitors (AChEIs), anti-Alzheimer's disease (AD) drug candidates. All the compounds were synthesized and tested for capacity for the inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. Specifically, the most promising derivative 3b (IC50 = 1.02 nM) had higher inhibitory potency compared to the reference drug, tacrine. Consequently, kinetic studies of 3b compound showed a mixed-type inhibition of both AChE and BuChE. Afterwards the best potent AChE inhibitor has been examined on amyloid ß (Aß) self-induced aggregation. Furthermore, 3b compound was tested in various concentrations and had moderate activity against Aß aggregation. Inhibition of Aß aggregation was 46.63% and 19.41% at 50 µM and 5  µM concentrations, respectively. Moreover, no cytotoxicity was observed for the mentioned concentrations. Therefore, 3b compound is a promising multipotent agent for the treatment of AD.