Aminothiazole Hybrids: Synthesis, In vitro Anticholinesterase Activity, and Binding Insights through Molecular Docking

BackgroundThe evaluation of the correlations between antioxidant and anti-acetylcholinesterase activities of methanol leaf extracts of three Nigerian endemic plants, Spondias mombin, Carica papaya and Kalanchoe crenata, was carried out. Their constituent phytochemicals were identified by HPLC–DAD fingerprinting. The antioxidant activity as typified by 2,2-diphenyl-1-picrylhydrazyl (DPPH·), 2,2′-azino-bis-(3-ethylbenthiazoline-6-sulfonic acid (ABTS·+) and nitric oxide (NO) scavenging activities were evaluated. The acetylcholinesterase (AChE) inhibitory activity of the extracts was also determined.ResultsThe extracts contained appreciable amounts of the flavonoids, quercetin and kaempferol. The extracts of Spondias mombin, Carica papaya and Kalanchoe crenata showed concentration-dependent inhibitory activities against DPPH· and ABTS·+ with IC50 of 43.29 ± 0.443 µg/mL, 59.27 ± 0.644 µg/mL and 80.20 ± 0.414 µg/mL; 25.43 ± 0.325 (µg/mL), 39.84 ± 0.163 µg/mL and 59.02 ± 0.376 (µg/mL), respectively. The IC50 for the NO scavenging activities of the Spondias mombin, Carica papaya and Kalanchoe crenata extracts were 41.99 ± 0.217 µg/mL, 50.44 ± 0.281 µg/mL and 60.12 ± 0.512 µg/mL, respectively. The IC50 for the inhibitory effects on AChE was 53.24 ± 0.327 µg/mL, 60.95 ± 0.290 µg/m and 70.5 ± 0.426 µg/mL, respectively. The effectiveness of the plant in all the experimental tests was in the following order: S. mombin > C. papaya > K. crenata. The total flavonoid and total phenolic contents have extremely significant positive correlations with the antioxidant activities and AChE inhibitory activity. The correlation coefficients (r2) of DPPH scavenging activity and NO scavenging activity with the AChE inhibitory activity were 0.8295 µg/mL and 0.7337 µg/mL, respectively (P < 0.0001). The molecular docking and pharmacokinetic analyses on some constituent phytochemicals showed that quercetin, kaempferol, ferulic acid, leucocyanidin, gallic acid and isorhamnetin fulfilled the requirements for an anti-Alzheimer drug.ConclusionsThe results suggest that the plant species provide a significant source of secondary metabolites that can act as natural antioxidants and acetylcholinesterase inhibitors, which will be helpful in the treatment of Alzheimer’s disease.

A series of 12 S-substituted tetrahydrobenzothienopyrimidines were designed and synthesized based on the donepezil scaffold. All the newly synthesized compounds were evaluated for their acetylcholinesterase (AChE) inhibitory activity and the most active compounds were tested for their butyrylcholinesterase (BuChE) inhibitory activity. Moreover, all the synthesized compounds were evaluated for their inhibitory effects against Aβ aggregation and antioxidant activity using the oxygen radical absorbance capacity method. Compounds 4b, 6b, and 8b displayed the most prominent AChE inhibitory action comparable to donepezil. Compound 6b showed the greatest AChE inhibitory action (IC50 = 0.07 ± 0.003 µM) and the most potent BuChE inhibitory action (IC50 = 0.059 ± 0.004 µM). Furthermore, the three compounds exhibited significant antioxidant activity. Compounds 6b and 8b exerted more inhibitory action on Aβ aggregation than donepezil. The cytotoxic activity of compounds 4b, 6b, and 8b against the WI-38 cell line in comparison with donepezil was examined using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay. The results revealed that compounds 6b and 8b were less cytotixic than donepezil, while compound 4b showed nonsignificant cytotoxicity compared to donepezil. For more insights about the binding patterns of the most promising compounds (4b, 6b, and 8b) with the AChE at molecular levels; molecular docking and molecular dynamics simulations were performed. The densityfunctional theory calculations and absorption, distribution, metabolism, excretion and toxicity properties were described as well. The results highlighted compound 6b, which incorporates a phenylpiperazine moiety coupled to a thienopyrimidone scaffold via two-atom spacer, to be a promising multifunctional therapeutic agent for the treatment of Alzheimer's disease. It is a potent dual AChE and BuChE inhibitor. Furthermore, it had stronger Aβ aggregation inhibitory action than donepezil. Additionally, compound 6b exerted significant antioxidant activity.

A new series of chiral hydrazide-hydrazone derivatives were synthesized and evaluated their acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase and urease inhibition and antioxidant activities. The chemical structures of newly synthesized chiral aryl hydrazide-hydrazone derivatives were clarified using UV-Vis, IR, 1H and 13C NMR, and mass spectroscopies. According to NMR data, due to the partial double bond character of the amide C-N bond, two conformational isomers (E and Z) exist in solution. Based on this information, the conformational properties of the synthesized compounds were investigated using temperature-dependent NMR spectroscopy and DFT. The results of DFT studies revealed that E(C=N)-E(C(O)-N) conformer is the most stable structure for the synthesized hydrazones. In addition, the enzyme inhibition potentials of the synthesized compounds were evaluated. Among all chiral hydrazide-hydrazones, compound 3b (containing nitro group in the hydrazone part) had the best inhibition profile against AChE, whereas compound 3d was found to be the most active compound against BChE. In addition, compound 3d, which carries a methoxy group in both the benzamide and the hydrazone moiety, attracted attention due to its good activity against all examined enzymes. Furthermore, molecular docking calculations were performed to get insights into the interaction patterns between the synthesized compounds and the selected target protein.

To investigate chemical constituents of the stems and branches of Adina polycephala and their pharmacological activities. The constituents were isolated by a combination of various chromatographic techniques including column chromatography on silica gel, Sephadex LH-20, and C-18, as well as reversed-phase HPLC. Structures of the isolates were identified by spectroscopic data analysis. In vitro cytotoxic, anti-inflammatory, anti-oxidant, anti-HIV, neuroprotective and anti-diabetic activities were screened by using cell-based models. Twenty-eight constituents were isolated. Their structures were identified as clemochinenoside B (1), kelampayoside A (2), osmanthuside H (3), 4-hydroxy-3-methoxyphenol-beta-D-[6-O-(4-hydroxy-3,5-dimethoxylbenzoate)]-glucopyranoside (4), and syringic acid beta-D-glucopyranosyl ester (5). Ten iridoidal glycosides: geniposidic acid (6), geniposide (7), 6beta-hydroxygeniposide (8), 6beta-hydroxygeniposide (9), ixoside (10), ixoside 11-methyl ester (11), 11-methyl forsythide (12), 7beta-hydroxysplendoside (13), gardoside (14) and mussaenosidic acid (15), (+) -pinoresinol (16), (+) -medioresinol (17), (+) -syringaresinol (18), (-)-lariciresinol (19), evofolin-B (20), alpha-hydroxyacetovaillone (21), syringic acid (22), vanillin (23), 3, 4, 5-trimethoxyphenol (24), and 2,6-dimethoxy-1, 4-benzoquinone (25), beta-sitosterol (26), mannitol (27), and daucosterol (28). At a concentration of 1.0 x 10(-5) mol x L(-1), these compounds were inactive in the assays, including cytotoxicity against human tumor cell lines (HCT-8, Bel-7402, BGC-823, A549 and A2780), anti-inflammatory activity against the release of beta-glucuronidase in rat polymorphonuclear leukocytes (PMNs) induced by platelet-activating factor (PAF), antioxidant activity in Fe(2+)-cystine-induced rat liver microsomal lipid peroxidation, anti-HIV activity against HIV-1 replication, neuroprotective activity against serum deprivation or glutamate induced neurotoxicity in cultures of PC12 cells, and the inhibitory activity against protein tyrosine phosphatase 1B (PTP1B). Compounds 1-20 were obtained from the genus Adina for the first time. The 13C-NMR data of compounds 10 and 11 were reassigned. A further evaluation of pharmacological activity of these compounds is expected.

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.

Background: Natural antioxidants in the plant kingdom play an essential role in reducing the risk of various chronic diseases and maintaining a healthy life. In addition, acetylcholinesterase, butyrylcholinesterase, α-glucosidase, α-amylase, and tyrosinase are involved in the occurrence and pathology of some as Alzheimer’s and diabetes, have become an important strategic target in the effective treatment of these diseases. Phlomis lycia D. DON is traditionally used as an appetizer, stimulant, carminative, tonic, and against stomach pain and dyspeptic complaints. There is limited knowledge on this species except for preliminary studies such as botanical and phytochemicals and biological properties. The aerial parts of this plant contained phenolic compounds, such as lignan, phenylethanoid, and iridoid derivatives which can be responsible for the potential biological effects. Therefore, the present study was aimed to investigate the antioxidant and enzyme inhibition activity of the methanol and water extracts obtained from aerial parts of P. lycia in the flora of Turkey. Material and Methods: Antioxidant potentials were determined spectrophotometrically by DPPH and ABTS radical scavenging, iron chelating, and β-Carotene/linoleic acid emulsion method. We evaluated the inhibitory activities of methanol and water extracts of P. lycia against various enzymes (acetylcholinesterase, butyrylcholinesterase, α-glucosidase, α-amylase, and tyrosinase) by using 96-well plate methods. Results: According to the results, the methanol extract was more active than water extract in terms of antioxidant activity. On the other hand, although the methanol and water extracts were observed to demonstrate similar enzyme inhibitory activity, the water extract exhibited more inhibition activity on α-glucosidase. Conclusions: Our results suggested that Phlomis lycia could potentially be used for the isolation of potent antioxidants from the methanol extract. To the best of our knowledge, this study represents the first time that Phlomis lycia was reported in the literature with glucosidase inhibition activity.

Bioactive constituents from Medicago sativa L. with antioxidant, neuroprotective and acetylcholinesterase inhibitory activities

Recent epidemiologic studies have demonstrated a link between the consumption of daily functional fruits rich in phenols and the prevention of disease for neurodegenerative disorders. Hawthorn products are derived from the functional fruit hawthorn, which is rich in phenols and has been used around the world for centuries. In order to explore the phenolic components in hawthorn, the investigation of the ethanol extract led to the separation of five new phenol compounds (1a/1b, 2-4), including one pair of enantiomers (1a/1b), along with seven disclosed analogs (5-11). Their structures were elucidated based on extensive spectroscopic analyses and electronic circular dichroism (ECD). The compounds (1-11) were tested for antioxidant activities by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonicacid) (ABTS), and ferric reducing antioxidant power (FRAP) methods. Apart from that, monomeric compounds 2, 4, and 6 exhibited more potent protective capabilities against H2O2 (hydrogen peroxide)-induced SH-SY5Y cells. Meanwhile, electronic analyses were performed using the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) to analyze compounds 2, 4, and 6. Furthermore, compounds (1-11) measured acetylcholinesterase (AChE) inhibitory activities, and 2, 4, and 6 possessed greater AChE inhibitory activity than donepezil. At the same time, molecular docking was used to investigate the possible mechanism of the interaction between active compounds (2, 4, and 6) and AChE.

Illicium lanceolatum is a medicinal and aromatic plant widely distributed in the south of China. The reports on chemical composition and biological activities of its essential oils (EOs) were very limited. In this study, Illicium lanceolatum EOs were extracted by hydro distillation, and analyzed by GC–MS and GC-FID. DPPH radical scavenging assay, ABTS cation radical scavenging assay and ferric reducing/antioxidant power (FRAP) assay were used for antioxidant activity evaluation. Minimum inhibitory concentrations (MICs) and minimum microbiocidal concentrations (MMCs) against 9 microorganisms were determined. The inhibitory effects on tyrosinase, α-glucosidase and cholinesterases were evaluated and cytotoxic activities were evaluated using MTT assay. The results revealed 110 identified compounds, with asaricin, eucalyptol, linalool and caryophyllene oxide as major compounds. Eucalyptol was the most abundant compound in the stem, leaf and fruit EOs while asaricin accounted for 50.52 ± 0.33 % in the root EO. Very weak radical scavenging capacities were noticed for all EOs, but the root EO showed moderate antioxidant activity (176.33 ± 4.52 mg TE/g of EO) in the FRAP assay, which could be attributed to asaricin. The root EO displayed better antimicrobial activities than other three EOs, with MIC values as 3.13 mg/mL against three bacteria including Staphylococcus aureus BNCC 186335, Bacillus cereus BNCC 103930 and Listeria monocytogenes BNCC 336877. Camphor and borneol were found to be important antimicrobial compounds. No inhibitory effect on α-glucosidase was found. The leaf EO displayed better acetylcholinesterase inhibitory activity (17.79 ± 0.32 mg GE/g of EO) while the root EO showed better tyrosinase (30.34 ± 0.40 mg KAE/g of EO) and butyrylcholinesterase (43.25 ± 1.50 mg GE/g of EO) inhibitory activities. Molecular docking between active compounds and enzymes revealed the main interactions as hydrophobic interaction, hydrogen bond and π-stacking. All EOs displayed weak cytotoxicity to HK-2 cells of normal kidney at six tested concentrations. The leaf EO showed strong anticancer activities to HepG2 cells at the concentration of 500 μg/mL. I. lanceolatum EOs showed promising prospects with possible applications in pharmaceutical and cosmetic industries.

The present study aimed to determine the biological properties of an extract of Solanum aculeatissimum aqueous extract (SaCE) alone as well as silver nanoparticles (AgNPs) generated by green synthesis utilizing S. aculeatissimum aqueous extract (SaCE). These synthesized SaCE AgNPs were characterized using UV-VIS spectrophotometry, scanning transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), zeta potential (ZP), dynamic light scattering (DLS). Determination of total polyphenols, flavonoids, saponins content was conducted. In addition, high performance liquid chromatography-mass spectrometry (HPLC-MS) was employed to identify constituents in this extract. Antioxidant activity was determined by DPPH radical scavenging and ferric ion reducing power (FRAP) methods. Antiglycation activity was demonstrated through relative mobility in electrophoresis (RME) and determination of free amino groups. The inhibitory activity on tyrosinase was also examined. Molecular docking analyses were performed to assess the molecular interactions with DNA and tyrosinase. The antitumor activity SaCE was also measured. Phytochemical analysis of SaCE and AgNPs showed presence polyphenols (1000.41 and 293.37 mg gallic acid equivalent/g), flavonoids (954.87 and 479.87 mg rutin equivalent/g), saponins (37.89 and 23.01% total saponins), in particular steroidal saponins (aculeatiside A and B). Both SaCE and AgNPs exhibited significant antioxidant (respectively, 73.97%, 56.27% in DPPH test, 874.67 and 837.67 μM Trolox Equivalent/g in FRAP test) and antiglycation activities (72.81 and 67.98% free amino groups, results observed in RME). SaCE and AgNPs presented 33.2, 36.1% inhibitory activity on tyrosinase, respectively. In silico assay demonstrated interaction between steroidal saponins, DNA or tyrosinase. SaCE exhibited antitumor action against various human tumor cells. Data demonstrated that extracts SaCE alone and AgNPs synthesized from SaCE presented biological properties of interest for application in new therapeutic formulations in medicine.

The dried root of Ampelopsis japonica (Thunb.) Makino (A. japonica.) is a traditional medicine used to treat fever, pain, and wound healing. It exhibits anti-inflammatory, antitumor, antityrosinase, and antimelanogenic activities. In this paper, we used different solvent extracts from the root of A. japonica to determine their antioxidant activity. Acetone extract showed relatively strong antioxidant properties by 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH), superoxide radical scavenging activity, and ferric reducing antioxidant power (FRAP) assays. In addition, these extracts also showed significant α-glucosidase and acetylcholinesterase (AChE) inhibitory activities. Acetone extract significantly inhibited α-glucosidase with an IC50 value of 8.30 ± 0.78 μg/mL, and ethanol extract remarkably inhibited AChE with an IC50 value of 37.08 ± 7.67 μg/mL. Using HPLC analysis and comparison with the chemical composition of various solvent extracts, we isolated seven active compounds and assessed their antioxidant, anti-α-glucosidase, and anti-AChE activities. Catechin (1), gallic acid (2), kaempferol (3), quercetin (4), resveratrol (6), and epicatechin (7) were the main antioxidant components in the root of A. japonica. According to the results of DPPH, ABTS, and superoxide radical scavenging assays, these isolates showed stronger antioxidant capacity than butylated hydroxytoluene (BHT). Moreover, 1, 3, 4, euscaphic acid (5), 6, and 7 also expressed stronger anti-α-glucosidase activity than the positive control acarbose, and all the isolated compounds had a good inhibitory effect on AChE. Molecular docking models and hydrophilic interactive modes for AChE assays suggest that 1 and 5 exhibit unique anti-AChE potency. This study indicates that A. japonica and its active extracts and components may be a promising source of natural antioxidants, α-glucosidase, and AChE inhibitors.

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.

Design, synthesis and in vitro biological activities of coumarin linked 1,3,4-oxadiazole hybrids as potential multi-target directed anti-Alzheimer agents

Context: Rhizophora mucronata Lam. (Rhizophoraceae), commonly known as Asiatic mangrove, has been used traditionally among Asian countries as folk medicine.Objective: This study investigates the cholinesterase inhibitory potential and antioxidant activities of R. mucronata.Materials and method: Rhizophora mucronata leaves were successively extracted using solvents of varying polarity and a dosage of 100–500 µg/ml were used for each assay. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were assessed according to the method of Ellman. In vitro antioxidant activity was assessed using free radical scavenging, reducing power, and metal-chelating activity (duration – 3 months). Total phenolic and flavonoid content were quantified spectrophotometrically. Compound characterization was done using column chromatography, NMR, FTIR, and LC-MS analysis.Results: Methanolic leaf extract (500 µg/ml) exhibited the highest inhibitory activity against AChE (92.73 ± 0.54%) and BuChE (98.98 ± 0.17%), with an IC50 value of 59.31 ± 0.35 and 51.72 ± 0.33 µg/ml, respectively. Among the different solvent extracts, methanolic extract exhibited the highest antioxidant activity with an IC50 value of 47.39 ± 0.43, 401.45 ± 18.52, 80.23 ± 0.70, and 316.47 ± 3.56 µg/ml for DPPH, hydroxyl, nitric oxide radical, and hydrogen peroxide, respectively. Total polyphenolic and flavonoid contents in methanolic extract were observed to be 598.13 ± 1.85 µg of gallic acid equivalent and 48.85 ± 0.70 μg of rutin equivalent/mg of extract. Compound characterization illustrated (+)-catechin as the bioactive compound responsible for cholinesterase inhibitory and antioxidant activities.Conclusion: The presence of rich source of flavonoids, in particular catechin, might be responsible for its cholinesterase inhibitory and antioxidant activities.

Neuroprotective effects of bergenin in Alzheimer’s disease: Investigation through molecular docking, in vitro and in vivo studies