Biogenic synthesis of gold nanoparticles from Terminalia arjuna bark extract: assessment of safety aspects and neuroprotective potential via antioxidant, anticholinesterase, and antiamyloidogenic effects.

The development of neuroprotective drugs through eco-friendly production routes is a major challenge for current pharmacology. The present study was carried out to synthesize gold nanoparticles (AuNPs) through biogenic route using ethanolic bark extract of Terminalia arjuna, a plant of high interest in Asian traditional medicine, and to evaluate its neuroprotective effects. The synthesized AuNPs were characterized by UV-Vis spectroscopy, FTIR spectroscopy, XRD, FESEM, EDX, HRTEM, DLS, and zeta potential analyses. UV-Vis spectroscopy showed a characteristics SPR absorption band at 536 nm specific for AuNPs. XRD, TEM, and FESEM analyses revealed the formation of face-centered cubic crystalline, spherical and triangular shaped AuNPs, with size ranging between 20 and 50 nm. DLS and ZP analysis illustrated that the average size of AuNPs was 30 nm, which was found to be stable at 45 mv. The neuroprotective potential of AuNPs was evaluated by assessing its antioxidant, cholinesterase inhibitory, and antiamyloidogenic activities. AuNPs showed dose-dependant inhibition of acetylcholinesterase and butyrylcholinesterase with IC50 value of 4.25 ± 0.02 and 5.05 ± 0.02 µg/ml, respectively. In vitro antioxidant assays illustrated that AuNPs exhibited the highest reducing power and DPPH radical scavenging activity. In addition, AuNPs also efficiently suppressed the fibrillation of Aß and destabilized the preformed mature fibrils. Results of toxicity studies in PBMC and adult zebra fish illustrated that AuNPs are non-toxic and biocompatible. Overall, our results highlighted the AuNPs promising potential in terms of antioxidant, anticholinesterase, antiamyloidogenic effects, and non-lethality allowing us to propose these nanomaterials as a suitable candidate for the development of drugs helpful in the treatment of neurodegenerative disorders like Alzheimer's disease. Graphical abstract ᅟ.

Assessment of Enzyme Inhibition: A Review with Examples from the Development of Monoamine Oxidase and Cholinesterase Inhibitory Drugs.

The actions of many drugs involve enzyme inhibition. This is exemplified by the inhibitors of monoamine oxidases (MAO) and the cholinsterases (ChE) that have been used for several pharmacological purposes. This review describes key principles and approaches for the reliable determination of enzyme activities and inhibition as well as some of the methods that are in current use for such studies with these two enzymes. Their applicability and potential pitfalls arising from their inappropriate use are discussed. Since inhibitor potency is frequently assessed in terms of the quantity necessary to give 50% inhibition (the IC50 value), the relationships between this and the mode of inhibition is also considered, in terms of the misleading information that it may provide. Incorporation of more than one functionality into the same molecule to give a multi-target-directed ligands (MTDLs) requires careful assessment to ensure that the specific target effects are not significantly altered and that the kinetic behavior remains as favourable with the MTDL as it does with the individual components. Such factors will be considered in terms of recently developed MTDLs that combine MAO and ChE inhibitory functions.

Assessment of anti-cholinesterase activity and cytotoxicity of cagaita (Eugenia dysenterica) leaves.

Eugenia dysenterica ex DC Mart. (Myrtaceae) is a Brazilian tree with pharmacological and biological properties. The aqueous leaf extract, rich in polyphenols, was tested in the human neuroblastoma cell line SH-SY5Y to evaluate its effect on cell viability. The extract and two isolated compounds were also assessed for the potential inhibitory activity on acetylcholinesterase, an enzyme related to Alzheimer's disease. A simple chromatographic method using Sephadex LH-20 was developed to separate catechin and quercetin from the aqueous leaf extract of E. dysenterica. Identification was carried out by spectroscopic techniques IR, UV, and 1H and 13C NMR. The IC50 values were obtained by constructing dose-response curves on a graph with percentage inhibition versus log of inhibitor concentration and compared with physostigmine, a well-known AChE inhibitor. The extract was toxic for SH-SY5Y cells at concentrations higher than 7.8 µg/ml given for 24 h. The decline in SH-SY5Y cell viability appears to be related to its antiproliferative activity. The extract also showed relatively moderate acetylcholinesterase inhibitory activity of 66.33% ± 0.52% at 1.0 mg/ml with an IC50 value of 155.20 ± 2.09 µg/ml. Physostigmine, quercetin, and catechin showed IC50 values of 18.69 ± 0.07, 46.59 ± 0.49, and 42.39 ± 0.67 µg/ml, respectively.

Synthesis and Biological Assessment of Racemic Benzochromenopyrimidinimines as Antioxidant, Cholinesterase, and Aß1-42 Aggregation Inhibitors for Alzheimer's Disease Therapy.

Given the complex nature of Alzheimer's disease (AD), compounds that are able to simultaneously address two or more AD-associated targets show greater promise for development into drugs for AD therapy. Herein we report an efficient two-step synthesis and biological evaluation of new racemic benzochromene derivatives as antioxidants, inhibitors of cholinesterase and ß-amyloid (Aß1-42 ) aggregation. Based on the results of the primary screening, we identified 15-(3-methoxyphenyl)-9,11,12,15-tetrahydro-10H,14H-benzo[5,6]chromeno[2,3-d]pyrido[1,2-a]pyrimidin-14-imine (3 e) and 16-(3-methoxyphenyl)-9,10,11,12,13,16-hexahydro-15H-benzo[5',6']chromeno[2',3':4,5]pyrimido[1,2-a]azepin-15-imine (3 f) as new potential multitarget-directed ligands for AD therapy. Further in-depth biological analysis showed that compound 3 f is a good human acetylcholinesterase inhibitor [IC50 =(0.36±0.02) µm], has strong antioxidant activity (3.61 µmol Trolox equivalents), and moderate Aß1-42 antiaggregating power (40.3 %).

Synthesis, biological assessment and molecular modeling of new dihydroquinoline-3-carboxamides and dihydroquinoline-3-carbohydrazide derivatives as cholinesterase inhibitors, and Ca channel antagonists.

The synthesis, biological evaluation, and molecular modeling of new 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxamides(4), 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carbohydrazide (6), and some hexahydropyrimido[5,4-c]quinoline-2,5-diones (9) produced earlier by our laboratory, as AChE/BuChE inhibitors, is described. From these analyses compound 4c resulted equipotent regarding the inhibition of cholinesterases'; inhibitors 6k, 9a, 9b were selective for AChE, whereas product 4d proved selective for BuChE. Docking analysis has been carry out in order to identify the binding mode in the active site, and to explain the observed selectivities. Only compound 9a has been shown to decrease K(+)-induced calcium signals in bovine chromaffin cells.

Development of square wave voltammetry method for the assessment of organophosphorus compound impact on the cholinesterase of Pheretima with 2,6-dichloroindophenol as a redox indicator.

A square wave voltammetry method was developed for the assessment of organophosphorus (OPs) compound impact on the cholinesterase of Pheretima with 2,6-dichloroindophenol (2,6-DCIP) as a redox indicator. The substrate of acetylthiocholine is hydrolysed by the cholinesterase (ChE) from soil animal pheretima, and the produced thiocholine reacts with the 2,6-DCIP to give obvious shift of electrochemical signal. The inhibition of ChE was assessed by measuring the enzyme activity before and after incubating with parathion-methyl. The reduction peak current of 2,6-DCIP decreases with the time of enzymatical reaction. The ChE loses almost 32.74% activity after 10 min incubation with 1ng mL(-1) paraoxon and 54.62% with 10 microg mL(-1) paraoxon, while the activity that corresponds to 100 microg mL(-1) paraoxon was nearly completely inhibited. This method can be employed to assess the inhibition of ChE and investigate OPs impact on environmental animals.

New friendly tools for users of ESTHER, the database of the alpha/beta-hydrolase fold superfamily of proteins.

The structural alpha/beta-hydrolase fold is characterized by a beta-sheet core of five to eight strands connected by alpha-helices to form a alpha/beta/alpha sandwich. The superfamily members, exemplified by the cholinesterases, diverged from a common ancestor into a number of hydrolytic enzymes displaying a wide range of substrate specificities, along with proteins with no recognized hydrolytic activity. In the enzymes, the catalytic triad residues are presented on loops of which one, the nucleophile elbow, is the most conserved feature of the fold. Of the other proteins, which all lack from one to all of the catalytic residues, some may simply be 'inactive' enzymes while others have been shown to be involved in heterologous surface recognition functions. The ESTHER (for esterases, alpha/beta-hydrolase enzymes and relatives) database (http://bioweb.ensam.inra.fr.esther) gathers and annotates all the published pieces of information (gene and protein sequences; biochemical, pharmacological, and structural data) related to the superfamily, and connects them together to provide the bases for studying structure-function relationships within the superfamily. The most recent developments of the database are presented.

Common EF-hand motifs in cholinesterases and neuroligins suggest a role for Ca2+ binding in cell surface associations.

Comparisons of protein sequence via cyclic training of Hidden Markov Models (HMMs) in conjunction with alignments of three-dimensional structure, using the Combinatorial Extension (CE) algorithm, reveal two putative EF-hand metal binding domains in acetylcholinesterase. Based on sequence similarity, putative EF-hands are also predicted for the neuroligin family of cell surface proteins. These predictions are supported by experimental evidence. In the acetylcholinesterase crystal structure from Torpedo californica, the first putative EF-hand region binds the Zn2+ found in the heavy metal replacement structure. Further, the interaction of neuroligin 1 with its cognate receptor neurexin depends on Ca2+. Thus, members of the alpha,beta hydrolase fold family of proteins contain potential Ca2+ binding sites, which in some family members may be critical for heterologous cell associations.