Acetylcholinesterase inhibitory activity, anti-inflammatory, and neuroprotective potential of Hippeastrum psittacinum (Ker Gawl.) herb (Amaryllidaceae).

Hippeastrum psittacinum, Amaryllidaceae, is used in traditional medicine as a purgative, aphrodisiac, and anticough remedy. The ethanol extract (EE) and alkaloid-rich fractions (ARF) from H. psittacinum bulbs were evaluated for their acetylcholinesterase (AChE) inhibition. The EE cytotoxic and anti-inflammatory effects in RAW 264.7 cells, and the neuroprotective and genotoxic activities in SH-SY5Y cells, were also estimated. Fifteen alkaloids were identified in the EE by gas chromatography-mass spectrometry. ARFs were less active for AChE inhibition than EE. The viability of both cell lines was higher than 70% with EE concentrations below 25 µg/mL. The EE decreased nitrite release in RAW cells stimulated with lipopolysaccharide, showing values of 83, 67, and 53% at 6.25, 12.5, and 25 µg/mL, respectively. Furthermore, the EE partially protected SH-SY5Y cells from hydrogen peroxide-mediated deleterious effects by approximately 50% at the same concentrations. The micronucleus assays showed that the extract caused chromosomal missegregation at concentrations above 12.5 µg/mL. The in silico analyses showed that some alkaloids presented properties of permeation of the blood-brain barrier and the intestine. Our findings present new evidence of the potential of H. psittacinum potential as an AChE inhibitor, as well as an anti-inflammatory and neuroprotective agent.

From dual binding site acetylcholinesterase inhibitors to allosteric modulators: A new avenue for disease-modifying drugs in Alzheimer's disease.

The lack of an effective treatment for Alzheimer' disease (AD), an increasing prevalence and severe neurodegenerative pathology boost medicinal chemists to look for new drugs. Currently, only acethylcholinesterase (AChE) inhibitors and glutamate antagonist have been approved to the palliative treatment of AD. Although they have a short-term symptomatic benefits, their clinical use have revealed important non-cholinergic functions for AChE such its chaperone role in beta-amyloid toxicity. We propose here the design, synthesis and evaluation of non-toxic dual binding site AChEIs by hybridization of indanone and quinoline heterocyclic scaffolds. Unexpectely, we have found a potent allosteric modulator of AChE able to target cholinergic and non-cholinergic functions by fixing a specific AChE conformation, confirmed by STD-NMR and molecular modeling studies. Furthermore the promising biological data obtained on human neuroblastoma SH-SY5Y cell assays for the new allosteric hybrid 14, led us to propose it as a valuable pharmacological tool for the study of non-cholinergic functions of AChE, and as a new important lead for novel disease modifying agents against AD.

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.

Galanthamine decreases genotoxicity and cell death induced by ß-amyloid peptide in SH-SY5Y cell line.

Biochemically, Alzheimers disease (AD) is characterized by the presence of abnormal deposition of beta amyloid peptide (Aß(1-42)), which is generated by proteolytic processing from its precursor, the amyloid precursor protein (APP) in a non-physiological pathway. The presence of Aß(1-42) in the brain is strongly correlated with cognitive impairment, cholinergic deficiency, bioenergetics disruption, cell death and DNA damage. Galanthamine is an acetylcholinesterase inhibitor (AChEI) used to symptomatic treatment of Alzheimers disease (AD). Several studies have showed that galanthamine has antioxidant properties, anti-apoptotic action and also promotes neurogenesis; however, it is unknown whether galanthamine may present protection mechanisms against Aß(1-42)-induced genomic instability. To understand the mechanisms of this neuroprotection, we studied the effects of galanthamine on the cell toxicity and DNA strand breaks induced by Aß(1-42) using a set of biomarkers such as clonogenic assay, cytokinesis block micronucleus cytome (CBNM-cyt) and comet assay. The results showed that galanthamine treatments were capable to significantly reduce the Aß(1-42)-induced cytotoxicity and genotoxicity. In conclusion, this study demonstrated that in addition to inhibition of acetylcholinesterase (AChE), galanthamine exerts antigenotoxic properties. This relevant property of galanthamine is worthwhile exploring further which may improve the development of new diseases-modifying agents.