Geissoschizoline, a promising alkaloid for Alzheimer's disease: Inhibition of human cholinesterases, anti-inflammatory effects and molecular docking

Alkaloids as drug leads in Alzheimer's treatment: Mechanistic and therapeutic insights

Alzheimer's disease (AD) has few effective treatment options and continues to be a major global health concern. AD is a neurodegenerative disease that typically affects elderly people. Alkaloids have potential sources for novel drug discovery due to their diverse chemical structures and pharmacological activities. Alkaloids, natural products with heterocyclic nitrogen-containing structures, are considered potential treatments for AD. This review explores the neuroprotective properties of alkaloids in AD, focusing on their ability to regulate pathways such as amyloid-beta aggregation, oxidative stress, synaptic dysfunction, tau hyperphosphorylation, and neuroinflammation. The FDA has approved alkaloids such as acetylcholinesterase inhibitors like galantamine and rivastigmine. This article explores AD's origins, current market medications, and clinical applications of alkaloids in AD therapy. This review explores the development of alkaloid-based drugs for AD, focusing on pharmacokinetics, blood-brain barrier penetration, and potential adverse effects. Future research should focus on the clinical evaluation of promising alkaloids, developing recently discovered alkaloids, and the ongoing search for novel alkaloids for medical treatment. A pharmaceutical option containing an alkaloid may potentially slow down the progression of AD while enhancing its symptoms. This review highlights the potential of alkaloids as valuable drug leads in treating AD, providing a comprehensive understanding of their mechanisms of action and therapeutic implications.

A catalytic process enables efficient and programmable access to precisely altered indole alkaloid scaffolds

A compound's overall contour impacts its ability to elicit biological response, rendering access to distinctly shaped molecules desirable. A natural product's framework can be modified, but only if it is abundant and contains suitably modifiable functional groups. Here we introduce a programmable strategy for concise synthesis of precisely altered scaffolds of scarce bridged polycyclic alkaloids. Central to our approach is a scalable catalytic multi-component process that delivers diastereo- and enantiomerically enriched tertiary homoallylic alcohols bearing differentiable alkenyl moieties. We used one product to launch progressively divergent syntheses of a naturally occurring alkaloid and its precisely expanded, contracted and/or distorted framework analogues (average number of steps/scaffold of seven). In vitro testing showed that a skeleton expanded by one methylene in two regions is cytotoxic against four types of cancer cell line. Mechanistic and computational studies offer an account for several unanticipated selectivity trends.

Naturally Occurring Cholinesterase Inhibitors from Plants, Fungi, Algae, and Animals: A Review of the Most Effective Inhibitors Reported in 2012-2022

Since the development of the "cholinergic hypothesis" as an important therapeutic approach in the treatment of Alzheimer's disease (AD), the scientific community has made a remarkable effort to discover new and effective molecules with the ability to inhibit the enzyme acetylcholinesterase (AChE). The natural function of this enzyme is to catalyze the hydrolysis of the neurotransmitter acetylcholine in the brain. Thus, its inhibition increases the levels of this neurochemical and improves the cholinergic functions in patients with AD alleviating the symptoms of this neurological disorder. In recent years, attention has also been focused on the role of another enzyme, butyrylcholinesterase (BChE), mainly in the advanced stages of AD, transforming this enzyme into another target of interest in the search for new anticholinesterase agents. Over the past decades, Nature has proven to be a rich source of bioactive compounds relevant to the discovery of new molecules with potential applications in AD therapy. Bioprospecting of new cholinesterase inhibitors among natural products has led to the discovery of an important number of new AChE and BChE inhibitors that became potential lead compounds for the development of anti-AD drugs. This review summarizes a total of 260 active compounds from 142 studies which correspond to the most relevant (IC50 ≤ 15 μM) research work published during 2012-2022 on plant-derived anticholinesterase compounds, as well as several potent inhibitors obtained from other sources like fungi, algae, and animals.

Determination of Anti-Alzheimer's Disease Activity of Selected Plant Ingredients

Neurodegenerative diseases, among which one of the more common is Alzheimer’s disease, are the one of the biggest global public health challenges facing our generation because of the increasing elderly population in most countries. With the growing burden of these diseases, it is essential to discover and develop new treatment options capable of preventing and treating them. Neurodegenerative diseases, among which one of the most common is Alzheimer’s disease, are a multifactorial disease and therefore demand multiple therapeutic approaches. One of the most important therapeutic strategies is controlling the level of acetylcholine—a neurotransmitter in cholinergic synapses—by blocking the degradation of acetylcholine using acetylcholinesterase inhibitors such as tacrine, galantamine, donepezil and rivastigmine. However, these drugs can cause some adverse side effects, such as hepatotoxicity and gastrointestinal disorder. Thus, the search for new, more effective drugs is very important. In the last few years, different active constituents from plants have been tested as potential drugs in neurodegenerative disease therapy. The availability, lower price and less toxic effects of herbal medicines compared with synthetic agents make them a simple and excellent choice in the treatment of neurodegenerative diseases. The empirical approach to discovering new drugs from the systematic screening of plant extracts or plant-derived compounds is still an important strategy when it comes to finding new biologically active substances. The aim of this review is to identify new, safe and effective compounds that are potential candidates for further in vivo and clinical tests from which more effective drugs for the treatment of Alzheimer’s disease could be selected. We reviewed the methods used to determine anti-Alzheimer’s disease activity. Here, we have discussed the relevance of plant-derived compounds with in vitro activity. Various plants and phytochemical compounds have shown different activity that could be beneficial in the treatment of Alzheimer’s disorders. Most often, medicinal plants and their active components have been investigated as acetylcholinesterase and/or butyrylcholinesterase activity inhibitors, modifiers of β-amyloid processing and antioxidant agents. This study also aims to highlight species with assessed efficacy, usable plant parts and the most active plant components in order to identify species and compounds of interest for further study. Future research directions are suggested and recommendations made to expand the use of medicinal plants, their formulations and plant-derived active compounds to prevent, mitigate and treat Alzheimer’s disease.

An Integrated NMR, LC-DAD-MS, LC-QTOF Metabolomic Characterization of Sartoria hedysaroides: Correlation of Antioxidant and Enzyme Inhibitory Activity with Chemical Composition by Multivariate Data Analysis

Sartoria hedysaroides Boiss and Heldr. (Fabaceae) is an endemic plant of Turkey that has received little scientific consideration so far. In the present study, the chemical profiles of extracts from the aerial part and roots of S. hedysaroides obtained using solvents with different polarities were analyzed combining integrated NMR, LC-DAD-MSⁿ, and LC-QTOF methods. In vitro antioxidant and enzyme inhibitory activities were evaluated, and the results were combined with chemical data using multivariate approaches. Phenolic acids, flavonoids, ellagitannins, and coumarins were identified and quantified in the extracts of aerial part and roots. Methanolic extract of S. hedysaroides aerial part showed the highest phenolic content and the highest antioxidant activity and cupric ion reducing antioxidant capacity. Dichloromethane extract of S. hedysaroides roots showed the highest inhibition of butyryl cholinesterase, while methanolic extract of S. hedysaroides aerial part was the most active tyrosinase inhibitor. Multivariate data analysis allowed us to observe a good correlation between phenolic compounds, especially caffeoylquinic derivatives and flavonoids and the antioxidant activity of extracts. Acetylcholinesterase inhibition was correlated with the presence of caffeoylquinic acids and coumarins. Overall, the present study appraised the biological potential of understudied S. hedysaroides, and provided a comprehensive approach combining metabolomic characterization of plant material and multivariate data analysis for the correlation of chemical data with results from multi-target biological assays.

Antioxidant, Anti-Inflammatory, and Inhibition of Acetylcholinesterase Potentials of Cassia timoriensis DC. Flowers

Despite being widely used traditionally as a general tonic, especially in South East Asia, scientific research on Cassia timoriensis, remains scarce. In this study, the aim was to evaluate the in vitro activities for acetylcholinesterase (AChE) inhibitory potential, radical scavenging ability, and the anti-inflammatory properties of different extracts of C. timoriensis flowers using Ellman’s assay, a DPPH assay, and an albumin denaturation assay, respectively. With the exception of the acetylcholinesterase activity, to the best of our knowledge, these activities were reported for the first time for C. timoriensis flowers. The phytochemical analysis confirmed the existence of tannins, flavonoids, saponins, terpenoids, and steroids in the C. timoriensis flower extracts. The ethyl acetate extract possessed the highest phenolic and flavonoid contents (527.43 ± 5.83 mg GAE/g DW and 851.83 ± 10.08 mg QE/g DW, respectively) as compared to the other extracts. In addition, the ethyl acetate and methanol extracts exhibited the highest antioxidant (IC₅₀ 20.12 ± 0.12 and 34.48 ± 0.07 µg/mL, respectively), anti-inflammatory (92.50 ± 1.38 and 92.22 ± 1.09, respectively), and anti-AChE (IC₅₀ 6.91 ± 0.38 and 6.40 ± 0.27 µg/mL, respectively) activities. These results suggest that ethyl acetate and methanol extracts may contain bioactive compounds that can control neurodegenerative disorders, including Alzheimer’s disease, through high antioxidant, anti-inflammatory, and anti-AChE activities.