Cholinesterase and Prolyl Oligopeptidase Inhibitory Activities of Alkaloids from Argemone platyceras (Papaveraceae)

Bitter yet beneficial: The dual role of dietary alkaloids in managing diabetes and enhancing cognitive function

With the rising prevalence of diabetes and its association with cognitive impairment, interest in the use of dietary alkaloids and other natural products has grown significantly. Understanding how these compounds manage diabetic cognitive dysfunction (DCD) is crucial. This comprehensive review explores the etiology of DCD and the effects of alkaloids in foods and dietary supplements that have been investigated as DCD therapies. Data on how dietary alkaloids like berberine, trigonelline, caffeine, capsaicin, 1-deoxynojirimycin, nuciferine, neferine, aegeline, tetramethylpyrazine, piperine, and others regulate cognition in diabetic disorders were collected from PubMed, Research Gate, Web of Science, Science Direct, and other relevant databases. Dietary alkaloids could improve memory in behavioral models and modulate the mechanisms underlying the cognitive benefits of these compounds, including their effects on glucose metabolism, gut microbiota, vasculopathy, neuroinflammation, and oxidative stress. Evidence suggests that dietary alkaloids hold promise for improving cognition in diabetic patients and could open exciting avenues for future research in diabetes management.

Cholinesterase Inhibitory and In Silico Toxicity Assessment of Thirty-Four Isoquinoline Alkaloids - Berberine as the Lead Compound

BACKGROUND

Cholinesterase (ChE) inhibitors used currently in clinics for the treatment of Alzheimer's disease (AD) are the most prescribed drug class with nitrogen-containing chemical formula. Galanthamine, the latest generation anti-ChE drug, contains an isoquinoline structure.

OBJECTIVE

The aim of the current study was to investigate the inhibitory potential of thirty-four isoquinoline alkaloids, e.g. (-)-adlumidine, β-allocryptopine, berberine, (+)-bicuculline, (-)-bicuculline, (+)-bulbocapnine, (-)-canadine, (±)-chelidimerine, corydaldine, (±)-corydalidzine, (-)-corydalmine, (+)-cularicine, dehydrocavidine, (+)-fumariline, (-)-fumarophycine, (+)-α-hydrastine, (+)-isoboldine, 13-methylcolumbamine, (-)-norjuziphine, norsanguinarine, (-)-ophiocarpine, (-)-ophiocarpine-Noxide, oxocularine, oxosarcocapnine, palmatine, (+)-parfumine, protopine, (+)-reticuline, sanguinarine, (+)-scoulerine, (±)-sibiricine, (±)-sibiricine acetate, (-)-sinactine, and (-)-stylopine isolated from several Fumaria (fumitory) and Corydalis species towards acetyl- (AChE) and butyrylcholinesterase (BChE) by microtiter plate assays. The alkaloids with strong ChE inhibition were proceeded to molecular docking simulations as well as in silico toxicity screening for their mutagenic capacity through VEGA QSAR (AMES test) consensus model and VEGA platform as statistical approaches. The inputs were evaluated in a simplified molecular input-line entry system (SMILES).

METHODS

ChE inhibition assays indicated that the highest AChE inhibition was caused by berberine (IC50: 0.72 ± 0.04 μg/mL), palmatine (IC50: 6.29 ± 0.61 μg/mL), β-allocryptopine (IC50: 10.62 ± 0.45 μg/mL), (-)-sinactine (IC50: 11.94 ± 0.44 μg/mL), and dehydrocavidine (IC50: 15.01 ± 1.87 μg/mL) as compared to that of galanthamine (IC50: 0.74 ± 0.01 μg/mL), the reference drug with isoquinoline skeleton. Less number of the tested alkaloids exhibited notable BChE inhibition. Among them, berberine (IC50: 7.67 ± 0.36 μg/mL) and (-)-corydalmine (IC50: 7.78 ± 0.38 μg/mL) displayed a stronger inhibition than that of galanthamine (IC50: 12.02 ± 0.25 μg/mL). The mutagenic activity was shown for β-allocryptopine, (+)- and (-)-bicuculline, (±)-corydalidzine, (-)-corydalmine, (+)-cularicine, (-)- fumarophycine, (-)-norjuziphine, (-)-ophiocarpine-N-oxide, (+)-scoulerine, (-)-sinactine, and (-)- stylopine by means of in silico experiments.

RESULTS

The results obtained by molecular docking simulations of berberine, palmatine, and (-)- corydalmine suggested that the estimated free ligand-binding energies of these compounds inside the binding domains of their targets are reasonable to make them capable of establishing strong polar and nonpolar bonds with the atoms of the active site amino acids.

CONCLUSION

Our findings revealed that berberine, palmatin, and (-)-corydalmine stand out as the most promising isoquinoline alkaloids in terms of ChE inhibition. Among them, berberine has displayed a robust dual inhibition against both ChEs and could be evaluated further as a lead compound for AD.

New trends in the practical use of isoquinoline alkaloids as potential drugs applicated in infectious and non-infectious diseases

In the last years, traditional natural products have been the center of attention for the scientific community and exploration of their therapeutic abilities is proceeding permanently. Isoquinoline alkaloids have always attracted scientific interest due to either their positive or negative effects on human organism. The present review describes research on isoquinoline alkaloids isolated from different plant species. Alkaloids are one of the most important classes of plant derived compounds among these isoquinoline alkaloids possess varied biological activities such as anticancer, antineurodegenerative diseases, antidiabetic, antiinflammatory, antimicrobial, and many others. The use of plants against different disorders is entrenched in traditional medicine around the globe. Recent progress in modern therapeutics has stimulated the use of natural products worldwide for various ailments and diseases. The review provides a collection of information on the capabilities of some isoquinoline alkaloids, its potential for the treatment of various diseases and is designed to be a guide for future research on different biologically active isoquinoline alkaloids and plant species containing them. The authors are aware that they were not able to cover the whole area of the topic related to biological activity of isoquinoline alkaloids. This review is intended to suggest directions for further research and can also help other researchers in future studies.

Research progress of plant-derived natural alkaloids in central nervous system diseases

Central nervous system (CNS) disease is one of the most important causes of human death. Because of their complex pathogenesis, more and more attention has been paid to them. At present, drug treatment of the CNS is the main means; however, most drugs only relieve symptoms, and some have certain toxicity and side effects. Natural compounds derived from plants can provide safer and more effective alternatives. Alkaloids are common nitrogenous basic organic compounds found in nature, which exist widely in many kinds of plants and have unique application value in modern medicine. For example, Galantamine and Huperzine A from medicinal plants are widely used drugs on the market to treat Alzheimer's disease. Therefore, the main purpose of this review is to provide the available information on natural alkaloids with the activity of treating central nervous system diseases in order to explore the trends and perspectives for the further study of central nervous system drugs. In this paper, 120 alkaloids with the potential effect of treating central nervous system diseases are summarized from the aspects of sources, structure types, mechanism of action and structure-activity relationship.

Advances in the discovery of heterocyclic-based drugs against Alzheimer's disease

INTRODUCTION

Alzheimer's disease is a multifactorial neurodegenerative disorder characterized by beta-amyloid accumulation and tau protein hyperphosphorylation. The disease involves interconnected mechanisms, which can be clustered into two target-packs based on the affected proteins. Pack-1 focuses on beta-amyloid accumulation, oxidative stress, and metal homeostasis dysfunction, and Pack-2 involves tau protein, calcium homeostasis, and neuroinflammation. Against this background heterocyclic system, there is a powerful source of pharmacophores to develop effective small drugs to treat multifactorial diseases like Alzheimer's.

AREAS COVERED

This review highlights the most promising heterocyclic systems as potential hit candidates with multi-target capacity for the development of new drugs targeting Alzheimer's disease. The selection of these heterocyclic systems was based on two crucial factors: their synthetic versatility and their well-documented biological properties of therapeutic potential in neurodegenerative diseases.

EXPERT OPINION

The synthesis of small drugs against Alzheimer's disease requires a multifactorial approach that targets the key pathological proteins. In this context, the utilization of heterocyclic systems, with well-established synthetic processes and facile functionalization, becomes a crucial element in the design phases. Furthermore, the selection of hit heterocyclic should be guided by a full understanding of their biological activities. Thus, the identification of promising heterocyclic scaffolds with known biological effects increases the potential to develop effective molecules against Alzheimer's disease.

A Study of the Chemical Composition and Biological Activity of Michelia macclurei Dandy Heartwood: New Sources of Natural Antioxidants, Enzyme Inhibitors and Bacterial Inhibitors

The wood of Michelia macclurei Dandy (MD) is an excellent material that is widely used in the furniture, handicraft, and construction industries. However, less research has been conducted on the chemical composition and biological activity of heartwood, which is the main valuable part of the wood. This study aimed to investigate the chemical composition and biological activities of the heartwood of Michelia macclurei Dandy (MDHW) and to confirm the active ingredients. Triple quadrupole gas chromatography-mass spectrometry (GC-MS) was used to characterize the volatile components of MDHW, while ultra-performance liquid chromatography-mass spectrometry was used to analyze the non-volatile components (UPLC-MS). The total reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging assays, acetylcholinesterase and α-glucosidase inhibition assays, and an antimicrobial test of 4 gram bacteria were used to describe the in vitro bioactivities. The GC-MS analysis showed that the volatile components of MDHW were mainly fatty compounds and terpenoids, with sesquiterpenes and their derivatives dominating the terpene composition. β-elemene was the main terpene component in the steam distillation (11.88%) and ultrasonic extraction (8.2%) methods. A total of 67 compounds, comprising 45 alkaloids, 9 flavonoids, 6 lignans, and others, were found by UPLC-MS analysis. The primary structural kinds of the non-volatile components were 35 isoquinoline alkaloids. Alkaloids were the predominant active constituent in all MDHW extracts, including crude extracts, alkaloid fractions, and non-alkaloid fractions. These extracts all demonstrate some biological effects in terms of antioxidant, enzyme inhibition, and bacterial inhibition. The findings of this study show that MDHW is abundant in chemical structure types, has great bioactivity assessment, and has the potential to be used to create natural antioxidants, products that postpone Alzheimer's disease and lower blood sugar levels and antibacterial agents.

Chemical Synthesis and Biological Activities of Amaryllidaceae Alkaloid Norbelladine Derivatives and Precursors

Amaryllidaceae alkaloids (AAs) are a structurally diverse family of alkaloids recognized for their many therapeutic properties, such as antiviral, anti-cholinesterase, and anticancer properties. Norbelladine and its derivatives, whose biological properties are poorly studied, are key intermediates required for the biosynthesis of all ~650 reported AAs. To gain insight into their therapeutic potential, we synthesized a series of O-methylated norbelladine-type alkaloids and evaluated their cytotoxic effects on two types of cancer cell lines, their antiviral effects against the dengue virus (DENV) and the human immunodeficiency virus 1 (HIV-1), and their anti-Alzheimer’s disease (anti-cholinesterase and -prolyl oligopeptidase) properties. In monocytic leukemia cells, norcraugsodine was highly cytotoxic (CC50 = 27.0 μM), while norbelladine was the most cytotoxic to hepatocarcinoma cells (CC50 = 72.6 μM). HIV-1 infection was impaired only at cytotoxic concentrations of the compounds. The 3,4-dihydroxybenzaldehyde (selectivity index (SI) = 7.2), 3′,4′-O-dimethylnorbelladine (SI = 4.8), 4′-O-methylnorbelladine (SI > 4.9), 3′-O-methylnorbelladine (SI > 4.5), and norcraugsodine (SI = 3.2) reduced the number of DENV-infected cells with EC50 values ranging from 24.1 to 44.9 μM. The O-methylation of norcraugsodine abolished its anti-DENV potential. Norbelladine and its O-methylated forms also displayed butyrylcholinesterase-inhibition properties (IC50 values ranging from 26.1 to 91.6 μM). Altogether, the results provided hints of the structure−activity relationship of norbelladine-type alkaloids, which is important knowledge for the development of new inhibitors of DENV and butyrylcholinesterase.

Two new isoquinoline alkaloids from Cryptocarya wrayi and their biological activities

Two new isoquinoline alkaloids, cryptowrayines A (1) and B (2), along with one known pavine alkaloid (-)-12-hydroxyeschscholtzidine (3), were isolated from the twigs of Cryptocarya wrayi. The structures of new compounds were elucidated by extensive spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Both compounds 1 and 2 exhibited moderate quinone reductase inducing activity in Hepa 1c1c7 cells.

Recent Progress on Biological Activity of Amaryllidaceae and Further Isoquinoline Alkaloids in Connection with Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive age-related neurodegenerative disease recognized as the most common form of dementia among elderly people. Due to the fact that the exact pathogenesis of AD still remains to be fully elucidated, the treatment is only symptomatic and available drugs are not able to modify AD progression. Considering the increase in life expectancy worldwide, AD rates are predicted to increase enormously, and thus the search for new AD drugs is urgently needed. Due to their complex nitrogen-containing structures, alkaloids are considered to be promising candidates for use in the treatment of AD. Since the introduction of galanthamine as an antidementia drug in 2001, Amaryllidaceae alkaloids (AAs) and further isoquinoline alkaloids (IAs) have been one of the most studied groups of alkaloids. In the last few years, several compounds of new structure types have been isolated and evaluated for their biological activity connected with AD. The present review aims to comprehensively summarize recent progress on AAs and IAs since 2010 up to June 2021 as potential drugs for the treatment of AD.

First Total Synthesis of the Pavine Alkaloid (±)-Neocaryachine and Its Optical Resolution

The first total synthesis of (±)-neocaryachine (1) was achieved using a radical cyclization to produce the dibenzo-9-azabicyclo[3.3.1]nonane pavine skeleton, following a Bischler-Napieralski reaction to construct an intermediate benzylisoquinoline. The resulting racemic mixture was separated by chiral column chromatography to provide pure (+)- and (-)-1.

Flavopereirine-An Alkaloid Derived from Geissospermum vellosii-Presents Leishmanicidal Activity In Vitro

Chemotherapy is limited in the treatment of leishmaniasis due to the toxic effects of drugs, low efficacy of alternative treatments, and resistance of the parasite. This work assesses the in vitro activity of flavopereirine on promastigote cultures of Leishmania amazonensis. In addition, an in silico evaluation of the physicochemical characteristics of this alkaloid is performed. The extract and fractions were characterized by thin-layer chromatography and HPLC-DAD, yielding an alkaloid identified by NMR. The antileishmanial activity and cytotoxicity were assayed by cell viability test (MTT). The theoretical molecular properties were calculated on the Molinspiration website. The fractionation made it possible to isolate a beta-carboline alkaloid (flavopereirine) in the alkaloid fraction. Moreover, it led to obtaining a fraction with greater antileishmanial activity, since flavopereirine is very active. Regarding the exposure time, a greater inhibitory effect of flavopereirine was observed at 24 h and 72 h (IC₅₀ of 0.23 and 0.15 μg/mL, respectively). The extract, fractions, and flavopereirine presented low toxicity, with high selectivity for the alkaloid. Furthermore, flavopereirine showed no violation of Lipinski's rule of five, showing even better results than the known inhibitor of oligopeptidase B, antipain, with three violations. Flavopereirine also interacted with residue Tyr-499 of oligopeptidase B during the molecular dynamics simulations, giving a few insights of a possible favorable mechanism of interaction and a possible inhibitory pathway. Flavopereirine proved to be a promising molecule for its antileishmanial activity.

Chemical constituents from Valeriana polystachya Smith and evaluation of their effects on the acetylcholinesterase and prolyl oligopeptidase activities

Two new iridoids (1-2) and a new decomposition product of valepotriates (3), together with fifteen known compounds (4-18) were isolated from the roots and rhizomes of Valeriana polystachya Smith, a native species from the Pampa Biome. Their structures were elucidated by means of NMR spectroscopy, mass spectrometry and optical rotation. The structures of 3 and 18 were further confirmed by single crystal X-ray diffraction analysis. In the group of the isolated compounds, 6β-hydroxysitostenone, hydroxymaltol and isovillosol were isolated from the Valeriana genus for the first time. The extracts and isolated compounds were evaluated for their in vitro activities against acetylcholinesterase (AChE) and prolyloligopeptidase (POP). Compounds 7, 9 and 11 showed weak inhibitory activity against AChE, while 3 and 5 displayed exceptional POP inhibitory activity, with IC₅₀ values of 5.3 ± 0.07 and 7.9 ± 0.4 μM, respectively.

Identification and characterization of a novel prolyl oligopeptidase in filarial parasite Setaria cervi

A 75 kDa serine protease having prolyl oligopeptidase activity has been purified from Setaria cervi, a bovine filarial parasite. The MALDI-MS/MS analysis of the purified protein revealed 6 peptides showing nearest match S9A (prolyl oligopeptidase) family protein from Plesiocystis pacifica. The ScPOP was found to be unique compared to mammalian POP with respect to its kinetic properties. To elucidate its role, filarial parasites were exposed to specific inhibitor of POP, Z-Pro-prolinal (ZPP) for 8 h. The inhibition of POP induced calcium signaling via phospholipase c stimulation which further triggered mitochondrial mediated apoptosis in filarial parasites.