Dual BACE1 and Cholinesterase Inhibitory Effects of Phlorotannins from Ecklonia cava-An In Vitro and in Silico Study

The Advancements of Marine Natural Products in the Treatment of Alzheimer's Disease: A Study Based on Cell and Animal Experiments

As life expectancy rises and the aging population grows, Alzheimer's disease (AD) has become a significant global health concern. AD is a complex neurodegenerative disorder with an unclear etiology. Current hypotheses primarily focus on β-amyloid (Aβ) aggregation, tau protein hyperphosphorylation, and neuroinflammation as key pathological processes. Given the limited efficacy of existing therapeutic strategies, there is an urgent need to explore novel treatment options. Marine natural products have garnered significant attention due to their unique chemical structures and diverse bioactivities, demonstrating potential for multi-target interventions in AD. This review systematically summarizes the roles of marine-derived compounds, including polysaccharides, carotenoids, and polyphenols, in modulating Aβ aggregation, mitigating tau protein pathology, and regulating gut-brain axis dysfunction. Furthermore, the challenges of current research are discussed, with an emphasis on improving blood-brain barrier permeability and optimizing drug delivery systems to facilitate clinical translation.

A Narrative Review on the Neuroprotective Potential of Brown Macroalgae in Alzheimer's Disease

Systematic Alzheimer's disease (AD) is a neurodegenerative disease increasingly prevalent in the aging population. AD is characterized by pathological features such as β-amyloid (Aβ) plaque accumulation, tau neurofibrillary tangles formation, oxidative stress, an impaired cholinergic system, and neuroinflammation. Many therapeutic drugs have been developed to slow the progression of AD by targeting these pathological mechanisms. However, synthetic drugs, such as donepezil and memantine, can often lead to side effects. In this context, seaweeds have been drawing attention as a nutrient source and a potential source of health-improving metabolites. Studies have shown that extracts from brown macroalgae can potentially reduce the inflammation associated with neurodegenerative diseases by inhibiting proinflammatory cytokine expression. Furthermore, their bioactive compounds exhibit antioxidant properties vital in combating oxidative stress. Antioxidants, mainly carotenoids and phenolic compounds, have been linked to improved cognitive function and a reduced risk of neurodegenerative disorders by protecting neuronal cells through their ability to scavenge free radicals. In addition, omega-3 fatty acids found in certain macroalgae have the potential to support brain health and cognitive function, further enhancing their neuroprotective effects. In conclusion, this review has comprehensively evaluated the research conducted on brown macroalgae in the last five years, covering their potential bioactive compounds, methods of obtaining these compounds, and their neuroprotective properties against AD. The limited number of clinical studies in the literature highlights the need for further research. This narrative review provides a basic framework for new approaches to neuroprotective strategies, such as those associated with brown macroalgae natural resources. Furthermore, they may play an increasingly important role in developing functional foods and nutraceuticals that can support human health in preventing and managing neurodegenerative diseases.

Tannins-enriched fraction of TeMac™ protects against aluminum chloride induced Alzheimer's disease-like pathology by modulating aberrant insulin resistance and alleviating oxidative stress in diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease is the most common neurodegenerative disease with therapeutic limitations. Insulin resistance plays a role in the progression of Alzheimer's disease. Therapies that modulate insulin secretion and signaling, as well as oxidative stress in the brain are now being investigated for their potential role in the prevention of Alzheimer's disease (AD). Terminalia macroptera (Combretaceae) is a plant that different parts have been used traditionally for the treatment of metabolic and neurological conditions. Previous study has indicated that the crude extract exhibit anti-diabetic property. In addition, the plant is a rich source of tannins, phenolic acids, flavonoids, triterpenes. However, there is no study on its protective effect against biochemical alterations of AD in diabetic rats.

AIM OF THE STUDY

The present research study investigated the neuroprotective effects of TeMac™ on Alzheimer-like pathology induced by aluminum chloride (AlCl3) in diabetic rats.

METHODS

A phytochemical analysis of TeMac™ was carried out to quantify tannins. The potential effect of the tannins-enriched fraction (TEF) of TeMac™ to prevent the formation of senile plaques was conducted by its ability to inhibit the activities of β-secretase (EC 3.4.23.46), monoamine oxidase A (EC 1.4.3.4) and the fibrillation of Aβ. A diabetic model was induced from female Wistar rats by a single intraperitoneal injection of streptozotocin (STZ, 35 mg/kg BW). After that, the blood glucose level was measured to confirm the induction of diabetes. Three days after induction, animals received AlCl3 (75 mg/kg BW) alone (AD control) or concomitantly with 400 mg/kg BW of TEF of TeMac™ or 5 mg/kg BW Daonil by daily gavage for 42 days. At the end of the experiment, rats were sacrificed, blood and brains were collected. The levels of amyloid fibrils, glucose, albumin and the activities of DPP4, β-secretase and phosphatase, and markers of oxidative stress in the brain were assessed.

RESULTS

TEF of TeMac™ displays a potential ability to inhibit the activities of β-secretase, monoamine oxidase, and Aβ fibrillation. Treatment with TEF of TeMac™ significantly inhibited DPP4 and BACE1 activities and reduced brain glucose and amyloid fibril levels, and improved cerebral albumin levels and modulated oxidative stress markers.

CONCLUSION

Our findings indicate that TEF of TeMac™ prevents Alzheimer's-type pathology linked to insulin resistance in rats. TEF of TeMac™ may be a potential drug candidate for the treatment of diabetes-associated cognitive impairment.

Exploring the potential of Scabiosa columbaria in Alzheimer's disease treatment: An in silico approach

Objectives

Alzheimer's disease (AD) is posing an increasing global threat and currently lacks effective treatments. Therefore, this study was aimed at exploring phytochemicals in Scabiosa columbaria (S. columbaria) as inhibitors of acetylcholinesterase (AChE), β-site APP cleavage enzyme 1 (BACE1), and TNF-α converting enzyme (TACE) in AD. S. columbaria contains various bioactive compounds, such as chlorogenic acid, linalool, and catechins, which are known for their detoxification properties, capacity to resist and manage harmful moisture buildup, and therapeutic roles in COVID-19. Several studies have also shown that S. columbaria extract has strong antioxidant activity, and may potentially decrease neuroinflammation in AD. Therefore, this study investigated the interactions between S. columbaria phytochemicals and key enzymes associated with AD, thus providing opportunities for the development of new therapeutic candidates.

Methods

A total of 27 phytochemicals were evaluated for their inhibitory activity against AChE, BACE1, and TACE with YASARA Structure. ADMET profiles and toxicity were assessed. The top candidate compounds underwent 100 ns MD simulations.

Results

All ligands met Lipinski's rule and showed low toxicity. Catechins, compared with the known drug galantamine, showed higher inhibitory activity and interacted with additional active sites on AChE, thus suggesting potentially higher efficacy. Moreover, chlorogenic acid showed stronger inhibitory activity against TACE than the control drug (aryl-sulfonamide), thereby suggesting a different mechanism of action. MD simulation revealed that the formed complexes had good stability. However, further exploration is necessary.

Conclusion

S. columbaria derivative compounds are promising drug candidates because of their properties, including the affinity of chlorogenic acid toward TACE and hydrogen bond enhancing ligand-receptor interactions. MD simulation indicated stable ligand-protein complexes, and the radius of gyration and MM-PBSA calculations revealed favorable binding and interaction energies. Our findings demonstrate the identified compounds' potential for further drug development.

Marine Pharmacology in 2019-2021: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The current 2019-2021 marine pharmacology literature review provides a continuation of previous reviews covering the period 1998 to 2018. Preclinical marine pharmacology research during 2019-2021 was published by researchers in 42 countries and contributed novel mechanism-of-action pharmacology for 171 structurally characterized marine compounds. The peer-reviewed marine natural product pharmacology literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral mechanism-of-action studies for 49 compounds, 87 compounds with antidiabetic and anti-inflammatory activities that also affected the immune and nervous system, while another group of 51 compounds demonstrated novel miscellaneous mechanisms of action, which upon further investigation, may contribute to several pharmacological classes. Thus, in 2019-2021, a very active preclinical marine natural product pharmacology pipeline provided novel mechanisms of action as well as new lead chemistry for the clinical marine pharmaceutical pipeline targeting the therapy of several disease categories.

Phytochemical constituents analysis in laminaria digitata for Alzheimer's disease: molecular docking and in-silico toxicity approach

Alzheimer's disease (AD) is a common brain disease associated with cognitive impairment and dementia. donepezil, an acetylcholinesterase (AChE) inhibitor drug as a commercial AD drug represents a non-cost-effective treatment with the toxic effects reported. As the prevalence of AD increases, the development of effective therapeutic treatments is urgently required. Laminaria digitata is a brown seaweed claimed to be able to prevent and treat neurodegenerative diseases. Therefore, this study measured and compared the binding affinity and toxicity of seven common phytoconstituents in Laminaria digitata against acetylcholinesterase (AChE) with those of donepezil using a molecular docking approach. The binding free energy values of donepezil, dieckol, eckol, fucodiphlorethol G, 7-Phloroecol, laminaran, alginic acid, and fucoidan with acetylcholinesterase (AChE) were -12.3, -13.5, -10.5, -8,7, -9.7, -8.0, -10.3, and -7.4 kcal/mol. All ligands constantly interacted with the AChE amino acid residues, namely Tyr124. Dieckol, with the strongest and most stable interaction, is classified as class IV toxicity, with an LD50 value of 866 mg/kg. It has aryl hydrocarbon receptor (AhR) and mitochondrial membrane potential (MMP) toxicity at certain doses. Theoretically, based on Lipinski's rule, dieckol is likely to have poor absorption and permeation properties; therefore, several considerations during the drug discovery process are needed.

Phytochemical compounds with promising biological activities from Ascophyllum nodosum extracts using microwave-assisted extraction

Phytochemical-rich antioxidant extracts were obtained from Ascophyllum nodosum (AN) using microwave-assisted extraction (MAE). Critical extraction factors such as time, pressure, and ethanol concentration were optimized by response surface methodology with a circumscribed central composite design. Under the optimal MAE conditions (3 min, 10.4 bar, 46.8 % ethanol), the maximum recovery of phytochemical compounds (polyphenols and fucoxanthin) with improved antioxidant activity from AN was obtained. In addition, the optimized AN extract showed significant biological activities as it was able to scavenge reactive oxygen and nitrogen species, inhibit central nervous system-related enzymes, and exhibit cytotoxic activity against different cancer cell lines. In addition, the optimized AN extract showed antimicrobial, and anti-quorum sensing activities, indicating that this extract could offer direct and indirect protection against infection by pathogenic microorganisms. This work demonstrated that the sustainably obtained AN extract could be an emerging, non-toxic, and natural ingredient with potential to be included in different applications.

Evaluation of antioxidant properties and cytotoxicity of brown algae (nizamuddinia zanardinii) in uterine (hela) and pancreatic cancer cell lines (paca-2)

INTRODUCTION

Pancreatic cancer and cervical cancer are among the most common cancers. Brown algae have anti-inflammatory, anti-cancer, anti-fungal, antioxidant, and immune-boosting properties. This study investigated the antioxidant properties and the effect of brown algae extract on pancreatic and uterine cancer cells.

MATERIALS AND METHODS

In this study, Cervical (Hela) and pancreas (Paca-2) cancer cell lines were examined. The algae materials were extracted by sequential maceration method and amount of fucoxanthin content in the sample was determined by using High Performance Liquid Chromatography (HPLC) system. The cytotoxic effect of different concentrations of brown algae was measured by the MTT assay. All statistical calculations for comparing IC50 were analyzed using Graph Pad Prism software.

RESULTS

the algal sample contained an average of 102.52 ± 0.12 μg of fucoxanthin per 100 g. IC50 for 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide free radical scavenging activity for methanolic extract was 2.02 and 11.98 ± 0.13 respectively. Brown algae in all fractions inhibited cell growth and survival. In Hela cell lines, the methanolic extract was the most effective inhibitor, while in Paca cell lines, hexane and methanolic extracts were particularly potent. The methanolic extract was more toxic than other fractions on Hela and Paca cell lines.

CONCLUSION

This study highlights brown algae extracts strong anticancer effects on uterine and pancreatic cancer cells, suggesting its potential as a natural anticancer drug. Different fractions of the extract showed superior apoptotic and cytotoxic effects, with higher concentrations leading to increased apoptotic effects and reduced survival rates of cancer cells.

The Neuropharmacological Evaluation of Seaweed: A Potential Therapeutic Source

The most common neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD) and Parkinson's disease (PD), are the seventh leading cause of mortality and morbidity in developed countries. Clinical observations of NDD patients are characterized by a progressive loss of neurons in the brain along with memory decline. The common pathological hallmarks of NDDs include oxidative stress, the dysregulation of calcium, protein aggregation, a defective protein clearance system, mitochondrial dysfunction, neuroinflammation, neuronal apoptosis, and damage to cholinergic neurons. Therefore, managing this pathology requires screening drugs with different pathological targets, and suitable drugs for slowing the progression or prevention of NDDs remain to be discovered. Among the pharmacological strategies used to manage NDDs, natural drugs represent a promising therapeutic strategy. This review discusses the neuroprotective potential of seaweed and its bioactive compounds, and safety issues, which may provide several beneficial insights that warrant further investigation.

Investigating the Potential Anti-Alzheimer's Disease Mechanism of Marine Polyphenols: Insights from Network Pharmacology and Molecular Docking

Marine polyphenols, including eckol(EK), dieckol(DK), and 8,8'-bieckol(BK), have attracted attention as bioactive ingredients for preventing Alzheimer's disease (AD). Since AD is a multifactorial disorder, the present study aims to provide an unbiased elucidation of unexplored targets of AD mechanisms and a systematic prediction of effective preventive combinations of marine polyphenols. Based on the omics data between each compound and AD, a protein-protein interaction (PPI) network was constructed to predict potential hub genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to provide further biological insights. In the PPI network of the top 10 hub genes, AKT1, SRC, EGFR, and ESR1 were common targets of EK and BK, whereas PTGS2 was a common target of DK and BK. GO and KEGG pathway analysis revealed that the overlapped genes between each compound and AD were mainly enriched in EGFR tyrosine kinase inhibitor resistance, the MAPK pathway, and the Rap1 and Ras pathways. Finally, docking validation showed stable binding between marine polyphenols and their top hub gene via the lowest binding energy and multiple interactions. The results expanded potential mechanisms and novel targets for AD, and also provided a system-level insight into the molecular targets of marine polyphenols against AD.

Antioxidant and anti-Alzheimer activities of Clivia miniata (Lindl) roots, bulbs, and aerial parts: In-vitro and in-silico studies

Clivia miniata (Lindl) is a member of the family Amaryllidaceae known for its chemically diverse alkaloids with a wide range of biological activities. Many reports revealed a direct role of oxidative stress in the early stage of Alzheimer's disease (AD). Meanwhile, β-site amyloid precursor protein cleavage enzyme 1 (BACE-1) is a molecular target for the treatment of AD. We aimed to investigate C. miniata root, bulb, and aerial part chemical profiling, antioxidant, BACE-1, and AChE enzyme inhibitory activities. Results showed that the total root had the most potent radical scavenging activity as compared to the total bulb and aerial part, respectively. Ethanol root extract had the most potent BACE-1 inhibitory activity (IC50 = 0.02 ± 0.001 µg/mL) as compared to the bulb and aerial part (IC50 = 0.93 ± 0.13, 1.80 ± 0.24 µg/mL), respectively. Moreover, the total root extract mitigated AChE enzyme activity more than total bulb and aerial fractions with IC50 values of (0.06 ± 0.02, 0.58 ± 0.3, and 1.89 ± 0.42 µg/mL, respectively. Bioassay-guided acid-base fractionation confirmed superior BACE-1 inhibitory activity of the root fractions particularly, methylene chloride and ethyl acetate fractions with (IC50 values of 0.21 ± 0.60 and 0.01 ± 0.001 µg/mL), respectively. UPLC-MS analysis of ethyl acetate and methylene chloride fractions of C. miniata root led to the identification of eight phenolics and thirteen alkaloids, respectively. Molecular docking studies against BACE-1 protein revealed that lycorine di-hexoside, miniatine, and cliviaaline were the most promising hits. Further investigation of anti-AD potential of the aforementioned small molecules is required.

Marine Macroalgae Polyphenols as Potential Neuroprotective Antioxidants in Neurodegenerative Diseases

Polyphenols are beneficial natural compounds with antioxidant properties that have recently gain a lot of interest for their potential therapeutic applications. Marine polyphenols derived from marine macroalgae have been discovered to possess interesting antioxidant properties; therefore, these compounds can be included in several areas of drug development. Authors have considered the use of polyphenol extracts from seaweeds as neuroprotective antioxidants in neurodegenerative diseases. Marine polyphenols may slow the progression and limit neuronal cell loss due to their antioxidant activity; therefore, the use of these natural compounds would improve the quality of life for patients affected with neurodegenerative diseases. Marine polyphenols have distinct characteristics and potential. Among seaweeds, brown algae are the main sources of polyphenols, and present the highest antioxidant activity in comparison to red algae and green algae. The present paper collects the most recent in vitro and in vivo evidence from investigations regarding polyphenols extracted from seaweeds that exhibit neuroprotective antioxidant activity. Throughout the review, oxidative stress in neurodegeneration and the mechanism of action of marine polyphenol antioxidant activity are discussed to evidence the potential of algal polyphenols for future use in drug development to delay cell loss in patients with neurodegenerative disorders.

First Insight into the Neuroprotective and Antibacterial Effects of Phlorotannins Isolated from the Cell Walls of Brown Algae Fucus vesiculosus and Pelvetia canaliculata

Phaeophyceae (brown algae) essentially contribute to biotopes of cold and temperate seas. Their thalli are rich in biologically active natural products, which are strongly and universally dominated with phlorotannins—polyphenols of complex and diverse structure based on multiple differently arranged phloroglucinol units and well known as strong antioxidants with a broad spectrum of biological activities. In the algal cells, phlorotannins can either accumulate in the cytoplasm or can be secreted into the cell wall (CW). The biological activities of extractable intracellular phlorotannins have been comprehensively characterized, whereas the properties of the CW-bound polyphenol fraction are still mostly unknown. Recently, we identified dibenzodioxin bonding as the principal structural feature of the CW-bound phlorotannins in fucoid algae, whereas soluble intracellular phlorotannins rely on aryl and ether bonds. However, profiles of biological activity associated with these structural differences are still unknown. Therefore, to the best of our knowledge, for the first time we address the antioxidant, cytotoxic, neuroprotective, and antibacterial properties of the CW-bound phlorotannin fractions isolated from two representatives of the order Fucales—Fucus vesiculosus and Pelvetia canaliculata. The CW-bound phlorotannins appeared to be softer antioxidants, stronger antibacterial agents and were featured with essentially less cytotoxicity in comparison to the intracellular fraction. However, the neuroprotective effects of both sub-cellular phlorotannin fractions of F. vesiculosus and P. canaliculata were similar. Thus, due to their lower cytotoxicity, CW-bound phlorotannins can be considered as promising antioxidants and neuroprotectors.

A Bioactive Substance Derived from Brown Seaweeds: Phlorotannins

Phlorotannins are a type of natural active substance extracted from brown algae, which belong to a type of important plant polyphenol. Phloroglucinol is the basic unit in its structure. Phlorotannins have a wide range of biological activities, such as antioxidant, antibacterial, antiviral, anti-tumor, anti-hypertensive, hypoglycemic, whitening, anti-allergic and anti-inflammatory, etc. Phlorotannins are mainly used in the fields of medicine, food and cosmetics. This paper reviews the research progress of extraction, separation technology and biological activity of phlorotannins, which will help the scientific community investigate the greater biological significance of phlorotannins.

Comment on Budryn et al. Hydroxybenzoic Acids as Acetylcholinesterase Inhibitors: Calorimetric and Docking Simulation Studies. Nutrients 2022, 14, 2476

It is with great interest that we read the article entitled "Hydroxybenzoic Acids as Acetylcholinesterase Inhibitors: Calorimetric and Docking Simulation Studies" published in Nutrients 2022, 14, 2476 [...].

Anti-Alzheimer's disease potential of traditional chinese medicinal herbs as inhibitors of BACE1 and AChE enzymes

Alzheimer's disease (AD) is a common neurodegenerative disease that often occurs in the elderly population. At present, most drugs for AD on the market are single-target drugs, which have achieved certain success in the treatment of AD. However, the efficacy and safety of single-target drugs have not achieved the expected results because AD is a multifactorial disease. Multi-targeted drugs act on multiple factors of the disease network to improve efficacy and reduce adverse reactions. Therefore, the search for effective dual-target or even multi-target drugs has become a new research trend. Many of results found that the dual-target inhibitors of the beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) and acetylcholinesterase (AChE) found from traditional Chinese medicine have a good inhibitory effect on AD with fewer side effects. This article reviews sixty-six compounds extracted from Chinese medicinal herbs, which have inhibitory activity on BACE1 and AChE. This provides a theoretical basis for the further development of these compounds as dual-target inhibitors for the treatment of AD.

Phenolics as GABAA Receptor Ligands: An Updated Review

Natural products can act as potential GABA modulators, avoiding the undesirable effects of traditional pharmacology used for the inhibition of the central nervous system such as benzodiazepines (BZD). Phenolics, especially flavonoids and phlorotannins, have been considered as modulators of the BZD-site of GABA_A receptors (GABA_ARs), with sedative, anxiolytic or anticonvulsant effects. However, the wide chemical structural variability of flavonoids shows their potential action at more than one additional binding site on GABA_ARs, which may act either negatively, positively, by neutralizing GABA_ARs, or directly as allosteric agonists. Therefore, the aim of the present review is to compile and discuss an update of the role of phenolics, namely as pharmacological targets involving dysfunctions of the GABA system, analyzing both their different compounds and their mechanism as GABAergic modulators. We focus this review on articles written in English since the year 2010 until the present. Of course, although more research would be necessary to fully establish the type specificity of phenolics and their pharmacological activity, the evidence supports their potential as GABA_AR modulators, thereby favoring their inclusion in the development of new therapeutic targets based on natural products. Specifically, the data compiled in this review allows for the directing of future research towards ortho-dihydroxy diterpene galdosol, the flavonoids isoliquiritigenin (chalcone), rhusflavone and agathisflavone (biflavonoids), as well as the phlorotannins, dieckol and triphlorethol A. Clinically, flavonoids are the most interesting phenolics due to their potential as anticonvulsant and anxiolytic drugs, and phlorotannins are also of interest as sedative agents.

Selected Natural Products in Neuroprotective Strategies for Alzheimer's Disease-A Non-Systematic Review

Neurodegenerative disorders such as Alzheimer's disease (AD) are distinguished by the irreversible degeneration of central nervous system function and structure. AD is characterized by several different neuropathologies-among others, it interferes with neuropsychiatrical controls and cognitive functions. This disease is the number one neurodegenerative disorder; however, its treatment options are few and, unfortunately, ineffective. In the new strategies devised for AD prevention and treatment, the application of plant-based natural products is especially popular due to lesser side effects associated with their taking. Moreover, their neuroprotective activities target different pathological mechanisms. The current review presents the anti-AD properties of several natural plant substances. The paper throws light on products under in vitro and in vivo trials and compiles information on their mechanism of actions. Knowledge of the properties of such plant compounds and their combinations will surely lead to discovering new potent medicines for the treatment of AD with lesser side effects than the currently available pharmacological proceedings.

Mixture of Phlorotannin and Fucoidan from Ecklonia cava Prevents the Aβ-Induced Cognitive Decline with Mitochondrial and Cholinergic Activation

The anti-amnesic effect of a mixture (4:6 = phlorotannin:fucoidan from Ecklonia cava, P4F6) was evaluated on amyloid-beta peptide (Aβ)-induced cognitive deficit mice. The cognitive function was examined by Y-maze, passive avoidance, and Morris water maze tests, and the intake of the mixture (P4F6) showed an ameliorating effect on Aβ-induced learning and memory impairment. After the behavioral tests, superoxide dismutase (SOD) activity and thiobarbituric acid-reactive substances (TBARS) contents were confirmed in brain tissue, and in the results, the mixture (P4F6) attenuated Aβ-induced oxidative stress. In addition, mitochondrial activity was evaluated by mitochondrial reactive oxygen species (ROS) content, mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) content, and mitochondria-mediated apoptotic signaling pathway, and the mixture (P4F6) enhanced mitochondrial function. Furthermore, the mixture (P4F6) effectively regulated tau hyperphosphorylation by regulating the protein kinase B (Akt) pathway, and promoted brain-derived neurotrophic factor (BDNF) in brain tissue. Moreover, in the cholinergic system, the mixture (P4F6) ameliorated acetylcholine (ACh) content by regulating acetylcholinesterase (AChE) activity and choline acetyltransferase (ChAT) expression in brain tissue. Based on these results, we suggest that this mixture of phlorotannin and fucoidan (P4F6) might be a substance for improving cognitive function by effectively regulating cognition-related molecules.

1,3,5-Triazine Nitrogen Mustards with Different Peptide Group as Innovative Candidates for AChE and BACE1 Inhibitors

A series of new analogs of nitrogen mustards (4a–4h) containing the 1,3,5-triazine ring substituted with dipeptide residue were synthesized and evaluated for the inhibition of both acetylcholinesterase (AChE) and β-secretase (BACE1) enzymes. The AChE inhibitory activity studies were carried out using Ellman’s colorimetric method, and the BACE1 inhibitory activity studies were carried out using fluorescence resonance energy transfer (FRET). All compounds displayed considerable AChE and BACE1 inhibition. The most active against both AChE and BACE1 enzymes were compounds A and 4a, with an inhibitory concentration of AChE IC₅₀ = 0.051 µM; 0.055 µM and BACE1 IC₅₀ = 9.00 µM; 11.09 µM, respectively.

Dual-target compounds for Alzheimer's disease: Natural and synthetic AChE and BACE-1 dual-inhibitors and their structure-activity relationship (SAR)

Alzheimer's disease (AD) is a chronic neurodegenerative disease and represents the major cause of dementia worldwide. Currently, there are no available treatments capable to deliver disease-modifying effects, and the available drugs can only alleviate the symptoms. The exact pathology of AD is not yet fully understood and several hallmarks such as the presence of amyloid-β (Aβ) senile plaques, neurofibrillary tangles (NFTs) as well as the loss of cholinergic function have been associated to AD. Distinct pharmacological targets have been validated to address AD, with acetylcholinesterase (AChE) and β-secretase-1 (BACE-1) being two of the most explored ones. A great deal of research has been devoted to the development of new AChE and BACE-1 effective inhibitors, tackled separately or in combination of both. The multi-factorial nature of AD conducted to the development of multi-target directed ligands (MTDLs), defined as single molecules capable to modulate more than one biological target, as an alternative approach to the old paradigm one-target one-drug. In this context, this review describes a collection of natural and synthetic compounds with dual-inhibitory properties towards both AChE and BACE-1 in the MTDLs context. Furthermore, this review also provides a critical comprehensive analysis of structure-activity relationships (SAR) of the synthetic compounds.

Recent Developments in New Therapeutic Agents against Alzheimer and Parkinson Diseases: In-Silico Approaches

Neurodegenerative diseases (ND), including Alzheimer's (AD) and Parkinson's Disease (PD), are becoming increasingly more common and are recognized as a social problem in modern societies. These disorders are characterized by a progressive neurodegeneration and are considered one of the main causes of disability and mortality worldwide. Currently, there is no existing cure for AD nor PD and the clinically used drugs aim only at symptomatic relief, and are not capable of stopping neurodegeneration. Over the last years, several drug candidates reached clinical trials phases, but they were suspended, mainly because of the unsatisfactory pharmacological benefits. Recently, the number of compounds developed using in silico approaches has been increasing at a promising rate, mainly evaluating the affinity for several macromolecular targets and applying filters to exclude compounds with potentially unfavorable pharmacokinetics. Thus, in this review, an overview of the current therapeutics in use for these two ND, the main targets in drug development, and the primary studies published in the last five years that used in silico approaches to design novel drug candidates for AD and PD treatment will be presented. In addition, future perspectives for the treatment of these ND will also be briefly discussed.

Dieckol Ameliorates Aβ Production via PI3K/Akt/GSK-3β Regulated APP Processing in SweAPP N2a Cell

The proteolytic processing of amyloid precursor protein (APP) by β-secretase (BACE1) and γ-secretase releases amyloid-β peptide (Aβ), which deposits in amyloid plaques and contributes to the initial causative events of Alzheimer’s disease (AD). In the present study, the regulatory mechanism of APP processing of three phlorotannins was elucidated in Swedish mutant APP overexpressed N2a (SweAPP N2a) cells. Among the tested compounds, dieckol exhibited the highest inhibitory effect on both intra- and extracellular Aβ accumulation. In addition, dieckol regulated the APP processing enzymes, such as α-secretase (ADAM10), β-secretase, and γ-secretase, presenilin-1 (PS1), and their proteolytic products, sAPPα and sAPPβ, implying that the compound acts on both the amyloidogenic and non-amyloidogenic pathways. In addition, dieckol increased the phosphorylation of protein kinase B (Akt) at Ser473 and GSK-3β at Ser9, suggesting dieckol induced the activation of Akt, which phosphorylated GSK-3β. The specific phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 triggered GSK-3β activation and Aβ expression. In addition, co-treatment with LY294002 noticeably blocked the effect of dieckol on Aβ production, demonstrating that dieckol promoted the PI3K/Akt signaling pathway, which in turn inactivated GSK-3β, resulting in the reduction in Aβ levels.

Ecklonia cava Attenuates PM2.5-Induced Cognitive Decline through Mitochondrial Activation and Anti-Inflammatory Effect

To evaluate the effects of Ecklonia cava (E. cava) on ambient-pollution-induced neurotoxicity, we used a mouse model exposed to particulate matter smaller than 2.5 µm in aerodynamic diameter (PM2.5). The intake of water extract from E. cava (WEE) effectively prevented the learning and memory decline. After a behavioral test, the toll-like receptor (TLR)-4-initiated inflammatory response was confirmed by PM2.5 exposure in the lung and brain tissues, and the WEE was regulated through the inhibition of nuclear factor-kappa B (NF-κB)/inflammasome formation signaling pathway and pro-inflammatory cytokines (IL-6 and IFN-γ). The WEE also effectively improved the PM2.5-induced oxidative damage of the lungs and brain through the inhibition of malondialdehyde (MDA) production and the activation of mitochondrial activity (mitochondrial ROS content, mitochondria membrane potential (MMP), adenosine triphosphate (ATP) content, and mitochondria-mediated apoptotic molecules). In particular, the WEE regulated the cognition-related proteins (a decreased amyloid precursor protein (APP) and p-Tau, and an increased brain-derived neurotrophic factor (BDNF)) associated with PM2.5-induced cognitive dysfunction. Additionally, the WEE prevented the inactivation of acetylcholine (ACh) synthesis and release as a neurotransmitter by regulating the acetylcholinesterase (AChE) activity, choline acetyltransferase (ChAT), and ACh receptor (AChR)-α3 in the brain tissue. The bioactive compounds of the WEE were detected as the polysaccharide (average Mw; 160.13 kDa) and phenolic compounds including 2'-phloroeckol.

Discovery of Natural Inhibitors of Cholinesterases from Hydrangea: In Vitro and In Silico Approaches

Alzheimer's disease (AD) is a neurodegenerative disease conceptualized as a clinical-biological neurodegenerative construct where amyloid-beta pathophysiology is supposed to play a role. The loss of cognitive functions is mostly characterized by the rapid hydrolysis of acetylcholine by cholinesterases including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Moreover, both enzymes are responsible for non-catalytic actions such as interacting with amyloid β peptide (Aβ) which further leads to promote senile plaque formation. In searching for a natural cholinesterase inhibitor, the present study focused on two isocoumarines from hydrangea, thunberginol C (TC) and hydrangenol 8-O-glucoside pentaacetate (HGP). Hydrangea-derived compounds were demonstrated to act as dual inhibitors of both AChE and BChE. Furthermore, the compounds exerted selective and non-competitive mode of inhibition via hydrophobic interaction with peripheral anionic site (PAS) of the enzymes. Overall results demonstrated that these natural hydrangea-derived compounds acted as selective dual inhibitors of AChE and BChE, which provides the possibility of potential source of new type of anti-cholinesterases with non-competitive binding property with PAS.

Polyphenols from Brown Seaweeds (Ochrophyta, Phaeophyceae): Phlorotannins in the Pursuit of Natural Alternatives to Tackle Neurodegeneration

Globally, the burden of neurodegenerative disorders continues to rise, and their multifactorial etiology has been regarded as among the most challenging medical issues. Bioprospecting for seaweed-derived multimodal acting products has earned increasing attention in the fight against neurodegenerative conditions. Phlorotannins (phloroglucinol-based polyphenols exclusively produced by brown seaweeds) are amongst the most promising nature-sourced compounds in terms of functionality, and though research on their neuroprotective properties is still in its infancy, phlorotannins have been found to modulate intricate events within the neuronal network. This review comprehensively covers the available literature on the neuroprotective potential of both isolated phlorotannins and phlorotannin-rich extracts/fractions, highlighting the main key findings and pointing to some potential directions for neuro research ramp-up processes on these marine-derived products.

In vitro multifunctionality of phlorotannin extracts from edible Fucus species on targets underpinning neurodegeneration

Bioprospecting for seaweed-derived multimodal acting products have earned increasing attention in the fight against diseases of multifactorial origin, such as neurodegenerative conditions. This is a pioneer study on the in vitro screening of neuroactive properties of phlorotannin-targeted extracts from edible Fucus species. Phlorotannin extracts exhibited multifunctional antioxidant properties, which were suggested to be responsible for counteracting glutamate toxicity in neuronal human-derived SH-SY5Y cells. They also inhibited the activity of enzymes (cholinesterases, monoaminoxidases A and B, and tyrosinase) linked to a set of events that contribute to the onset/progression of neurodegeneration. In general, the bioactivities were correlated with the total phlorotannin content and phloroglucinol tetramers were suggested to be behind the observed effects. The capacity of the phlorotannin extracts to interact with multiple in vitro targets underpinning neurodegeneration points to the potential interest of the selected seaweed species for development of new added-value products and promising neuroactive agents.

Tongqiaohuoxue Hinders Development and Progression of Atherosclerosis: A Possible Role in Alzheimer's Disease

Simple Summary

Alzheimer’s disease and coronary heart disease are two ever-increasing major health concerns worldwide. Scientific studies revealed a link between Alzheimer’s disease and atherosclerosis, a major causality of coronary heart disease. Herbal medicine has been widely prescribed to treat Alzheimer’s disease and atherosclerosis. In the current study, we explored the possible therapeutic effect of Tongqiaohuoxue, a herbal medicine developed during the Qing dynasty of China for the prevention and treatment of cardiovascular disease, on Alzheimer’s disease and atherosclerosis. We discovered Tongqiaohuoxue showed therapeutic effects not only on atherosclerosis but also on Alzheimer’s disease. Tongqiaohuoxue treatment into the animal model of Alzheimer’s disease and atherosclerosis attenuated atherosclerotic plaque and brain amyloid formations, abnormalities that are characteristic of coronary heart disease and Alzheimer’s disease, respectively. Based on these findings, Tongqiaohuxue showed promising therapeutic effects for the treatment of patients with both Alzheimer’s disease and coronary heart disease.

Abstract

Atherosclerosis is closely associated with Alzheimer’s disease (AD). Tongqiaohuoxue decoction (THD) is a classical herbal prescription in traditional Chinese medicine widely used for the prevention and treatment of cerebrovascular disease. This study aimed to explore the therapeutic effects of THD on atherosclerosis and AD. Eight-week-old C57BL6/J wild-type and ApoE-deficient (ApoE-/-) mice were fed a high-fat and high-cholesterol diet for eight weeks, followed by oral phosphate-buffered saline vehicle or THD treatment for eight weeks further. In ApoE-/- mice, THD attenuated lipid deposition in the aorta and the brain, and abrogated atherosclerotic changes without affecting serum lipid profiles while decreasing amyloid plaque formation. In vitro assays undertaken to understand THD’s effects on lipid clearance in the aorta and brain vessels revealed that THD treatment inhibited the lipid uptake, stimulated by oxidized low-density lipoprotein, resulted in decreased endothelial cell activation through reduction in intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and monocyte chemoattractant protein-1 levels. Serum analysis revealed inhibitory effects of THD on resistin production, which has important roles in the development of both atherosclerosis and AD. In conclusion, the current study demonstrates beneficial effects of THD on the development and progression of atherosclerosis, and a possible protective role against AD.

The influence of in vitro gastrointestinal digestion on the Perilla frutescens leaf extract: Changes in the active compounds and bioactivities

In this study, the influence of in vitro gastrointestinal digestion on the Perilla frutescens leaf extract (PFLE) were measured. Results revealed that total phenolic content (TPC) and total flavonoid content (TFC) were significantly decreased after simulated digestion (ca. 53% of phenolics and 40% of flavonoids). The IC₅₀ value of DPPH· scavenging activity and ABTS⁺ scavenging ability increased by 23% and 56%, respectively, while ferric reducing antioxidant power reduced by 53%. For the inhibition ability on α-glucosidase, acetylcholinesterase, and MCF-7 cell proliferation, their IC₅₀ values increased by 360%, 197%, and 25%, respectively. Three phenolic acids and one flavonoid in PFLE were quantified by high-performance liquid chromatography. Overall, although significant losses of the active components and biological activities occurred during in vitro gastrointestinal digestion, it still showed the potential as an oral agent for treatment and prevention of oxidative stress, cancer, diabetes, and Alzheimer's disease. PRACTICAL APPLICATIONS: As an important annual herbaceous plant with rich biochemical compounds and many biological functions, Perilla frutescens leave is widely used in the food and traditional Chinese medicine. However, the dynamic changes of its active compounds and activities during the digestion process are unclear. In this study, the digestion results in significant loss of the active ingredients and biological activities of P. frutescens leaf extract (PFLE), particularly in the gastric digestion. In addition, PFLE remains to show certain antioxidant activity, α-glucosidase inhibitory ability, acetylcholinesterase inhibitory ability, and MCF-7 cell proliferation inhibitory ability after digestion. Therefore, this research might facilitate further research and development of P. frutescens.

Pharmacological and Cosmeceutical Potential of Seaweed Beach-Casts of Macaronesia

Seaweed beach-casts are a seasonal phenomenon that regularly deposits tons of algae biomass on beaches, which are usually disposed of in landfills. The present work aimed to contribute to the valorization of this biomass by studying bioactivities that reveal its potential in the pharmaceutical and/or cosmeceutical industries. Methanol and ethanol extracts and fractions from 15 beach-casts biomass were tested for a range of bioactivities. Eight of the most active samples exhibit IC50 values between 11.38 µg/mL and 19.28 µg/mL and selectivity indexes higher than 3.8, against NCI-H1299 (lung cancer) and T47D (breast cancer). Concerning antiaging potential, all the extracts tested presented UV protection, with SPF values above 30, like the standard sunscreen. Regarding aging-related enzymes, 24 samples were tyrosinase inhibitors exhibiting IC50 values from 9.01 µg/mL to 200.09 µg/mL. Eight extracts inhibited collagenase (IC50 < 248.76 µg/mL), two of them more actively than positive control EDTA (IC50 = 59.26 µg/mL). In addition to UV protection, the cumulative effect of antityrosinase and anticollagenase activities shown by the samples suggest that they may play a significant role in preventing skin photoaging. The results obtained demonstrate the high potential of beach-cast seaweed biomass as sources of cosmetic bioproducts with antiaging effects, and of selective cytotoxic metabolites.

A Perspective on Enzyme Inhibitors from Marine Organisms

Marine habitats are promising sources for the identification of novel organisms as well as natural products. Still, we lack detailed knowledge on most of the marine biosphere. In the last decade, a number of reports described the potential of identifying novel bioactive compounds or secondary metabolites from marine environments. This is, and will be, a promising source for candidate compounds in pharma research and chemical biology. In recent years, a number of novel techniques were introduced into the field, and it has become easier to actually prospect for natural products, such as enzyme inhibitors. These novel compounds then need to be characterized and evaluated in comparison to well-known representatives. A number of current research projects target the exploitation of marine organisms and thus the corresponding diversity of metabolites. These are often encountered as potential drugs or biological active compounds. Among these, the class of enzyme inhibitors is an important group of compounds. There is room for new discoveries, and some more recent discoveries are highlighted herein.

Seaweed Phenolics: From Extraction to Applications

Seaweeds have attracted high interest in recent years due to their chemical and bioactive properties to find new molecules with valuable applications for humankind. Phenolic compounds are the group of metabolites with the most structural variation and the highest content in seaweeds. The most researched seaweed polyphenol class is the phlorotannins, which are specifically synthesized by brown seaweeds, but there are other polyphenolic compounds, such as bromophenols, flavonoids, phenolic terpenoids, and mycosporine-like amino acids. The compounds already discovered and characterized demonstrate a full range of bioactivities and potential future applications in various industrial sectors. This review focuses on the extraction, purification, and future applications of seaweed phenolic compounds based on the bioactive properties described in the literature. It also intends to provide a comprehensive insight into the phenolic compounds in seaweed.

Neuroprotective Potentials of Marine Algae and Their Bioactive Metabolites: Pharmacological Insights and Therapeutic Advances

Beyond their significant contribution to the dietary and industrial supplies, marine algae are considered to be a potential source of some unique metabolites with diverse health benefits. The pharmacological properties, such as antioxidant, anti-inflammatory, cholesterol homeostasis, protein clearance and anti-amyloidogenic potentials of algal metabolites endorse their protective efficacy against oxidative stress, neuroinflammation, mitochondrial dysfunction, and impaired proteostasis which are known to be implicated in the pathophysiology of neurodegenerative disorders and the associated complications after cerebral ischemia and brain injuries. As was evident in various preclinical studies, algal compounds conferred neuroprotection against a wide range of neurotoxic stressors, such as oxygen/glucose deprivation, hydrogen peroxide, glutamate, amyloid β, or 1-methyl-4-phenylpyridinium (MPP+) and, therefore, hold therapeutic promise for brain disorders. While a significant number of algal compounds with promising neuroprotective capacity have been identified over the last decades, a few of them have had access to clinical trials. However, the recent approval of an algal oligosaccharide, sodium oligomannate, for the treatment of Alzheimer's disease enlightened the future of marine algae-based drug discovery. In this review, we briefly outline the pathophysiology of neurodegenerative diseases and brain injuries for identifying the targets of pharmacological intervention, and then review the literature on the neuroprotective potentials of algal compounds along with the underlying pharmacological mechanism, and present an appraisal on the recent therapeutic advances. We also propose a rational strategy to facilitate algal metabolites-based drug development.

New Tetrahydroacridine Hybrids with Dichlorobenzoic Acid Moiety Demonstrating Multifunctional Potential for the Treatment of Alzheimer's Disease

A series of new tetrahydroacridine and 3,5-dichlorobenzoic acid hybrids with different spacers were designed, synthesized, and evaluated for their ability to inhibit both cholinesterase enzymes. Compounds 3a, 3b, 3f, and 3g exhibited selective butyrylcholinesterase (EqBuChE) inhibition with IC₅₀ values ranging from 24 to 607 nM. Among them, compound 3b was the most active (IC₅₀ = 24 nM). Additionally, 3c (IC₅₀ for EeAChE = 25 nM and IC₅₀ for EqBuChE = 123 nM) displayed dual cholinesterase inhibitory activity and was the most active compound against acetylcholinesterase (AChE). Active compound 3c was also tested for the ability to inhibit Aβ aggregation. Theoretical physicochemical properties of the compounds were calculated using ACD Labs Percepta and Chemaxon. A Lineweaver–Burk plot and docking study showed that 3c targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. Moreover, 3c appears to possess neuroprotective activity and could be considered a free-radical scavenger. In addition, 3c did not cause DNA damage and was found to be less toxic than tacrine after oral administration; it also demonstrated little inhibitory activity towards hyaluronidase (HYAL), which may indicate that it possesses anti-inflammatory properties. The screening for new in vivo interactions between 3c and known receptors was realized by yeast three-hybrid technology (Y3H).

Eckol from Ecklonia cava Suppresses Immunoglobulin E-mediated Mast Cell Activation and Passive Cutaneous Anaphylaxis in Mice

Eckol, a precursor compound belonging to the dibenzo-1,4-dioxin class of phlorotannins, is a phloroglucinol derivative that exerts various activities. In the present study, we investigated the antiallergic effects of eckol isolated from the marine brown algae, Ecklonia cava using immunoglobulin E (IgE)/bovine serum albumin (BSA)-stimulated mouse bone marrow-derived cultured mast cells (BMCMC) and a mouse model of anaphylaxis. Eckol inhibited IgE/BSA-induced BMCMC degranulation by reducing β-hexosaminidase release. A flow cytometric analysis revealed that eckol decreases FcεRI expression on cell surface and IgE binding to the FcεRI in BMCMC. Moreover, eckol suppressed the production of the cytokines, interleukin (IL)-4, IL-5, IL-6, and IL-13 and the chemokine, thymus activation-regulated chemokine (TARC) by downregulating, IκB-α degradation and NF-κB nuclear translocation. Furthermore, it attenuated the passive cutaneous anaphylactic reaction induced by IgE/BSA-stimulation in the ear of BALB/c mice. These results suggest that eckol is a potential therapeutic candidate for the prevention and treatment of allergic disorders.

Slow-Binding Inhibition of Tyrosinase by Ecklonia cava Phlorotannins

Tyrosinase inhibitors improve skin whitening by inhibiting the formation of melanin precursors in the skin. The inhibitory activity of seven phlorotannins (1-7), triphlorethol A (1), eckol (2), 2-phloroeckol (3), phlorofucofuroeckol A (4), 2-O-(2,4,6-trihydroxyphenyl)-6,6'-bieckol (5), 6,8'-bieckol (6), and 8,8'-bieckol (7), from Ecklonia cava was tested against tyrosinase, which converts tyrosine into dihydroxyphenylalanine. Compounds 3 and 5 had IC50 values of 7.0 ± 0.2 and 8.8 ± 0.1 μM, respectively, in competitive mode, with Ki values of 8.2 ± 1.1 and 5.8 ± 0.8 μM. Both compounds showed the characteristics of slow-binding inhibitors over the time course of the enzyme reaction. Compound 3 had a single-step binding mechanism and compound 5 a two-step-binding mechanism. With stable AutoDock scores of -6.59 and -6.68 kcal/mol, respectively, compounds 3 and 5 both interacted with His85 and Asn260 at the active site.