Exploring the therapeutic potential of natural compounds for Alzheimer's disease: Mechanisms of action and pharmacological properties

A stilbenoid, rhapontigenin, isolated from the root of Rheum palmatum L. acts as a potent BACE1 inhibitor

Seven compounds, comprising three anthraquinones and four stilbenoids, were isolated from the roots of Rheum palmatum L. These compounds include chrysophanol (1), aloe-emodin (2), aloe-emodin 8-O-β-D-glucopyranoside (3), desoxyrhapontigenin (4), rhapontigenin (5), desoxyrhaponticin (6), and piceatannol 3'-O-β-D-glucopyranoside (7). Among these, compound 5 showed potent β-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitory activity with an IC50 value of 0.256 ± 0.008 μM, making it the most effective inhibitor obtained from herbal extracts to date, followed by compounds 3 (1.164 ± 0.108 μM), 6 (1.213 ± 0.193 μM), 7 (1.270 ± 0.130 μM), and 4 (2.028 ± 0.108 μM). Furthermore, kinetic analysis revealed that compound 5 acted as a mixed type-I inhibitor with an inhibition constant Ki value of 0.28 ± 0.07 μM. Notably, compound 2 exhibited potent Aβ aggregation inhibition with an IC50 value of 3.56 ± 0.19 μM, whereas compound 5 showed low Aβ aggregation inhibition with an IC50 value of >40 μM. The docking simulations revealed that compound 5 had a high binding affinity and interacted with TYR132, predicting it as a key residue for inhibition via hydrophobic interaction, and with THR133 via hydrogen bonding, in the flap region of BACE1. These results suggest that stilbenoids generally exhibit higher BACE1 inhibitory activity than that of anthraquinones, and that compound 5 (rhapontigenin) could be a promising candidate for the treatment of Alzheimer's disease as a potent BACE1 inhibitor.

LC-ESI-QTOF-MS/MS Characterization of Phenolic Compounds in the Stem, Roots, and Leaves of Syzygium cumini and Their Antioxidant Potential

Syzygium cumini, commonly known as Jamun or Indian Blackberry, is a fruit-bearing tree native to the Indian subcontinent, revered for its medicinal uses, and characterized by a rich phytochemical profile abundant in polyphenols. This study aimed to characterize various fractions, including the roots, stem, and leaves of S. cumini (SC). Purposefully, conventional extraction was carried out by using ethanol (70%) with formic acid (1%) to extract the phytochemicals. The resultant extracts were subjected to phenolic contents (TPC, TFC, TTC) and antioxidant activity estimation (DPPH, FRAP, ABTS RPA, OH, FICA, and TAC). Further, LC-ESI-QTOF-MS/MS identification of phenolics was also performed. The outcomes showed that S. cumini leaf exhibited the highest phenolic content and antioxidant activity among different fractions compared to stem and root. The recorded TPC, TFC, and TTC in the leaf were 52.17 ± 1.60 mg GAE/g, 2.76 ± 0.054 mg QE/g, and 17.22 ± 0.43 mg ce/g, respectively. Correlation analysis revealed a strong positive correlation (0.50 < r < 0.80, p < 0.01) between TPC, TFC, and TTC. The LC-ESI-QTOF-MS/MS screening showed the presence of 12 compounds in the stem, leaf, and root of S. cumini, showing the diversity of phenolics between different parts. The majority of the compounds belonged to flavonoids (4), phenolic acids (3), other polyphenols (3) and lignans (2). Among the notable compounds, naringin 4'-O-glucoside, 3,4-O-dimethylgallic acid, scutellarein, and demethyloleuropein were identified, highlighting the therapeutic potential of different fractions of S. cumini. In conclusion, the results indicated that SC fractions contained a considerable amount of phenolics, thus showcasing higher antioxidant activity. Moreover, the concentration of different phenolics varied among fractions, as confirmed through a Venn diagram.

Xanthohumol Sensitizes Melanoma Cells to Vemurafenib by Lowering Membrane Cholesterol and Increasing Membrane Fluidity

Chemoresistance remains one of the major obstacles to cancer treatment. The search for specific molecules that could improve cancer treatment has become one of the objectives of biomedical research. Identifying new natural molecules to enhance chemotherapy treatment or improve sensitization to conventional therapies has become a key objective. Here, we evaluated the effect of Xanthohumol (XN) extracted from hop on SKMEL-28 melanoma cells and their sensitization to vemurafenib (VEM) treatment. We measured the XN effect on cell viability and apoptosis. We also assessed the effect of XN on membrane fluidity and membrane cholesterol levels. Finally, we studied the impact of XN on cell sensitization to VEM. Here, we showed that XN reduced SKMEL-28 cell viability through an apoptotic mechanism. Our results demonstrated the potential role of XN in sensitizing cancer cells to VEM with a less toxic effect on non-tumor cells. A study of XN's molecular mechanism showed that XN was able to induce cholesterol depletion and increased fluidity in SKMEL-28 cancer cells. This leads to an increase in VEM incorporation. Here, we describe the importance of the strategy to modulate membrane fluidity by XN in order to significantly improve anticancer therapy.

Accelerating antiviral drug discovery: early hazard detection with a dual zebrafish and cell culture screen of a 403 compound library

The constant emergence of new viral pathogens underscores the need for continually evolving, effective antiviral drugs. A key challenge is identifying compounds that are both efficacious and safe, as many candidates fail during development due to unforeseen toxicity. To address this, the embryonic zebrafish morphology, mortality, and behavior (ZBE) screen and the SYSTEMETRIC® Cell Health Screen (CHS) were employed to evaluate the safety of 403 compounds from the Cayman Antiviral Screening Library. Of these compounds, 114 were FDA-approved, 17 were discontinued, and 97 remained on the market. CHS identified 25% (104 compounds) as toxic, with a Cell Health Index™ (CHI) > 0.5. The embryonic zebrafish model identified an additional 20% as toxic (79), bringing the total to 183. ZBEscreen flagged 19 toxic hits among compounds still on the market, seven of which were also identified by CHS. The combined use of CHS and zebrafish models enhanced hazard detection. Together, CHS and ZBEscreen identified 45.5% of the library as potentially hazardous. Notably, the zebrafish non-hazardous compounds correlated strongly with over-the-counter or prescribed antiviral drugs, confirming their known safety profile. Over 130 hazard-associated compounds warranted further investigation. Using self-organizing maps, six distinct neighborhoods of compound similarity were identified. This dual approach streamlined the early detection of hazards associated with promising leads and is expected to facilitate faster, safer antiviral discovery.

Trojan Horse Delivery Strategies of Natural Medicine Monomers: Challenges and Limitations in Improving Brain Targeting

Central nervous system (CNS) diseases, such as brain tumors, Alzheimer's disease, and Parkinson's disease, significantly impact patients' quality of life and impose substantial economic burdens on society. The blood-brain barrier (BBB) limits the effective delivery of most therapeutic drugs, especially natural products, despite their potential therapeutic effects. The Trojan Horse strategy, using nanotechnology to disguise drugs as "cargo", enables them to bypass the BBB, enhancing targeting and therapeutic efficacy. This review explores the applications of natural products in the treatment of CNS diseases, discusses the challenges posed by the BBB, and analyzes the advantages and limitations of the Trojan Horse strategy. Despite the existing technical challenges, future research is expected to enhance the application of natural drugs in CNS treatment by integrating nanotechnology, improving delivery mechanisms, and optimizing targeting characteristics.

Free radicals and their impact on health and antioxidant defenses: a review

Free radicals, characterized by the presence of unpaired electrons, are highly reactive species that play a significant role in human health. These molecules can be generated through various endogenous processes, such as mitochondrial respiration and immune cell activation, as well as exogenous sources, including radiation, pollution, and smoking. While free radicals are essential for certain physiological processes, such as cell signaling and immune defense, their overproduction can disrupt the delicate balance between oxidants and antioxidants, leading to oxidative stress. Oxidative stress results in the damage of critical biomolecules like DNA, proteins, and lipids, contributing to the pathogenesis of various diseases. Chronic conditions such as cancer, cardiovascular diseases, neurodegenerative disorders, and inflammatory diseases have been strongly associated with the harmful effects of free radicals. This review provides a comprehensive overview of the characteristics and types of free radicals, their mechanisms of formation, and biological impacts. Additionally, we explore natural compounds and extracts studied for their antioxidant properties, offering potential therapeutic avenues for managing free radical-induced damage. Future research directions are also discussed to advance our understanding and treatment of free radical-associated diseases.

Brazilian kefir fraction mitigates the Alzheimer-like phenotype in Drosophila melanogaster with β-amyloid overexpression model

Alzheimer's disease (AD) is a progressive neurodegenerative condition and the primary form of dementia among elderly people. The amyloidogenic hypothesis is the main theory that explains this phenomenon and describes the extracellular accumulation of amyloid beta (Aβ) peptides. Model organisms such as Drosophila melanogaster have been utilized to improve the understanding of this disease and its treatment. This study evaluated the effects of peptide and metabolic fractions of Brazilian kefir on a strain of D. melanogaster that expresses human Aβ peptide 1-42 in the eye. The parameters assessed included ommatidial organization, vacuole area, retinal thickness, and Aβ peptide quantification. The present study revealed that the fractions, particularly the peptidic fraction, significantly reduced the vacuole area and increased the retina thickness in treated flies, indicating an improvement in neurodegeneration phenotype. The peptidic fraction was also found to alter Aβ aggregation dynamics, inhibiting Aβ fibril formation, as revealed by dynamic light scattering. This study demonstrated that kefir fractions, particularly the peptidic fraction < 10 kDa, have the potential to regulate Aβ aggregation and alleviate neurodegeneration in a Drosophila melanogaster AD-like model. These findings suggest that kefir fractions could be viable for the bioprospection of novel drug prototypes for AD treatment, providing valuable insights into strategies targeting Aβ aggregation and neurodegeneration in AD.

Quercetin ameliorates neuroinflammatory and neurodegenerative biomarkers in the brain and improves neurobehavioral parameters in a repeated intranasal amyloid-beta exposed model of Alzheimer's disease

Objectives: The aim of the present study was to study the potential therapeutic effects of quercetin in protection against repeated intranasal exposure of an amyloid-beta-induced mouse model. Methods: Mice received intranasal Aβ1-42 (5 μg/10 μL) exposure once daily for seven consecutive days. Quercetin was orally administered to them at 30 mg kg-1 and 100 mg kg-1 doses for one week starting from day five following Aβ1-42 peptide administration. Following this, the animals were evaluated for neurobehavioral parameters using a Morris water maze test and a novel object recognition test. Further to this, the biomarkers for neuroinflammation and neurodegeneration were evaluated in the hippocampus and cortex regions of the brain in these animals. Results: Multiple exposures to intranasal Aβ led to a significant decline in the learning and cognitive memory of the animals, whereas oral treatment with quercetin at dosages of 30 and 100 mg kg-1 alleviated Aβ-induced effects. Quercetin treatment significantly reduced Aβ accumulation, oxidative stress and proinflammatory cytokine biomarkers in the brain. In addition, it also alleviated the activation of astrocytic biomarkers, amyloid precursor protein and phosphorylated-tau proteins in the brain. Conclusion: Quercetin was found to be a potent antioxidant, anti-inflammatory compound with protection against neurodegenerative damage and improved learning and cognitive memory in a repeated Aβ-exposure model of AD.

Moringa oleifera leaves ethanolic extract counteracts cortical neurodegeneration induced by aluminum chloride in rats

Background

Aluminum, a well-recognized neurotoxin, is implicated in various neurodegenerative disorders. Moringa oleifera (M. oleifera), known as a miracle tree, is utilized as a functional food and nutritional supplement. This study investigates the potential preventive effects of M. oleifera extract on aluminum chloride (AlCl3)-induced cortical neurodegeneration in rats.

Materials and methods

Therefore, 24 adult male Wistar rats were randomly divided into four distinct groups: negative control, M. oleifera extract (MOE), AlCl3, and AlCl3 + MOE. Treatments were administered orally for 28 consecutive days. Cognitive performance, brain oxidative/nitrosative stress, neuroinflammation, apoptotic-cell death, and associated histopathological alterations were assessed.

Results

Our results showed that MOE improved spatial learning and memory, enhanced antioxidant superoxide dismutase enzyme activity, antagonized nitrosative stress, reduced inflammatory cytokines (tumor necrosis factor-alpha and interleukin-6), decreased caspase-3, increased Bcl-2, and facilitated repair of cortical and hippocampal structures.

Conclusions

We concluded that MOE exhibits protective effects against cortical neurodegeneration, making it a promising supplement to counteract aluminum-induced neurotoxic effects.

ADME profiling, molecular docking, DFT, and MEP analysis reveal cissamaline, cissamanine, and cissamdine from Cissampelos capensis L.f. as potential anti-Alzheimer's agents

The current pharmacotherapies for Alzheimer's disease (AD) demonstrate limited efficacy and are associated with various side effects, highlighting the need for novel therapeutic agents. Natural products, particularly from medicinal plants, have emerged as a significant source of potential neuroprotective compounds. In this context, Cissampelos capensis L.f., renowned for its medicinal properties, has recently yielded three new proaporphine alkaloids; cissamaline, cissamanine, and cissamdine. Despite their promising bioactive profiles, the biological targets of these alkaloids in the context of AD have remained unexplored. This study undertakes a comprehensive in silico examination of the binding affinity and molecular interactions of these alkaloids with human protein targets implicated in AD. The drug likeness and ADME analyses indicate favorable pharmacokinetic profiles for these compounds, suggesting their potential efficacy in targeting the central nervous system. Molecular docking studies indicate that cissamaline, cissamanine, and cissamdine interact with key AD-associated proteins. These interactions are comparable to, or in some aspects slightly less potent than, those observed with established AD drugs, highlighting their potential as novel therapeutic agents for Alzheimer's disease. Crucially, Density Functional Theory (DFT) calculations offer deep insights into the electronic and energetic characteristics of these alkaloids. These calculations reveal distinct electronic properties, with differences in total energy, binding energy, HOMO-LUMO gaps, dipole moments, and electrophilicity indices. Such variations suggest unique reactivity profiles and molecular stability, pertinent to their pharmacological potential. Moreover, Molecular Electrostatic Potential (MEP) analyses provide visual representations of the electrostatic characteristics of these alkaloids. The analyses highlight areas prone to electrophilic and nucleophilic attacks, indicating their potential for specific biochemical interactions. This combination of DFT and MEP results elucidates the intricate electronic, energetic, and electrostatic properties of these compounds, underpinning their promise as AD therapeutic agents. The in silico findings of this study shed light on the promising potential of cissamaline, cissamanine, and cissamdine as agents for AD treatment. However, further in vitro and in vivo studies are necessary to validate these theoretical predictions and to understand the precise mechanisms through which these alkaloids may exert their therapeutic effects.

Unveiling the Molecular Interactions Between Human Transferrin and Limonene: Natural Compounds in Alzheimer's Disease Therapeutics

Background

Neurodegeneration is a term describing an irreversible process of neuronal damage. In recent decades, research efforts have been directed towards deepening our knowledge of numerous neurodegenerative disorders, with a particular focus on conditions such as Alzheimer's disease (AD). Human transferrin (htf) is a key player in maintaining iron homeostasis within brain cells. Any disturbance in this equilibrium gives rise to the emergence of neurodegenerative diseases and associated pathologies, particularly AD. Limonene, a natural compound found in citrus fruits and various plants, has shown potential neuroprotective properties.

Objective

In this study, our goal was to unravel the binding of limonene with htf, with the intention of comprehending the interaction mechanism of limonene with htf.

Methods

Binding was scrutinized using fluorescence quenching and UV-Vis spectroscopic analyses. The binding mechanism of limonene was further investigated at the atomic level through molecular docking and extensive 200 ns molecular dynamic simulation (MD) studies.

Results

Molecular docking uncovered that limonene interacted extensively with the deep cavity located within the htf binding pocket. MD results indicated that binding of limonene to htf did not induce substantial structural alterations, ultimately forming stable complex. The findings from fluorescence binding indicated a pronounced interaction between limonene and htf, limonene binds to htf with a binding constant (K) of 0.1×105 M-1. UV spectroscopy also advocated stable htf-limonene complex formation.

Conclusions

The study deciphered the binding mechanism of limonene with htf, providing a platform to use limonene in AD therapeutics in context of iron homeostasis.

Enzyme ChE, cholinergic therapy and molecular docking: Significant considerations and future perspectives

Enzyme Che plays an essential role in cholinergic and non-cholinergic functions. It is present in the fertilized/unfertilized eggs and sperm of different species. Inclusion criteria for data collection from electronic databases NCBI and Google Scholar are enzyme AChE/BChE, cholinergic therapy, genomic organization and gene transcription, enzyme structure, biogenesis, transport, processing and localization, molecular signaling and biological function, polymorphism and influencing factors. Enzyme Che acts as a signaling receptor during hematopoiesis, protein adhesion, amyloid fiber formation, neurite outgrowth, bone development, and maturation, explaining the activity out of synaptic neurotransmission. Polymorphism in the Che genes correlates to various diseases and diverse drug responses. In particular, change accompanies cancer, neurodegenerative, and cardiovascular disease. Literature knowledge indicates the importance of Che inhibitors that influence biochemical and molecular pathways in disease treatment, genomic organization, gene transcription, structure, biogenesis, transport, processing, and localization of Che enzyme. Enzyme Che polymorphism changes indicate the possibility of efficient and new inhibitor drug target mechanisms in diverse research areas.