Multifunctional Anti-Alzheimer’s Disease Effects of Natural Xanthone Derivatives: A Primary Structure-Activity Evaluation

The regulation of miRNAs using curcumin and other polyphenols during the prevention and treatment of Alzheimer's disease

Alzheimer's disease (AD), a prevalent neurodegenerative disorder, predominantly affects individuals over the age of 65 and poses significant challenges in terms of effective management and treatment. The disease's pathogenesis involves complex molecular pathways including misfolded proteins accumulation, neuroinflammation, and synaptic dysfunction. Recent insights have highlighted the role of microRNAs (miRNAs) as critical regulators within these pathways, where they influence gene expression and contribute to the pathophysiological landscape of AD. Notably, emerging research has demonstrated that polyphenols, including curcumin, might modulate miRNA activity, thus offering a novel approach to mitigate AD symptoms and progression. This review explores the potential mechanisms through which polyphenols regulate miRNA expression and activity, specifically focusing on autophagy enhancement and inflammation reduction in the context of AD. We provide a detailed examination of key studies linking miRNA dysregulation to AD pathogenesis and discuss how polyphenols might correct these aberrations. The findings presented here underscore the therapeutic potential of polyphenols in AD treatment via miRNA modulation, pointing to new directions in disease management strategies and highlighting the need for targeted research into miRNA-based interventions.

The Effects and Mechanisms of Xanthones in Alzheimer's Disease: A Systematic Review

Xanthones are natural secondary metabolites that possess great potential as neuroprotective agents due to their prominent biological effects on Alzheimer's disease (AD). However, their underlying mechanisms in AD remain unclear. This study aimed to systematically review the effects and mechanisms of xanthones in cell culture and animal studies, gaining a better understanding of their roles in AD. A comprehensive literature search was conducted in the Medline and Scopus databases using specific keywords to identify relevant articles published up to June 2023. After removing duplicates, all articles were imported into the Rayyan software. The article titles were screened based on predefined inclusion and exclusion criteria. Relevant full-text articles were assessed for biases using the OHAT tool. The results were presented in tables. Xanthones have shown various pharmacological effects towards AD from the 21 preclinical studies included. Cell culture studies demonstrated the anti-cholinesterase activity of xanthones, which protects against the loss of acetylcholine. Xanthones exhibited neuroprotective effects by promoting cell viability, reducing the accumulation of β-amyloid and tau aggregation. The administration of xanthones in animal models resulted in a reduction in neuronal inflammation by decreasing microglial and astrocyte burden. In terms of molecular mechanisms, xanthones prevented neuroinflammation through the modulation of signaling pathways, including TLR4/TAK1/NF-κB and MAPK pathways. Mechanisms such as activation of caspase-3 and -9 and suppression of endoplasmic reticulum stress were also reported. Despite the various neuroprotective effects associated with xanthones, there are limited studies reported on their underlying mechanisms in AD. Further studies are warranted to fully understand their potential roles in AD.

An overview of structure-based activity outcomes of pyran derivatives against Alzheimer's disease

Pyran is a heterocyclic group containing oxygen that possesses a variety of pharmacological effects. Pyran is also one of the most prevalent structural subunits in natural products, such as xanthones, coumarins, flavonoids, benzopyrans, etc. Additionally demonstrating the neuroprotective properties of pyrans is the fact that this heterocycle has recently attracted the attention of scientists worldwide. Alzheimer's Disease (AD) treatment and diagnosis are two of the most critical research objectives worldwide. Increased amounts of extracellular senile plaques, intracellular neurofibrillary tangles, and a progressive shutdown of cholinergic basal forebrain neuron transmission are often related with cognitive impairment. This review highlights the various pyran scaffolds of natural and synthetic origin that are effective in the treatment of AD. For better understanding synthetic compounds are categorized as different types of pyran derivatives like chromene, flavone, xanthone, xanthene, etc. The discussion encompasses both the structure-activity correlations of these compounds as well as their activity against AD. Because of the intriguing actions that were uncovered by these pyran-based scaffolds, there is no question that they are at the forefront of the search for potential medication candidates that could treat Alzheimer's disease.

Anti-Neuroinflammatory Potential of Natural Products in the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is an age-related chronic progressive neurodegenerative disease, which is the main cause of dementia in the elderly. Much evidence shows that the onset and late symptoms of AD are caused by multiple factors. Among them, aging is the main factor in the pathogenesis of AD, and the most important risk factor for AD is neuroinflammation. So far, there is no cure for AD, but the relationship between neuroinflammation and AD may provide a new strategy for the treatment of AD. We herein discussed the main etiology hypothesis of AD and the role of neuroinflammation in AD, as well as anti-inflammatory natural products with the potential to prevent and alleviate AD symptoms, including alkaloids, steroids, terpenoids, flavonoids and polyphenols, which are available with great potential for the development of anti-AD drugs.

Polyphenols: Natural food grade biomolecules for treating neurodegenerative diseases from a multi-target perspective

As natural functional bioactive ingredients found in foods and plants, polyphenols play various antioxidant and anti-inflammatory roles to prevent the development of disease and restore human health. The multi-target modulation of polyphenols provides a novel practical therapeutic strategy for neurodegenerative diseases that are difficult to treat with traditional drugs like glutathione and cholinesterase inhibitors. This review mainly focuses on the efficacy of polyphenols on ischemic stroke, Parkinson's disease and Alzheimer's disease, including in vivo and in vitro experimental studies. It is further emphasized that polyphenols exert neuroprotective effects primarily through inhibiting production of oxidative stress and inflammatory cytokines, which may be the underlying mechanism. However, polyphenols are still rarely used as medicines to treat neurodegenerative diseases. Due to the lack of clinical trials, the mechanism of polyphenols is still in the stage of insufficient exploration. Future large-scale multi-center randomized controlled trials and in-depth mechanism studies are still needed to fully assess the safety, efficacy and side effects of polyphenols.

Honokiol and Alpha-Mangostin Inhibit Mayaro Virus Replication through Different Mechanisms

Mayaro virus (MAYV) is an emerging arbovirus with an increasing circulation across the Americas. In the present study, we evaluated the potential antiviral activity of the following natural compounds against MAYV and other arboviruses: Sanguinarine, (R)-Shikonin, Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin. Sanguinarine and Shikonin showed significant cytotoxicity, whereas Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin were well tolerated in all the cell lines tested. Honokiol and α-Mangostin treatment protected Vero-E6 cells against MAYV-induced damage and resulted in a dose-dependent reduction in viral progeny yields for each of the MAYV strains and human cell lines assessed. These compounds also reduced MAYV viral RNA replication in HeLa cells. In addition, Honokiol and α-Mangostin disrupted MAYV infection at different stages of the virus life cycle. Moreover, Honokiol and α-Mangostin decreased Una, Chikungunya, and Zika viral titers and downmodulated the expression of E1 and nsP1 viral proteins from MAYV, Una, and Chikungunya. Finally, in Honokiol- and α-Mangostin-treated HeLa cells, we observed an upregulation in the expression of type I interferon and specific interferon-stimulated genes, including IFNα, IFNβ, MxA, ISG15, OAS2, MDA-5, TNFα, and IL-1β, which may promote an antiviral cellular state. Our results indicate that Honokiol and α-Mangostin present potential broad-spectrum activity against different arboviruses through different mechanisms.