Natural polyphenol: Their pathogenesis-targeting therapeutic potential in Alzheimer's disease

Exploring the therapeutic role of Moringa oleifera in neurodegeneration: antioxidant, anti-inflammatory, and neuroprotective mechanisms

Neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, and other cognitive impairment conditions in elderly are defined by progressive loss of neurons, based mostly on oxidative stress, long-term neuroinflammation, and compromised neuroplasticity. In the midst of increasing investigation for natural drugs, Moringa oleifera, a plant highly accepted for its high nutritional and phytochemical constitution, has become an active candidate with multi-oriented neuroprotective activity. This review discusses the therapeutic potential of Moringa oleifera in neurodegeneration, based on its antioxidant, anti-inflammatory, and neuroprotective activities. The plant's bioactive molecules, flavonoids, phenolic acids, and vitamins exhibit potent free radical-scavenging activity and the ability to modulate crucial inflammatory signaling pathways, like NF-κB and MAPK signaling. Additionally, Moringa oleifera is shown to possess the potential for enhancing neurogenesis, facilitating synaptic plasticity, and neuronal apoptosis protection. Preclinical evidence supports its efficacy in decreasing neuropathological alterations and enhancing cognitive function, whereas initial clinical data suggest a benign safety profile. In spite of these promising observations, additional work is required to confirm its action in human subjects and to standardize therapeutic regimens. This review highlights the promise of Moringa oleifera as an adjunct treatment for the prevention and management of neurodegenerative disorders and points to avenues for future investigation and clinical utility.

The effect of curcumin supplementation on cognitive function: an updated systematic review and meta-analysis

Background

Previous randomized controlled trials (RCTs) did not draw a consistent conclusion about the effect of curcumin on cognitive function.

Methods

We searched Web of Science, PubMed, Cochrane Library and Embase, and 9 RCTs (including 12 independent comparisons) with 501 subjects were included in the present meta-analysis.

Results

Compared with placebo, supplementation of curcumin significantly improved global cognitive function (SMD, 0.82; 95% CI, 0.19 to 1.45; p = 0.010). A curvilinear dose-response effect was observed, and the optimal dose is 0.8 g/day. Subgroup analysis indicated that the beneficial effect of curcumin on cognition was significant only if duration ≥24 weeks (SMD, 1.15; 95% CI, 0.13 to 2.18; p = 0.027), age of participants ≥60 years (SMD, 1.12; 95% CI, 0.03 to 2.21; p = 0.044), or participants from Asian countries (SMD, 0.96; 95% CI, 0.08 to 1.83; p = 0.032). Otherwise, this effect became non-significant (p > 0.05). Sensitivity analysis by excluding each study one by one or excluding all studies with high risk of bias did not obviously influence the final results. No significant publication bias was observed (P for Begg's Test and Egger's test = 0.150 and 0.493, respectively).

Conclusion

Supplementation of curcumin can effectively improve global cognitive function, and the optimal dose and duration is 0.8 g/day and ≥24 weeks. The beneficial effect of curcumin on cognition is more potent in older and Asian participants than younger and Western ones.

Disruption of fibrillar assemblies of L-phenylalanine using polyphenol-passivated nanocarbon as a potential therapeutic strategy against phenylketonuria

One of the pathological manifestations of phenylketonuria (PKU) is the formation of fibrillar assemblies of the aromatic amino acid L-phenylalanine at pathological concentrations. As a possible therapeutic strategy for PKU, we introduce a nanocarbon system passivated with polyphenol gallic acid (CNPGA), which has the ability to disrupt and inhibit the formation of fibrillar assemblies. The CNPGA was prepared using a rapid and facile microwave-assisted one-pot method from an aqueous solution of sucrose and gallic acid and fully characterized using UV-Vis, FT-IR, XRD, XPS, TEM, zeta potential and DLS measurements. The CNPGA-mediated inhibition and disruption of L-phenylalanine fibrils was examined using a thioflavin T (ThT) assay. The change in the conformation of the fibrils upon CNPGA treatment was assessed by means of circular dichroism spectroscopy. Visual analysis of the rupture of fibrillar assemblies was performed using SEM. Finally, the biocompatibility of CNPGA was evaluated in two normal cell lines, HaCaT (human epidermal keratinocyte cell line) and Vero (African green monkey kidney cell line) cells.

Ginger leaf polyphenols mitigate β-amyloid toxicity via JNK/FOXO pathway activation in Caenorhabditis elegans

β-Amyloid (Aβ) aggregation is the major pathological feature of Alzheimer's disease (AD), resulting in oxidative stress and further exacerbating Aβ aggregation. Ginger leaf polyphenols (GLP) have been found to possess antioxidant activity, evidencing their potential in addressing AD. GLP is mainly composed of 12 polyphenols, 8 organic acids, and 6 glycosides, of which polyphenols are predominantly composed of apigenin, kaempferol, and quercetin derivatives. Moreover, GLP alleviates reproductive toxicity, longevity toxicity, and neurotoxicity induced by Aβ via regulating the antioxidase system in Caenorhabditis elegans. As shown by the network pharmacology results, GLP might activate the JNK/Foxo signaling pathway to regulate the antioxidase system, which was evidenced by the up-regulation of gene expression levels of jnk-1, daf-16, sod-3, and hsp-16.2. Overall, GLP might be a potential antioxidant for combating AD.

Depolymerized peanut skin-derived proanthocyanidins alleviate cognitive dysfunction by inhibiting Aβ42 aggregation in Alzheimer's disease

Peanut skin proanthocyanidins (PSP) are natural polyphenols with antioxidant properties that mitigate Alzheimer's disease (AD), a complex progressive neurodegenerative disorder whose underlying biological mechanisms includes the aggregation of insoluble amyloid plaques. However, the high degree of polymerization of PSP, extracted using conventional methods, limits its bioavailability. This study established the optimal processes for ultrasound-assisted alkaline depolymerization to produce oligomeric proanthocyanidins (OPSP) from PSP content (2.7 mg/mL), depolymerization temperature (54.8 °C), ultrasonic power (480 W, 28 Hz), ultrasonic duration (28.7 min), and pH (12.1). Under these conditions, the degree of polymerization of the proanthocyanidins decreased from 6.74 to 2.87. Physicochemical characteristics of PSP and OPSP were analyzed. Both PSP and OPSP exhibited shared structural bonding and a repeating 288 Da unit, with Proanthocyanidin A identified as the predominant type. Furthermore, compared with PSP, OPSP demonstrated enhanced stability and antioxidant activity. Using in vitro detection of amyloid-beta (Aβ42) inhibition, this study demonstrated that OPSP exhibited greater inhibition of Aβ42 fibrillogenicity than underpolymerized PSP, and OPSP significantly inhibited Aβ42-induced cytotoxicity. In addition, the effect of OPSP was investigated in a rat model of Alzheimer's disease. The results indicated that OPSP improved the memory performance of AD rats in the water maze and decreased the levels of inflammatory factors IL-6, IL-1β, and TNF-α. Moreover, OPSP ameliorated histopathological changes and reduced Aβ42 plaque deposition in the brains of AD rats. These findings regarding OPSP are anticipated to facilitate high-value utilization of peanut by-products, expand their applications, and provide guidance for the use of OPSP in the development of natural healthcare pharmaceuticals and mitigation and treatment of Alzheimer's disease.

Targeting natural antioxidant polyphenols to protect neuroinflammation and neurodegenerative diseases: a comprehensive review

Polyphenols, naturally occurring phytonutrients found in plant-based foods, have attracted significant attention for their potential therapeutic effects in neurological diseases and neuroinflammation. These compounds possess diverse neuroprotective capabilities, including antioxidant, anti-inflammatory, and anti-amyloid properties, which contribute to mitigating the progression of neurodegenerative conditions such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Dementia, Multiple Sclerosis (MS), Stroke, and Huntington's Disease (HD). Polyphenols have been extensively studied for their ability to regulate inflammatory responses by modulating the activity of pro-inflammatory genes and influencing signal transduction pathways, thereby reducing neuroinflammation and neuronal death. Additionally, polyphenols have shown promise in modulating various cellular signaling pathways associated with neuronal viability, synaptic plasticity, and cognitive function. Epidemiological and clinical studies highlight the potential of polyphenol-rich diets to decrease the risk and alleviate symptoms of neurodegenerative disorders and neuroinflammation. Furthermore, polyphenols have demonstrated their therapeutic potential through the regulation of key signaling pathways such as Akt, Nrf2, STAT, and MAPK, which play critical roles in neuroprotection and the body's immune response. This review emphasizes the growing body of evidence supporting the therapeutic potential of polyphenols in combating neurodegeneration and neuroinflammation, as well as enhancing brain health. Despite the substantial evidence and promising hypotheses, further research and clinical investigations are necessary to fully understand the role of polyphenols and establish them as advanced therapeutic targets for age-related neurodegenerative diseases and neuroinflammatory conditions.

Natural products targeting amyloid-β oligomer neurotoxicity in Alzheimer's disease

Alzheimer's disease (AD) constitutes a major global health issue, characterized by progressive neurodegeneration and cognitive impairment, for which no curative treatment is currently available. Current therapeutic approaches are focused on symptom management, highlighting the critical need for disease-modifying therapy. The hallmark pathology of AD involves the aggregation and accumulation of amyloid-β (Aβ) peptides in the brain. Consequently, drug discovery efforts in recent decades have centered on the Aβ aggregation cascade, which includes the transition of monomeric Aβ peptides into toxic oligomers and, ultimately, mature fibrils. Historically, anti-Aβ strategies focused on the clearance of amyloid fibrils using monoclonal antibodies. However, substantial evidence has highlighted the critical role of Aβ oligomers (AβOs) in AD pathogenesis. Soluble AβOs are now recognized as more toxic than fibrils, directly contributing to synaptic impairment, neuronal damage, and the onset of AD. Targeting AβOs has emerged as a promising therapeutic approach to mitigate cognitive decline in AD. Natural products (NPs) have demonstrated promise against AβO neurotoxicity through various mechanisms, including preventing AβO formation, enhancing clearance mechanisms, or converting AβOs into non-toxic species. Understanding the mechanisms by which anti-AβO NPs operate is useful for developing disease-modifying treatments for AD. In this review, we explore the role of NPs in mitigating AβO neurotoxicity for AD drug discovery, summarizing key evidence from biophysical methods, cellular assays, and animal models. By discussing how NPs modulate AβO neurotoxicity across various experimental systems, we aim to provide valuable insights into novel therapeutic strategies targeting AβOs in AD.

Bioactive Compounds and Antioxidant Capacity of Pulp, Peel and Seeds from Jeriva (Syagrus romanzoffiana)

Jeriva (Syagrus romanzoffiana) is a fruit from palm trees of the Arecaceae family, widely distributed in tropical and subtropical areas of Latin America. It has low production costs and high productivity throughout the year; however, its consumption is very low, and the production goes almost entirely to feed animals or to waste. To improve its consumption, a good characterization of the whole fruit is necessary. The objective of this work was to evaluate the jeriva pulp, peel and seeds according to carotenoids, phenolic compounds, vitamin C, tocopherols and antioxidant potential using HPLC, microplate readers and spectrophotometric methods. Every part of the fruit exhibited antioxidant capacity in the ORAC and TEAC tests, which can be attributed to its high concentration of polyphenols. Carotenoids were more present in the pulp and peel and almost absent in the seeds. Vitamin C ranged from 12 ± 1 for the seeds up to 92 ± 3 mg/100 g for the pulp. The total phenolic content was quantified between 473 ± 39 for the seeds and 1089 ± 32 mg of gallic acid equivalents (GAEs)/100 g for the pulp. These results demonstrate that all parts of this fruit have important bioactive nutrients, with promising perspectives for further scientific approaches and for composing formulations of food products to enhance functional properties.