Myricitrin - a flavonoid isolated from the Indian olive tree (Elaeocarpus floribundus) - inhibits Monoamine oxidase in the brain and elevates striatal dopamine levels: therapeutic implications against Parkinson's disease

Pressurized liquid extraction of oak leaf polyphenols: Solvent selection via Hansen parameters, antioxidant evaluation and monoamine-oxidase-a inhibition analysis

This study focuses on the extraction of bioactive compounds from Quercus sideroxyla Bonpl., leaves which have been shown to possess health benefits. The extraction process was done using pressurized liquid extraction (PLE), which is efficient and preserves heat-sensitive compounds. Key factors in the process included the choice of solvents, pressure, temperature, and extraction duration. The Hansen solubility parameters analysis aided in selecting effective solvents, such as ethanol and benzyl alcohol. The extracts were found to contain phenolic compounds, flavonoids, and polyphenols with antioxidant properties. The UPLC-PDA-ESI-QqQ was employed for the precise identification and quantification of these compounds, demonstrating superior extraction of quinic acid and gallic acid at elevated temperatures. Notably, the extracts obtained through PLE exhibited significant inhibitory activity of the MAO-A enzyme, linked to neuronal and cognitive health, suggesting potential benefits in these areas.

Smoking, coffee intake, and Parkinson's disease: Potential protective mechanisms and components

Parkinson's disease (PD) is a common progressive neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Environmental and lifestyle factors, such as smoking and coffee drinking, have been associated with a decreased risk for PD. However, the biological mechanisms underlying protective effects on PD are still not fully understood. It has been suggested that non-nicotine components in cigarette smoke and non-caffeine components in coffee may contribute to this protective effect. The aim of this review was to explore candidate molecules and mechanisms behind the effects of smoking and coffee drinking on PD by integrating findings from previous studies. By cross-referencing an index of tobacco constituents and a list of coffee constituents with existing literature on natural compounds and their structural analogs that show inhibitory activities against monoamine oxidase B, catechol O-methyltransferase, and α-synuclein fibrillation, we have identified tobacco and coffee components that inhibit these targets. Furthermore, tobacco and coffee components potentially play roles in suppressing neuroinflammation, activating the Nrf2 pathway as natural activators, and altering the gut microbiome. This review suggests that the phenolic compounds from tobacco and coffee investigated may contribute to the low incidence of PD in smokers and coffee drinkers, showing moderate to strong potential as therapeutic interventions. The current review suggests that multifunctional molecules found in coffee and cigarette smoke may have potential neuroprotective effects, but none of the data indicates that multifunctionality is required for these effects. This review will deepen our understanding of how smoking and coffee drinking are linked to a reduced risk of PD and will also be important in elucidating the mechanisms underlying the protective effects of smoking and coffee drinking on PD.

Gut-brain axis and brain health: modulating neuroinflammation, cognitive decline, and neurodegeneration

The microbiota-gut-brain axis is a pivotal medium of crosstalk between the central nervous system (CNS) and the gastrointestinal tract. It is an intricate network of synergistic molecular pathways that exert their effects far beyond their local vicinity and even affect the systemic functioning of the body. The current review explores the involvement of the gut-brain axis (GBA) in the functioning of the nervous system, with a special emphasis on the neurodegeneration, cognitive decline, and neuroinflammation that occur in Alzheimer's disease (AD) and Parkinson's disease (PD). Gut-derived microbial metabolites play an important role in facilitating this interaction. We also highlighted the complex interaction between gut-derived metabolites and CNS processes, demonstrating how microbial dysbiosis might result in clinical disorders. Short-chain fatty acids have neuroprotective properties, whereas branched-chain amino acids, trimethylamine-N-oxide (TMAO), and tryptophan derivatives such as indole have negative effects at high concentrations. Furthermore, we cover pharmaceutical and nonpharmacological approaches for restoring the gut microbial balance and promoting neurological health. We further expanded on nutritional therapies and lifestyle changes, such as the Mediterranean diet and exercise. Next, we focused on food-controlling habits such as caloric restriction and intermittent fasting. Moreover, interventional techniques such as prebiotics, probiotics, and pharmacological medications have also been utilized to modify the GBA. Historical microbiome research from early discoveries to recent studies linking gut health to cognitive and emotional well-being has increased our understanding of the GBA.

Novel insights into the molecular mechanisms underlying anti-nociceptive effect of myricitrin against reserpine-induced fibromyalgia model in rats: Implication of SIRT1 and miRNAs

ETHNOPHARMACOLOGICAL RELEVANCE

Manilkara zapota (L.) P. Royen, also termed sapodilla or chikoo, is a significant plant in ethnomedicine because of its long history of traditional medical applications. In diverse cultures, sapodilla is believed to protect against oxidative stress, inflammation, and some chronic diseases because of its high antioxidant content. The naturally occurring antioxidant myricitrin (MYR) flavonoid is primarily found in the leaves and other plant parts of sapodilla and it is well-known for having therapeutic qualities and possible health advantages.

AIM OF THE STUDY

To appraise the possible impact of MYR on a rat model of reserpine-induced fibromyalgia (FM) and explore its mechanism of action.

MATERIALS AND METHODS

Isolation and identification of MYR with more than 99% purity from Manilkara zapota leaves were primarily done and confirmed through chromatographic and spectrophotometric techniques. To develop FM model, reserpine (RSP) was injected daily (1 mg/kg, s.c.) for three successive days. Then, MYR (10 mg/kg, i.p.) and pregabalin (PGB, 30 mg/kg, p.o.) were given daily for another five days. Behavioral changes were assessed through open field test (OFT), hot plate test, and forced swimming test (FST). Further analyses of different brain parameters and signaling pathways were performed to assess monoamines levels, oxidative stress, inflammatory response, apoptotic changes as well as silent information regulator 1 (SIRT1) and micro RNAs (miRNAs) expressions.

RESULTS

From High-Performance Liquid Chromatography (HPLC) analysis, the methanol extract of sapodilla leaves contains 166.17 μg/ml of MYR. Results of behavioral tests showed a significant improvement in RSP-induced nociceptive stimulation, reduced locomotion and exploration and depressive-like behavior by MYR. Biochemical analyses showed that MYR significantly ameliorated the RSP-induced imbalance in brain monoamine neurotransmitters. In addition, MYR significantly attenuated oxidative stress elicited by RSP via up-regulating nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) protein expressions, enhancing superoxide dismutase (SOD) and catalase (CAT) activities, and reducing malondialdehyde (MDA) content in brain. The RSP-provoked inflammatory response was also diminished by MYR treatment as shown by a significant decreased NOD-like receptor protein 3 (NLRP3) inflammasome expression along with reduced levels of interleukin 1 beta (IL-1β) and nuclear factor-κB (NF-κB). Furthermore, the anti-apoptotic activity of MYR was demonstrated by a marked rise in Bcl-2-associated X protein (BAX)/B cell lymphoma-2 (Bcl-2) ratio by lowering Bcl-2 while increasing BAX levels. In addition, MYR treatment significantly boosted the expression of SIRT1 deacetylase in RSP-treated animals. Interestingly, molecular docking showed the ability of MYR to form a stable complex in the binding site of SIRT1. Regarding miRNAs, MYR effectively ameliorated RSP-induced changes in miR-320 and miR-107 gene expressions.

CONCLUSION

Our findings afford new insights into the anti-nociceptive profile of MYR in the RSP-induced FM model in rats. The underlying mechanisms involved direct binding and activation of SIRT1 to influence different signaling cascades, including Nrf2 and NF-κB/NLRP3 together with modulation of miRNAs. However, more in-depth studies are needed before proposing MYR as a new clinically relevant drug in the management of FM.

Monoamine oxidase and neurodegeneration: Mechanisms, inhibitors and natural compounds for therapeutic intervention

Mammalian flavoenzyme Monoamine oxidase (MAO) resides on the outer mitochondrial membrane (OMM) and it is involved in the metabolism of different monoamine neurotransmitters in brain. During MAO mediated oxidative deamination of relevant substrates, H2O2 is released as a catalytic by-product, thus serving as a major source of reactive oxygen species (ROS). Under normal conditions, MAO mediated ROS is reported to propel the functioning of mitochondrial electron transport chain and phasic dopamine release. However, due to its localization onto mitochondria, sudden elevation in its enzymatic activity could directly impact the form and function of the organelle. For instance, in the case of Parkinson's disease (PD) patients who are on l-dopa therapy, the enzyme could be a concurrent source of extensive ROS production in the presence of uncontrolled substrate (dopamine) availability, thus further impacting the health of surviving neurons. It is worth mentioning that the expression of the enzyme in different brain compartments increases with age. Moreover, the involvement of MAO in the progression of neurological disorders such as PD, Alzheimer's disease and depression has been extensively studied in recent times. Although the usage of available synthetic MAO inhibitors has been instrumental in managing these conditions, the associated complications have raised significant concerns lately. Natural products have served as a major source of lead molecules in modern-day drug discovery; however, there is still no FDA-approved MAO inhibitor which is derived from natural sources. In this review, we have provided a comprehensive overview of MAO and how the enzyme system is involved in the pathogenesis of different age-associated neuropathologic conditions. We further discussed the applications and drawbacks of the long-term usage of presently available synthetic MAO inhibitors. Additionally, we have highlighted the prospect and worth of natural product derived molecules in addressing MAO associated complications.

Effectiveness of Flavonoid-Rich Diet in Alleviating Symptoms of Neurodegenerative Diseases

Over the past decades, there has been a significant increase in the burden of neurological diseases, including neurodegenerative disorders, on a global scale. This is linked to a widespread demographic trend in which developed societies are aging, leading to an increased proportion of elderly individuals and, concurrently, an increase in the number of those afflicted, posing one of the main public health challenges for the coming decades. The complex pathomechanisms of neurodegenerative diseases and resulting varied symptoms, which differ depending on the disease, environment, and lifestyle of the patients, make searching for therapies for this group of disorders a formidable challenge. Currently, most neurodegenerative diseases are considered incurable. An important aspect in the fight against and prevention of neurodegenerative diseases may be broadly understood lifestyle choices, and more specifically, what we will focus on in this review, a diet. One proposal that may help in the fight against the spread of neurodegenerative diseases is a diet rich in flavonoids. Flavonoids are compounds widely found in products considered healthy, such as fruits, vegetables, and herbs. Many studies indicated not only the neuroprotective effects of these compounds but also their ability to reverse changes occurring during the progression of diseases such as Alzheimer's, Parkinson's and amyotrophic lateral sclerosis. Here, we present the main groups of flavonoids, discussing their characteristics and mechanisms of action. The most widely described mechanisms point to neuroprotective functions due to strong antioxidant and anti-inflammatory effects, accompanied with their ability to penetrate the blood-brain barrier, as well as the ability to inhibit the formation of protein aggregates. The latter feature, together with promoting removal of the aggregates is especially important in neurodegenerative diseases. We discuss a therapeutic potential of selected flavonoids in the fight against neurodegenerative diseases, based on in vitro studies, and their impact when included in the diet of animals (laboratory research) and humans (population studies). Thus, this review summarizes flavonoids' actions and impacts on neurodegenerative diseases. Therapeutic use of these compounds in the future is potentially possible but depends on overcoming key challenges such as low bioavailability, determining the therapeutic dose, and defining what a flavonoid-rich diet is and determining its potential negative effects. This review also suggests further research directions to address these challenges.

Exploring beetroot (Beta vulgaris L.) for diabetes mellitus and Alzheimer's disease dual therapy: in vitro and computational studies

This study explored the flavonoid-rich extract of beetroot (Beta vulgaris L.) for type 2 diabetes mellitus (T2D) and Alzheimer's disease (AD) dual therapy by using in vitro and molecular simulation studies. Flavonoid-rich extracts of B. vulgaris fruit were evaluated for their antidiabetic and anti-alzheimic activities. Molecular docking and dynamic simulation were performed to identify potential bioactive flavonoids with dual therapeutic effects on T2D and AD. Flavonoid-rich extracts of B. vulgaris fruit (IC50 = 73.062 ± 0.480 μg mL-1) had moderate activity against α-amylase compared to the standard acarbose (IC50 = 27.104 ± 0.270 μg mL-1). Compared with acarbose, flavonoid-rich extracts of B. vulgaris fruit had appreciable activity against α-glucosidase (IC50 = 17.389 ± 0.436 μg mL-1) (IC50 = 37.564 ± 0.620 μg mL-1). For AChE inhibition, flavonoid-rich extracts of B. vulgaris fruit exhibited (p < 0.0001) inhibitory activity (IC50 = 723.260 ± 5.466 μg mL-1), albeit weaker than that of the standard control, galantamine (IC50 = 27.950 ± 0.122 μg mL-1). Similarly, flavonoid-rich extracts of B. vulgaris fruit showed considerable (p < 0.0001) inhibitory effects on BChE (IC50 = 649.112 ± 0.683 μg mL-1). In contrast, galantamine (IC50 = 23.126 ± 0.683 μg mL-1) is more potent than the extracts of B. vulgaris fruit. Monoamine oxidase (MAO) activity increased in FeSO4-induced brain damage. In contrast, flavonoid-rich extracts of B. vulgaris fruit protected against Fe2+-mediated brain damage by suppressing MAO activity in a concentration-dependent manner. HPLC-DAD profiling of the extracts identified quercetrin, apigenin, rutin, myricetin, iso-quercetrin, p-coumaric acid, ferulic acid, caffeic acid, and gallic acid. Molecular docking studies revealed quercetrin, apigenin, rutin, iso-queretrin, and myricetin were the top docked bioactive flavonoids against the five top target proteins (α-amylase, α-glucosidase AchE, BchE, and MAO). Molecular dynamic simulations revealed that the complexes formed remained stable over the course of the simulation. Collectively, the findings support the prospect of flavonoid-rich extracts of B. vulgaris root functioning as a dual therapy for T2D and AD.

High-throughput discovery of highly selective reversible hMAO-B inhibitors based on at-line nanofractionation

Human monoamine oxidase B (hMAO-B) has emerged as a pivotal therapeutic target for Parkinson's disease. Due to adverse effects and shortage of commercial drugs, there is a need for novel, highly selective, and reversible hMAO-B inhibitors with good blood-brain barrier permeability. In this study, a high-throughput at-line nanofractionation screening platform was established with extracts from Chuanxiong Rhizoma, which resulted in the discovery of 75 active compounds, including phenolic acids, volatile oils, and phthalides, two of which were highly selective novel natural phthalide hMAO-B inhibitors that were potent, selective, reversible and had good blood‒brain permeability. Molecular docking and molecular dynamics simulations elucidated the inhibition mechanism. Sedanolide (IC50 = 103 nmol/L; SI = 645) and neocnidilide (IC50 = 131 nmol/L; SI = 207) demonstrated their excellent potential as hMAO-B inhibitors. They offset the limitations of deactivating enzymes associated with irreversible hMAO-B inhibitors such as rasagiline. In SH-SY5Y cell assays, sedanolide (EC50 = 0.962 μmol/L) and neocnidilide (EC50 = 1.161 μmol/L) exhibited significant neuroprotective effects, comparable to the positive drugs rasagiline (EC50 = 0.896 μmol/L) and safinamide (EC50 = 1.079 μmol/L). These findings underscore the potential of sedanolide as a novel natural hMAO-B inhibitor that warrants further development as a promising drug candidate.

α-Viniferin, a dietary phytochemical, inhibits Monoamine oxidase and alleviates Parkinson's disease associated behavioral deficits in a mice model

Parkinson's disease (PD) is one of the most prevalent age-related neurodegenerative disorders. Behavioral complexities worsen over time due to progressive dopaminergic (DArgic) neuronal loss at substantia nigra region of brain. Available treatments typically aim to increase dopamine (DA) levels at striatum. DA is degraded by Monoamine oxidase (MAO), thus dietary phytochemicals with MAO inhibitory properties can contribute to elevate DA levels and reduce the ailment. Characterization of naturally occurring dietary MAO inhibitors is inadequate. Based on available knowledge, we selected different classes of molecules and conducted a screening process to assess their potential as MAO inhibitors. The compounds mostly derived from food sources, broadly belonging to triterpenoids (ursane, oleanane and hopane), alkaloid, polyphenolics, monoterpenoids, alkylbenzene, phenylpropanoid and aromatic alcohol classes. Among all the molecules, highest level of MAO inhibition is offered by α-viniferin, a resveratrol trimer. Cell viability, mitochondrial morphology and reactive oxygen species (ROS) generation remained unaltered by 50 μM α-viniferin treatment in-vitro. Toxicity studies in Drosophila showed unchanged gross neuronal morphology, ROS level, motor activity or long-term survival. α-Viniferin inhibited MAO in mice brain and elevated striatal DA levels. PD-related akinesia and cataleptic behavior were attenuated by α-viniferin due to increase in striatal DA. Our study implies that α-viniferin can be used as an adjunct phytotherapeutic agent for mitigating PD-related behavioral deterioration.

Therapeutic Potential of Myricetin in the Treatment of Neurological, Neuropsychiatric, and Neurodegenerative Disorders

Myricetin (MC), 3,5,7,3',4',5'-hexahydroxyflavone, chemically belongs to a flavonoid category known to confer antioxidant, antimicrobial, antidiabetic, and neuroprotective effects. MC is known to suppress the generation of Reactive Oxygen Species (ROS), lipid peroxidation (MDA), and inflammatory markers. It has been reported to improve insulin function in the human brain and periphery. Besides this, it modulates several neurochemicals including glutamate, GABA, serotonin, etc. MC has been shown to reduce the expression of the enzyme Mono Amine Oxidase (MAO), which is responsible for the metabolism of monoamines. MC treatment reduces levels of plasma corticosterone and restores hippocampal BDNF (full form) protein in stressed animals. Further, MC has shown its protective effect against amyloid-beta, MPTP, rotenone, 6-OHDA, etc. suggesting its potential role against neurodegenerative disorders. The aim of the present review is to highlight the therapeutic potential of MC in the treatment of several neurological, neuropsychiatric, and neurodegenerative disorders.

Calcineurin inhibition protects against dopamine toxicity and attenuates behavioral decline in a Parkinson's disease model

BACKGROUND

Parkinson's disease (PD), a highly prevalent neuro-motor disorder is caused due to progressive loss of dopaminergic (DAergic) neurons at substantia nigra region of brain. This leads to depleted dopamine (DA) content at striatum, thus affecting the fine tuning of basal ganglia. In patients, this imbalance is manifested by akinesia, catalepsy and tremor. PD associated behavioral dysfunctions are frequently mitigated by l-DOPA (LD) therapy, a precursor for DA synthesis. Due to progressive neurodegeneration, LD eventually loses applicability in PD. Although DA is cytotoxic, it is unclear whether LD therapy can accelerate PD progression or not. LD itself does not lead to neurodegeneration in vivo, but previous reports demonstrate that LD treatment mediated excess DA can potentiate neurotoxicity when PD associated genetic or epigenetic aberrations are involved. So, minimizing DA toxicity during the therapy is an absolute necessity to halt or slowdown PD progression. The two major contributing factors associated with DA toxicity are: degradation by Monoamine oxidase and DAquinone (DAQ) formation.

RESULTS

Here, we report that apoptotic mitochondrial fragmentation via Calcineurin (CaN)-DRP1 axis is a common downstream event for both these initial cues, inhibiting which can protect cells from DA toxicity comprehensively. No protective effect is observed, in terms of cell survival when only PxIxIT domain of CaN is obstructed, demonstrating the importance to block DRP1-CaN axis specifically. Further, evaluation of the impact of DA exposure on PD progression in a mice model reveal that LD mediated behavioral recovery diminishes with time, mostly because of continued DAergic cell death and dendritic spine loss at striatum. CaN inhibition, alone or in combination with LD, offer long term behavioral protection. This protective effect is mediated specifically by hindering CaN-DRP1 axis, whereas inhibiting interaction between CaN and other substrates, including proteins involved in neuro-inflammation, remained ineffective when LD is co-administered.

CONCLUSIONS

In this study, we conclude that DA toxicity can be circumvented by CaN inhibition and it can mitigate PD related behavioral aberrations by protecting neuronal architecture at striatum. We propose that CaN inhibitors might extend the therapeutic efficacy of LD treatment.

Natural product-based pharmacological studies for neurological disorders

Central nervous system (CNS) disorders and diseases are expected to rise sharply in the coming years, partly because of the world's aging population. Medicines for the treatment of the CNS have not been successfully made. Inadequate knowledge about the brain, pharmacokinetic and dynamic errors in preclinical studies, challenges with clinical trial design, complexity and variety of human brain illnesses, and variations in species are some potential scenarios. Neurodegenerative diseases (NDDs) are multifaceted and lack identifiable etiological components, and the drugs developed to treat them did not meet the requirements of those who anticipated treatments. Therefore, there is a great demand for safe and effective natural therapeutic adjuvants. For the treatment of NDDs and other memory-related problems, many herbal and natural items have been used in the Ayurvedic medical system. Anxiety, depression, Parkinson's, and Alzheimer's diseases (AD), as well as a plethora of other neuropsychiatric disorders, may benefit from the use of plant and food-derived chemicals that have antidepressant or antiepileptic properties. We have summarized the present level of knowledge about natural products based on topological evidence, bioinformatics analysis, and translational research in this review. We have also highlighted some clinical research or investigation that will help us select natural products for the treatment of neurological conditions. In the present review, we have explored the potential efficacy of phytoconstituents against neurological diseases. Various evidence-based studies and extensive recent investigations have been included, which will help pharmacologists reduce the progression of neuronal disease.