Mechanistic study of the inhibitory activity of Geum urbanum extract against α-Synuclein fibrillation

Role of medicinal plants in inhibiting SARS-CoV-2 and in the management of post-COVID-19 complications

BACKGROUND

The worldwide corona virus disease outbreak, generally known as COVID-19 pandemic outbreak resulted in a major health crisis globally. The morbidity and transmission modality of COVID-19 appear more severe and uncontrollable. The respiratory failure and following cardiovascular complications are the main pathophysiology of this deadly disease. Several therapeutic strategies are put forward for the development of safe and effective treatment against SARS-CoV-2 virus from the pharmacological view point but till date there are no specific treatment regimen developed for this viral infection.

PURPOSE

The present review emphasizes the role of herbs and herbs-derived secondary metabolites in inhibiting SARS-CoV-2 virus and also for the management of post-COVID-19 related complications. This approach will foster and ensure the safeguards of using medicinal plant resources to support the healthcare system. Plant-derived phytochemicals have already been reported to prevent the viral infection and to overcome the post-COVID complications like parkinsonism, kidney and heart failure, liver and lungs injury and mental problems. In this review, we explored mechanistic approaches of herbal medicines and their phytocomponenets as antiviral and post-COVID complications by modulating the immunological and inflammatory states.

STUDY DESIGN

Studies related to diagnosis and treatment guidelines issued for COVID-19 by different traditional system of medicine were included. The information was gathered from pharmacological or non-pharmacological interventions approaches. The gathered information sorted based on therapeutic application of herbs and their components against SARSCoV-2 and COVID-19 related complications.

METHODS

A systemic search of published literature was conducted from 2003 to 2021 using different literature database like Google Scholar, PubMed, Science Direct, Scopus and Web of Science to emphasize relevant articles on medicinal plants against SARS-CoV-2 viral infection and Post-COVID related complications.

RESULTS

Collected published literature from 2003 onwards yielded with total 625 articles, from more than 18 countries. Among these 625 articles, more than 95 medicinal plants and 25 active phytomolecules belong to 48 plant families. Reports on the therapeutic activity of the medicinal plants belong to the Lamiaceae family (11 reports), which was found to be maximum reported from 4 different countries including India, China, Australia, and Morocco. Other reports on the medicinal plant of Asteraceae (7 reports), Fabaceae (8 reports), Piperaceae (3 reports), Zingiberaceae (3 reports), Ranunculaceae (3 reports), Meliaceae (4 reports) were found, which can be explored for the development of safe and efficacious products targeting COVID-19.

CONCLUSION

Keeping in mind that the natural alternatives are in the priority for the management and prevention of the COVID-19, the present review may help to develop an alternative approach for the management of COVID-19 viral infection and post-COVID complications from a mechanistic point of view.

Brazilin Removes Toxic Alpha-Synuclein and Seeding Competent Assemblies from Parkinson Brain by Altering Conformational Equilibrium

Alpha-synuclein (α-syn) fibrils, a major constituent of the neurotoxic Lewy Bodies in Parkinson's disease, form via nucleation dependent polymerization and can replicate by a seeding mechanism. Brazilin, a small molecule derived from red cedarwood trees in Brazil, has been shown to inhibit the fibrillogenesis of amyloid-beta (Aβ) and α-syn as well as remodel mature fibrils and reduce cytotoxicity. Here we test the effects of Brazilin on both seeded and unseeded α-syn fibril formation and show that the natural polyphenol inhibits fibrillogenesis of α-syn by a unique mechanism that alters conformational equilibria in two separate points of the assembly mechanism: Brazilin preserves the natively unfolded state of α-syn by specifically binding to the compact conformation of the α-syn monomer. Brazilin also eliminates seeding competence of α-syn assemblies from Parkinson's disease patient brain tissue, and reduces toxicity of pre-formed assemblies in primary neurons by inducing the formation of large fibril clusters. Molecular docking of Brazilin shows the molecule to interact both with unfolded α-syn monomers and with the cross-β sheet structure of α-syn fibrils. Our findings suggest that Brazilin has substantial potential as a neuroprotective and therapeutic agent for Parkinson's disease.

Protective effect of Vigna unguiculata extract against aging and neurodegeneration

Aging and age-related neurodegeneration are among the major challenges in modern medicine because of the progressive increase in the number of elderly in the world population. Nutrition, which has important long-term consequences for health, is an important way to prevent diseases and achieve healthy aging. The beneficial effects of Vigna unguiculata on metabolic disorders have been widely documented. Here, we show that an aqueous extract of V. unguiculata beans delays senescence both in Saccharomyces cerevisiae and Drosophila melanogaster, in a Snf1/AMPK-dependent manner. Consistently, an increased expression of FOXO, SIRT1, NOTCH and heme oxygenase (HO) genes, already known to be required for the longevity extension in D. melanogaster, is also shown. Preventing α-synuclein self-assembly is one of the most promising approaches for the treatment of Parkinson's disease (PD), for which aging is a risk factor. In vitro aggregation of α-synuclein, its toxicity and membrane localization in yeast and neuroblastoma cells are strongly decreased in the presence of bean extract. In a Caenorhabditis elegans model of PD, V. unguiculata extract substantially reduces the number of the age-dependent degeneration of the cephalic dopaminergic neurons. Our findings support the role of V. unguiculata beans as a functional food in age-related disorders.

Scientific basis for the industrialization of traditionally used plants of the Rosaceae family

Plants have been traditionally used for the treatment of different types of illness, due to biomolecules with recognised benefits. Rosaceae family is used in traditional Galician medicine. The following plants Agrimonia eupatoria, Crataegus monogyna, Filipendula ulmaria, Geum urbanum, Potentilla erecta and Rosa canina are usually found in treatments. The aim of this study is to perform an ethnobotanical review about the bioactive compounds of these plants and their different bioactivities, both studied in vitro and in vivo. The nature of the bioactive compounds is varied, highlighting the presence of different phenolic compounds, such as phenolic acids, flavonoids or tannins. Understanding the beneficial effects of the administration of the whole plant or target tissues from A. eupatoria, C. monogyna, F. ulmaria, G. urbanum, P. erecta and R. canina as well as those from their individual compounds could lead to the development of new drugs based on the use of natural ingredients.

Plant Extracts and Phytochemicals Targeting α-Synuclein Aggregation in Parkinson's Disease Models

α-Synuclein (α-syn) is a presynaptic protein that regulates the release of neurotransmitters from synaptic vesicles in the brain. α-Syn aggregates, including Lewy bodies, are features of both sporadic and familial forms of Parkinson's disease (PD). These aggregates undergo several key stages of fibrillation, oligomerization, and aggregation. Therapeutic benefits of drugs decline with disease progression and offer only symptomatic treatment. Novel therapeutic strategies are required which can either prevent or delay the progression of the disease. The link between α-syn and the etiopathogenesis and progression of PD are well-established in the literature. Studies indicate that α-syn is an important therapeutic target and inhibition of α-syn aggregation, oligomerization, and fibrillation are an important disease modification strategy. However, recent studies have shown that plant extracts and phytochemicals have neuroprotective effects on α-syn oligomerization and fibrillation by targeting different key stages of its formation. Although many reviews on the antioxidant-mediated, neuroprotective effect of plant extracts and phytochemicals on PD symptoms have been well-highlighted, the antioxidant mechanisms show limited success for translation to clinical studies. The identification of specific plant extracts and phytochemicals that target α-syn aggregation will provide selective molecules to develop new drugs for PD. The present review provides an overview of plant extracts and phytochemicals that target α-syn in PD and summarizes the observed effects and the underlying mechanisms. Furthermore, we provide a synopsis of current experimental models and techniques used to evaluate plant extracts and phytochemicals. Plant extracts and phytochemicals were found to inhibit the aggregation or fibril formation of oligomers. These also appear to direct α-syn oligomer formation into its unstructured form or promote non-toxic pathways and suggested to be valuable drug candidates for PD and related synucleinopathy. Current evidences from in vitro studies require confirmation in the in vivo studies. Further studies are needed to ascertain their potential effects and safety in preclinical studies for pharmaceutical/nutritional development of these phytochemicals or dietary inclusion of the plant extracts in PD treatment.

Early Stage Alpha-Synuclein Amyloid Fibrils are Reservoirs of Membrane-Binding Species

The presence of αSN fibrils indisputably associates with the development of synucleinopathies. However, while certain fibril morphologies have been linked to downstream pathological phenotypes, others appear less harmful, leading to the concept of fibril strains, originally described in relation to prion disease. Indeed, the presence of fibrils does not associate directly with neurotoxicity. Rather, it has been suggested that the toxic compounds are soluble amyloidogenic oligomers, potentially co-existing with fibrils. Here, combining synchrotron radiation circular dichroism, transmission electron microscopy and binding assays on native plasma membrane sheets, we reveal distinct biological and biophysical differences between initial and matured fibrils, transformed within the timespan of few days. Immature fibrils are reservoirs of membrane-binding species, which in response to even gentle experimental changes release into solution in a reversible manner. In contrast, mature fibrils, albeit macroscopically indistinguishable from their less mature counterparts, are structurally robust, shielding the solution from the membrane active soluble species. We thus show that particular biological activity resides transiently with the fibrillating sample, distinct for one, but not the other, spontaneously formed fibril polymorph. These results shed new light on the principles of fibril polymorphism with consequent impact on future design of assays and therapeutic development.

A Possible Connection Between Plant Longevity and the Absence of Protein Fibrillation: Basis for Identifying Aggregation Inhibitors in Plants

The ability of proteins to aggregate to form well-organized β-sheet rich amyloid fibrils is increasingly viewed as a general if regrettable property of the polypeptide chain. Aggregation leads to diseases such as amyloidosis and neurodegeneration in humans and various mammalian species but is also found in a functional variety in both animals and microbes. However, there are to our knowledge no reports of amyloid formation in plants. Plants are also the source of a large number of aggregation-inhibiting compounds. We reasoned that the two phenomena could be connected and that one of (many) preconditions for plant longevity is the ability to suppress unwanted protein aggregation. In support of this, we show that while protein extracts from the sugar maple tree Acer saccharum fibrillate readily on their own, this process is efficiently abolished by addition of small molecule extracts from the same plant. Further analysis of 44 plants showed a correlation between plant longevity and ability to inhibit protein aggregation. Extracts from the best performing plant, the sugar maple, were subjected to chromatographic fractionation, leading to the identification of a large number of compounds, many of which were shown to inhibit aggregation in vitro. One cautious interpretation is that it may have been advantageous for plants to maintain an efficient collection of aggregation-inhibiting metabolites as long as they do not impair metabolite function. From a practical perspective, our results indicate that long-lived plants may be particularly appropriate sources of new anti-aggregation compounds with therapeutic potential.

Andrographolide inhibits human serum albumin fibril formations through site-specific molecular interactions

Protein misfolding and fibrillation are the fundamental traits in degenerative diseases like Alzheimer's, Parkinsonism, and diabetes mellitus. Bioactives such as flavonoids and terpenoids from plant sources are known to express protective effects against an array of diseases including diabetes, Alzheimer's and obesity. Andrographolide (AG), a labdane diterpenoid is prescribed widely in the Indian and Chinese health care systems for classical efficacy against a number of degenerative diseases. This work presents an in depth study on the effects of AG on protein fibrillating pathophysiology. Thioflavin T fluorescence spectroscopy and DLS results indicated concentration dependent inhibition of human serum albumin (HSA) fibrillation. The results were confirmed by electron microscopy studies. HSA fibril formations were markedly reduced in the presence of AG. Fluorescence studies and UV-Vis experiments confirmed further that AG molecularly interacts with HSA at site. In silico molecular docking studies revealed hydrogen bonding and hydrophobic interactions with HSA in the native state. Thus AG interacts with HSA, stabilizes the native protein structure and inhibits fibrillation. The results demonstrated that the compound possesses anti-amyloidogenic properties and can be promising against some human degenerative diseases.

Andrographolide inhibited HSA protein fibrillation through site specific interactions.

The Medicinal Chemistry of Natural and Semisynthetic Compounds against Parkinson's and Huntington's Diseases

Among the diseases affecting the central nervous system (CNS), neurodegenerations attract the interest of both the clinician and the medicinal chemist. The increasing average age of population, the growing number of patients, and the lack of long-term effective remedies push ahead the quest for novel tools against this class of pathologies. We present a review on the state of the art of the molecules (or combination of molecules) of natural origin that are currently under study against two well-defined pathologies: Parkinson's disease (PD) and Huntington's disease (HD). Nowadays, very few tools are available for preventing or counteracting the progression of such diseases. Two major parameters were considered for the preparation of this review: particular attention was reserved to these research works presenting well-defined molecular mechanisms for the studied compounds, and where available, papers reporting in vivo data were preferred. A literature search for peer-reviewed articles using PubMed, Scopus, and Reaxys databases was performed, exploiting different keywords and logical operators: 91 papers were considered (preferentially published after 2015). The review presents a brief overview on the etiology of the studied neurodegenerations and the current treatments, followed by a detailed discussion of the natural and semisynthetic compounds dividing them in different paragraphs considering their several mechanisms of action.

Looking at the recent advances in understanding α-synuclein and its aggregation through the proteoform prism

Despite attracting the close attention of multiple researchers for the past 25 years, α-synuclein continues to be an enigma, hiding sacred truth related to its structure, function, and dysfunction, concealing mechanisms of its pathological spread within the affected brain during disease progression, and, above all, covering up the molecular mechanisms of its multipathogenicity, i.e. the ability to be associated with the pathogenesis of various diseases. The goal of this article is to present the most recent advances in understanding of this protein and its aggregation and to show that the remarkable structural, functional, and dysfunctional multifaceted nature of α-synuclein can be understood using the proteoform concept.

Screening of plants used in the European traditional medicine to treat memory disorders for acetylcholinesterase inhibitory activity and anti amyloidogenic activity

ETHNOPHARMACOLOGICAL RELEVANCE

Plants used in the traditional medicine of Europe to treat memory dysfunction and/or to enhance memory were investigated for activity against the underlying mechanisms of Alzheimer's disease.

AIM OF THE STUDY

To investigate 35 ethanolic extracts of plants, selected using an ethnopharmacological approach, for anti-amyloidogenic activity as well as an ability to inhibit the enzymatic activity of acetylcholinesterase.

MATERIALS AND METHODS

The anti-amyloidogenic activity of the extracts against amyloid beta was investigated by Thioflavin T fibrillation assays and the ability to inhibit the enzymatic activity of acetylcholinesterase was evaluated monitoring the hydrolysis of acetylthiocholine RESULTS: Under the experimental conditions investigated, extracts of two plants, Carum carvi and Olea sylvestris, inhibited amyloid beta fibrillation considerably, eight plant extracts inhibited amyloid beta fibrillation to some extent, 16 plant extracts had no effect on amyloid beta fibrillation and nine extracts accelerated fibrillation of amyloid beta. Furthermore, five plant extracts from Corydalis species inhibited the enzymatic activity of acetylcholinesterase considerably, one plant extract inhibited the enzymatic activity of acetylcholinesterase to some extent and 29 plant extract had no effect on the enzymatic activity of acetylcholinesterase.

CONCLUSIONS

An optimal extract in this study would possess acetylcholinesterase inhibitory activity as well as anti-amyloidogenic activity in order to address multiple facets of Alzheimer's disease, until the molecular origin of the disease is unraveled. Unfortunately no such extract was found.