Interaction between Plectranthus barbatus herbal tea components and acetylcholinesterase: binding and activity studies

Studies on the binding of wedelolactone to human serum albumin with multi-spectroscopic analysis, molecular docking and molecular dynamic simulation

Wedelolactone (WEL) is a small molecule compound isolated from Eclipta prostrate L., which has been reported to possess various biological activities such as anti-hepatotoxicity, anti-hypertension, anti-tumour, anti-phospholipase A2 and detoxification activity against snake venom. In the present study, we investigated the interaction of WEL with human serum albumin (HSA) using simultaneous fluorescence, UV-visible spectroscopy, 3D fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), molecular docking technique and molecular dynamics simulation. We found that the interaction between HSA and WEL can exhibit a static fluorescence burst mechanism, and the binding process is essentially spontaneous, with the main forces manifested as hydrogen bonding, van der Waals force and electrostatic interactions. Competitive binding and molecular docking studies showed that WEL preferentially bound to HSA in substructural region IIA (site I); molecular dynamics simulations showed that HSA interacted with WEL to form a stable complex, which also induced conformational changes in HSA. The study of the interaction between WEL and HSA can provide a reference for a more in-depth study of the pharmacodynamic mechanism of WEL and its further development and utilisation.

Genista tridentata Phytochemical Characterization and Biological Activities: A Systematic Review

Genista tridentata (L.) Willk., known as "prickled broom", is a Leguminosae (Fabaceae) species native to the Iberian Peninsula, Morocco, Algeria, and Tunisia. It is used in folk medicine as an anti-inflammatory, for gastrointestinal and respiratory disorders, rheumatism, and headaches, to lower blood pressure, against hypercholesterolemia and hyperglycemia. This study aimed to systematically review the literature on the bioactivities and phytochemical profile of Genista tridentata to understand its pharmacological potential. For this, four electronic databases (PubMed, GoogleScholar, Repositórios Cientificos de Acesso Aberto de Portugal (RCCAP), and ScienceDirect) were searched from inception up to 31 December 2022. From a total of 264 potentially eligible studies considered for screening, 34 papers were considered eligible for this systematic review. The sampling included 71 extracts, collected mainly in Portugal. Genista tridentata extracts present a high level of flavonoids and phenolic compounds. The flowers and aerial parts of the plant were the most studied, and aqueous extracts were the most used. The results predict a high potential for the application of Genista tridentata as a new source of natural antioxidants and preservatives for the food industry with subsequent health benefits, such as the production of nutraceuticals. Moreover, the results indicate that the plant can be collected at all seasons of the year, which represents a benefit for the industry.

Unveiling interaction mechanisms between myricitrin and human serum albumin: Insights from multi-spectroscopic, molecular docking and molecular dynamic simulation analyses

Myricitrin is a natural polyhydroxy flavonoid and is mainly derived from the bark and leaves of the Chinese Bayberry tree (Myrica rubra). It has different pharmacological activities, including antioxidative, anti-inflammatory, hypoglycemic, antiviral, liver protection and cholagogue properties, and may be added to foods, pharmaceuticals, and cosmetic products for antioxidant purposes. In this study, the interaction mechanism between myricitrin and human serum albumin (HSA) was investigated using spectroscopic methods, molecular docking techniques, and molecular dynamic simulations. We showed that the HSA/myricitrin interaction exhibited a static fluorescence quenching mechanism, and that binding processes were spontaneous in nature, with the main forces exemplified by hydrogen bonding, hydrophobic interactions, and electrostatic interactions. Fluorescence spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, synchronous fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy, micro-Fourier transform infrared spectroscopy (micro-FTIR), and circular dichroism (CD) spectroscopy showed that myricitrin binding altered the HSA conformation to some extent. Competitive binding and molecular docking studies showed that the preferred binding of myricitrin on HSA was in the sub-structural domain IIA (Site I); molecular dynamic simulations revealed that myricitrin interacted with HSA to produce a well stabilized complex, and it also generated a conformational change in HSA. The antioxidant capacity of the HSA-myricitrin complex was reduced when compared with free myricitrin. The identification of HSA-myricitrin binding mechanisms provides valuable insights for the application of myricitrin to the food and pharmaceutical industries.

In vitro inhibition of acetylcholinesterase activity by yellow field pea (Pisum sativum) protein-derived peptides as revealed by kinetics and molecular docking

Compounds with structural similarities to the neurotransmitter (acetylcholine) are mostly used to inhibit the activity of acetylcholinesterase (AChE) in Alzheimer’s disease (AD) therapy. However, the existing drugs only alleviate symptoms of moderate to mild conditions and come with side effects; hence, the search is still on for potent and safer options. In this study, High performance liquid chromatography (HPLC) fractionations of AChE-inhibitory pea protein hydrolysates obtained from alcalase, flavourzyme and pepsin digestions were carried out followed by sequence identification of the most active fractions using mass spectrometry. Subsequently, 20 novel peptide sequences identified from the active fractions were synthesized and five peptides, QSQS, LQHNA, SQSRS, ETRSQ, PQDER (IC₅₀ = 1.53 – 1.61 μg/mL) were selected and analyzed for ability to change AChE protein conformation (fluorescence emission and circular dichroism), kinetics of enzyme inhibition, and enzyme-ligand binding configurations using molecular docking. The kinetics studies revealed different inhibition modes by the peptides with relatively low (<0.02 mM and <0.1 mM) inhibition constant and Michaelis constant, respectively, while maximum velocity was reduced. Conformational changes were confirmed by losses in fluorescence intensity and reduced α-helix content of AChE after interactions with different peptides. Molecular docking revealed binding of the peptides to both the catalytic anionic site and the peripheral anionic site. The five analyzed peptides all contained glutamine (Q) but sequences with Q in the penultimate N-terminal position (LQHNA, SQSRS, and PQDER) had stronger binding affinity. Results from the different analysis in this study confirm that the peptides obtained from enzymatic digestion of pea protein possess the potential to be used as novel AChE-inhibitory agents in AD management.

An ethnopharmacological review on the therapeutical properties of flavonoids and their mechanisms of actions: A comprehensive review based on up to date knowledge

Flavonoids -a class of low molecular weight secondary metabolites- are ubiquitous and cornucopia throughout the plant kingdom. Structurally, the main structure consists of C6-C3-C6 rings with different substitution patterns so that many sub-classes are obtained, for example: flavonols, flavonolignans, flavonoid glycosides, flavans, anthocyanidins, aurones, anthocyanidins, flavones, neoflavonoids, chalcones, isoflavones, flavones and flavanones. Flavonoids are evaluated to have drug like nature since they possess different therapeutic activities, and can act as cardioprotective, antiviral, antidiabetic, anti-inflammatory, antibacterial, anticancer, and also work against Alzheimer's disease and others. However, information on the relationship between their structure and biological activity is scarce. Therefore, the present review tries to summarize all the therapeutic activities of flavonoids, their mechanisms of action and the structure activity relationship.

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Latest updated ethnopharmacological review of the therapeutic effects of flavonoids.

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Flavonoids are attracting attention because of their therapeutic properties.

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Flavonoids are valuable candidates for drug development against many dangerous diseases.

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This overview summarizes the most important therapeutic effect and mechanism of action of flavonoids.

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General knowledge about the structure activity relationship of flavonoids is summarized.

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Substitution of chemical groups in the structure of flavonoids can significantly change their biological and chemical properties.

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The chemical properties of the basic flavonoid structure should be considered in a drug-based structural program.

Role of Phenolic Compounds in Human Disease: Current Knowledge and Future Prospects

Inflammation is a natural protective mechanism that occurs when the body's tissue homeostatic mechanisms are disrupted by biotic, physical, or chemical agents. The immune response generates pro-inflammatory mediators, but excessive output, such as chronic inflammation, contributes to many persistent diseases. Some phenolic compounds work in tandem with nonsteroidal anti-inflammatory drugs (NSAIDs) to inhibit pro-inflammatory mediators' activity or gene expression, including cyclooxygenase (COX). Various phenolic compounds can also act on transcription factors, such as nuclear factor-κB (NF-κB) or nuclear factor-erythroid factor 2-related factor 2 (Nrf-2), to up-or downregulate elements within the antioxidant response pathways. Phenolic compounds can inhibit enzymes associated with the development of human diseases and have been used to treat various common human ailments, including hypertension, metabolic problems, incendiary infections, and neurodegenerative diseases. The inhibition of the angiotensin-converting enzyme (ACE) by phenolic compounds has been used to treat hypertension. The inhibition of carbohydrate hydrolyzing enzyme represents a type 2 diabetes mellitus therapy, and cholinesterase inhibition has been applied to treat Alzheimer's disease (AD). Phenolic compounds have also demonstrated anti-inflammatory properties to treat skin diseases, rheumatoid arthritis, and inflammatory bowel disease. Plant extracts and phenolic compounds exert protective effects against oxidative stress and inflammation caused by airborne particulate matter, in addition to a range of anti-inflammatory, anticancer, anti-aging, antibacterial, and antiviral activities. Dietary polyphenols have been used to prevent and treat allergy-related diseases. The chemical and biological contributions of phenolic compounds to cardiovascular disease have also been described. This review summarizes the recent progress delineating the multifunctional roles of phenolic compounds, including their anti-inflammatory properties and the molecular pathways through which they exert anti-inflammatory effects on metabolic disorders. This study also discusses current issues and potential prospects for the therapeutic application of phenolic compounds to various human diseases.

Serum Albumin Modulates the Bioactivity of Rosmarinic Acid

Rosmarinic acid (RA) is a phenolic compound with biological activity. The objective of the present study was to investigate whether this compound kept its biological activity in the presence of proteins. For this purpose, bovine serum albumin (BSA) was used as a model protein, and the capacity of the RA to inhibit acetylcholinesterase (AChE) and affect antioxidant activity was evaluated in the absence and presence of BSA. A mixture of phenolic compounds containing RA, obtained from a medicinal plant was added to this study. The AChE inhibitory activity of RA was reduced by ∼57% in the presence of BSA, while the antioxidant activity increased. These results lead to the investigation of the effect of RA on the BSA structure using Fourier transform infrared spectroscopy (FTIR). At 37°C and higher temperatures, RA caused a decrease in the temperature modifications on the protein structure. Furthermore, FTIR and native-gel analysis revealed that protein aggregation/precipitation, induced by temperature, was reduced in the presence of RA. The novelty of the present work resides in the study of the enzyme inhibitory activity and antioxidant capacity of polyphenols, such as RA, in the presence of a protein. The findings highlight the need to consider the presence of proteins when assessing biological activities of polyphenols in vitro and that enzyme inhibitory activity may be decreased, while the antioxidant capacity remains or even increases.

Cholinesterase targeting by polyphenols: A therapeutic approach for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive irreversible neurodegenerative disorder characterized by excessive deposition of β-amyloid (Aβ) oligomers, and neurofibrillary tangles (NFTs), comprising of hyperphosphorylated tau proteins. The cholinergic system has been suggested as the earliest and most affected molecular mechanism that describes AD pathophysiology. Moreover, cholinesterase inhibitors (ChEIs) are the potential class of drugs that can amplify cholinergic activity to improve cognition and global performance and reduce psychiatric and behavioral disturbances. Approximately, 60%-80% of all cases of dementia in the world are patients with AD. In view of the continuous rise of this disease especially in the aged population, there is a dire need to come up with a novel compound and/or mixture that could work against this devastating disease. In this regard, the best is to rely on natural compounds rather than synthetic ones, because natural compounds are easily available, cost-effective, and comparatively less toxic. To serve this purpose, lately, scientific community has started exploring the possibility of using different polyphenols either solitary or in combination that can serve as therapeutics against AD. In the current article, we have summarized the role of various polyphenols, namely quercetin, resveratrol, curcumin, gallocatechins, cinnamic acid, caffeine, and caffeic acid as an inhibitor of cholinesterase for the treatment of AD. We have also tried to uncover the mechanistic insight on the action of these polyphenols against AD pathogenicity.

Phytochemical profiling and in vitro screening for anticholinesterase, antioxidant, antiglucosidase and neuroprotective effect of three traditional medicinal plants for Alzheimer's Disease and Diabetes Mellitus dual therapy

Background

Extensive epidemiological and clinical studies revealed that Alzheimer’s Disease (AD) and Type 2 Diabetes Mellitus (T2D) are most likely to appear simultaneously in aged people as T2D is a major risk factor for AD. Therefore, development of potential multifunctional agents for dual therapy of AD and T2D has received much attention. Buchanania axillaris, Hemidesmus indicus and Rhus mysorensis have been used extensively in popular medicine. The present study was aimed at phytochemical profiling and evaluating multifunctional ability of titled plants in the AD and T2D dual therapy.

Methods

Methanolic extracts and their derived fractions were evaluated for their inhibitory capacities against acetylcholinesterase (AChE) & butyrylcholinesterase (BuChE), and α– & β–glucosidase besides kinetic analysis of inhibition using methods of Elmann and Shibano, respectively. Antioxidant potency of active fractions was assessed by their DPPH and ABTS radical scavenging activities. Active fractions were tested by the MTT assay to verify cytotoxicity and neuroprotective ability in human nueroblastoma cell lines. Phytochemical screening was done with the aid of spectrophotometric methods.

Results

All the methanolic extracts of test plants (BAM, HIM, RMM) showed concentration dependent inhibitory activities against AChE, BuChE, α– and β–glucosidase enzymes. Subsequent fractionation and evaluation revealed that chloroform fractions BAC, HIC and RMC with IC₅₀ values of 12.29±2.14, 9.94±2.14, 16.65±1.99 and 27.38±1.24; 28.14±0.9, 5.16±0.22, 11.03±0.5 and 87.64±15.41; 41.35±1.6, 15.86±7.3, 26.04±0.37 and 25.33±0.3 were most prominent with regard to inhibition potential against AChE, BuChE, α– and β–glucosidase, respectively. Kinetic analysis of these active fractions proved that they disclosed mixed-type inhibition against AChE, BuChE, α– and β–glucosidase enzymes. In the MTT assay, active fractions BAC, HIC, RMC showed significant cell viability at high concentrations (400 μg). Moreover, in MTT assay, the active fractions displayed excellent neuroprotective effects against oxidative stress induced cell death and significant cell viability in SK N SH cells at all concentrations.

Conclusion

The strong anticholinesterase, antiglucosidase, antioxidant and neuroprotective activities of methanolic extracts and their derived chloroform fractions indicate the potential of Buchanania axillaris, Hemidesmus indicus and Rhus mysorensis as multifunctional therapeutic remedies for the dual therapy of T2D and AD.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2140-x) contains supplementary material, which is available to authorized users.

Phytochemical Characterization and Biological Evaluation of the Aqueous and Supercritical Fluid Extracts from Salvia sclareoides Brot

Plants belonging to the genus Salvia (Lamiaceae) are known to have a wide range of biological properties. In this work, extracts obtained from the aerial parts of Salvia sclareoides Brot. were evaluated to investigate their chemical composition, toxicity, bioactivity, and stability under in vitro gastrointestinal conditions. The composition of the supercritical fluid extract was determined by GC and GC-MS, while the identification of the infusion constituents was performed by HPLC-DAD and LC-MS. The in vitro cytotoxicity of both extracts (0-2 mg/mL) was evaluated in Caco-2 cell lines by the MTT assay. The anti-inflammatory and anticholinesterase activities were determined through the inhibition of cyclooxygenase-1 and acetylcholinesterase enzymes, while β-carotene/linoleic acid bleaching test and the DPPH assays were used to evaluate the antioxidant activity. The infusion inhibited cyclooxygenase-1 (IC50 = 271.0 μg/mL), and acetylcholinesterase (IC50 = 487.7 μg/ mL) enzymes, also demonstrated significant antioxidant properties, as evaluated by the DPPH (IC50 = 10.4 μg/mL) and β-carotene/linoleic acid (IC50 = 30.0 μg/mL) assays. No remarkable alterations in the composition or in the bioactivities of the infusion were observed after in vitro digestion, which supports the potential of S. sclareoides as a source of bioactive ingredients with neuroprotective, anti-inflammatory and antioxidant properties.

Quercus ilex L.: How season, Plant Organ and Extraction Procedure Can Influence Chemistry and Bioactivities

Quercus species have a plethora of applications, either in wine and wood industries, in human and animal nutrition or in human health. In order to improve the knowledge on this genus, the aim of the present study was to correlate, for the first time, the phenolic composition of different Quercus ilex L. plant tissues (leaves in two maturation stages, acorns, teguments and cotyledons) and different extraction procedures with scavenging and anticholinesterase activities. The hydromethanolic and aqueous extracts obtained showed strong radical scavenging activity against DPPH, superoxide anion radical and nitric oxide radical, leaves exhibiting higher total phenolic content and revealing the best antioxidant properties, followed by tegument and acorns. Concerning the phenolic profile, fifteen compounds were identified and quantified by HPLC-DAD, ranging from 1568.43 to 45,803.16 mg/kg dried extract. The results indicate that Q. ilex can be a source of strong antioxidant phenolic compounds with possible interest for food and pharmaceutical industries.

Inhibition of flavonoids on acetylcholine esterase: binding and structure–activity relationship

Hydroxyl groups on the aromatic rings of flavonoids are favorable for inhibiting AChE, and the hydroxylation increases the affinities for AChE. However, methoxylation may decrease or increase the activities depending on the class of flavonoids.