Inhibitory Mechanism of Baicalein on Acetylcholinesterase: Inhibitory Interaction, Conformational Change, and Computational Simulation

Anti-glycemic mechanism of dihydromyricetin from Ampelopsis grossedentata on α-glucosidase by multispectroscopic investigation and in silico molecular simulation

As a potential anti-glycemic candidate in Ampelopsis grossedentata, the binding behavior of dihydromyricetin (DMY) on α-glucosidase (α-GLA) was investigated by multispectral techniques and in silico molecular docking coupled with molecular dynamic simulation. The results revealed that DMY had potent inhibition on α-GLA with the IC50 of 38 ± 0.025 μM in a mixed competitive mode. It could attenuate the endogenous fluorescence of α-GLA through the static quenching manner. The thermodynamic analysis indicated hydrogen bonding and van der Waals forces were two major driving forces to maintain the stability of the complex, resulting in the decline of α-helix and β-turn and enhancement of β-sheet and random coil correspondingly, evidenced by Fourier transform infrared spectroscopy and circular dichroism approaches. Isothermal titration calorimetry directly measured the dissociation constant Kd for the bound α-GLA-DMY complex was 2.39 ± 0.034 μM with enthalpy change of -33.8 ± 2.85 kJ·mol-1 and entropy change of -24.1 ± 1.76 J·mol-1·K-1. As expected with the microenvironmental changes, the docking conformation followed by dynamic simulation within 200 ns further corroborated the surrounding catalytic sites of α-GLA was non-covalently bound by DMY, in which GLU411, ARG442, ARG315 and PRO312 as hydrogen bond acceptors were double-connected by -OH of DMY at C7 in the A ring and C5' in the B ring, and reinforced by the hydroxyl substitution at C3 due to the hydrogenation on C2C3 bond in C ring. Our findings would boost DMY as a spectacular α-GLA inhibitor for hypoglycemic foods application.

Bioactive flavonoids from Leucosceptrum canum with nematicidal efficacy and mechanistic insights through acetylcholinesterase inhibition and docking study

Leucosceptrum canum, a rare Himalayan plant, shows significant bioactive properties, with its nematicidal potential investigated here for the first time. This study isolated and characterized flavonoids from L. canum, assessing their efficacy against the plant-parasitic nematode Meloidogyne incognita. Bioassay-guided fractionation identified three active flavonoids: Pectolinarigenin, 5,6,7-Trihydroxy-4'-methoxyflavone and Acacetin, structurally elucidated using spectroscopic techniques and literature comparisons. The flavonoids exhibited dose-dependent nematicidal activity, with percent mortalities after 96 h of 100 %, 92 %, and 59 %, respectively. LC₅₀ values of Pectolinarigenin (11.79 μg/mL), 5,6,7-Trihydroxy-4'-methoxyflavone (230.54 μg/mL), and Acacetin (679.67 μg/mL) were recorded, comparable to the standard nematicide Nimitz (LC₅₀: 0.01 μg/mL). These flavonoids also showed strong to moderate acetylcholinesterase (AChE) inhibitory activity, with IC₅₀ values of 17.09, 86.72, and 142.2 μg/mL, respectively, nearing the efficacy of standard, physostigmine (IC₅₀: 19.37 μg/mL), suggesting a neuromuscular mechanism of action. The enzyme kinetics analysis of pectolinarigenin revealed it to be a reversible inhibitor of AChE exhibiting mixed-type inhibition, with inhibition constant of 15.94 μg/mL. Molecular docking revealed strong binding affinities (-7.8 to -7.2 kcal/mol) at the AChE active site, highlighting key hydrogen bonds and hydrophobic interactions. ADMET analysis confirmed favorable pharmacokinetic and safety profiles, underscoring the potential of these flavonoids as eco-friendly nematicidal alternatives. This study establishes L. canum as a valuable source of flavonoids with dual nematicidal and AChE inhibitory properties, supported by integrated in vitro and in silico studies. It underscores the untapped phytochemical wealth of Himalayan flora for sustainable nematode management.

Developing multifaceted drug synergistic therapeutic strategy against neurological disorders

Drug synergism can alter the ultimate biological effects and bioavailability of phytoconstituents. Acetylcholinesterase (AChE) inhibitors as symptomatic drugs are potent therapeutic regimen for neurodegenerative diseases. In this context, this study characterized the synergistic antioxidant, anti-inflammatory and anti-AChE effects of the selected phytochemicals including standard drugs followed by enzyme kinetics, structure-based ligands screening and molecular dynamics simulation study. The synergistic interactions were evaluated through Isoradiation and Synergy finder 3.0 methods. The combinations of Quercetin (QCT), Folic acid (FA), and Swertiamarin (SWT) with specific reference drugs were studied. The combinations of SWT + GA (Gallic acid) and FA + GA at 1:1 (γ:0.10 & 0.08, respectively) showed the significant synergistic antioxidant effect via ABTS assay. Further, in combination, QCT + SWT showed the maximum synergistic effect (γ: 0.02-0.13) in anti-inflammatory assay. Moreover, the combinations QCT, FA, and SWT with reference drug, Donepezil (DP), illustrated potent synergistic activity as anti-AChE in 1:1 proportion (γ: 0.18). The interaction pattern of phytochemicals significantly exhibited synergism (γ < 1) depicting their optimum activity in combinations compared to individual components. Enzyme kinetics evaluation showed the competitive binding of SWT with AChE as of donepezil. All the parameters of ADMET study proposed the QCT and SWT as acceptable oral drug molecules. Computational docking study revealed that QCT and SWT with lowest RMSD (1.096, 2.104) and lowest docking score (-9.831, -7.435 kcal/mol) showed maximum binding efficacy. Furthermore, molecular simulation study depicted the stability of protein-ligand complexes. These findings provide novel insight in the development of dietary treatment based on their synergistic effects for neurological disorders as optimum alternative therapeutic agents.

Targeting Human Papillomavirus 33 E2 DNA Binding Domain With Polyphenols: Unveiling Interactions Through Biophysical and In Silico Methods

The human papillomavirus (HPV) 33 is a high-risk strain that causes lesions with potential cancerous outcomes. Its E2 protein regulates the viral protein transcription and life cycle maintenance. The DNA binding domain (DBD) of the E2 protein plays a crucial role in the viral life cycle. The DBD region of the E2 protein is particularly interesting for targeting and finding potential inhibitors to inhibit its function or dimerization. Given the limited research on HPV 33 and its proteins, the present work delved into the interaction of two natural polyphenolic compounds, resveratrol, and baicalein, with the E2 DBD of HPV 33 using biophysical and in silico studies. Fluorescence studies of the E2 DBD-polyphenol complexes showed fluorescence quenching with a binding constant of the order of 106 M-1. Circular dichroism data reveal conformational changes upon binding with the polyphenols, possibly due to distinct binding sites of the E2 DBD. Differential scanning calorimetry exhibited higher melting temperatures for the two complexes than alone DBD, suggesting the complexes' stability. ITC experiment suggested favorable binding reactions with k d values in the micromolar range. Molecular docking and dynamic simulation studies revealed that the resveratrol binds to the helical region and baicalein near the central dimeric interface of E2 DBD with a good binding affinity, forming a stable protein-ligand complex during the run of 100 ns simulation. Therefore, the current study identifies both polyphenolic compounds as promising candidates for potential antiviral drug development.

Therapeutic considerations of bioactive compounds in Alzheimer's disease and Parkinson's disease: Dissecting the molecular pathways

Leading neurodegenerative diseases Alzheimer's disease (AD) and Parkinson's disease (PD) are characterized by the impairment of memory and motor functions, respectively. Despite several breakthroughs, there exists a lack of disease-modifying treatment strategies for these diseases, as the available drugs provide symptomatic relief and bring along side effects. Bioactive compounds are reported to bear neuroprotective properties with minimal toxicity, however, a detailed elucidation of their modes of neuroprotection is lacking. The review elucidates the neuroprotective mechanism(s) of some of the major phyto-compounds in pre-clinical and clinical studies of AD and PD to understand their potential in combating these diseases. Curcumin, eugenol, resveratrol, baicalein, sesamol and so on have proved efficient in countering the pathological hallmarks of AD and PD. Curcumin, resveratrol, caffeine and so on have reached the clinical phases of these diseases, while aromadendrin, delphinidin, cyanidin and xanthohumol are yet to be extensively explored in pre-clinical phases. The review highlights the need for extensive investigation of these compounds in the clinical stages of these diseases so as to utilize their disease-modifying abilities in the real field of treatment. Moreover, poor pharmacokinetic properties of natural compounds are constraints to their therapeutic yields and this review suggests a plausible contribution of nanotechnology in overcoming these limitations.

Inhibition mechanism of α-glucosidase inhibitors screened from Tartary buckwheat and synergistic effect with acarbose

Tartary buckwheat has been shown to provide a good antihyperglycemic effect. However, it is unclear which active compounds play a key role in attenuating postprandial hyperglycemia. Presently, acetone extract from the hull of Tartary buckwheat had the best effect for α-glucosidase inhibition (IC₅₀ = 0.02 mg/mL). Twelve potential α-glucosidase inhibitors from Tartary buckwheat were screened and identified by the combination of ultrafiltration and high-performance liquid chromatography coupled with mass spectrometry. Myricetin and quercetin exhibited the highest anti-α-glucosidase activity with IC₅₀ values of 0.02 and 0.06 mg/mL, respectively. These inhibitors manifested different types of inhibition manners against α-glucosidase via direct interaction with the amino acid residues. The results of structure-activity relationships indicated that an increase in the number of -OH on the B-ring greatly strengthened α-glucosidase inhibitory activity, but glucoside and rutinoside replacement on the C-ring obviously weakened this influence. Furthermore, a synergistic effect was observed between inhibitors with different inhibition manners.

The Combination of Baicalein and Memantine Reduces Oxidative Stress and Protects against β-amyloid-Induced Alzheimer’s Disease in Rat Model

Alzheimer’s disease (AD) is a neuronal condition causing progressive loss of memory and cognitive dysfunction particularly in elders. An upsurge in the global old age population has led to a proportionate increase in the prevalence of AD. The current treatments for AD are symptomatic and have debilitating side effects. A literature review and current research have directed scientists to explore natural products with better safety and efficacy profiles as new treatment options for AD. Baicalein, belonging to the flavone subclass of flavonoids, has been reported for its anti-oxidant, anti-inflammatory, AChE enzyme inhibitory activity and anti-amyloid protein aggregation activity, which collectively demonstrates its benefits as a neuroprotective agent. Presently, memantine, a NMDAR antagonist, is one of the important drugs used for treatment of Alzheimer’s disease. The current study aims to investigate the effect of baicalein in combination with memantine in β-amyloid-induced AD in albino Wistar rats. Baicalein (10 mg/kg) alone, 5 mg/kg and 10 mg/kg in combination with memantine (20 mg/kg) was administered for 21 days. Treatment with baicalein in combination with memantine showed significant improvement in behavioural studies. The combination treatment decreased oxidative stress, β-amyloid plaque formation and increased the expression of brain-derived neurotrophic factor (BDNF) in the brain. From the results, it can be concluded that treatment with baicalein and memantine could be beneficial for reducing the progression of neurodegeneration in rats. Baicalein has an additive effect in combination with memantine, making it a potential option for the treatment of AD.

Effects of baicalein with memantine on aluminium chloride-induced neurotoxicity in Wistar rats

Alzheimer's disease is a progressive neurodegenerative condition. It is one of the most common 28 forms of dementia accounting for 60-80% of people suffering from dementia. There are very few medications that are approved for the treatment of Alzheimer's disease. Baicalein, belonging to the flavone subclass of flavonoids, has been reported to have a neuroprotective effect by reducing oxidative stress and neuroinflammation, inhibiting the AChE enzyme, and reducing amyloid protein aggregation and toxicity. Memantine is one of the most important drugs used for treating Alzheimer's disease. The purpose of this work was to study the effect of baicalein with memantine on aluminum chloride-induced neurotoxicity in Wistar rats. Aluminum chloride (100 mg/kg p.o.) was administered for 42 days in male Wistar rats to induce neurotoxicity. Baicalein alone (10 mg/kg) and a combination of baicalein (5 mg/kg and 10 mg/kg) with memantine (20 mg/kg) were administered for 42 days. Treatment of baicalein with memantine showed significant improvement in behavioral parameters. The combination reduced oxidative stress and the formation of β-Amyloid plaques and increased brain-derived neurotrophic factor (BDNF) expression. Based on findings, it can be concluded that treatment with baicalein and memantine may slow the progression of neurodegeneration in rats.

Exploring the Inhibition of Quercetin on Acetylcholinesterase by Multispectroscopic and In Silico Approaches and Evaluation of Its Neuroprotective Effects on PC12 Cells

This study investigated the inhibitory mechanism of quercetin in acetylcholinesterase (AChE) and its neuroprotective effects on β-amyloid_25-35-induced oxidative stress injury in PC12 cells. Quercetin inhibited AChE in a reversible mixed manner with an IC₅₀ of 4.59 ± 0.27 µM. The binding constant of quercetin with AChE at 25 °C was (5.52 ± 0.05) × 10⁴ L mol^-1. Hydrogen bonding and van der Waals forces were the main interactions in forming the stable quercetin-AChE complex. Computational docking revealed that quercetin was dominant at the peripheral aromatic site in AChE and induced enzymatic allosterism; meanwhile, it extended deep into the active center of AChE and destabilized the hydrogen bond network, which caused the constriction of the gorge entrance and prevented the substrate from entering the enzyme, thus resulting in the inhibition of AChE. Molecular dynamics (MD) simulation emphasized the stability of the quercetin-AChE complex and corroborated the previous findings. Interestingly, a combination of galantamine hydrobromide and quercetin exhibited the synergistic inhibition effect by binding to different active sites of AChE. In a β-amyloid_25-35-induced oxidative stress injury model in PC12 cells, quercetin exerted neuroprotective effects by increasing the glutathione level and reducing the malondialdehyde content and reactive oxygen species levels. These findings may provide novel insights into the development and application of quercetin in the dietary treatment of Alzheimer's disease.

In silico study of tacrine and acetylcholine binding profile with human acetylcholinesterase: docking and electronic structure

Alzheimer disease (AD) is a neurodegenerative process, one of the most common and incident dementia in the population over 60 years. AD manifests the presence of complex biochemical processes involved in neuronal degeneration, such as the formation of senile plaques containing amyloid-β peptides, the development of intracellular neurofibrillary tangles, and the suppression of the acetylcholine neurotransmitter. In this way, we performed a set of theoretical tests of tacrine ligand and acetylcholine neurotransmitter against the human acetylcholinesterase enzyme. Molecular docking was used to understand the most important interactions of these molecules with the enzyme. Computational chemistry calculation was carried out using MP2, DFT, and semi-empirical methods, starting from molecular docking structures. We have also performed studies regarding the non-covalent interactions, electron localization function, molecular electrostatic potential and explicit water molecule influence. For Trp86 residue, we show two main interactions in accordance to the results of the literature for TcAChE. First, intermolecular interactions of the cation-π and sigma-π type were found. Second, close stacking interactions were stablished between THA+ and Trp86 residue on one side and with Tyr337 residue on the other side.

Structure Identification and Functional Mechanism of Natural Active Components: A Special Issue

The natural active components derived from plants have attracted widespread attention due to their abundant species and source advantages [...]