Novel insights on acetylcholinesterase inhibition by Convolvulus pluricaulis, scopolamine and their combination in zebrafish

Acute exposure to environmentally relevant concentrations of pharmaceutical pollutants induces neurobehavioral toxicity in zebrafish (Danio rerio)

Pharmaceutical waste from point and non-point sources enters, persists, or disseminates in the environment and is known as environmentally persistent pharmaceutical pollutants. Understanding the impacts of pharmaceutical pollutants on the environment and health is essential. This study investigates the behavioral impacts of pharmaceutical pollutants on aquatic organisms and delineates the possible nexus of oxidative stress. The male zebrafish were exposed to four major representative pharmaceutical pollutants, viz., acetaminophen, carbamazepine, metformin, and trimethoprim at environmentally relevant concentrations individually as well as in a mixture for seven days. Substantial alterations in social interaction, aggressive nature, novel tank exploration, and light and dark zone preferences were recorded and the degree varied to different pharmaceutical pollutants. The activity of oxidative stress markers, superoxide dismutase, glutathione-S-transferase, and catalase, was found to be suppressed to 66-20%, 42-25%, and 59-20% respectively with the elevated malondialdehyde generation (180-260%) compared to control. The activity level of acetylcholine esterase was found to be increased to 200-500% across all treatment groups. Despite the synergistic impacts of pharmaceutical pollutants on the whole system that could not be ascertained, this comprehensive study highlights their toxicity nature to induce neurobehavioral toxicity in zebrafish through oxidative stress mechanisms and altered cholinergic systems.

Chemically engineered essential oils prepared through thiocyanation under solvent-free conditions: chemical and bioactivity alteration

The generation of chemically engineered essential oils (CEEOs) prepared from bi-heteroatomic reactions using ammonium thiocyanate as a source of bioactive compounds is described. The impact of the reaction on the chemical composition of the mixtures was qualitatively demonstrated through GC-MS, utilizing univariate and multivariate analysis. The reaction transformed most of the components in the natural mixtures, thereby expanding the chemical diversity of the mixtures. Changes in inhibition properties between natural and CEEOs were demonstrated through acetylcholinesterase TLC autography, resulting in a threefold increase in the number of positive events due to the modification process. The chemically engineered Origanum vulgare L. essential oil was subjected to bioguided fractionation, leading to the discovery of four new active compounds with similar or higher potency than eserine against the enzyme. The results suggest that the directed chemical transformation of essential oils can be a valuable strategy for discovering new acetylcholinesterase (AChE) inhibitors.

Polyherbal and Multimodal Treatments: Kaempferol- and Quercetin-Rich Herbs Alleviate Symptoms of Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder impairing cognition and memory in the elderly. This disorder has a complex etiology, including senile plaque and neurofibrillary tangle formation, neuroinflammation, oxidative stress, and damaged neuroplasticity. Current treatment options are limited, so alternative treatments such as herbal medicine could suppress symptoms while slowing cognitive decline. We followed PRISMA guidelines to identify potential herbal treatments, their associated medicinal phytochemicals, and the potential mechanisms of these treatments. Common herbs, including Ginkgo biloba, Camellia sinensis, Glycyrrhiza uralensis, Cyperus rotundus, and Buplerum falcatum, produced promising pre-clinical results. These herbs are rich in kaempferol and quercetin, flavonoids with a polyphenolic structure that facilitate multiple mechanisms of action. These mechanisms include the inhibition of Aβ plaque formation, a reduction in tau hyperphosphorylation, the suppression of oxidative stress, and the modulation of BDNF and PI3K/AKT pathways. Using pre-clinical findings from quercetin research and the comparatively limited data on kaempferol, we proposed that kaempferol ameliorates the neuroinflammatory state, maintains proper cellular function, and restores pro-neuroplastic signaling. In this review, we discuss the anti-AD mechanisms of quercetin and kaempferol and their limitations, and we suggest a potential alternative treatment for AD. Our findings lead us to conclude that a polyherbal kaempferol- and quercetin-rich cocktail could treat AD-related brain damage.

Inhibition of Human Cholinesterases and in vitro β-Amyloid Aggregation by Rationally Designed Peptides

The multifactorial nature of Alzheimer's disease (AD) is now widely recognized, which has increased the interest in compounds that can address more than one AD-associated targets. Herein, we report the inhibitory activity on the human cholinesterases (acetylcholinesterase, hAChE and butyrylcholinesterase, hBChE) and on the AChE-induced β-amyloid peptide (Aβ) aggregation by a series of peptide derivatives designed by mutating aliphatic residues for aromatic ones. We identified peptide W3 (LGWVSKGKLL-NH2 ) as an interesting scaffold for the development of new anti-AD multitarget-directed drugs. It showed the lowest IC50 value against hAChE reported for a peptide (0.99±0.02 μM) and inhibited 94.2 %±1.2 of AChE-induced Aβ aggregation at 10 μM. Furthermore, it inhibited hBChE (IC50 , 15.44±0.91 μM), showed no in vivo toxicity in brine shrimp and had shown moderated radical scavenging and Fe2+ chelating capabilities in previous studies. The results are in line with multiple reports showing the utility of the indole moiety for the development of cholinesterase inhibitors.

Novel Chromone-Containing Allylmorpholines Induce Anxiolytic-like and Sedative Effects in Adult Zebrafish

Chromone-containing allylmorpholines (CCAMs) are a novel class of compounds that have demonstrated acetyl- and butyryl-cholinesterase-inhibiting and N-methyl-D-aspartate (NMDA) receptor-blocking properties in vitro, but their in vivo pharmacological activity remains underexplored. In this work, we evaluated the psychotropic activity of five different CCAMs (1 (9a), 2 (9j), 3 (9l), 4 (33a), and 5 (33b)) using the novel tank test (NTT) and light/dark box (LDB) test in adult zebrafish. The CCAMs were screened in the NTT at a range of concentrations, and they were found to induce a dose-dependent sedative effect. Compound 4 (33a) was also evaluated using the LDB test, and it was found to have anxiolytic-like properties at low concentrations. To assess the potential contribution of the glutamate and cholinergic mechanisms in the effects of the CCAMs, we conducted experiments with pre-exposure to putative antagonists, NMDA and biperiden. Neither biperiden nor NMDA were able to diminish or cancel the effects of the CCAMs, countering the in vitro data obtained in previous studies. The apparent discrepancy could be related to the specifics of CCAM metabolism or to the interspecies differences between the putative target proteins, possibly due to the relatively low identity percentage of their sequences. Although further research in mammals is required in order to establish their pharmacological properties, novel CCAMs may represent an appealing group of psychoactive drug candidates.

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.

Role of Shankhpushpi (Convolvulus pluricaulis) in Neurological Disorders: An Umbrella Review Covering Evidence from Ethnopharmacology to Clinical Studies

C. pluricaulis Choisy (C. pluricaulis), a perennial herb aka C. microphyllus Sieb. and C. Prostratus Forsk. is being used as a traditional folk medicine for a variety of ailments. In this article, we collected information about C. pluricaulis through electronic search using PubMed, SciFinder, Google Scholar, and Web of Science as well as network pharmacology is done. This comprehensive review sheds light on the plant profile, phytochemistry, neuropharmacological, and toxicological data of C. pluricaulis. The crude herb and its metabolites have exhibited a wide range of in vitro and in vivo neuropharmacological effects, including memory enhancement, anxiolytic, tranquilizing, anti-depressant, anti-stress, neurodegenerative, anti-inflammatory, anti-oxidant, analgesic, sedative, anti-convulsant, and Alzheimer's disease-reversing effects. Network pharmacology results indicate that compounds from C. pluricaulis interact with various proteins, neuro synapses, signaling pathways, and serotonergic synapse which plays a crucial role in neurotransmission, Alzheimer's disease, long-term depression, addictions to alcohol, cognitive disorders, psychological conditions, and increasing serotonin concentration in synapses.

The Brilliance of the Zebrafish Model: Perception on Behavior and Alzheimer's Disease

Alzheimer's disease (AD) has become increasingly prevalent in the elderly population across the world. It's pathophysiological markers such as overproduction along with the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFT) are posing a serious challenge to novel drug development processes. A model which simulates the human neurodegenerative mechanism will be beneficial for rapid screening of potential drug candidates. Due to the comparable neurological network with humans, zebrafish has emerged as a promising AD model. This model has been thoroughly validated through research in aspects of neuronal pathways analogous to the human brain. The cholinergic, glutamatergic, and GABAergic pathways, which play a role in the manifested behavior of the zebrafish, are well defined. There are several behavioral models in both adult zebrafish and larvae to establish various aspects of cognitive impairment including spatial memory, associative memory, anxiety, and other such features that are manifested in AD. The zebrafish model eliminates the shortcomings of previously recognized mammalian models, in terms of expense, extensive assessment durations, and the complexity of imaging the brain to test the efficacy of therapeutic interventions. This review highlights the various models that analyze the changes in the normal behavioral patterns of the zebrafish when exposed to AD inducing agents. The mechanistic pathway adopted by drugs and novel therapeutic strategies can be explored via these behavioral models and their efficacy to slow the progression of AD can be evaluated.