Alkaloids from the roots of Stichoneuron caudatum and their acetylcholinesterase inhibitory activities

Naturally Occurring Cholinesterase Inhibitors from Plants, Fungi, Algae, and Animals: A Review of the Most Effective Inhibitors Reported in 2012-2022

Since the development of the "cholinergic hypothesis" as an important therapeutic approach in the treatment of Alzheimer's disease (AD), the scientific community has made a remarkable effort to discover new and effective molecules with the ability to inhibit the enzyme acetylcholinesterase (AChE). The natural function of this enzyme is to catalyze the hydrolysis of the neurotransmitter acetylcholine in the brain. Thus, its inhibition increases the levels of this neurochemical and improves the cholinergic functions in patients with AD alleviating the symptoms of this neurological disorder. In recent years, attention has also been focused on the role of another enzyme, butyrylcholinesterase (BChE), mainly in the advanced stages of AD, transforming this enzyme into another target of interest in the search for new anticholinesterase agents. Over the past decades, Nature has proven to be a rich source of bioactive compounds relevant to the discovery of new molecules with potential applications in AD therapy. Bioprospecting of new cholinesterase inhibitors among natural products has led to the discovery of an important number of new AChE and BChE inhibitors that became potential lead compounds for the development of anti-AD drugs. This review summarizes a total of 260 active compounds from 142 studies which correspond to the most relevant (IC50 ≤ 15 μM) research work published during 2012-2022 on plant-derived anticholinesterase compounds, as well as several potent inhibitors obtained from other sources like fungi, algae, and animals.

Chemical profile, anti-hepatoma activity, anti-acetylcholinesterase and antioxidant activity of aerial part of Aconitum carmichaeli Debx

Five extracts of the aerial parts of Aconitum carmichaeli were obtained by different solvent extraction or macroporous adsorption resin purification: ethyl acetate layer extract (EAE), n-butanol layer extract (BuE), water layer extract (WE), extract eluted by 10% ethanol from macroporous resin (10%EE), extract eluted by 80% ethanol from macroporous resin (80%EE). Antioxidant activities of the five extracts were determined by ABTS, DPPH, FRAP assays, anti-AChE activities by modified Ellman's method, in vitro anti-hepatoma activities by CCK-8 assay, and chemical constituents of 80%EE were identified by UPLC-QE-Orbitrap-MS. The results demonstrated that the 80%EE showed the best in vitro anti-hepatoma activity on Huh-7 cell line with an IC50 of 103.91 ± 11.02 μg/mL. 10%EE and 80%EE gave the highest antioxidant activity. Furthermore, current findings demonstrated that the aerial part of Aconitum carmichaeli Debx. has high medicinal value and may be a good natural medicine.

Pd(0)-Catalyzed Asymmetric 7-Endo Hydroacyloxylative Cyclization of 1,6-Enyne Enabled by an Anion Ligand-Directed Strategy

Despite diversity in reaction mechanisms, the palladium-catalyzed cyclization of 1,6-enyne generally proceeds in a 5-exo manner. Herein, we report the development of a Pd(0)-catalyzed hydroacyloxylative cyclization of 1,6-enyne in either 7-endo-trig or 6-exo-trig fashion when paired with an appropriate dihaloacetic acid reactant, such as F₂HCCO₂H and Cl₂HCCO₂H. Using the combination of Pd₂(dba)₃ and a chiral phosphine ligand, the hydroacyloxylative cyclization of 1,6-enyne bearing a 1,1-disubstituted alkene moiety readily gives highly enantiopure seven-membered heterocycles while the reaction of those having a 1,2-disubstituted alkene affords six-membered rings with moderate enantioselectivity. Preliminary experimental studies suggest a reaction mechanism featuring an unusual E-to-Z vinyl-Pd(II) isomerization and alkene trans-oxypalladation, which is proven to be governed by the rationally selected carboxylate.

Origin of High Diastereoselectivity in Reactions of Seven-Membered-Ring Enolates

Unlike many reactions of their six-membered-ring counterparts, the reactions of chiral seven-membered-ring enolates are highly diastereoselective. Diastereoselectivity was observed for a range of substrates, including lactam, lactone, and cyclic ketone derivatives. The stereoselectivity arises from torsional and steric interactions that develop when electrophiles approach the diastereotopic π-faces of the enolates, which are distinguished by subtle differences in the orientation of nearby atoms of the ring.

Potential therapeutic natural products against Alzheimer's disease with Reference of Acetylcholinesterase

Alzheimer's disease (AD), is the most common type of dementia primarily affecting the later years of life. Its prevalence is likely to increase in any aging population and will be a major burden on healthcare system by the mid of the century. Despite scientific and technological breakthroughs in the last 50 years, that have expanded our understanding of the disease on a system, cellular and molecular level, therapies that could stop or slow the progression of the disease are still unavailable. The Food and Drug Administration (FDA), has approved acetylcholinesterase (AChE) inhibitors (donepezil, galantamine, tacrine and rivastigmine) and glutamate receptor antagonist (memantine) for the treatment of AD. In this review we summarize the studies reporting phytocompounds and extracts from medicinal plants that show AChE inhibitory activities and could be of potential benefit in AD. Future research directions are suggested and recommendations made to expand the use of medicinal plants and their formulations to prevent, mitigate and treat AD.

Phytochemical, Synthetic and Biological Studies on Stemona and Stichoneuron Plants and Alkaloids: A Personal Perspective

This report is an overview of our research on phytochemical, synthetic and biological studies of the Stemona and Stichoneuron species of plants.

Exploring sesquiterpene alkaloid-like scaffolds via Beckmann-transannular remodelling of beta-caryophyllene

Cascaded Beckmann-transannular protocol transformed macrocyclic beta-caryophyllene into poly-heterocyclic unnatural skeletal types.

Pd(ii)-catalyzed asymmetric addition of arylboronic acids to cyclic N-sulfonyl ketimine esters and a DFT study of its mechanism

A highly efficient palladium-catalyzed asymmetric arylation of cyclic ketimine esters is developed, which provides the desired product in up to 99% yield with up to 99% ee. The mechanism of enantioselection is studied using DFT calculation.