Cholinesterase-inhibitory diterpenoids and chemical constituents from aerial parts of Caryopteris mongolica

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.

Abietane diterpenoids and iridoids from Caryopteris mongolica

Six new abietane diterpenoids (1-6) and five undescribed iridoids (7-11) have been isolated from the aerial parts of Caryopteris mongolica. The intricate structural characterization of these compounds was meticulously undertaken using an array of advanced spectroscopic techniques. This process was further enhanced by the application of DP4+ probability analyses and electronic circular dichroism (ECD) calculations. Following isolation and structural elucidation, the cytotoxicity of these compounds was evaluated. Among them, compound 3 stood out, displaying significant cytotoxic activity against HeLa cells with an IC50 value of 7.83 ± 1.28 μmol·L-1. Additionally, compounds 1, 2, 4, 9, and 10 manifested moderate cytotoxic effects on specific cell lines, with IC50 values ranging from 11.7 to 20.9 μmol·L-1.

Inhibitory properties of quinopimaric acid derivatives towards cholinesterases

A series of new diterpene quinopimaric acid derivatives modified at the hydroxyl group with different pharmacophore fragments has been synthesised and their (along with previously obtained compounds) inhibitory properties towards cholinesterases were studied. Thereby an indole-3-acetyl derivative 7 and a propargyl substituted compound 28 were shown to be excellent and acetylcholinesterase-selective inhibitors. Both compounds inhibited the enzyme as a mixed type inhibitor, and Ki values of 0.41 and 0.44 µM and Ki' values of 0.98 and 2.26 µM were determined. The binding interactions between all active compounds and ligands protein were confirmed through molecular docking study.

A new abietane diterpene tuurgan a from caryopteris mongholica

Five abietane diterpenes compounds were separated from petroleum ether extraction sites of ethanol extract of Caryopteris Mongholica, and Compound 1 was identified as a new abietane diterpenes compound by NMR and mass spectrometry, named as Tuurgan A of Caryopteris Mongholica; and Compounds 2-5 separated from Caryopteris Mongholica for the first time were identified as Ferruginol (2), Taxodione (3), Caryopterisoid Q (4), and Huperphlegmarin B (5). The anti-lung cancer activity of the Compounds 1-5 were determined, which results showed that they all had high A549 cytotoxicity.

Two New Abietane Diterpenes From the Stems of Clerodendrum trichotomum Thunb

Two new abietane diterpenoids (4 S, 5 S, 10 S)-12-( β-D-glucopyranosyl)oxy-11-hydroxyabieta-8,11,13-triene-19-oic acid β-D-glucopyranosyl-(1→6)- β-D-glucopyranosyl ester (1) and (3 S, 5 S, 10 S, 15 S)-3 β-[ β-D-glucopyranosyl-(1→6)- β-D-glucopyranosyl]oxy-12-( β-D-glucopyranosyl)oxyabieta-8,11,13-triene-11,16-diol (2), along with 5 known terpene glycosides (3–7) were isolated from the n-butanol extract of the stems of Clerodendrum trichotomum Thunb. The structures of the new compounds were determined by analysis of spectroscopic data, chemical correlations, and electronic circular dichroism calculations. Besides, all compounds were evaluated for cytotoxic activities against cultured K562, MCF-7, A549, and HepG2 cell lines. None of them showed good antitumor activities.

Plant Terpenoids as the Promising Source of Cholinesterase Inhibitors for Anti-AD Therapy

Simple Summary

Plant-derived terpenes have been a research interest in the recent years, as they are believed to possess the ability to function as a cholinesterase inhibitor. As the deficit of cholinergic activity is one of the factors that causes cognitive impairment in Alzheimer’s disease patients, it serves as a great therapeutic target. It has been found that various terpenoids, such as diterpenoids, triterpenoids and sesquiterpenoids, do have the ability to inhibit cholinesterase activity, and their chemical structures do play a role in this. As terpenoids possess anti-cholinesterase properties, it is encouraged to have future research on drug discovery and development in treating Alzheimer’s disease.

Abstract

Plant-derived terpenes are the prolific source of modern drugs such as taxol, chloroquine and artemisinin, which are widely used to treat cancer and malaria infections. There are research interests in recent years on terpene-derived metabolites (diterpenes, triterpenes and sesquiterpenes), which are believed to serve as excellent cholinesterase inhibitors. As cholinesterase inhibitors are the current treatment for Alzheimer’s disease, terpene-derived metabolites will have the potential to be involved in the future drug development for Alzheimer’s disease. Hence, a bibliographic search was conducted by using the keywords “terpene”, “cholinesterase” and “Alzheimer’s disease”, along with cross-referencing from 2011 to 2020, to provide an overview of natural terpenes with potential anticholinesterase properties. This review focuses on the extraction, chemical structures and anti-cholinesterase mechanisms of terpenes, which support and encourage future research on drug discovery and development in treating Alzheimer’s disease.

Evaluation of Mongolian compound library for potential antimalarial and anti-Toxoplasma agents

179 compounds in a Mongolian compound library were investigated for their inhibitory effect on the in vitro growth of Plasmodium falciparum and Toxoplasma gondii. Among these compounds, brachangobinan A at a half-maximal inhibition concentration (IC₅₀) of 2.62 μM and a selectivity index (SI) of 27.91; 2-(2'-hydroxy-5'-O-methylphenyl)-5-(2″,5″-dihydroxyphenyl)oxazole (IC₅₀ 3.58 μM and SI 24.66); chrysosplenetin (IC₅₀ 3.78 μM and SI 15.26); 4,11-di-O-galloylbergenin (IC₅₀ 3.87 μM and SI 13.38); and 2-(2',5'-dihydroxyphenyl)-5-(2″-hydroxyphenyl)oxazole (IC₅₀ 6.94 μM and SI 11.48) were identified as potential inhibitors of P. falciparum multiplication. Additionally, tricin (IC₅₀ 12.94 μM and SI > 23.40) was identified as a potential inhibitor of T. gondii multiplication. Our findings represent a good starting point for developing novel antimalarial and anti-Toxoplasma therapeutics from Mongolian compounds.

Biological activity evaluations of chemical constituents derived from Mongolian medicinal forage plants and their applications in combating infectious diseases and addressing health problems in humans and livestock

Mongolian nomadic people possess traditional knowledge of wild plants that grow in their areas of habitation. Many of these are forage plants in nature and are consumed by livestock. However, these plants are known to have medicinal and/or toxic properties. To establish a scientific understanding of the plants, and in turn, offer sound knowledge on their applications and effective use, it is essential to collect data pertaining to the chemical constituents of each plant. Therefore, the first objective of this study was to identify and determine the structural constituents of the forage plants that were available to our research group. Furthermore, in an attempt to demonstrate the biological activities of the isolated chemical compounds, we focused on solving some of the social issues affecting Mongolian communities, including protozoan diseases affecting livestock, vectors of infectious diseases, and the general health of humans and their livestock. The results of the chemical constituents derived from Mongolian medicinal plants and their biological activities that were studied in the recent decade are also described herein.

Biological Activities of Extracts from Different Parts of two Cultivars of Prunus persica ‘Akatsuki’ and ‘Fastigiata’

We investigated the antioxidant, anti-lipase and anti-dementia activities of peach ( Prunus persica (L.) Batsch) fruit and its by-products. The ethanol extracts of branch showed relatively high activity in all biological activities. Then, the extract was fractionated, and eight compounds were isolated from the ethyl acetate fraction. Results showed 4,2’,4'-trihydroxy-6'-methoxychalcone 4'- O-β-D-glucopyranoside (5) and quercetin 3- O-β-D-glucopyranoside (7) as newly identified compounds in P. persica. From the biological investigation, it was considered that quercetin 3- O-β-D-glucopyranoside (7) was the main active compound of antioxidant activity. The main active compound of anti-lipase activity in these was oleanolic acid (1). In addition, (+)-4'- O-methylcatechin (4), 4,2’,4'-trihydroxy-6'-methoxychalcone 4'- O-β-D-glucopyranoside (5) and ferulic acid (6) were the main active compounds of anti-dementia activity with acetylcholinesterase inhibitory assay. The results obtained suggested that these active compounds from peach branches of P. persica could be exploited as natural antioxidants, anti-lipase and anti-dementia materials in the future.

Nepetaefolins A-J, Cytotoxic Chinane and Abietane Diterpenoids from Caryopteris nepetaefolia

Nepetaefolins A-J (1-10) and seven known compounds were isolated from the whole plant of Caryopteris nepetaefolia. The absolute configurations of 1-3 were determined from single-crystal X-ray diffraction and spectroscopic data. Compounds 6 and 7, with IC₅₀ values of 6.3-9.0 μM, showed higher cytotoxicity than paclitaxel in one non-small-cell lung cancer, patient-derived xenograft (PDX) model when tested using PDX models and the adenosine triphosphate-tumor chemosensitivity assay (ATP-TCA).

Ferulic Acid and Naturally Occurring Compounds Bearing a Feruloyl Moiety: A Review on Their Structures, Occurrence, and Potential Health Benefits

The ubiquitous compound 4-hydroxy-3-methoxycinnamic acid, also known as ferulic acid (FA), constitutes a bioactive ingredient of many foods that may offer beneficial effects against disorders related to oxidative stress, including cancer, diabetes, and neurodegenerative diseases. This review discusses the antioxidant properties of FA, establishing relationships to several biological activities already described for this natural product. Next, 387 naturally occurring compounds, all isolated from plants and published between 1990 and 2015, the structures of which bear 1 or more feruloyl moieties, are covered in this review along with their structural formulas, botanical sources, and bioactivities. The compounds' distribution, structural patterns, bioactivities, and perspectives on food research are also succinctly discussed.

Phenolic composition, enzyme inhibitory, and antioxidant activity of Bituminaria bituminosa

This study aimed to evaluate the in vitro antioxidant and enzyme inhibitory activities of ethyl acetate, methanol, and water extracts of Bituminaria bituminosa. In phosphomolybdenum assay, the methanol extract showed the highest activity (166.78 μmol TEs/g dry plant). The water extract exhibited the highest scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH^∙) and 2,2-azino-bis (3-ethylbenzothiazloine-6-sulphonic acid) (ABTS^∙+). In addition, it exhibited the highest activity in cupric ion reducing (CUPRAC) and ferric reducing antioxidant power (FRAP) assays (41.26 and 46.82 μmol TEs/g dry plant). The extracts did not show cholinesterase and tyrosinase inhibitory activity. However, α-glucosidase inhibition assay resulted in the superiority of water extract (1233.86 μmol ACEs/g dry plant). In the case of α-amylase inhibitory assay, the ethyl acetate extract showed the highest activity (53.65 μmol ACEs/g dry plant). The water extract exhibited the highest phenolic content (31.70 μmol GAEs/g dry plant). In contrast, the methanol extract was found rich in flavonoid compounds (5.29 μmol REs/g dry plant). The water extract contained considerable amounts of rosmarinic acid, luteolin, quercetin, and rutin. Therefore, it can be used as a source of new and alternative antioxidant and enzyme inhibitory agents.

Abietane diterpenoids from Caryopteris incana (Thunb.) Miq

Twelve new diterpenes, caryopincaolide A-L (1-4, 11-12, 16-19, 27-28), together with twenty-eight known diterpenes, have been isolated from the whole plant of Caryopteris incana (Thunb.) Miq. Their structures were elucidated on the basis of 1D and 2D NMR, IR, X-ray crystal diffraction and mass spectroscopic data, as well as ECD calculations. All compounds were tested for in vitro dipeptidyl peptidase IV (DPP-IV) inhibitory activity, with compounds 3, 4, 28, 29, and 40 exhibiting DPP-IV inhibitory effects with IC50 values ranging from 54.2 to 228.9 μM. Compounds 1, 3 and 4 also showed potent activity toward the inhibition of the growth of human cancer cells and 1 can induce apoptosis in Hey and A-549 cells.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, pimaranes, abietanes, kauranes, cembranes and their cyclization products. The literature from January to December, 2015 is reviewed.

An antibacterial ortho-quinone diterpenoid and its derivatives from Caryopteris mongolica

To identify antibacterial components in traditional Mongolian medicinal plant Caryopteris mongolica, an ortho-quinone abietane caryopteron A (1) and three its derivatives caryopteron B-D (2-4) were isolated from the roots of the plant together with three known abietanes demethylcryptojaponol (5), 6α-hydroxydemethyl cryptojaponol (6), and 14-deoxycoleon U (7). The chemical structures of these abietane derivatives were elucidated on the basis of spectroscopic data. Compounds 1-4 had C-13 methylcyclopropane substructures, and 2-4 had a hexanedioic anhydride ring C instead of ortho-quinone in 1. The stereochemistry of these compound was assumed from NOE spectra and ECD Cotton effects. Compounds 1 and 5-7 showed antibacterial activities against the Gram-positive bacteria Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and Micrococcus luteus, being 1 the more potent.