Furofuranone Lignans from Leucophyllum ambiguum

Chemical Composition of Volatile and Extractive Components of Canary (Tenerife) Propolis

The vegetation of the Canary Islands is characterized by a large number of endemic species confined to different altitudinal levels. It can be assumed that these circumstances determine the characteristic features of the chemical composition of local beekeeping products, including propolis. We report, for the first time, the chemical composition of propolis from Tenerife (Canary Islands). The volatile emissions of three propolis samples collected from different apiaries are represented by 162 C1-C20 compounds, of which 144 were identified using the HS-SPME/GC-MS technique. The main group of volatiles, consisting of 72 compounds, is formed by terpenoids, which account for 42-68% of the total ion current (TIC) of the chromatograms. The next most numerous groups are formed by C6-C17 alkanes and alkenes (6-32% TIC) and aliphatic C3-C11 carbonyl compounds (7-20% TIC). The volatile emissions also contain C1-C6 aliphatic acids and C2-C8 alcohols, as well as their esters. Peaks of 138 organic C3-C34 compounds were recorded in the chromatograms of the ether extracts of the studied propolis. Terpene compounds form the most numerous group, but their number and content in different samples is within very wide limits (9-63% TIC), which is probably due to the origin of the samples from apiaries located at different altitudes. A peculiarity of the chemical composition of the extractive substances is the almost complete absence of phenylcarboxylic acids and flavonoids, characteristic of Apis mellifera propolis from different regions of Eurasia and North America. Aromatic compounds of propolis from Tenerife are represented by a group of nine isomeric furofuranoid lignans, as well as alkyl- and alkenyl-substituted derivatives of salicylic acid and resorcinol.

9,9'-epoxylignans from Syringa pinnatifolia: A typical case of stereochemical assignment by a quantum chemical calculation with MAEΔΔδ parameter

In the current study, twenty-two stereochemical 9,9'-epoxylignans including 19 undescribed ones were isolated from the ethanol extract of Syringa pinnatifolia in our continuing effort to understand the overall chemical spectrum of this species. These isolates were structurally elucidated by extensive spectroscopic data analysis, X-ray diffraction, modified Mosher's method, and quantum chemical calculations. Meanwhile, the utilization of 13C NMR calculation and the MAEΔΔδ parameter facilitated the stereochemical assignment of groups of lignan stereoisomers. The 13C NMR data were corrected by the averaged errors at each corresponding carbon position in groups of lignan stereoisomers, which improved the theoretic 13C NMR calculation. The finding of the stereochemical structures of 9,9'-epoxylignans is significant. It is helpful to determine the absolute configurations of molecules with the similar core. In addition, these lignans exhibited potential cardioprotective activities on H9c2 cardiomyocytes in vitro and presented significant antioxidant effect.

Furofuranoid-Type Lignans and Related Phenolics from Anisacanthus virgularis (Salisb.) Nees with Promising Anticholinesterase and Anti-Ageing Properties: A Study Supported by Molecular Modelling

Lignan phytomolecules demonstrate promising anti-Alzheimer activity by alleviating dementia and preserving nerve cells. The purpose of this work is to characterize the lignans of Anisacanthus virgularis and explore their potential anti-acetylcholinesterase and anti-ageing effects. Phytochemical investigation of A. virgularis aerial parts afforded a new furofuranoid-type lignan (1), four known structural analogues, namely pinoresinol (2), epipinoresinol (3), phillyrin (4), and pinoresinol 4-O-β-d-glucoside (5), in addition to p-methoxy-trans-methyl cinnamate (6) and 1H-indole-3-carboxaldehyde (7). The structures were established from thorough spectroscopic analyses and comparisons with the literature. Assessment of the anticholinesterase activity of the lignans 1-5 displayed noticeable enzyme inhibition of 1 (IC50 = 85.03 ± 4.26 nM) and 5 (64.47 ± 2.75 nM) but lower activity of compounds 2-4 as compared to the reference drug donepezil. These findings were further emphasized by molecular docking of 1 and 5 with acetylcholinesterase (AChE). Rapid overlay chemical similarity (ROCS) and structure-activity relationships (SAR) analysis highlighted and rationalized the anti-AD capability of these compounds. Telomerase activation testing of the same isolates revealed 1.64-, 1.66-, and 1.72-fold activations in cells treated with compounds 1, 5, and 4, respectively, compared to untreated cells. Our findings may pave the way for further investigations into the development of anti-Alzheimer and/or anti-ageing drugs from furofuranoid-type lignans.

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.

A new anti-inflammatory thujane monoterpenoid glycoside ester from Pittosporum heterophyllum Franch

Phytochemical investigation of EtOH extract of Pittosporum heterophyllum led to one new esterified thujane monoterpenoid glycoside, pitheteroside A (1), together with one eudesmane sesquiterpenoid (2) and twelve lignans (3－14). Their structures were elucidated by extensive spectroscopic analysis, including 1D and 2D NMR, ECD calculation and HRESIMS spectra. Pitheteroside A is an unreported and highly esterified monoterpenoid glycoside. All isolates were evaluated for their nitric oxide production inhibition against LPS-induced BV-2 microglial cells. Among them, compounds 1, 6 and 8 showed significant activities with IC50 values less than 10 μM. The results indicated the metabolisms from P. heterophyllum possess potential anti-inflammatory effects.

Review of lignans from 2019 to 2021: Newly reported compounds, diverse activities, structure-activity relationships and clinical applications

Lignans, with various biological activities, such as antitumor, antioxidant, antibacterial, and antiviral activities, are widely distributed in nature and mainly exist in the xylem of plants. In this paper, we summarized the structures and bioactivities of lignans reported in recent years (2019-2021) from five parts, including (1) a summary and classification of newly reported compounds; (2) the pharmacological activities of lignans; (3) molecular resources and activity distribution; (4) the structure-activity relationships; and (5) the clinical application of lignans. This review covers all undescribed compounds that were reported within the covered period of time and all bioactivity data about previously isolated lignans. The distribution of lignans in different plants and families is visualized, which improves the efficiency of searching for specific molecules. The diverse activities of different types of lignans provide an important reference for the rapid screening of these compounds. Discussion about the structure-activity relationships of lignans provides a direction for the structural modification of skeleton molecules. Combined with the clinical application of such molecules, this work will provide a valuable reference for pharmaceutical chemists.

Essential oils from the leaves and flowers of Leucophyllum frutescens (Scrophulariaceae): phytochemical analysis and inhibitory effects against elastase and collagenase in vitro

Leucophyllum frutescens (Scrophulariaceae) is a medicinal plant of Mexican traditional medicine. The aim of this study was to analyse the volatile components from the leaves and flowers by GC/MS and to assess their anti-aging activity for the first time. A total of 30 compounds were identified where 1-octen-3-ol (73.56%) and D-limonene (11.12%) represented the major ingredients in the leaves, while n-heneicosane (32.30%) and dehydroepingaione (15.15%) were the major components in the flowers. In vitro anti-aging activity was measured via assessing collagenase and elastase inhibition. Essential oils from the leaves and flowers showed potential collagenase inhibitory activity with IC₅₀ of 55.7 and 47.4 µg/mL. However, the oils from the leaves and flowers showed moderate anti-elastase activity with IC₅₀ of 60.8 and 97.7 µg/mL. Therefore, the oil of Leucophyllum frutescens could afford a promising natural anti-aging drug.

Non-Alkaloid Cholinesterase Inhibitory Compounds from Natural Sources

Alzheimer's disease (AD) is a severe neurodegenerative disorder of different brain regions accompanied by distresses and affecting more than 25 million people in the world. This progressive brain deterioration affects the central nervous system and has negative impacts on a patient's daily activities such as memory impairment. The most important challenge concerning AD is the development of new drugs for long-term treatment or prevention, with lesser side effects and greater efficiency as cholinesterases inhibitors and the ability to remove amyloid-beta(Aβ) deposits and other related AD neuropathologies. Natural sources provide promising alternatives to synthetic cholinesterase inhibitors and many have been reported for alkaloids while neglecting other classes with potential cholinesterase inhibition. This review summarizes information about the therapeutic potential of small natural molecules from medicinal herbs, belonging to terpenoids, coumarins, and phenolic compounds, and others, which have gained special attention due to their specific modes of action and their advantages of low toxicity and high efficiency in the treatment of AD. Some show superior drug-like features in comparison to synthetic cholinesterase inhibitors. We expect that the listed phytoconstituents in this review will serve as promising tools and chemical scaffolds for the discovery of new potent therapeutic leads for the amelioration and treatment of Alzheimer's disease.