AChE inhibitory activity of N-substituted natural galanthamine derivatives.

Galanthamine derivatives are known for their AChE inhibitory activity. Among them, galanthamine has been approved for treatment of Alzheimer's disease. N-Acetylnorgalanthamine (narcisine) and N-(2'-methyl)allylnorgalanthamine (the most potent natural AChE inhibitor of galanthamine type) were synthetized using N-norgalanthamine as a precursor. The NMR data described previously for narcisine were revised by two-dimensional 1H-1H and 1H-13C chemical shift correlation experiments. AChE inhibitory assays showed that N-acetylnorgalanthamine and N-formylnorgalanthamine (with previously unknown activity) are 4- and 43-times, respectively, less potent than galanthamine. In vitro (AChE inhibitory) and in silico (docking, ADME) assays and comparison of N-(2'-methyl)allylnorgalanthamine with galanthamine prove that this molecule is a very promising natural AChE inhibitor (33-times more potent than galanthamine) which further in vivo studies would provide better estimation about its applicability as a drug.

Identification of isoquinoline alkaloids from Corydalis mucronifera and their acetylcholinesterase inhibitory effects.

Four new spirobenzylisoquinoline mucroniferanines N - Q (1-4) and a rare chlorinated isoquinoline mucroniferanine R (5) were isolated from Corydalis mucronifera Maxim. Their structures were elucidated based on extensive spectroscopic data analysis of HRESIMS, 1D and 2D NMR, and their absolute configurations were confirmed by ECD data. The isolated compounds were evaluated for acetylcholinesterase (AChE) inhibitory activities. Mucroniferanine R showed significant activities with IC50 values of 0.78 µM compared to galanthamine (1.34 µM). The AChE inhibitory activity was further supported by the molecular docking analysis that exhibited the accommodation of mucroniferanine R in the active site of human AChE.

Alstomaphylines A-K, monoterpenoid bisindole alkaloids from Alstonia macrophylla with AChE inhibitory activity and cytotoxicity.

Eleven undescribed monoterpenoid bisindole alkaloids, alstomaphyines A-K (1-11), along with three known analogues were isolated from the leaves and stem bark of the Alstonia macrophylla. Compounds 1-3 were unprecedented dimerization alkaloids incorporating a macroline-type motif with an ajmaline-type motif via a C-C linkage. Their structures and absolute configurations were elucidated by extensive spectroscopic analysis, electronic circular dichroism (ECD) calculation, and CD exciton chirality method. Compounds 1-3 displayed potential inhibitory bioactivity against AChE with IC50 values of 4.44 ± 0.35, 3.59 ± 0.18, and 3.71 ± 0.23 µM, respectively. Enzyme kinetic study revealed compounds 1-3 as mixed competitive AChE inhibitors. Besides, compounds 8 and 12-14 exhibited better cytotoxicity against human cancer cell line HT-29 than cisplatin. Flow cytometry data revealed that compounds 8, 13, and 14 significantly induced the HT-29 cells arrest in G0/G1 phase in a concentration-dependent manner.

Metabolic profiling of Vitex Pubescens Vahl bark via UPLC-ESI-QTOF/MS/MS analysis and evaluation of its antioxidant and acetylcholinesterase inhibitory activities.

BACKGROUND: Alzheimer's disease is a neurodegenerative age-related disease that primarily affects the elderly population leading to progressive memory impairments and neural deficits. It is counted as a major cause of geriatric dependency and disability. The pathogenesis of Alzheimer's disease incidence is complex and involves various hypotheses, including the cholinergic hypothesis, deposition of ß-amyloid plaques, neuroinflammation, oxidative stress, and apoptosis. Conventional treatments such as donepezil aim to delay the symptoms but do not affect the progression of the disease and may cause serious side effects like hepatoxicity. The use of natural candidates for Alzheimer's disease treatment has drawn the attention of many researchers as it offers a multitargeted approach. METHODS: This current study investigates the metabolic profiles of total defatted methanolic extract of Vitex pubescens bark and its polar fractions, viz. ethyl acetate and n-butanol, using ultra-performance liquid chromatography-electrospray ionization-quadrupole time-of-flight tandem mass spectrometry(UPLC-ESI-QTOF/MS/MS) technique as well as evaluate the antioxidant using free radical scavenging assays, viz. DPPH and ABTS assays and in-vitro acetylcholinesterase inhibitory activities using Ellman's microplate assay. RESULTS: Metabolic profiling revealed a total of 71, 43, and 55 metabolites tentatively identified in the defatted methanolic extract, ethyl acetate, and n-butanol fractions, respectively. Phenolic acids were the most abundant class, viz. benzoic acids, and acyl quinic acid derivatives followed by flavonoids exemplified mainly by luteolin-C-glycosides and apigenin-C-glycosides. Quantification of the total phenolic and flavonoid contents in the total defatted methanolic extract confirmed its enrichment with phenolics and flavonoids equivalent to 138.61 ± 9.39 µg gallic acid/mg extract and 119.63 ± 4.62 µg rutin/mg extract, respectively. Moreover, the total defatted methanolic extract exhibited promising antioxidant activity confirmed through DPPH and ABTS assays with a 50% inhibitory concentration (IC50) value equivalent to 52.79 ± 2.16 µg/mL and 10.02 ± µg/mL, respectively. The inhibitory activity of acetylcholine esterase (AchE) was assessed using in-vitro Ellman's colorimetric assay, the total defatted methanolic extract, ethyl acetate, and n-butanol fractions exhibited IC50 values of 52.9, 15.1 and 108.8 µg/mL that they proved the significant inhibition of AchE activity. CONCLUSION: The results obtained herein unraveled the potential use of the total methanolic extract of Vitex pubescens bark and its polar fractions as natural candidates for controlling Alzheimer's disease progression.

Bioactive Alkaloids from the Mangrove-Derived Fungus Nigrospora oryzae SYSU-MS0024.

Chemical investigation of marine fungus Nigrospora oryzae SYSU-MS0024 cultured on solid-rice medium led to the isolation of three new alkaloids, including a pair of epimers, nigrosporines A (1) and B (2), and a pair of enantiomers, (+)-nigrosporine C (+)-3, and (-)-nigrosporine C (-)-3, together with eight known compounds (4-11). Their structures were elucidated based on extensive mass spectrometry (MS) and 1D/2D nuclear magnetic resonance (NMR) spectroscopic analyses and compared with data in the literature. The absolute configurations of compounds 1-3 were determined by a combination of electronic circular dichroism (ECD) calculations, Mosher's method, and X-ray single-crystal diffraction technique using Cu Kα radiation. In bioassays, compound 2 exhibited moderate inhibition on NO accumulation induced by lipopolysaccharide (LPS) on BV-2 cells in a dose-dependent manner at 20, 50, and 100 µmol/L and without cytotoxicity in a concentration of 100.0 µmol/L. Moreover, compound 2 also showed moderate acetylcholinesterase (AChE) inhibitory activities with IC50 values of 103.7 µmol/L. Compound 5 exhibited moderate antioxidant activity with EC50 values of 167.0 µmol/L.

Molecular properties, structure and chiral resolution of secondary metabolites from the leaves of Viburnum chingii.

A chemical investigation of leaves of Viburnum chingii afforded eleven compounds, including one undescribed lignan (1), a pair of known phenylpropanoid enantiomers (2a/2b), and eight known lignans (3-10). Their structures were elucidated by detailed spectroscopic and comparative literature data analysis. The absolute configurations of compounds 1 was determined by comparing the experimental ECD data with the calculated values. The compounds 2a/2b were separated successfully by a chiral chromatographic column. In addition, the acetylcholinesterase (AChE) inhibitory activities of described compounds were evaluated.

Five new biflavonoids with acetylcholinesterase inhibitory activity from Diphylleia sinensis.

Five new biflavonoids, diphybiflavonoids A - E (1-5), were isolated from the roots and rhizomes of Diphylleia sinensis. Their structures were elucidated by extensive spectroscopic data, including UV, IR, HR-ESI-MS and 2D NMR. Their absolute configurations were determined by ECD spectra. All isolated compounds were evaluated for acetylcholinesterase (AChE) inhibitory activity. Compounds 1-4 exhibited the potent AChE inhibitory activities with IC50 values of 1.62, 2.10, 2.08, and 5.15 µM, respectively. The preliminary structure-activity relationship study indicated that the connection mode (C2-O-C4'''/C3-O-C3''' or C2-O-C3'''/C3-O-C4''') of biflavonoid subunits, and 3-hydroxy group of flavonol subunit were important structural factors for AChE inhibitory activity. Biflavonoids, containing a C2-O-C4'''/C3-O-C3''' or C2-O-C3'''/C3-O-C4''' linkage, can be a potentially useful platform for development of cholinesterase inhibitors.

The Polyketides with Antimicrobial Activities from a Mangrove Endophytic Fungus Trichoderma lentiforme ML-P8-2.

Five new polyketides, including two chromones (1-2), two phenyl derivatives (4-5), and a tandyukusin derivative (6), along with five known polyketides (3 and 7-10) were isolated from mangrove endophytic fungus Trichoderma lentiforme ML-P8-2. The planar structures of compounds were elucidated via detailed 1D, 2D NMR, and HR-ESI-MS analysis. ECD spectra, optical rotation values calculation, and alkali hydrolysis were applied in the determination of the absolute configuration of the new compounds. In bioassays, 6 and 9 exhibited promising antifungal activities against Penicillium italicum, with an MIC value of 6.25 µM for both compounds. Moreover, 3 displayed moderate AChE inhibitory activity with an IC50 value of 20.6 ± 0.3 µM.

Quinolinones Alkaloids with AChE Inhibitory Activity from Mangrove Endophytic Fungus Penicillium citrinum YX-002.

Acetylcholinesterase (AChE) inhibitory activity-guided studies on the mangrove-derived endophytic fungus Penicillium citrinum YX-002 led to the isolation of nine secondary metabolites, including one new quinolinone derivative, quinolactone A (1), a pair of epimers quinolactacin C1 (2) and 3-epi-quinolactacin C1 (3), together with six known analogs (4-9). Their structures were elucidated based on extensive mass spectrometry (MS) and 1D/2D nuclear magnetic resonance (NMR) spectroscopic analyses, and compared with data in the literature. The absolute configurations of compounds 1-3 was determined by combination of electronic circular dichroism (ECD) calculations and X-Ray single crystal diffraction technique using CuKα radiation. In bioassays, compounds 1, 4 and 7 showed moderate AChE inhibitory activities with IC50 values of 27.6, 19.4 and 11.2 µmol/L, respectively. The structure-activity relationships (SARs) analysis suggested that the existence of carbonyl group on C-3 and the oxygen atom on the five-membered ring were beneficial to the activity. Molecular docking results showed that compound 7 had a lower affinity interaction energy (-9.3 kcal/mol) with stronger interactions with different sites in AChE activities, which explained its higher activities.

Bioactive secondary metabolites isolated from the soft coral derived Penicillium sp. SCSIO 41038.

Chemical investigation of the Penicillium sp. SCSIO 41038 led to the isolation and characterization of one new cyclopiazonic acid-type alkaloid, speradine I (1), and one new phloroglucinol derivative, speradine J (8), along with 13 known compounds. Their structures were determined on the basis of extensive spectroscopic analysis, and by a comparison with data from the literature. All the compounds were evaluated for their antitumor (22Rv1 and PC-3) and enzyme inhibitory activity against acetylcholinesterase (AChE) in vitro.

From Foxtail Millet Husk (Waste) to Bioactive Phenolic Extracts Using Deep Eutectic Solvent Extraction and Evaluation of Antioxidant, Acetylcholinesterase, and α-Glucosidase Inhibitory Activities.

Foxtail millet husk (FMH) is generally removed and discarded during the first step of millet processing. This study aimed to optimize a method using deep eutectic solvents (DESs) combined with ultrasonic-assisted extraction (UAE) to extract phenols from FMH and to identify the phenolic compositions and evaluate the biological activities. The optimized DES comprised L-lactic acid and glycol with a 1:2 molar ratio by taking the total flavonoid content (TFC) and total phenolic content (TPC) as targets. The extraction parameters were optimized to maximize TFC and TPC, using the following settings: liquid-to-solid ratio of 25 mL/g, DES with water content of 15%, extraction time of 41 min and temperature of 51 °C, and ultrasonic power at 304 W. The optimized UAE-DES, which produced significantly higher TPC, TFC, antioxidant activity, α-glucosidase, and acetylcholinesterase inhibitory activities compared to conventional solvent extraction. Through UPLC-MS, 12 phenolic compounds were identified, with 1-O-p-coumaroylglycerol, apigenin-C-pentosyl-C-hexoside, and 1-O-feruloyl-3-O-p-coumaroylglycerol being the main phenolic components. 1-O-feruloyl-3-O-p-coumaroylglycerol and 3,7-dimethylquercetin were identified first in foxtail millet. Our results indicated that FMH could be exploited by UAE-DES extraction as a useful source of naturally derived antioxidants, along with acetylcholinesterase and α-glucosidase inhibitory activities.

Structurally diverse alkaloids with nine frameworks from Zephyranthes candida and their acetylcholinesterase inhibitory and anti-inflammatory activities.

Twenty-six structurally diverse Amaryllidaceae alkaloids, including ten undescribed compounds named zephyranines A-I and 6-O-ethylnerinine, two undescribed natural products zephyranthine-6-one and 3-O-deacetyl-sternbergine, were isolated from whole plants of Zephyranthes candida. Their structures were determined by HRESIMS, 1D and 2D NMR, CD data analysis, NMR and ECD calculations, and single-crystal X-ray diffraction analysis. All structures were classified into nine framework types: 10b,11-seco-crinine, graciline, crinine, homolycorine, trisphaeridine, lycorine, galasine, tazettine, and belladine. Zephyranine A represents the first naturally occurring 10b,11-seco-crinine type alkaloid, and zephyranine B is the sixth graciline type alkaloid. 6-O-ethylnerinine is an artifact from the extraction and isolation. All isolates were evaluated for their acetylcholinesterase (AChE) inhibitory and anti-inflammatory activities. Zephyranines A, G, and H exhibited moderate AChE inhibitory activities, with IC50 values of 8.2, 39.0, and 10.8 µM, respectively. Zephyranine B, haemanthamine, haemanthidine, 11-hydroxyvittatine, and 8-demethoxy-10-O-methylhostasine exhibited potent anti-inflammatory activity on the LPS-induced NO production in RAW264.7 mouse macrophages with IC50 values of 21.3, 4.6, 12.2, 5.6, and 17.4 µM, respectively. Structure-activity-relationship analysis and docking studies indicated that interactions with the key Trp286 and Tyr337 residues are required for potent AChE inhibitors.

Indole diketopiperazine alkaloids and aromatic polyketides from the Antarctic fungus Penicillium sp. SCSIO 05705.

A new indole diketopiperazine alkaloid, named penilline D (1), together with five known indole alkaloid analogues (2-5, 11), two meroterpenoids (6 and 12), and four butenolide derivatives (7-10), were isolated from the Antarctic fungus Penicillium sp. SCSIO 05705. Extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation were used to elucidate the structure of penilline D (1), including its absolute configuration. All isolated compounds (1-12) were evaluated for their cytotoxic, antibacterial and enzyme inhibitory activities against acetylcholinesterase (AChE) and pancreatic lipase (PL). Among them, compound 5 exhibited moderate in vitro cytotoxic activity against the 143B cell line with IC50 value of 12.64 ± 0.78 µM. Compound 6 showed strong inhibitory activity against AChE with IC50 value of 0.36 nM (IC50 18.7 nM for Tacrine), while compounds 6 and 11 showed weak PL enzyme inhibitory activity. Furthermore, an in silico molecular docking study was also performed between 6 and AChE.

A new quinolone and acetylcholinesterase inhibitors from a sponge-associated fungus Penicillium sp. SCSIO41033.

The chemical investigation of the EtOAc extract from the solid rice medium cultured with a sponge-associated fungus Penicillium sp. SCSIO41033 led to the isolation of two quinolones including a new one, penicinolone (1), three xanthone derivatives (3-5), and four anthraquinones (6-9). Their structures were determined by comprehensive analysis of 1H and 13C NMR, COSY, HSQC, and HMBC spectroscopic, and HRESIMS mass spectrometric data. The bioactive assays revealed that compounds 1 and 2 showed no antimicrobial activities against five bacteria and eight fungi, and compounds 5, 8 and 9 exhibited inhibition against AChE with IC50 values of 45.9, 42.5 and 40.5 µg/mL. Molecular docking analysis was performed to explore the interactions between active molecules and AChE protein, which indicated that xanthone and anthraquinone derivatives had the potential for developing AChE inhibitors.

Thirteen cyathane diterpenoids with acetylcholinesterase inhibitory effects from the fungus Cyathus africanus.

Eight undescribed cyathane diterpenoids, representative specialised metabolites of the genus Cyathus, named cyathins Q-X, along with five known congeners, were isolated from the liquid fermentation of Cyathus africanus. Their structures and absolute configurations were elucidated by integrating NMR spectroscopic analyses, electronic circular dichroism (ECD) calculations, and X-ray diffraction. Reasonable correction to the C-12 configuration of cyathin I was corroborated by the crystal data. The structural identification in this research expanded the number of candidates to allow for more bioactivity-screening options. Among them, (12S)-11α,14α-epoxy-13α,14ß,15-trihydroxycyath-3-ene displayed significant acetylcholinesterase (AChE) inhibitory effect with an IC50 value of 4.60 ± 0.85 µM. Molecular docking studies were also performed to unravel the underlying modes of interactions with the active sites of AChE for active compounds.

Bisabolanoic acid A, a new polychiral sesquiterpene with AChE inhibitory activity from a mangrove-derived fungus Colletotrichum sp.

A new polychiral bisabolane sesquiterpene, bisabolanoic acid A (1), was isolated from the mangrove-derived fungus Colletotrichum sp. SCSIO KcB3-2. Its planar structure was identified on the basis of spectroscopic data analysis (HRESIMS, 1D, and 2D NMR), and the absolute configurations of three chiral carbons were determined by experimental and calculated electronic circular dichroism (ECD) and optical rotatory dispersion (ORD), together with Mo2(OAc)4-induced ECD methods. Bisabolanoic acid A (1) showed moderate inhibitory activity against acetylcholinesterase (AChE) with IC50 value of 2.2 µM, and the in silico molecular docking was also performed.

Discovery of Three New Monoterpenoid Indole Alkaloids from the Leaves of Gardneria multiflora and Their Vasorelaxant and AChE Inhibitory Activities.

Three novel monoterpenoid indole alkaloids gardflorine A (1), gardflorine B (2), and gardflorine C (3) were isolated from the leaves of Gardneria multiflora. Their structures, including absolute configurations, were established on the basis of spectroscopic methods (MS, UV, IR, 1D and 2D NMR) and circular dichroism experiments. All the compounds were evaluated for their vasorelaxant and acetylcholinesterase (AChE) inhibitory activities. Compound 1 exhibited potent vasorelaxant activity, with an EC50 value of 8.7 µM, and compounds 2 and 3 showed moderate acetylcholinesterase (AChE) inhibitory activities, with IC50 values of 26.8 and 29.2 µM, respectively.

Cyclic Peptides from the Soft Coral-Derived Fungus Aspergillus sclerotiorum SCSIO 41031.

Three novel cyclic hexapeptides, sclerotides C-E (1-3), and a new lipodepsipeptide, scopularide I (4), together with a known cyclic hexapeptide sclerotide A (5), were isolated from fermented rice cultures of a soft coral-derived fungus: Aspergillus sclerotiorum SCSIO 41031. The structures of the new peptides were determined by 1D and 2D NMR spectroscopic analysis, Marfey's method, ESIMS/MS analysis, and single crystal X-ray diffraction analysis. Scopularide I (4) exhibited acetylcholinesterase inhibitory activity with an IC50 value of 15.6 µM, and weak cytotoxicity against the human nasopharyngeal carcinoma cell line HONE-EBV with IC50 value of 10.1 µM.

Claulansine F-Donepezil Hybrids as Anti-Alzheimer's Disease Agents with Cholinergic, Free-Radical Scavenging, and Neuroprotective Activities.

The multifactorial nature of Alzheimer's disease (AD) calls for the development of multitarget agents addressing key pathogenic processes. A total of 26 Claulansine F-donepezil hybrids were designed and synthesized as multitarget drugs. Among these compounds, six compounds exhibited excellent acetylcholinesterase (AChE) inhibitory activity (half maximal inhibitory concentration (IC50) 1.63-4.62 µM). Moreover, (E)-3-(8-(tert-Butyl)-3,3-dimethyl-3,11-dihydropyrano[3,2-a]carbazol-5-yl)-N-((1-(2-chlorobenzyl)piperidin-4-yl)methyl)acrylamide (6bd) exhibited better neuroprotective effects against OGD/R (oxygen-glucose deprivation/reoxygenation) than lead compound Claulansine F. Furthermore, 6bd could cross the blood-brain barrier in vitro. More importantly, compared to edaravone, 6bd had stronger free-radical scavenging activity. Molecular docking studies revealed that 6bd could interact with the catalytic active site of AChE. All of these outstanding in vitro results indicate 6bd as a leading structure worthy of further investigation.

Chemical Constituents and their Antioxidant, Anti-Inflammatory and Anti-Acetylcholinesterase Activities from Pholidota cantonensis.

Alzheimer's disease (AD) has the third highest health expenditures after heart disease and cancer. It has emerged as a serious global health issue. The discovery of new drugs to prevent and treat AD is of utmost importance. Pholidota cantonensis is an edible medicinal plant consumed in China. It is widely used in traditional Chinese medicine to treat various diseases. P. cantonensis has been reported to have antioxidant, anti-inflammatory, antitumor and antibacterial activities. Among these properties, its potent antioxidant activity has attracted our attention, since oxidative stress is one of the important pathological mechanisms involved in AD. This study aimed to isolate the compounds from the active extract and evaluate their bioactivities. Fifteen compounds, including one new compound, were obtained. The isolates were tested for 2,2'-diphenyl-1-picrylhydrazyl (DPPH)/2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities, anti-acetylcholinesterase (anti-AChE) activities and inhibitory effects on nitrogen monoxide (NO) release in the BV-2 cells. Compounds 1, 2, 4, 6, 8, and 13-15 exhibited two kinds of AD-associated bioactivities. More importantly, compound 13 showed more potent NO inhibitory activity (IC50 = 0.72 ± 0.08 µM) than the positive control quercetin (IC50 = 12.94 ± 0.08 µM). Compound 13 also had a higher inhibitory rate (99.59 ± 0.43%) on AChE than that of the positive control galantamine (78.32 ± 1.16%) at the concentrate of 50 µg/mL. Our studies provide new insights into this plant in terms of its potential in the development of new multi-target anti-Alzheimer's disease (anti-AD) drugs.