Amino derivatives of glycyrrhetinic acid as potential inhibitors of cholinesterases

Diethoxyphosphoryloxy-oleanolic acid is a nanomolar-inhibitor of butyrylcholinesterase

A series of new betulin, lupeol, erythrodiol, and oleanolic acid phosphoryloxy- and furoyloxy-derivatives has been synthesized and their structure was confirmed by NMR spectroscopy. Synthesized compounds were subjected to Ellman's assays to determine their ability to inhibit the enzymes AChE and BChE. Among them, diethoxyphosphoryloxy-oleanolic acid inhibited BChE with a value of 99%, thereby acting as a mixed-type inhibitor holding very low Ki values of Ki = 6.59 nM and Ki ' = 1.97 nM, respectively.

Research progress of natural products and their derivatives against Alzheimer's disease

Alzheimer's disease (AD), a persistent neurological dysfunction, has an increasing prevalence with the aging of the world and seriously threatens the health of the elderly. Although there is currently no effective treatment for AD, researchers have not given up, and are committed to exploring the pathogenesis of AD and possible therapeutic drugs. Natural products have attracted considerable attention owing to their unique advantages. One molecule can interact with multiple AD-related targets, thus having the potential to be developed in a multi-target drug. In addition, they are amenable to structural modifications to increase interaction and decrease toxicity. Therefore, natural products and their derivatives that ameliorate pathological changes in AD should be intensively and extensively studied. This review mainly presents research on natural products and their derivatives for the treatment of AD.

Nose-to-brain delivery of 18β-Glycyrrhetinic acid using optimized lipid nanocapsules: A novel alternative treatment for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder and the most relevant form of dementia affecting people worldwide. AD was reported to be associated with increased oxidative stress ending up with neuronal damage. 18β-Glycyrrhetinic acid (GA), triterpenoid aglycone of glycyrrhizin, was reported for its powerful antioxidant activities. However, its high molecular weight and lipophilicity are two major obstacles that limit its use and cause very low brain bioavailability. The aim of the present study was to formulate the GA in lipid nanocapsules (LNCs) for enhanced nose-to-brain delivery, as well as to elucidate its potential neuroprotective effect in AD. The optimized GA-loaded LNCs exhibited nanometric size range, good stability over 6 months, sustained drug release over 24 h and high steady state flux and permeability coefficient across nasal mucosa over 8 h. In-vivo studies were conducted on five groups; control, scopolamine (SCOP)-treated, SCOP + GA-LNCs, SCOP + oral GA suspension, and SCOP + intranasal GA suspension groups. Intranasal administration of GA-LNCs, at a reduced dose of 1 mg/kg, improved scopolamine-induced memory impairment in rats evidenced by behavioral testing, histological examination, and oxidative stress markers; catalase and superoxide dismutase. Collectively, GA-loaded LNCs (with 50 times lower dose) may provide a promising remedy for AD patients worldwide.

Novel Triterpenic Acid—Benzotriazole Esters Act as Pro-Apoptotic Antimelanoma Agents

Pentacyclic triterpenes, such as betulinic, ursolic, and oleanolic acids are efficient and selective anticancer agents whose underlying mechanisms of action have been widely investigated. The introduction of N-bearing heterocycles (e.g., triazoles) into the structures of natural compounds (particularly pentacyclic triterpenes) has yielded semisynthetic derivatives with increased antiproliferative potential as opposed to unmodified starting compounds. In this work, we report the synthesis and biological assessment of benzotriazole esters of betulinic acid (BA), oleanolic acid (OA), and ursolic acid (UA) (compounds 1–3). The esters were obtained in moderate yields (28–42%). All three compounds showed dose-dependent reductions in cell viability against A375 melanoma cells and no cytotoxic effects against healthy human keratinocytes. The morphology analysis of treated cells showed characteristic apoptotic changes consisting of nuclear shrinkage, condensation, fragmentation, and cellular membrane disruption. rtPCR analysis reinforced the proapoptotic evidence, showing a reduction in anti-apoptotic Bcl-2 expression and upregulation of the pro-apoptotic Bax. High-resolution respirometry studies showed that all three compounds were able to significantly inhibit mitochondrial function. Molecular docking showed that compounds 1–3 showed an increase in binding affinity against Bcl-2 as opposed to BA, OA, and UA and similar binding patterns compared to known Bcl-2 inhibitors.

Identifying Possible AChE Inhibitors from Drug-like Molecules via Machine Learning and Experimental Studies

Acetylcholinesterase (AChE) is one of the most important drug targets for Alzheimer's disease (AD) treatment. In this work, a machine learning model was trained to rapidly and accurately screen large chemical databases for the potential inhibitors of AChE. The obtained results were then validated via in vitro enzyme assay. Moreover, atomistic simulations including molecular docking and molecular dynamics simulations were then used to understand molecular insights into the binding process of ligands to AChE. In particular, two compounds including benzyl trifluoromethyl ketone and trifluoromethylstyryl ketone were indicated as highly potent inhibitors of AChE because they established IC₅₀ values of 0.51 and 0.33 μM, respectively. The obtained IC₅₀ of two compounds is significantly lower than that of galantamine (2.10 μM). The predicted log(BB) suggests that the compounds may be able to traverse the blood-brain barrier. A good agreement between computational and experimental studies was observed, indicating that the hybrid approach can enhance AD therapy.

Glycyrrhetinic acid restricts mitochondrial energy metabolism by targeting SHMT2

Glycyrrhetinic acid (GA) is a natural product of licorice with mitochondria targeting properties and shows broad anticancer activities, but its targets and underlying mechanisms remain elusive. Here, we identified the mitochondrial enzyme serine hydroxymethyltransferase 2 (SHMT2) as a target of GA by using chemical proteomics. Binding to and inhibiting the activity of SHMT2 by GA were validated in vitro and in vivo. Knockout of SHMT2 or inhibiting SHMT2 with GA restricts mitochondrial energy supplies by downregulating mitochondrial oxidative phosphorylation (OXPHOS) and fatty acid β-oxidation, and consequently suppresses cancer cell proliferation and tumor growth. Crystal structures of GA derivatives indicate that GA occupies SHMT2 folate-binding pocket and regulates SHMT2 activity. Modifications at GA carboxylic group with diamines significantly improved its anticancer potency, demonstrating GA as a decent structural template for SHMT2 inhibitor development.

Novel β-Cyclodextrin-Based Heptavalent Glycyrrhetinic Acid Conjugates: Synthesis, Characterization, and Anti-Influenza Activity

In our continuing efforts toward the design of novel pentacyclic triterpene derivatives as potential anti-influenza virus entry inhibitors, a series of homogeneous heptavalent glycyrrhetinic acid derivatives based on β-cyclodextrin scaffold were designed and synthesized by click chemistry. The structure was unambiguously characterized by NMR, IR, and MALDI-TOF-MS measurements. Seven conjugates showed sufficient inhibitory activity against influenza virus infection based on the cytopathic effect reduction assay with IC50 values in the micromolar range. The interactions of conjugate 37, the most potent compound (IC50 = 2.86 μM, CC50 > 100 μM), with the influenza virus were investigated using the hemagglutination inhibition assay. Moreover, the surface plasmon resonance assay further confirmed that compound 37 bound to the influenza HA protein specifically with a dissociation constant of 5.15 × 10−7 M. Our results suggest the promising role of β-cyclodextrin as a scaffold for preparing a variety of multivalent compounds as influenza entry inhibitors.

A Mini-Review on Structure-Activity Relationships of Glycyrrhetinic Acid Derivatives with Diverse Bioactivities

Pentacyclic triterpenoids, consisting of six isoprene units, are a kind of natural active substance. At present, numerous pentacyclic triterpene have been observed and classified into four subgroups of oleanane, ursane, lupane, and xylene on the basis of the carbon skeleton. Among them, oleanane is the most popular due to its rich backbone and diverse bioactivities. 18β-Glycyrrhetinic acid (GA), an oleanane-type pentacyclic triterpene isolated from licorice roots, possesses diverse bioactivities including antitumor, anti-inflammatory, antiviral, antimicrobial, enzyme inhibitor, hepatoprotective and so on. It has received more attention in medicinal chemistry due to the advantages of easy-to-access and rich bioactivity. Thus, numerous novel lead compounds were synthesized using GA as a scaffold. Herein, we summarize the structure-activity relationship and synthetic methodologies of GA derivatives from 2010 to 2020 as well as the most active GA derivatives. Finally, we anticipate that this review can benefit future research on structural modifications of GA to enhance bioactivity and provide an example for developing pentacyclic triterpene-based novel drugs.

From Marine Metabolites to the Drugs of the Future: Squalamine, Trodusquemine, Their Steroid and Triterpene Analogues

This review comprehensively describes the recent advances in the synthesis and pharmacological evaluation of steroid polyamines squalamine, trodusquemine, ceragenins, claramine, and their diverse analogs and derivatives, with a special focus on their complete synthesis from cholic acids, as well as an antibacterial and antiviral, neuroprotective, antiangiogenic, antitumor, antiobesity and weight-loss activity, antiatherogenic, regenerative, and anxiolytic properties. Trodusquemine is the most-studied small-molecule allosteric PTP1B inhibitor. The discovery of squalamine as the first representative of a previously unknown class of natural antibiotics of animal origin stimulated extensive research of terpenoids (especially triterpenoids) comprising polyamine fragments. During the last decade, this new class of biologically active semisynthetic natural product derivatives demonstrated the possibility to form supramolecular networks, which opens up many possibilities for the use of such structures for drug delivery systems in serum or other body fluids.

Pentacyclic triterpene carboxylic acids derivatives integrated piperazine-amino acid complexes for α-glucosidase inhibition in vitro

Eighteen derivatives of pentacyclic triterpene carboxylic acids (Maslinic acid, Corosolic acid and Asiatic acid) have been prepared by coupling the piperazine complex of l-amino acids at the C-28 site of the parent compounds. The α-glucosidase inhibitory activities of the pristine derivatives were evaluated in vitro. The results indicated that the inhibitory activity of some compounds (15e IC₅₀ = 591 μM, 16e IC₅₀ = 423 μM) was closed to that of the reference acarbose (IC₅₀ = 347 μM) in ethanol-water system. In addition, compound 16e (IC₅₀ = 380 μM) showed superior inhibitory activity than acarbose (IC₅₀ = 493 μM) in the measurement system with DMSO as solvent. The comparison of two different solvent systems showed that the derivatives had better α-glucosidase inhibitory activity in the DMSO system than that of in ethanol-water system. Regrettably, all of the as-synthesized derivatives exhibited inferior α-glucosidase inhibitory activities than those of the parent compounds in both test solvent systems. Furthermore, the result of enzyme kinetics demonstrated that the inhibition mechanism of compound 16e was noncompetitive inhibition with the inhibition constant K_i = 552 μM.

Preclinical Evidence for the Pharmacological Actions of Glycyrrhizic Acid: A Comprehensive Review

Glycyrrhiza glabra L. (Family: Fabaceae) is one of the important traditional medicinal plant used extensively in folk medicine. It is known for its ethnopharmacological value in curing a wide variety of ailments. Glycyrrhizin, an active compound of G. glabra, possesses anti-inflammatory activity due to which it is mostly used in traditional herbal medicine for the treatment and management of chronic diseases. The present review is focused extensively on the pharmacology, pharmacokinetics, toxicology, and potential effects of Glycyrrhizic Acid (GA). A thorough literature survey was conducted to identify various studies that reported on the GA on PubMed, Science Direct and Google Scholar.

Trimethoxycinnamates and Their Cholinesterase Inhibitory Activity

A series of twelve nature-inspired 3,4,5-trimethoxycinnamates were prepared and characterized. All compounds, including the starting 3,4,5-trimethoxycinnamic acid, were tested for their ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro; the selectivity index (SI) was also determined. 2-Fluororophenyl (2E)-3-(3,4,5-trimethoxyphenyl)-prop-2-enoate demonstrated the highest SI (1.71) in favor of BChE inhibition. 2-Chlorophenyl (2E)-3-(3,4,5-trimethoxyphenyl)prop-2-enoate showed the highest AChE-inhibiting (IC50 = 46.18 µM) as well as BChE-inhibiting (IC50 = 32.46 µM) activity with an SI of 1.42. The mechanism of action of the most potent compound was determined by the Lineweaver–Burk plot as a mixed type of inhibition. An in vitro cell viability assay confirmed the insignificant cytotoxicity of the discussed compounds on the two cell lines. Trends between structure, physicochemical properties and activity were discussed.

Novel pentacyclic triterpenes exhibiting strong neuroprotective activity in SH-SY5Y cells in salsolinol- and glutamate-induced neurodegeneration models

Novel triterpene derivatives were prepared and evaluated in salsolinol (SAL)- and glutamate (Glu)-induced models of neurodegeneration in neuron-like SH-SY5Y cells. Among the tested compounds, betulin triazole 4 bearing a tetraacetyl-β-d-glucose substituent showed a highly potent neuroprotective effect. Further studies revealed that removal of tetraacetyl-β-d-glucose part (free triazole derivative 10) resulted in strong neuroprotection in the SAL model at 1 μM, but this derivative suffered from cytotoxicity at higher concentrations. Both compounds modulated oxidative stress and caspase-3,7 activity, but 10 showed a superior effect comparable to the Ac-DEVD-CHO inhibitor. Interestingly, while both 4 and 10 outperformed the positive controls in blocking mitochondrial permeability transition pore opening, only 4 demonstrated potent restoration of the mitochondrial membrane potential (MMP) in the model. Derivatives 4 and 10 also showed neuroprotection in the Glu model, with 10 exhibiting the strongest oxidative stress reducing effect among the tested compounds, while the neuroprotective activity of 4 was probably due recovery of the MMP.

Metabolic Engineering for Glycyrrhetinic Acid Production in Saccharomyces cerevisiae

Glycyrrhetinic acid (GA) is one of the main bioactive components of licorice, and it is widely used in traditional Chinese medicine due to its hepatoprotective, immunomodulatory, anti-inflammatory and anti-viral functions. Currently, GA is mainly extracted from the roots of cultivated licorice. However, licorice only contains low amounts of GA, and the amount of licorice that can be planted is limited. GA supplies are therefore limited and cannot meet the demands of growing markets. GA has a complex chemical structure, and its chemical synthesis is difficult, therefore, new strategies to produce large amounts of GA are needed. The development of metabolic engineering and emerging synthetic biology provide the opportunity to produce GA using microbial cell factories. In this review, current advances in the metabolic engineering of Saccharomyces cerevisiae for GA biosynthesis and various metabolic engineering strategies that can improve GA production are summarized. Furthermore, the advances and challenges of yeast GA production are also discussed. In summary, GA biosynthesis using metabolically engineered S. cerevisiae serves as one possible strategy for sustainable GA supply and reasonable use of traditional Chinese medical plants.

Synthesis and cholinesterase inhibiting potential of A-ring azepano- and 3-amino-3,4-seco-triterpenoids

In this study, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives were synthesized from betulin, oleanolic, ursolic and glycyrrhetinic acids aiming to develop new cholinesterase inhibitors. Azepanobetulin, azepanoerythrodiol and azepanouvaol were modified to give amide and tosyl derivatives, while azepano-anhydrobetulines and azepano-glycyrrhetols were obtained for the first time. Oleanane and ursane type 3-amino-3,4-seco-4(23)-en triterpenic alcohols were synthesized by reducing the corresponding 2-cyano-derivatives accessible from Beckmann type 2 rearrangements. The compounds were screened in colorimetric Ellman's assays to determine their ability to act as inhibitors for the enzymes acetylcholinesterase (AChE, from electric eel) and butyrylcholinesterase (BChE, from equine serum). While most of these compounds were only moderate inhibitors for AChE, several of them were shown to be inhibitors for BChE acting as mixed-type inhibitors. Azepanobetulin 1, its C28-amide derivatives 7 and 8, azepano-11-deoxo-glycyrrhetol 12 and azepanouvaol 18 held inhibition constants K_i ranging between 0.21 ± 0.06 to 0.68 ± 0.19 μM. Thus, they were approximately 4 to 10 times more active than standard galantamine hydrobromide. For all of the compounds reasonably high docking scores for BChE were obtained being in good agreement with the experimental results from the enzymatic studies. As a result, A-ring azepano-triterpenoids were found to be new scaffolds for the development of BChE inhibitors.

Effect of Glycyrrhizic Acid on Scopolamine-Induced Cognitive Impairment in Mice

Purpose

Cognitive impairment is one of the main symptoms of Alzheimer disease and other dementias. Glycyrrhiza uralensis is a natural product that has a protective effect against cognitive impairment. In this study, we investigated whether glycyrrhizic acid, among the main bioactive components of Glycyrrhiza uralensis, has a neuroprotective effect on scopolamine-induced cognitive impairment.

Methods

Twenty-week-old male Institute of Cancer Research mice were used in this study. The scopolamine-induced cognitive impairment mice model was used. Glycyrrhizic acid was orally administered to mice once daily for 21 days, while scopolamine (1 mg/kg) treatment was delivered 30 minutes before behavioral tests. Donepezil (2 mg/kg) was used as a positive drug control. To evaluate the effect of glycyrrhizic acid, the following assessments were performed on hippocampal tissue: Y-maze test, acetylcholinesterase activity, antioxidant enzymes’ activity (superoxide dismutase, catalase). Western blotting for phosphor-extracellular signal-regulated kinase, P38, and c-Jun NH2-terminal kinase was conducted.

Results

We found that glycyrrhizic acid administration significantly improved scopolamine-induced cognitive impairment in the Y-maze test. The acetylcholinesterase activity, superoxide dismutase, and catalase activity in the glycyrrhizic acid-treated group showed a significant reversal of cognitive impairment compared with the scopolamine-treated group.

Conclusions

Our results suggest that glycyrrhizic acid has a neuroprotective effect on cognitive function in scopolamine-induced cognitive impairment.

Exploring New Structural Features of the 18β-Glycyrrhetinic Acid Scaffold for the Inhibition of Anaplastic Lymphoma Kinase

Novel 18β-glycyrrhetinic acid derivatives possessing a carbamate moiety and structurally similar ester derivatives were developed and evaluated for their efficacy as antitumor inhibitors. In the cellular assays, most of the N-substituted carbamate derivatives at the C3-position exhibited potent activities. The results of SAR investigation revealed that the introduction of the morpholine group at the C30-COOH led to a significant loss of the inhibitory potency. Among the ester derivatives, the ester group at C3-position also determined a noticeable reduction in the efficacy. Compound 3j exhibited the most prominent antiproliferative activity against six human cancer cells (A549, HT29, HepG2, MCF-7, PC-3, and Karpas299). Furthermore, compound 3j exerted a moderate inhibiting effect on the ALK. The results of molecular docking analyses suggested that it could bind well to the active site of the receptor ALK, which was consistent with the biological data. These results might inspire further structural optimization of 18β-glycyrrhetinic acid aiming at the development of potent antitumor agents. The structures 4d, 4g, 4h, 4j, and 4n were studied by X-ray crystallographic analyses.

Ursolic and oleanolic acid derivatives with cholinesterase inhibiting potential

Triterpenoids are in the focus of scientific interest, and they were evaluated for many pharmacological applications among them their ability to act as inhibitors of cholinesterases. These inhibitors are still of interest as drugs that improve the life quality of patients suffering from age-related dementia illnesses especially of Alzheimer's disease. Herein, we prepared several derivatives of ursolic and oleanolic acid and screened them in Ellman's assays for their ability to inhibit acetylcholinesterase and/or butyrylcholinesterase, and for each of the active compounds the type of inhibition was determined. As a result, several compounds were shown as good inhibitors for acetylcholinesterase and butyrylcholinesterase even in a micromolar range. An ursolic acid derived hydroxyl-propinyl derivative 10 was a competitive inhibitor for butyrylcholinesterase with an inhibition constant of Ki = 4.29 μM, and therefore being twice as active as gold standard galantamine hydrobromide. The best inhibitor for acetylcholinesterase, however, was 2-methyl-3-oxo-methyl-ursoloate (18), acting as a mixed-type inhibitor showing Ki = 1.72 µM and Ki' = 1.28 μM, respectively.

Synthesis and structure-activity relationship studies of water-soluble β-cyclodextrin-glycyrrhetinic acid conjugates as potential anti-influenza virus agents

Glycyrrhetinic acid (GA) is a major constituent of the herb Glycyrrhiza glabra, and many of its derivatives demonstrate a broad spectrum of antiviral activities. In the current study, 18 water-soluble β-cyclodextrin (CD)-GA conjugates, in which GA was covalently coupled to the primary face of β-CD using 1,2,3-triazole moiety along with varying lengths of linker, were synthesized via copper-catalyzed azide-alkyl cycloaddition reaction. Benefited from the attached β-CD moiety, all these conjugates showed lower hydrophobicity (AlogP) compared with their parent compound GA. With the exception of per-O-methylated β-CD-GA conjugate (35), all other conjugates showed no significant cytotoxicity to MDCK cells, and these conjugates were then screened against A/WSN/33 (H1N1) virus using the cytopathic effect assay. The preliminary results indicated that six conjugates showed promising antiviral activity, and the C-3 and C-30 of GA could tolerate some modifications. Our findings suggested that GA could be used as a lead compound for the development of potential anti-influenza virus agents.

Investigation of salicylanilide and 4-chlorophenol-based N-monosubstituted carbamates as potential inhibitors of acetyl- and butyrylcholinesterase

Based on the presence of carbamate moiety, twenty salicylanilide N-monosubstituted carbamates concomitantly with their parent salicylanilides and five newly prepared 4-chlorophenyl carbamates obtained from isocyanates were investigated using Ellman's method for their in vitro inhibitory activity against acetylcholinesterase (AChE) from electric eel and butyrylcholinesterase (BChE) from equine serum. The carbamates and salicylanilides exhibited mostly a moderate inhibition of both cholinesterase enzymes with IC₅₀ values ranging from 5 to 235 µM. IC₅₀ values for AChE were in a narrower concentration range when compared to BChE, but many of the compounds produced a balanced inhibition of both cholinesterases. The derivatives were comparable or superior to rivastigmine for AChE inhibition, but only a few of carbamates also for BChE. Several structure-activity relationships were identified, e.g., N-phenethylcarbamates produce clearly favourable BChE inhibition. The compounds also share convenient physicochemical properties for CNS penetration.

Derivatization, molecular docking and in vitro acetylcholinesterase inhibitory activity of glycyrrhizin as a selective anti-Alzheimer agent

Acetylcholinesterase inhibitors (AChE-Is) increase both level and duration of action of acetylcholine (ACh); thus, alleviate symptoms of Alzheimer's disease (AD). Glycyrrhizin, is the main active compound in liquorice root. Its aglycone, glycyrrhetinic acid, has shown several beneficial pharmacological activities. This study reports the synthesis and screening of a series of glycyrrhetinic acid analogs as AChE-Is. Fourteen derivatives were prepared, of which five derivatives are recorded as new viz., 3-phenyl-carbamoyl-18β-glycyrrhetinic acid (J9), 3-acetyl-18β-glycyrrhetinic-30-anilinamide (J10), 3-acetyl-18β-glycyrrhetinic-30-ethanolamide (J11), 3-acetyl-18β-glycyrrhetinic-30-n-butylamide (J12) and 18β-glycyrrhetinic acid-30-prenyl ester (J14), in addition to nine known derivatives (J1-J8 & J13). Compounds J12, J11, J0 and J3 showed remarkable AChE-I activity with IC₅₀ values of 3.43, 5.39, 6.27 and 8.68 μM, respectively. These results are in full agreement with the docking study. The active compounds were non-cytotoxic to normal cells (WI-38).

Synthesis of new sarsasapogenin derivatives with antiproliferative and apoptotic effects in MCF-7 cells

Sarsasapogenin, a kind of mainly effective component of Anemarrhena asphodeloides Bunge, possesses good antitumor properties. Two series of new sarsasapogenin derivatives were synthesized and evaluated for their cytotoxicities against three human cancer cell lines (HepG2, A549, MCF-7) using the MTT assay. The structure-activity relationship revealed that the N, N-dimethylamino, pyrrolidinyl, and imidazolyl substituted at the C26 position could increase the antitumor efficacy of the 3-oxo sarsasapogenin series of compounds. Compound 4c with pyrrolidinyl substituted at the C26 position exhibited the greatest cytotoxic activity against MCF-7 cell line (IC₅₀ = 10.66 μM), which was 4.3-fold more potent than sarsasapogenin. Action mechanism investigations showed that 4c could inhibit the colony formation and induce the apoptosis of MCF-7 cells. Further researches showed that a decrease in mitochondrial membrane potential and increases in the expression level of cleaved-PARP and the ratio of Bax/Bcl-2 were observed in MCF-7 cells after treatment with 4c, suggesting that the mitochondrial pathway was involved in the 4c-mediated apoptosis. These results show that compound 4c may serve as a lead for further optimization.

Compound Schisandra-Ginseng-Notoginseng-Lycium Extract Ameliorates Scopolamine-Induced Learning and Memory Disorders in Mice

Schisandra, Ginseng, Notoginseng, and Lycium barbarum are traditional Chinese medicinal plants sharing cognitive-enhancing properties. To design a functional food to improve memory, we prepared a compound Schisandra-Ginseng-Notoginseng-Lycium (CSGNL) extract and investigated its effect on scopolamine-induced learning and memory loss in mice. To optimize the dose ratios of the four herbal extracts in CSGNL, orthogonal experiments were performed. Mice were administered CSGNL by gavage once a day for 30 days and then mouse learning and memory were evaluated by Morris water maze and step-through tests. The mechanisms of CSGNL improving learning and memory were investigated by assaying acetylcholine (ACh) levels and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in the brain tissues of treated mice. The results showed that CSGNL significantly ameliorated scopolamine-induced learning and memory impairment, at least in part, by modulating ACh levels and ChAT and AChE activities in the mouse brain. Our data support the use of CSGNL as a functional food for learning and memory enhancement.

Synthesis, characterization and in vitro evaluation of substituted N-(2-phenylcyclopropyl)carbamates as acetyl- and butyrylcholinesterase inhibitors

A serie of O-substituted N-2-phenylcyclopropylcarbamates was prepared and characterized. These carbamates were tested as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). It was found, that these compounds exhibit moderate inhibition activity with values of IC₅₀ in the range of 54.8-94.4 μM (for AChE) and up to 5.8 μM (for BChE). The AChE/BChE selectivity for each carbamate was calculated. These values varied from 0.50 to 9.46, two carbamate derivatives inhibited only AChE selectively. The most promising derivative was prepared in all optically pure forms (four isomers). It was found that individual stereoisomers differed only slightly in the inhibition ability. The cytotoxicity of all carbamates was evaluated using the standard in vitro test with Jurkat cells. With regard to their inhibition activity and cytotoxicity as well as easy preparation, O-substituted N-2-phenylcyclopropylcarbamates can be considered as promising compounds for potential medicinal applications.

Design, synthesis, and evaluation of 2-piperidone derivatives for the inhibition of β-amyloid aggregation and inflammation mediated neurotoxicity

A series of novel multipotent 2-piperidone derivatives were designed, synthesized and biologically evaluated as chemical agents for the treatment of Alzheimer's disease (AD). The results showed that most of the target compounds displayed significant potency to inhibit Aβ(1-42) self-aggregation. Among them, compound 7q exhibited the best inhibition of Aβ(1-42) self-aggregation (59.11% at 20 μM) in a concentration-dependent manner. Additionally, the compounds 6b, 7p and 7q as representatives were found to present anti-inflammation properties in lipopolysaccharide (LPS)-induced microglial BV-2 cells. They could effectively suppress the production of pro-inflammatory cytokines such as TNF-α, IL-1β and IL-6. Meanwhile, compound 7q could prevent the neuronal cell SH-SY5Y death by LPS-stimulated microglia cell activation mediated neurotoxicity. The molecular modeling studies demonstrated that compounds matched the pharmacophore well and had good predicted physicochemical properties and estimated IC50 values. Moreover, compound 7q exerted a good binding to the active site of myeloid differentiation factor 88 (MyD88) through the docking analysis and could interfere with its homodimerization or heterodimerization. Consequently, these compounds emerged as promising candidates for further development of novel multifunctional agents for AD treatment.

Novel Cholinesterase Inhibitors Based on O-Aromatic N,N-Disubstituted Carbamates and Thiocarbamates

Based on the presence of carbamoyl moiety, twenty salicylanilide N,N-disubstituted (thio)carbamates were investigated using Ellman's method for their ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). O-Aromatic (thio)carbamates exhibited weak to moderate inhibition of both cholinesterases with IC50 values within the range of 1.60 to 311.0 µM. IC50 values for BChE were mostly lower than those obtained for AChE; four derivatives showed distinct selectivity for BChE. All of the (thio)carbamates produced a stronger inhibition of AChE than rivastigmine, and five of them inhibited BChE more effectively than both established drugs rivastigmine and galantamine. In general, 5-chloro-2-hydroxy-N-[4-(trifluoromethyl)-phenyl]benzamide, 2-hydroxy-N-phenylbenzamide as well as N-methyl-N-phenyl carbamate derivatives led to the more potent inhibition. O-{4-Chloro-2-[(4-chlorophenyl)carbamoyl]phenyl} dimethylcarbamothioate was identified as the most effective AChE inhibitor (IC50 = 38.98 µM), while 2-(phenylcarbamoyl)phenyl diphenylcarbamate produced the lowest IC50 value for BChE (1.60 µM). Results from molecular docking studies suggest that carbamate compounds, especially N,N-diphenyl substituted representatives with considerable portion of aromatic moieties may work as non-covalent inhibitors displaying many interactions at peripheral anionic sites of both enzymes. Mild cytotoxicity for HepG2 cells and consequent satisfactory calculated selectivity indexes qualify several derivatives for further optimization.

Unprecedented copper-mediated oxidative demethylation of propionamides via bidentate-chelation assistance

The copper-mediated bidentate-chelation directing group assisted oxidative demethylation of substituted propionamides was developed for the first time.

Design, synthesis and bioactivity of novel phthalimide derivatives as acetylcholinesterase inhibitors

A series of novel phthalimide derivatives related to benzylpiperazine were synthesized and evaluated as cholinesterase inhibitors. The results showed that all compounds were able to inhibit acetylcholinesterase (AChE), with two of them dramatically inhibiting butyrylcholinesterase (BuChE). Most compounds exhibited potent anti-AChE activity in the range of nM concentrations. In particular, compounds 7aIII and 10a showed the most potent activity with the IC50 values of 18.44 nM and 13.58 nM, respectively. To understand the excellent activity of these compounds, the structure-activity relationship was further examined. The protein-ligand docking study demonstrated that the target compounds have special binding modes and these results are in agreement with the kinetic study.

Allobetulin derived seco-oleananedicarboxylates act as inhibitors of acetylcholinesterase

Ring opening of allobetulone gave either seco-acid 8 or di-acid 4. These acids were converted into esters that were screened by Ellman's assay. A dibutenylester of low cytotoxicity (NIH 3T3 murine embryonic fibroblasts) was shown to be a good mixed-type inhibitor (Ki=3.39, Ki'=2.26μM) for acetylcholinesterase.