Acetyl and butyrylcholinesterase-inhibiting triterpenoid alkaloids from Buxus papillosa

Pharmacological and phytochemical properties of the genus Buxus: A review

BACKGROUND

Buxus plants have been used in traditional medicine for a very long time. The Buxus genus has been used to cure a variety of illnesses.

OBJECTIVE

This review aimed to provide a literature review on the genus Buxus including its biological and phytochemical properties.

MATERIALS AND METHODS

The current study was conducted using several scientific databases. Correct plant names were verified from plantlist.org. The results of this search were interpreted, analyzed, and documented based on the obtained bibliographic information.

RESULTS

Within all the species of the family Buxaceae, 5 species of the genus Buxus are reported to be antibacterial, 3 species have been found to be antioxidant, 5 species are cytotoxic, 1 species is anti-inflammatory, 1 species is antidiabetic, and 4 species are antifungal. Alkaloids, terpenoids, tannins, flavonoids, peptides, and phenolic compounds are the main chemical components of this genus. The study of >11 Buxuss pecies has identified >201 compounds. Pharmacological research has demonstrated that crude extracts and some pure compounds obtained from Buxus have several pharmacological activities such as antibacterial, antioxidant, cytotoxic, anti-inflammatory, antidiabetic, and antifungal. Based on the study of the phytochemistry of Buxus species, it was concluded that all the studied plants have active compounds, among which 55 molecules showed interesting activities.

CONCLUSIONS

The numerous traditional uses of Buxus species have been supported by several studies. Before Buxus plants can be fully employed clinically, further research is necessary.

Structurally diverse alkaloids from the Buxus sinica and their cytotoxicity

Extensive phytochemical study of the methanol extract of twigs and leaves of Buxus sinica resulted in the identification of forty-one Buxus alkaloids, including twenty undescribed ones, namely cyclobuxusinines A-I (1-7, 16 and 20), as well as secobuxusinines A-K (8-15 and 17-19). Their structures were delineated by detailed analysis using various spectroscopic techniques. cyclobuxusinines B (2) was the first Buxus alkaloid, whose CH3-18 was oxidized, implying the presence of special oxidative enzymes in this plant. Secobuxusinines C (10), D (11), and E (12), whose C-12 or C-19 have an OH group substitution, enriched the substituent pattern in Buxus alkaloid and suggested more structurally diverse alkaloids in the Buxus spp. In the assessment of their bioactivities, some of them exhibited significant cytotoxic effects on two human tumor ovarian cancer cell lines. Notably, compound 36 displayed more potent cytotoxic effect against ES2 and A2780 cell lines with the IC50 value of 1.33 μM and 0.48 μM, respectively.

Review of Pharmacotherapeutic Targets in Alzheimer's Disease and Its Management Using Traditional Medicinal Plants

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and impaired daily functioning. While there is currently no cure for AD, several pharmacotherapeutic targets and management strategies have been explored. Additionally, traditional medicinal plants have gained attention for their potential role in AD management. Pharmacotherapeutic targets in AD include amyloid-beta (Aβ) aggregation, tau protein hyperphosphorylation, neuroinflammation, oxidative stress, and cholinergic dysfunction. Traditional medicinal plants, such as Ginkgo biloba, Huperzia serrata, Curcuma longa (turmeric), and Panax ginseng, have demonstrated the ability to modulate these targets through their bioactive compounds. Ginkgo biloba, for instance, contains flavonoids and terpenoids that exhibit neuroprotective effects by reducing Aβ deposition and enhancing cerebral blood flow. Huperzia serrata, a natural source of huperzine A, has acetylcholinesterase-inhibiting properties, thus improving cholinergic function. Curcuma longa, enriched with curcumin, exhibits anti-inflammatory and antioxidant effects, potentially mitigating neuroinflammation and oxidative stress. Panax ginseng's ginsenosides have shown neuroprotective and anti-amyloidogenic properties. The investigation of traditional medicinal plants as a complementary approach to AD management offers several advantages, including a lower risk of adverse effects and potential multi-target interactions. Furthermore, the cultural knowledge and utilization of these plants provide a rich source of information for the development of new therapies. However, further research is necessary to elucidate the precise mechanisms of action, standardize preparations, and assess the safety and efficacy of these natural remedies. Integrating traditional medicinal-plant-based therapies with modern pharmacotherapies may hold the key to a more comprehensive and effective approach to AD treatment. This review aims to explore the pharmacotherapeutic targets in AD and assess the potential of traditional medicinal plants in its management.

Natural coumarins from Murraya paniculata as mixed-type inhibitors of cholinesterases: In vitro and in silico investigations

Currently, acetylcholinesterase (AChE) inhibiting drugs in clinical use, such as tacrine, donepezil, rivastigmine, and galanthamine, are associated with serious side effects and short half-lives. In recent years, numerous phytochemicals have been identified as inhibitors of cholinesterases with potential applications in the management of Alzheimer’s disease (AD). In this study three natural coumarins, 2′-O-ethylmurrangatin (1), murranganone (2), and paniculatin (3) isolated previously by our group from the leaves of Murraya paniculata, were tested against the two cholinesterases (ChE) enzymes, AChE and butyrylcholinesterase (BChE) using in vitro assay. Molecular docking was performed to highlight the structural properties that contribute to the molecular recognition pattern in the inhibition of ChE and the structural differences resulting in the selectivity of these compounds toward AChE. Classical enzyme inhibition kinetics data suggested that compounds 2 and 3 were potent inhibitors of AChE and BChE, while 1 was found inactive against both enzymes. The findings from molecular docking studies revealed the competitive and non-competitive inhibition mechanisms of compounds 2 and 3 against both enzymes. Molecular docking and simulations have revealed that hydrogen bonding, mediated by ketone and hydroxyl functionalities in various positions, significantly contributes to the binding of the inhibitor to the receptor. According to MD simulation studies, the stability of the ligand-AChE complex for the most active compound (3) is found to be comparable to that of the widely used drug Tacrine. In addition, to evaluate the drug-likeness of compounds, in silico ADME evaluation was performed, and the compounds presented good ADME profiles. Data suggested that the coumarin nucleus having diverse side chains at the C-8 position can serve as a potential inhibitor of cholinesterases and can act as a lead to develop a new semisynthetic drug for the treatment of AD.

Chemistry and bioactivities of natural steroidal alkaloids

Steroidal alkaloids possess the basic steroidal skeleton with a nitrogen atom in rings or side chains incorporated as an integral part of the molecule. They have demonstrated a wide range of biological activities, and some of them have even been developed as therapeutic drugs, such as abiraterone acetate (Zytiga^®), a blockbuster drug, which has been used for the treatment of prostate cancer. Structurally diverse natural steroidal alkaloids present a wide spectrum of biological activities, which are attractive for natural product chemistry and medicinal chemistry communities. This review comprehensively covers the structural classification, isolation and various biological activities of 697 natural steroidal alkaloids discovered from 1926 to October 2021, with 363 references being cited.

Evaluation of Cholinesterase Inhibitory Potential of Different Genotypes of Ziziphus nummularia, Their HPLC-UV, and Molecular Docking Analysis

Ziziphus nummularia is an important source of valuable phytoconstituents, which are widely used in traditional medicine system of Indo-Pak sub-continent. In this study we investigated the distribution of phenolic compounds in the fruit pericarps of six different genotypes (ZNP01-06) of Z. nummularia growing in the unexplored hilly areas of Pakistan. The methanolic extracts of these genotypes were screened for total phenolic content (TPC), total flavonoid content (TFC), antioxidant, and cholinesterase inhibitory potentials. The observed biological potentials were explained in terms of the outcome of molecular docking and HPLC analyses. Among them, genotype ZNP02 displayed high TPC (88.50 ± 1.23 μg/mL) and showed potent scavenging activity against DPPH (67.03 ± 1.04 μg/mL) and ABTS (65.3 ± 1.74 μg/mL) in comparison to ascorbic acid (68.7 ± 0.47 μg/mL). Moreover, genotypes ZNP01, ZNP02, and ZNP04 displayed potent inhibition against acetyl and butyryl cholinesterases (AChE and BChE) with IC50 values of 21.2, 20.5, and 23.7 μg/mL (AChE) and 22.7, 24.4, and 33.1 μg/mL (BChE), respectively. Furthermore, the individual compounds in the most potent species ZNP01 responsible for potent enzyme inhibition (identified through HPLC-UV analysis), were computed via docking simulation software to the enzyme structures. Among these compounds rutin exhibited significant binding affinity with value of -9.20 kcal/mol. The differences amongst the phytochemical compositions of the selected genotypes highlighted the genotypic variations in them. Based on our results it was concluded that the selected plant can be used as remedy of oxidative stress and neurodegenerative diseases. However, further studies are needed to isolate responsible compounds and test the observed potential in vivo, along with toxicological evaluations in animal models.

In silico study for prediction of novel bioactivities of the endophytic fungal alkaloid, mycoleptodiscin B for human targets

Mycoleptodiscin B is a natural product extracted from the endophytic fungus Mycoleptodiscus sp. found in Sri Lanka and Panama with experimentally unexplored activities for human targets. In this study, a computational methodology was applied to determine druggable targets of mycoleptodiscin B. According to the computational toxicity and pharmacokinetics assessment, mycoleptodiscin B was proven to be a suitable drug candidate. Druggable targets for this compound, aromatase, acidic plasma glycoprotein and androgen receptor, were predicted using reverse docking. A two-step validation of those targets was performed using conventional molecular docking and molecular dynamic (MD) simulations, resulting in aromatase being determined as the potential therapeutic target. Based on molecular mechanics/Generalized Born Surface Area (GBSA) free energies and ligand stability inside the active site cavity during its 120 ns MD run, it can be concluded that mycoleptodiscin B is a potent aromatase inhibitor and could be subjected to further in vitro and in vivo experiments in the drug development pipeline. Consequently, natural product chemists can quickly identify the hidden medicinal properties of their miracle compounds using the computational approach applied in this research.

Taxonomic Distribution of Medicinal Plants for Alzheimer’s Disease: A Cue to Novel Drugs

Alzheimer’s disease (AD) is a neurodegenerative disorder manifested by decline in memory and mild cognitive impairment leading to dementia. Despite global occurrence of AD, the severity and hence onset of dementia vary among different regions, which was correlated with the customary use of medicinal herbs and exposure level to the causatives. In spite of execution of versatile therapeutic strategies to combat AD and other neurodegenerative diseases, success is only limited to symptomatic treatment. The role of natural remedies remained primitive and irreplaceable in all ages. In some examples, the extracted drugs failed to show comparable results due to lack of micro ingredients. Micro ingredients impart a peerless value to natural remedies which are difficult to isolate and/or determine their precise role during treatment. A variety of plants have been used for memory enhancement and other dementia-related complications since ages. Acetyl choline esterase inhibition, antioxidant potential, neuroprotection, mitochondrial energy restoration, and/or precipitated protein clearance put a vast taxonomic variety into a single group of anti-AD plants. Secondary metabolites derived from these medicinal plants have the potential to treat AD and other brain diseases of common pathology. This review summarizes the potential of taxonomically diverse medicinal plants in the treatment of AD serving as a guide to further exploration.

Secondary Metabolites Profiling, Biological Activities and Computational Studies of Abutilon figarianum Webb (Malvaceae)

This research endeavors to inspect the chemical and biological profiling of methanol and dichloromethane (DCM) extracts prepared from Abutilon figarianum Webb. Total bioactive constituents and secondary metabolites were assessed via ultra-high performance liquid chromatography (UHPLC-MS). Biological effects were evaluated via antioxidant and enzymes inhibitory assays. The methanol extract was able to give the highest phenolic (51.92 mg GAE/g extract) and flavonoid (72.59 mg QE/g extract) contents and was found to contain 11 bioactive metabolites, including flavonoid, alkaloid, phenolic and fatty acid derivatives, as accessed by UHPLC-MS analysis. Similarly, the phytochemical profiling of the DCM extract tentatively identified the 12 different secondary metabolites, most of these were fatty acid derivatives. The methanol extract was most active in the radical scavenging, reducing power and total antioxidant power assays, while dichloromethane extract showed the highest metal chelating activity. For enzyme inhibition, the DCM extract showed the highest activity against cholinesterases, glucosidase and amylase, whereas methanol extract was most active against tyrosinase. Docking studies have supported the observed biological activity, where isobergapten showed higher activity against tyrosinase (−7.63 kcal/mol) with inhibition constant (2.55 µM), as opposed to other enzymes. The observed antioxidant and inhibitory potentials of A. figarianum against the studied enzymes tend to endorse this plant as a prospective source of bioactive phytochemicals.

Buxaustroines A-N, a Series of 17(13→18)abeo-Cycloartenol Triterpenoidal Alkaloids from Buxus austro-yunnanensis and Their Cardioprotective Activities

Buxaustroines A-N (1-14), a series of triterpenoidal alkaloids featuring a novel 17(13→18)abeo motif, were obtained from the extract of Buxus austro-yunnanensis. Their structures were assigned based on NMR data analysis and X-ray diffraction crystallography. A putative biosynthetic pathway for one of the alkaloids from a co-isolate 15 is proposed. In the assessment of their bioactivities, some of the compounds displayed protective effects against doxorubicin-induced injury of myocardial cells. Preliminary structure-activity relationship studies of 1-14, which are based on the same skeleton, were conducted.

Acetylcholinesterase inhibitory activities and bioguided fractionation of the Ocotea percoriacea extracts: HPLC-DAD-MS/MS characterization and molecular modeling of their alkaloids in the active fraction

In vitro acetylcholinesterase activities of the hexane, dichloromethane, ethyl acetate, n-butanol and aqueous extracts of leaves of Ocotea percoriacea Kosterm. (Lauraceae) were evaluated. The bioguided fractionation of the most active extract (dichloromethane) using silica gel open-column chromatography led to an active alkaloidal fraction composed of isocorydine N-oxide, isocorydine N-oxide derivative, palmatine, roemerine and roemerine N-Oxide. The identification of the chemical structure of these compounds was carried out with high-performance liquid chromatography coupled to electrospray ionization multiple-stage mass spectrometry (HPLC-ESI-MS/MS). Aiming to understand their inhibitory activities, these alkaloids were docked into a 3D model of Electrophorus electricus Acetylcholinesterase (EelAChE) built in the Modeller 9.18 employing homology modeling approach. The results suggest that the alkaloids had the same binding mode and, possibly, the inhibition mechanism of classic drugs (ex. tacrine and donepezil). The structural difference of these compounds opens a new opportunity for the optimization of leading compounds.

An ethnobotanical study of medicinal plants used to treat skin diseases in northern Pakistan

Background

Skin diseases are a major health concern especially in association with human immune deficiency syndrome and acquired an immune deficiency. The aim of this study was to document the ethnomedicinal information of plants used to treat skin diseases in Northern Pakistan. This is the first quantitative ethnobotanical study of therapeutic herbs utilized by the indigenous people of Northern Pakistan for skin diseases.

Methods

Interviews were taken to obtain information from 180 participants. Quantitative methods including fidelity level (FL), Frequency of citation (FC), Use-value (UV), Jaccard indices (JI), Family importance value (FIV), Relative frequency of citation (RFC) and Chi-square test were applied. Medicinal plants uses are also compared with 50 national and international publications.

Results

In this study, we recorded 106 plant species belonged to 56 floral families for treatment of skin ailments. The dominant life form reported was herb while the preferred method of utilization was powder, along with leaf as the most used plant part. RFC ranges from 0.07 to 0.25% whereas the highest FIV was recorded for family Pteridaceae. FL values range from 36.8 to 100%. The study reported 88% of new plant reports for the treatment of skin diseases.

Conclusion

The present study revealed the importance of several plants used to treat skin diseases by the local communities of Northern Pakistan. The available literature supported the evidence of plant dermatological properties. Plants having high UV and RFC can be considered for further scientific analysis. There is dire need to create awareness among local, government and scientific communities for the preservation of medicinal species and ethnomedicinal knowledge in Northern Pakistan.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2605-6) contains supplementary material, which is available to authorized users.

Pharmacological, phytochemical and in-vivo toxicological perspectives of a xero-halophyte medicinal plant: Zaleya pentandra (L.) Jeffrey

This study endeavours to investigate the phytochemical composition, biological properties and in vivo toxicity of methanol and dichloromethane extracts of Zaleya pentandra (L.) Jeffrey. Total bioactive contents, antioxidant (phosphomolybdenum and metal chelating, DPPH, ABTS, FRAP and CUPRAC) and enzyme inhibition (cholinesterases, tyrosinase α-amylase, and α-glucosidase) potential were assessed utilizing in vitro bioassays. UHPLC-MS phytochemical profiling was carried out to identify the essential compounds. The methanol extract was found to contain highest phenolic (22.60 mg GAE/g) and flavonoid (31.49 mg QE/g) contents which correlate with its most significant radical scavenging, reducing potential and tyrosinase inhibition. The dichloromethane extract was most potent for phosphomolybdenum, ferrous chelation, α-amylase, α-glucosidase, and cholinesterase inhibition assays. UHPLC-MS analysis of methanol extract unveiled to identify 11 secondary metabolites belonging to five sub-groups, i.e., phenolic, alkaloid, carbohydrate, terpenoid, and fatty acid derivatives. Additionally, in vivo toxicity was conducted for 21 days and the methanol extract at different doses (150, 200, 250 and 300 mg/kg) was administered in experimental chicks divided into five groups each containing five individuals. Different physical, haematological and biochemical parameters along with the absolute and relative weight of visceral body organs were studied. Overall, no toxic effect was noted for the extract at tested doses.

Study of Antihyperglycemic, Antihyperlipidemic and Antioxidant Activities of Tannins Extracted from Warionia saharae Benth. & Coss

Methods:

Tannins (TE) were extracted from W. saharae using Soxhlet apparatus and different organic solvents. Single and once daily repeated oral administration of TE (10 mg/kg) for 15 days were used to evaluate the glucose and lipid-lowering activity in normal and diabetic rats. Furthermore, glucose test tolerance, liver histopathological examination and in vitro antioxidant activity of TE were carried out in this study.

Results:

The results showed that TE was able to exert antihyperglycemic and lowering total cholesterol effects as well as improvement of the high-density lipoprotein (HDL)-cholesterol serum level after 15 days of treatment. Furthermore, TE improved glucose tolerance, histopathological status of liver in diabetic rats and demonstrated interesting antioxidant activity.

Conclusion:

In conclusion, the present investigation revealed that TE possesses potent antidiabetic and antihyperlipidemic activities as claimed in different ethnopharmacological practices.

Cassia tora Linn.: A boon to Alzheimer's disease for its anti-amyloidogenic and cholinergic activities

BACKGROUND

Drug discovery from natural products as alternatives for Alzheimer's disease (AD) is a current trend. For which plant is an alternative for searching potential molecule for treating AD. Availability of Cassia tora as weed and abundance in nature makes it as potential source. Many plants group under Leguminosae family has potential medicinal property of which Cassia tora is an appropriate choice, to know potency against AD. Etiology of AD is described by senile plaques and neurofibrillary tangles. The Aβ₄₂ has key major role in forming plaques by forming structures like protobirils, oligomers and final fibrilar like structures. Even at in vitro conditions, the peptides have a fibrilar like structure, which was exploited to preliminary screening of natural sources that may be effective in treating AD.

HYPOTHESIS/PURPOSE

The design of the study was to unravel the potential medicinal property of Cassia tora for its antioxidant, cholinergic and aggregation inhibition activity.

STUDY DESIGN

We evidenced that the methanol (MeOH), n-hexane (n-hex), petroleum ether (PE) and aqueous (aq) extracts from the leaves of Cassia tora (C. tora) were investigated for their inhibitory activity against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and anti-amyloidogenic assays. The antioxidant effect using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, total phenolic and flavonoid contents of the extracts were determined using Folin-Ciocaltaeu's and aluminum chloride (AlCl₃) reagents, respectively.

RESULTS

The methanol extract of C. tora exerted the highest inhibition against AChE (55.38 ± 2.28%) and BChE inhibition (50.02 ± 0.79%) at 100µg/ml concentration. The methanol extract was also found more active in the antioxidant test. The aggregation kinetics was monitored using thioflavin-T (ThT) assay and transmission electron microscopy (TEM) technique.

CONCLUSION

The results showed that C. tora methanol extract is able to inhibit the Aβ₄₂ aggregation from monomers and oligomers and also able to dis-aggregate the pre-formed fibrils. The study provides an insight on finding new natural products for AD therapeutics.

Antispasmodic, bronchodilator, vasorelaxant and cardiosuppressant effects of Buxus papillosa

Background

The present research was carried out to investigate pharmacological properties of Buxus papillosa C.K. Schneid. (Buxaceae).

Methods

Buxus papillosa extracts of leaves (BpL), stem (BpS), roots (BpR) and BpL fractions: hexane (BpL-H), aqueous (BpL-A) also plant constituent, cyclomicrobuxine effect were studied in jejunum, atria, aorta and tracheal preparations from rabbit and guine-peg.

Results

Ca⁺⁺ antagonistic effect of BpS, BpR, BpL-H, BpL-A and cyclomicrobuxine were conclusively suggested, when spontaneous contractions of rabbit jejunal preparation was relaxed along with subsequent relaxation of potassium chloride (80 mM) induced contractions. Ca⁺⁺ antagonistic effect was further confirmed, when a prominent right shift like that of verapamil was observed in Ca⁺⁺ concentration-response curves, drawn in a tissue pretreated with BpL (0.3–1.0 mg/mL). In rabbit tracheal tissues BpL, BpS, BpR, BpL-H and BpL-A produced a prominent relaxation in contractions induced by potassium chloride (80 mM) and carbachol (1 μm). When tested in rabbit aortic rings, BpL, BpS, BpR, BpL-H and BpL-A showed concentration-dependent (0.1–3.0 mg/mL) vasorelaxant effect against phenylephrine (1 μM) and high K⁺-induced contractions. In isolated guinea-pig right atria, BpL, BpS, BpR, BpL-H and BpL-A suppressed atrial force of spontaneous contractions, with BpL-A being most potent.

Conclusions

Our results reveal that Buxus papillosa possesses gut, airways and cardiovascular inhibitory actions.

New Trends and Perspectives in the Evolution of Neurotransmitters in Microbial, Plant, and Animal Cells

The evolutionary perspective on the universal roles of compounds known as neurotransmitters may help in the analysis of relations between all organisms in biocenosis-from microorganisms to plant and animals. This phenomenon, significant for chemosignaling and cellular endocrinology, has been important in human health and the ability to cause disease or immunity, because the "living environment" influences every organism in a biocenosis relationship (microorganism-microorganism, microorganism-plant, microorganism-animal, plant-animal, plant-plant and animal-animal). Non-nervous functions of neurotransmitters (rather "biomediators" on a cellular level) are considered in this review and ample consideration is given to similarities and differences that unite, as well as distinguish, taxonomical kingdoms.

Quantification of steroidal alkaloids in Buxus papillosa using electrospray ionization liquid chromatography-triple quadrupole mass spectrometry

Buxus papillosa is one of the most extensively studied species of the genus Buxus known to possess steroidal alkaloids which can be used for assessing the various pharmacological activities of this plant. This paper describes the liquid chromatography-electrospray ionization triple quadrupole mass spectrometry (LC-ESI-QQQ-MS) method for the quantification of six steroidal alkaloids as chemical markers in the extracts of leaves, roots and stems of B. papillosa. Quantitative MS/MS analysis was carried out by optimization of the most sensitive transition for each analyte. This has yielded detection and quantification limits of 0.486-8.08 ng/mL and 1.473-24.268 ng/mL, respectively for all analytes. Linearity of response was also achieved and the regression coefficient found to be >0.99 for all analyzed compounds. The newly developed MRM (Multiple Reaction Monitoring) method showed excellent sensitivity for the quantification of steroidal alkaloids within 15 min run time. This paper describes the application of LC-QQQ-MS technique for steroidal alkaloids analysis in plant samples.

Cholinesterase inhibitors from botanicals

Alzheimer's disease (AD) is a progressive neurodegenerative disease, wherein a progressive loss of cholinergic synapses occurs in hippocampus and neocortex. Decreased concentration of the neurotransmitter, acetylcholine (ACh), appears to be critical element in the development of dementia, and the most appropriate therapeutic approach to treat AD and other form of dementia is to restore acetylcholine levels by inhibiting both major form of cholinesterase: Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Consequently, researches have focused their attention towards finding cholinesterase inhibitors from natural products. A large number of such inhibitors have been isolated from medicinal plants. This review presents a comprehensive account of the advances in field of cholinesterase inhibitor phytoconstituents. The structures of some important phytoconstituents (collected through www.Chemspider.com) are also presented and the scope for future research is discussed.

In vitro acetylcholinesterase activity of peptide derivatives isolated from two species of Leguminosae

CONTEXT

Cratylia mollis Martius ex Benth. and Cenostigma macrophyllum Tul. (Leguminosae) are both endemic Brazilian plants and they are used by the natives as medicinal plants, and the leaves of C. mollis are also employed as forage for cattle during the dry season of region.

OBJECTIVE

Isolation of the compounds responsible for the acetylcholinesterase (AChE) inhibition from the CHCl3 active extract.

MATERIALS AND METHODS

Two peptidic compounds were isolated by chromatographic techniques from the CHCl3 extract of the leaves of C. mollis and C. macrophyllum. They were identified by spectrometric data analysis (MS and NMR) and they were subjected to AChE inhibition employing Ellman's test.

RESULTS

The peptides were identified as N-benzoylphenylalaninoyl-phenlyalaninolacetate (aurentiamide acetate) (1) and N-benzoylphenylalaninyl-N-benzoylphenylalaninate (2). Both peptides 1 and 2 exhibit AChE inhibition, with IC50 values equal to 111.34 µM and 137.6 µM, respectively.

DISCUSSION AND CONCLUSION

Compound 1 (aurentiamide acetate) has rarely been isolated from the Leguminosae family, and N-benzoylphenylalaninyl-N-benzoylphenylalaninate (2) is a compound that has never previously been isolated from this family. Compound 1 is shown to be a potent inhibitor of AChE, with IC50 values similar to the physostigmine control (141.51 µM).

Alkaloids as a source of potential anticholinesterase inhibitors for the treatment of Alzheimer's disease

Objectives

The inhibition of acetylcholinesterase (AChE), the key enzyme in the breakdown of acetylcholine, is currently the main pharmacological strategy available for Alzheimer's disease (AD). In this sense, many alkaloids isolated from natural sources, such as physostigmine, have been long recognized as acetyl- and butyrylcholinesterase (BChE) inhibitors. Since the approval of galantamine for the treatment of AD patients, the search for new anticholinesterase alkaloids has escalated, leading to promising candidates such as huperzine A. This review aims to summarize recent advances in current knowledge on alkaloids as AChE and BChE inhibitors, highlighting structure–activity relationship (SAR) and docking studies.

Key findings

Natural alkaloids belonging to the steroidal/triterpenoidal, quinolizidine, isoquinoline and indole classes, mainly distributed within Buxaceae, Amaryllidaceae and Lycopodiaceae, are considered important sources of alkaloids with anti-enzymatic properties. Investigations into the possible SARs for some active compounds are based on molecular modelling studies, predicting the mode of interaction of the molecules with amino acid residues in the active site of the enzymes. Following this view, an increasing interest in achieving more potent and effective analogues makes alkaloids good chemical templates for the development of new cholinesterase inhibitors.

Summary

The anticholinesterase activity of alkaloids, together with their structural diversity and physicochemical properties, makes them good candidate agents for the treatment of AD.

Structure-fragmentation relationship and rapid dereplication of Buxus steroidal alkaloids by electrospray ionization-quadrupole time-of-flight mass spectrometry

RATIONALE

Tandem mass spectrometric studies of natural products revealed the identification of key fragments which can be helpful for their rapid dereplication in plant extracts utilizing a liquid chromatography/tandem mass spectrometry (LC/MS/MS) approach, particularly for the thermally labile compounds. The knowledge of the collision-induced dissociation (CID) fragmentation pattern of the molecule is essentially required prior to the analysis by LC/MS/MS.

METHODS

The fragmentation patterns of eleven Buxus steroidal alkaloids were studied by using a positive ion electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QqTOF-MS/MS) hybrid instrument. Chromatographic separation of a Buxus papillosa extract was achieved using a capillary HPLC system coupled with the mass instrument.

RESULTS

ESI-QqTOF-MS (positive ion mode) showed the presence of several characteristic fragments which can be used to rapidly identify various classes of Buxus steroidal alkaloids. The presence of a cyclopropane ring in the cycloartenol skeleton and the hydroxyl group at C-10 was found to effect on the fragmentation pattern and afford characteristic peaks. This study distinguishes between different types of Buxus steroidal alkaloids based on logical fragmentation pathways. This strategy was successfully applied in LC/ESI-QqTOF-MS/MS analysis of Buxus papillosa extract to investigate and characterize Buxus steroidal alkaloids and 14 compounds were identified as steroidal alkaloids.

CONCLUSIONS

The knowledge of the fragmentation pattern was used for the rapid identification of this bioactive group of biosynthetically unique steroidal alkaloids in complex plant extracts of Buxus species, especially in the absence of any reference material, by combining key fragments, exact mass measurements and relative abundances of diagnostic fragment ions.

Syringe test (modified larval immersion test): a new bioassay for testing acaricidal activity of plant extracts against Rhipicephalus microplus

We report a new bioassay "syringe test" (modified larval immersion test) for in vitro evaluation of acaricidal activity of crude plant extracts. Prepared syringes, containing eggs of tick, were incubated until 14 d after hatching of eggs, when the bioassay was performed on the larvae. Lethal concentrations for 50% of larvae (LC(50)), LC(90) and LC(99) values were calculated for each tested product. 95% confidence intervals for LC(50) were very narrow, indicating a high degree of repeatability for the new bioassay on larvae of R. microplus. Bioassays were applied to six crude aqueous-methanol extracts from five plants (Acacia nilotica, Buxus papillosa, Fumaria parviflora, Juniperus excelsa, and Operculina turpethum), of which three showed discernible effects. Twenty-four hours post exposure, LC(99) values were 11.9% (w/v) for F. parviflora, 20.8% (w/v) and 29.2% (w/v) for B. papillosa and A. nilotica, respectively. After six days of exposure these values were; 9.1% (w/v), 9.2% (w/v) and 15.5 (w/v) for F. parviflora, A. nilotica and B. papillosa, respectively.

Triterpenoid alkaloid derivatives from Buxus rugulosa

Four new triterpenoid alkaloid derivatives, buxrugulines A–D (1–4 ), together with four known ones (5–8 ), were isolated from the leaves and stems of Buxus rugulosa . The structures of compounds 1–4 were elucidated by NMR and MS spectroscopic analysis. All compounds were assayed for their cytotoxicities against HL-60, SMMC-7721, A549, MCF-7, and SW480 cells lines.

In silico modeling of the specific inhibitory potential of thiophene-2,3-dihydro-1,5-benzothiazepine against BChE in the formation of beta-amyloid plaques associated with Alzheimer's disease

Background

Alzheimer's disease, known to be associated with the gradual loss of memory, is characterized by low concentration of acetylcholine in the hippocampus and cortex part of the brain. Inhibition of acetylcholinesterase has successfully been used as a drug target to treat Alzheimer's disease but drug resistance shown by butyrylcholinesterase remains a matter of concern in treating Alzheimer's disease. Apart from the many other reasons for Alzheimer's disease, its association with the genesis of fibrils by β-amyloid plaques is closely related to the increased activity of butyrylcholinesterase. Although few data are available on the inhibition of butyrylcholinesterase, studies have shown that that butyrylcholinesterase is a genetically validated drug target and its selective inhibition reduces the formation of β-amyloid plaques.

Rationale

We previously reported the inhibition of cholinesterases by 2,3-dihydro-1, 5-benzothiazepines, and considered this class of compounds as promising inhibitors for the cure of Alzheimer's disease. One compound from the same series, when substituted with a hydroxy group at C-3 in ring A and 2-thienyl moiety as ring B, showed greater activity against butyrylcholinesterase than to acetylcholinesterase. To provide insight into the binding mode of this compound (Compound A), molecular docking in combination with molecular dynamics simulation of 5000 ps in an explicit solvent system was carried out for both cholinesterases.

Conclusion

Molecular docking studies revealed that the potential of Compound A to inhibit cholinesterases was attributable to the cumulative effects of strong hydrogen bonds, cationic-π, π-π interactions and hydrophobic interactions. A comparison of the docking results of Compound A against both cholinesterases showed that amino acid residues in different sub-sites were engaged to stabilize the docked complex. The relatively high affinity of Compound A for butyrylcholinesterase was due to the additional hydrophobic interaction between the 2-thiophene moiety of Compound A and Ile69. The involvement of one catalytic triad residue (His438) of butyrylcholinesterase with the 3'-hydroxy group on ring A increases the selectivity of Compound A. C-C bond rotation around ring A also stabilizes and enhances the interaction of Compound A with butyrylcholinesterase. Furthermore, the classical network of hydrogen bonding interactions as formed by the catalytic triad of butyrylcholinesterase is disturbed by Compound A. This study may open a new avenue for structure-based drug design for Alzheimer's disease by considering the 3D-pharmacophoric features of the complex responsible for discriminating these two closely-related cholinesterases.

Immunosuppressive activity of buxidin and E-buxenone from Buxus hyrcana

Buxidin (1) and E-Buxenone (2), steroidal alkaloids from Buxus hyrcana, are found to possess potent immunosuppressive properties. The activity was tested in vitro on oxidative burst, chemotaxis, T-cell proliferation, and cytokine production. Both compounds showed a significant immunomodulatory activity with clear suppressive effect on oxidative burst and chemotaxis in a dose-dependent manner. They also exhibited suppressive effect on the phytohemagglutinin-stimulated T-cell proliferation. The immunomodulatory activity was further confirmed by the suppression of IL-2 and IL-4 production. Furthermore, molecular docking studies were performed to investigate the binding mode of Buxidin (1) and E-Buxenone (2) with IL-2. Despite the structural differences between Buxidin (1) and E-Buxenone (2), docking results revealed that they adopt a similar binding pattern at the active site of the IL-2. A good agreement between practical and theoretic results indicates that the current docking study could provide an alternate tool for the structural optimization of recently identified ligand as more potent IL-2 inhibitors.

Screening for acetylcholinesterase inhibitory activity in cyanobacteria of the genus Nostoc

Fifty-four cyanobacterial strains of the genus Nostoc from different habitats were screened for acetylcholinesterase inhibitory activity. Water-methanolic extracts from freeze-dried biomasses were tested for inhibitory activity using Ellman's spectrophotometric method. Acetylcholinesterase inhibitory activity higher than 90% was found in the crude extracts of Nostoc sp. str. Lukesova 27/97 and Nostoc ellipsosporum Rabenh. str. Lukesova 51/91. Extracts from Nostoc ellipsosporum str. Lukesova 52/91 and Nostoc linckia f. muscorum (Ag.) Elenk. str. Gromov, 1988, CALU-980 inhibited AChE activity by 84.9% and 65.3% respectively. Moderate AChE inhibitory activity (29.1-37.5%) was found in extracts of Nostoc linckia Roth. str. Gromov, 1962/10, CALU-129, Nostoc muscorum Ag. str. Lukesova 127/97, Nostoc sp. str. Lhotsky, CALU-327 and Nostoc sp. str. Gromov, CALU-998. Extracts from another seven strains showed weak anti-AChE activities. The active component responsible for acetylcholinesterase inhibition was identified in a crude extract of Nostoc sp. str. Lukesova 27/97 using HPLC and found to occur in one single peak.

In vitro biological activity screening of Lycopodium complanatum L. ssp. chamaecyparissus (A. Br.) Doll

This article reports the results of selected biological activities, including anticholinesterase, antioxidant, antibacterial, antifungal and antiviral properties, of the petroleum ether, chloroform and methanol extracts as well as the alkaloid fraction of Lycopodium complanatum L. ssp. chamaecyparissus (A. Br.) Doll (LCC, Lycopodiaceae) growing in Turkey. Anticholinesterase effect of the extracts was tested against both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) at concentrations of 0.2 and 1 mg mL(-1) using microplate-reader assay based on Ellman method. Antioxidant activity of the LCC extracts was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging method at 0.2 mg mL(-1) using microplate-reader assay. Both DNA virus Herpes simplex (HSV) and RNA virus Parainfluenza (PI-3) were employed for antiviral assessment of LCC exracts using Madin-Darby Bovine Kidney and Vero cell lines. Antibacterial and antifungal activities of the extracts were screened against the bacteria: Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Acinobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis as well as the fungi: Candida albicans and C. parapsilosis. Only the petroleum ether extract of LCC possessed remarkable activity against both AChE and BChE at 1 mg mL(-1) (76.5 and 69.6%, respectively), whereas LCC extracts showed low free radical-scavenging activity. All of the extracts were found to be more effective against the ATCC strains than isolated ones, particularly S. aureus, while the extracts had moderate antifungal activity. On the other hand, we found that only the petroleum ether extract was active against HSV. In addition, we also analysed the content of the alkaloid fraction of the plant by capillary gas chromatography-mass spectrometry (GC-MS) and identified lycopodine as the major alkaloid (60.8%).

Acetylcholinesterase inhibitory activity and chemical composition of commercial essential oils

Commercially available essential oils extracted from Artemisia dracunculus L., Inula graveolens L., Lavandula officinalis Chaix, and Ocimum sanctum L. and the components of these oils were screened by the microplate assay method for determining their acetylcholinesterase (AChE) inhibitory activity. The composition profiles of the oils were characterized by gas chromatography-mass spectrometry (GC-MS) analysis, and the relationships between the oil components and the AChE inhibitory activity of the oils were outlined. The results showed that all of the oils, except that of A. dracunculus from Hungary, exhibited AChE inhibitory activity, and the A. dracunculus oil from France showed the most potent inhibitory activity [50% inhibition concentration (IC(50)) = 0.058 mg/mL]. The AChE inhibitory activity of I. graveolens oil has not been reported to date, and this study is the first to reveal this activity in the oil. Among the essential oil components, five components, namely, 1,8-cineole, α-pinene, eugenol, α-terpineol, and terpinen-4-ol, showed AChE inhibitory activity, with IC(50) values of 0.015, 0.022, 0.48, 1.3, and 3.2 mg/mL, respectively. Eugenol, in particular, was found to be a potent AChE inhibitor along with determination of the IC(50) value, a finding that has been reported for the first time in this study. However, the ratio of the contribution of the active components, including a novel AChE inhibitor, to the observed AChE inhibitory activity of the essential oils was not very high. The results of this study raise concerns about the AChE inhibitory activity of widely produced and readily accessible commercial essential oils.

Molecular interactions of cholinesterases inhibitors using in silico methods: current status and future prospects

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a low amount of acetylcholine (ACh) in hippocampus and cortex. Acetylcholinesterase (AChE) is one of the most important enzymes in many living organisms including human being and other vertebrates, insects like mosquitoes, among others. Several reports have been published where it has been clearly shown that the genesis of amyloid protein plaques associated with AD is connected to modifications of both AChE and butyrylcholinesterase (BChE), since the plaque is significantly decreased in AD patients using cholinesterase inhibitors (ChEIs). This review gives some examples of these inhibitors discovered during past couple of years that have shown very prominent interactions at the active site triad of the proteins as well as different other parts of the active site like, peripheral anionic site (PAS), oxyanionic hole, anionic subsite or acyl binding pocket (ABP). Most of the inhibition and their interactions have been visualized by X-ray crystallography, but some of the other inhibitors have been studied either by molecular docking or molecular dynamic (MD) simulations or by both the in silico methods. Some of these prominent studies have been crucially observed and reported here.

New natural cholinesterase inhibiting and calcium channel blocking quinoline alkaloids

During this study, one new coumarin; 7-O-beta-D-glucopyranoside-2H-1-benzopyran-2-one (1) and three quinoline alkaloids; 3-hydroxy, 2, 2, 6-trimethyl-3, 4, 5, 6-tetrahydro-2H-pyrano[3,2-c] quinoline 5-one (2), ribalinine (3) and methyl isoplatydesmine (4) were isolated from the aerial parts of Skimmia laureola and their structures established by spectroscopic studies. Compounds 2-4 were found to be linear mixed type inhibitors of acetylcholinesterase (K(i) = 110.0, 30.0 and 30.0 microM, respectively). Compounds 2 and 3 were also found to be linear mixed type inhibitors of butyrylcholinesterase, while compound 4 was a noncompetitive inhibitor of the enzyme (K(i) = 90.0, 70.0 and 19.0 microM, respectively). The inhibition of acetyl- and butyryl-cholinesterase enzymes persists as the most promising therapeutic strategy for activating the impaired cholinergic functions in Alzheimer's disease and related dementias. Compound 4 also showed dose-dependent spasmolytic activity in the isolated rabbit jejunum intestinal preparation by relaxing the spontaneous (EC50 = 0.1 mg/mL) and K(+)-induced contractions (EC50 = 0.4 mg/mL), suggesting that the spasmolytic effect of compound 4 is mediated through the blockade of voltage-dependent Ca2+ channels.

Short and Efficient Approach Towards Buxozine-C, an Alkaloid fromBuxus sempervirens

Buxus alkaloids display a wide range of interesting pharmacological activities. Here, we present a short and efficient approach towards one of the alkaloids, buxozine-C. The first synthesis has been achieved with 91% yield starting from cyclovirobuxine-D by forming a tetrahydro-oxazine ring with formaldehyde at room temperature.

Acetylcholinesterase inhibitors from plants and fungi

This review describes 183 compounds obtained from plants and fungi which have been shown to inhibit acetylcholinesterase. The mechanism of action of cholinesterase, together with the binding sites, and, where this is known, the mode of action of inhibitors is described. The relative activities of the different compounds are recorded. The strongest inhibitors are generally alkaloids although some meroterpenoids from fungi have also been found to be active and display better selectivity.

Withanolides, a new class of natural cholinesterase inhibitors with calcium antagonistic properties

The withanolides 1-3 and 4-5 isolated from Ajuga bracteosa and Withania somnifera, respectively, inhibited acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) enzymes in a concentration-dependent fashion with IC50 values ranging between 20.5 and 49,2 microm and 29.0 and 85.2 microm for AChE and BChE, respectively. Lineweaver-Burk as well as Dixon plots and their secondary replots indicated that compounds 1, 3, and 5 are the linear mixed-type inhibitors of AChE, while 2 and 4 are non-competitive inhibitors of AChE with K(i) values ranging between 20.0 and 45.0 microm. All compounds were found to be non-competitive inhibitors of BChE with K(i) values ranging between 27.7 and 90.6 microm. Molecular docking study revealed that all the ligands are completely buried inside the aromatic gorge of AChE, while compounds 1, 3, and 5 extend up to the catalytic triad. A comparison of the docking results showed that all ligands generally adopt the same binding mode and lie parallel to the surface of the gorge. The superposition of the docked structures demonstrated that the non-flexible skeleton of the ligands always penetrates the aromatic gorge through the six-membered ring A, allowing their simultaneous interaction with more than one subsite of the active center. The affinity of ligands with AChE was found to be the cumulative effects of number of hydrophobic contacts and hydrogen bonding. Furthermore, all compounds also displayed dose-dependent (0.005-1.0 mg/mL) spasmolytic and Ca2+ antagonistic potentials in isolated rabbit jejunum preparations, compound 4 being the most active with an ED50 value of 0.09 +/- 0.001 mg/mL and 0.22 +/- 0.01 microg/mL on spontaneous and K+ -induced contractions, respectively. The cholinesterase inhibitory potential along with calcium antagonistic ability and safe profile in human neutrophil viability assay could make compounds 1-5 possible drug candidates for further study to treat Alzheimer's disease and associated problems.

Structural basis of acetylcholinesterase inhibition by triterpenoidal alkaloids

Acetylcholinesterase plays a crucial role in the metabolism of neurotransmitter, acetylcholine. Inhibition of Torpedo californica acetylcholinesterase by triterpenoidal alkaloids buxamine-B (1) and buxamine-C (2) has been studied by enzyme kinetics and molecular docking experiments. Buxamine-C (2) has been found to be 20-fold potent than buxamine-B (1) (Ki = 5.5 and 110 microM, respectively). The ligand docking experiments predicted that the cyclopentanophenanthrene skeleton of both inhibitors properly fits into the aromatic gorge of the enzyme. The C-3 and C-20 amino groups of both alkaloids mimic the well-known bis-quaternary ammonium inhibitors such as decamethonium and interact with Trp84 and Trp279 residues of the enzyme, respectively. The C-3 amino group in buxamine-C (2) appears to be better positioned at the bottom of the aromatic gorge and thus seems to be crucial for the inhibitory activity of such inhibitors.