Indole alkaloids from Ervatamia hainanensis with potent acetylcholinesterase inhibition activities

Research progress of plant-derived natural alkaloids in central nervous system diseases

Central nervous system (CNS) disease is one of the most important causes of human death. Because of their complex pathogenesis, more and more attention has been paid to them. At present, drug treatment of the CNS is the main means; however, most drugs only relieve symptoms, and some have certain toxicity and side effects. Natural compounds derived from plants can provide safer and more effective alternatives. Alkaloids are common nitrogenous basic organic compounds found in nature, which exist widely in many kinds of plants and have unique application value in modern medicine. For example, Galantamine and Huperzine A from medicinal plants are widely used drugs on the market to treat Alzheimer's disease. Therefore, the main purpose of this review is to provide the available information on natural alkaloids with the activity of treating central nervous system diseases in order to explore the trends and perspectives for the further study of central nervous system drugs. In this paper, 120 alkaloids with the potential effect of treating central nervous system diseases are summarized from the aspects of sources, structure types, mechanism of action and structure-activity relationship.

Inhibition of Human Cholinesterases and in vitro β-Amyloid Aggregation by Rationally Designed Peptides

The multifactorial nature of Alzheimer's disease (AD) is now widely recognized, which has increased the interest in compounds that can address more than one AD-associated targets. Herein, we report the inhibitory activity on the human cholinesterases (acetylcholinesterase, hAChE and butyrylcholinesterase, hBChE) and on the AChE-induced β-amyloid peptide (Aβ) aggregation by a series of peptide derivatives designed by mutating aliphatic residues for aromatic ones. We identified peptide W3 (LGWVSKGKLL-NH2 ) as an interesting scaffold for the development of new anti-AD multitarget-directed drugs. It showed the lowest IC50 value against hAChE reported for a peptide (0.99±0.02 μM) and inhibited 94.2 %±1.2 of AChE-induced Aβ aggregation at 10 μM. Furthermore, it inhibited hBChE (IC50 , 15.44±0.91 μM), showed no in vivo toxicity in brine shrimp and had shown moderated radical scavenging and Fe2+ chelating capabilities in previous studies. The results are in line with multiple reports showing the utility of the indole moiety for the development of cholinesterase inhibitors.

Natural Inhibitors of Cholinesterases: Chemistry, Structure-Activity and Methods of Their Analysis

This article aims to provide an updated description and comparison of the data currently available in the literature (from the last 15 years) on the studied natural inhibitors of cholinesterases (IChEs), namely, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). These data also apply to the likely impact of the structures of the compounds on the therapeutic effects of available and potential cholinesterase inhibitors. IChEs are hitherto known compounds with various structures, activities and origins. Additionally, multiple different methods of analysis are used to determine the cholinesterase inhibitor potency. This summary indicates that natural sources are still suitable for the discovery of new compounds with prominent pharmacological activity. It also emphasizes that further studies are needed regarding the mechanisms of action or the structure-activity correlation to discuss the issue of cholinesterase inhibitors and their medical application.

Rational drug design strategies for the development of promising multi-target directed indole hybrids as Anti-Alzheimer agents

Alzheimer's disease (AD) is a neurological disorder that leads to dementia i.e., progressive memory loss accompanied with worsening of thinking ability of an individual. The cause of AD is not fully understood but it progresses with age where brain cells gradually die over time. According to the World Health Organization (WHO), currently 50 million people worldwide are affected by dementia and 60-70% of the cases belong to AD. Cumulative research over the past few decades have shown that molecules that act at a single target possess limited efficacy since these investigational drugs are not able to act against complex pathologies and thus do not provide permanent cure. Designing of multi-target directed ligands (MTDLs) appears to be more beneficial and a rational approach to treat chronic complex diseases including neurodegenerative diseases. Recently, MTDLs are being extensively researched by the medicinal chemists for the development of drugs for the treatment of various multifactorial diseases. Indole is one of the privileged scaffolds which is considered as an essential mediator between the gut-brain axis because of its neuroprotective, anti-inflammatory, β-amyloid anti-aggregation and antioxidant activities. Herein, we have reviewed the potential of some indole-hybrids acting at multiple targets in the pathogenesis of AD. We have reviewed research articles from the year 2014-2021 from various scientific databases and highlighted the synthetic strategies, mechanisms of neuroprotection, toxicity, structure activity relationships and molecular docking studies of various indole-hybrid derivatives. This literature review of published data on indole derivatives indicated that developing indole hybrids have improved the pharmacokinetic profile with lower toxicity, provided synergistic effect, helped to develop more potent compounds and prevented drug-drug interactions. It is evident that this class of compounds have potential to inhibit multiple enzymes targets involved in the pathogenesis of AD and therefore indole hybrids as MTDLs may play an important role in the development of anti-AD molecules.

Iboga-type alkaloids with Indolizidino[8,7-b]Indole scaffold and bisindole alkaloids from Tabernaemontana bufalina Lour

Phytochemical investigation on the aerial parts of Tabernaemontana bufalina Lour. (Apocynaceae) led to the identification of four undescribed monoterpenoid indole alkaloids named taberbufamines A-D, an undescribed natural product, and fourteen known indole alkaloids. The structures of the undescribed alkaloids were established by spectroscopic and computational methods, and their absolute configurations were further determined by quantum chemical TDDFT calculations and the experimental ECD spectra. Taberbufamines A and B possessed an uncommon skeleton incorporating an indolizidino [8,7-b]indole motif with a 2-hydroxymethyl-butyl group attached at the pyrrolidine ring. Biosynthetically, Taberbufamines A and B might be derived from iboga-type alkaloid through rearrangement. Vobatensine C showed significant bioactivity against A-549, Bel-7402, and HCT-116 cells with IC₅₀ values of 2.61, 1.19, and 1.74 μM, respectively. Ervahanine A showed antimicrobial activity against Bacillus subtilis, Mycobacterium smegmatis, and Helicobacter pylori with MIC values of 4, 8, and 16 μg/mL, respectively. 19(S)-hydroxyibogamine was shown as butyrylcholinesterase inhibitor (IC₅₀ of 20.06 μM) and α-glycosidase inhibitor (IC₅₀ of 17.18 μM), while tabernamine, ervahanine B, and ervadivaricatine B only showed α-glycosidase inhibitory activities with IC₅₀ values in the range of 0.95-4.61 μM.

Biosynthesis and synthetic biology of psychoactive natural products

Psychoactive natural products play an integral role in the modern world. The tremendous structural complexity displayed by such molecules confers diverse biological activities of significant medicinal value and sociocultural impact. Accordingly, in the last two centuries, immense effort has been devoted towards establishing how plants, animals, and fungi synthesize complex natural products from simple metabolic precursors. The recent explosion of genomics data and molecular biology tools has enabled the identification of genes encoding proteins that catalyze individual biosynthetic steps. Once fully elucidated, the "biosynthetic pathways" are often comparable to organic syntheses in elegance and yield. Additionally, the discovery of biosynthetic enzymes provides powerful catalysts which may be repurposed for synthetic biology applications, or implemented with chemoenzymatic synthetic approaches. In this review, we discuss the progress that has been made toward biosynthetic pathway elucidation amongst four classes of psychoactive natural products: hallucinogens, stimulants, cannabinoids, and opioids. Compounds of diverse biosynthetic origin - terpene, amino acid, polyketide - are identified, and notable mechanisms of key scaffold transforming steps are highlighted. We also provide a description of subsequent applications of the biosynthetic machinery, with an emphasis placed on the synthetic biology and metabolic engineering strategies enabling heterologous production.

Plant-Based Indole Alkaloids: A Comprehensive Overview from a Pharmacological Perspective

Plant-based indole alkaloids are very rich in pharmacological activities, and the indole nucleus is considered to contribute greatly to these activities. This review's fundamental objective is to summarize the pharmacological potential of indole alkaloids that have been derived from plants and provide a detailed evaluation of their established pharmacological activities, which may contribute to identifying new lead compounds. The study was performed by searching various scientific databases, including Springer, Elsevier, ACS Publications, Taylor and Francis, Thieme, Wiley Online Library, ProQuest, MDPI, and online scientific books. A total of 100 indole compounds were identified and reviewed. The most active compounds possessed a variety of pharmacological activities, including anticancer, antibacterial, antiviral, antimalarial, antifungal, anti-inflammatory, antidepressant, analgesic, hypotensive, anticholinesterase, antiplatelet, antidiarrheal, spasmolytic, antileishmanial, lipid-lowering, antimycobacterial, and antidiabetic activities. Although some compounds have potent activity, some only have mild-to-moderate activity. The pharmacokinetic profiles of some of the identified compounds, such as brucine, mitragynine, 7-hydroxymitragynine, vindoline, and harmane, were also reviewed. Most of these compounds showed promising pharmacological activity. An in-depth pharmacological evaluation of these compounds should be performed to determine whether any of these indoles may serve as new leads.

Chemical Diversity and Bioactivities of Monoterpene Indole Alkaloids (MIAs) from Six Apocynaceae Genera

By the end of the twentieth century, the interest in natural compounds as probable sources of drugs has declined and was replaced by other strategies such as molecular target-based drug discovery. However, in the recent times, natural compounds regained their position as extremely important source drug leads. Indole-containing compounds are under clinical use which includes vinblastine and vincristine (anticancer), atevirdine (anti-HIV), yohimbine (erectile dysfunction), reserpine (antihypertension), ajmalicine (vascular disorders), ajmaline (anti-arrhythmic), vincamine (vasodilator), etc. Monoterpene Indole Alkaloids (MIAs) deserve the curiosity and attention of researchers due to their chemical diversity and biological activities. These compounds were considered as an impending source of drug-lead. In this review 444 compounds, were identified from six genera belonging to the family Apocynaceae, will be discussed. These genera (Alstonia, Rauvolfia, Kopsia, Ervatamia, and Tabernaemontana, and Rhazya) consist of 400 members and represent 20% of Apocynaceae species. Only 30 (7.5%) species were investigated, whereas the rest are promising to be investigated. Eleven bioactivities, including antibacterial, antifungal, anti-inflammatory and immunosuppressant activities, were reported. Whereas cytotoxic effect represents 47% of the reported activities. Convincingly, the genera selected in this review are a wealthy source for future anticancer drug lead.

Monoterpene indole alkaloids with diverse skeletons from the stems of Rauvolfia vomitoria and their acetylcholinesterase inhibitory activities

Nine undescribed monoterpene indole alkaloids, rauvomitorine A-I, including an unprecedented C-9-methoxymethylene-sarpagine framework alkaloid, two rare suaveoline framework type alkaloids, and six yohimbine framework type alkaloids, as well as eleven known alkaloids, were isolated from the stems of Rauvolfia vomitoria Afzel. (Apocynaceae). The structures of the unreported alkaloids were elucidated by extensive spectroscopic analysis and single-crystal X-ray diffraction analysis with Cu Kα radiation. Rauvomitorine A with an unreported framework type represents the first example of C-9-methoxymethylene-sarpagine alkaloids and its plausible biosynthetic pathway was proposed. All the isolated alkaloids were evaluated their acetylcholinesterase inhibitory (AChE) activities and cytotoxicity against five cancer cell lines and some of them exhibited potential anti-AChE activities with IC₅₀ values ranging from 49.76 to 186.62 μM. Importantly, this is the first report of the AChE inhibitory activities on suaveoline framework type alkaloids, suggesting this type of alkaloids may be valuable sources for the discovery of AChE inhibitory agents. A preliminary structure-activity relationship for AChE inhibitory activities of the isolated alkaloids is also discussed, providing some clues to designing lead compounds for AChE inhibitors.

Traditional Chinese medicine for anti-Alzheimer's disease: berberine and evodiamine from Evodia rutaecarpa

Alzheimer's disease (AD) is one of the most common diseases in elderly people with a high incidence of dementia at approximately 60-80%. The pathogenesis of AD was quite complicated and currently there is no unified conclusion in the academic community, so no efficiently clinical treatment is available. In recent years, with the development of traditional Chinese medicine (TCM), researchers have proposed the idea of relying on TCM to prevent and treat AD based on the characteristic of multiple targets of TCM. This study reviewed the pathological hypothesis of AD and the potential biomarkers found in the current researches. And the potential targets of berberine and evodiamine from Evodia rutaecarpa in AD were summarized and further analyzed. A compound-targets-pathway network was carried out to clarify the mechanism of action of berberine and evodiamine for AD. Furthermore, the limitations of current researches on the TCM and AD were discussed. It is hoped that this review will provide some references for development of TCM in the prevention and treatment of AD.

Monoterpene indole alkaloids with acetylcholinesterase inhibitory activity from the leaves of Rauvolfia vomitoria

Seventeen monoterpene indole alkaloids, including seven new alkaloids (1-7) and ten known analogues (8-17), were isolated and identified from the leaves of R. vomitoria. The structures of new alkaloids were elucidated by extensive spectroscopic analysis and single-crystal X-ray diffraction analysis. Rauvomitorine I (1) represents the first example of an unprecedented C₂₂ yohimbine-type monoterpene indole alkaloid featuring a carboxymethyl at C-14. The exceedingly rare vobasenal (2-3) and affinisine oxindole (5-6) framework type alkaloids are first reported from the Rauvolfia genus. Most notably, the structure of vobasenal-type alkaloids (2-3) were first determined by single-crystal X-ray diffraction analyses. Alkaloids 1-17 were tested their cytotoxicity against five cancer cell lines, however, none of them showed significant cytotoxicity at a concentration of 40 μM. All the isolated alkaloids were evaluated their acetylcholinesterase (AChE) inhibitory activities. Alkaloid 3 exhibited significant anti-AChE activity with an IC₅₀ value of 16.39 ± 1.41 μM and alkaloids 8 and 10 showed moderate anti-AChE activities whereas the others (2, 9, 13, and 17) were weak inhibitors. This is the first report of vobasenal-type alkaloids as AChE inhibitors, indicating this type of alkaloids may be important sources for the discovery of new AChE inhibitors. A preliminary structure-activity relationship for AChE inhibitory activities showed the presence of the N-methyl group in vobasenal-type alkaloids may be essential for anti-AChE activity. Further molecular docking studies of vobasenal-type alkaloids revealed that interaction with Trp133 and Trp86 residues at hydrophobic subsite are necessary for the AChE inhibitory activities. This study not only enriches the chemical diversity of alkaloids in Apocynaceae plants but also provides new potential leading compounds and versatile scaffolds for the design and development of new AChE inhibitors to treat AD.

The indole-based subincanadine alkaloids and their biogenetic congeners

The tryptamine-derived polycyclic bridged bioactive indole alkaloids subincanadines A-G were isolated in 2002 by Ohsaki and coworkers from the bark of the Brazilian medicinal plant Aspidosperma subincanum. Kobayashi proposed that subincanadines D-F could be biosynthetically resulting from stemmadenine via two different pathways and, furthermore, that the subincanadines A-C could be biogenetically resulting from subincanadines D and E. Kam and coworkers, in their focused efforts, isolated five indole alkaloids from Malaysian Kopsia arborea species, namely valparicine, apparicine, arboridinine, arborisidine, and arbornamine in combination with subincanadine E. On the basis of structural features, it has been proposed and proved in some examples that subincanadine E is a biogenetic precursor of these five different bioactive indole alkaloids bearing complex structural architectures. All important information on isolation, characterization, bioactivity, probable biogenetic pathways, and more specifically racemic and enantioselective total synthesis of subincanadine alkaloids and their biogenetic congeners are summarized in the present chapter. Special importance is given to the total synthesis and the synthetic strategies intended therein, comprising a set of main reactions.

Glucoconjugated Monoterpene Indole Alkaloids from Uncaria rhynchophylla

Twenty-six glucoconjugated monoterpene indole alkaloids, including 12 new compounds, rhynchophyllosides A-L (1-12), and 14 known ones, 13-26, were obtained from the hook-bearing stems of Uncaria rhynchophylla (Miq.) Miq. ex Havil. Their structures were unambiguously elucidated by analyses of UV, MS, NMR, ECD, and single-crystal X-ray diffraction data. The ESI-MSⁿ behavior of the new glucoalkaloids was also elucidated. Although comprising the same glucosyl moiety, the aglycone skeletons and glucosidic numbers and linkage varied greatly, implying the diversity in biosynthetic pathways. This is the first report of such structurally diverse glucoconjugated monoterpene indole alkaloids from U. rhynchophylla. Compound 1 represents a new subtype of oxindole alkaloid with a seven-membered D-ring, 10 is a rare monoterpene indole alkaloid with the glucosyl moiety located at C-9, 4 and 5 are the first two oxindole alkaloid diglycosides, and 11 and 12 represent the first two examples of alkaloids with a quinolone nucleus from the genus Uncaria. Compound 10 exhibited moderate acetylcholinesterase (AChE) inhibitory activity with an IC₅₀ value of 10.5 μM. Molecular docking was performed to explore the binding mode of inhibitor 10 at the active site of AChE.

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.

Comparison of analytical techniques for the identification of bioactive compounds from natural products

Covering: 2000 to 2016Natural product extracts are a rich source of bioactive compounds. As a result, the screening of natural products for the identification of novel biologically active metabolites has been an essential part of several drug discovery programs. It is estimated that more than 70% of all drugs approved from 1981 and 2006, were either derived from or structurally similar to nature based compounds indicating the necessity for the development of a rapid method for the identification of novel compounds from plant extracts. The screening of biological matrices for the identification of novel modulators is nevertheless still challenging. In this review we discuss current techniques in phytochemical analysis and the identification of biologically active components.

Bioinspired Collective Syntheses of Iboga-Type Indole Alkaloids

We present the application of a bioinspired collective synthesis strategy in the total syntheses of seven iboga-type indole alkaloids: (±)-tabertinggine, (±)-ibogamine, (±)-ibogaine, (±)-ibogaine hydroxyindolenine, (±)-3-oxoibogaine hydroxyindolenine, (±)-iboluteine, and (±)-ervaoffines D. In particular, tabertinggine and its congeners serve as iboga precursors for the subsequent biomimetic transformations into other iboga-type alkaloids.

Ervatamines A-I, Anti-inflammatory Monoterpenoid Indole Alkaloids with Diverse Skeletons from Ervatamia hainanensis

Nine new monoterpenoid indole alkaloids, ervatamines A-I (1-9), and five known ones (10-14), were isolated from Ervatamia hainanensis. The new structures were elucidated by extensive spectroscopic analysis and comparison to known compounds. Their absolute configurations were determined by various methods including computational methods, X-ray diffraction analysis, and electronic circular dichroism spectroscopy, as well as chemical transformations. Ervatamine A (1) is a ring-C-contracted ibogan-type monoterpenoid indole alkaloid with an unusual 6/5/6/6/6 pentacyclic rearranged ring system. Ervatamines B-E (2-5) display a nitrogen-containing 9/6 ring system, which is rarely observed in nature. The epimeric ervatamines B (2) and C (3) possess a 22-nor-monoterpenoid indole alkaloid carbon skeleton, which was only found in deformylstemmadenine. Compounds 10 and 14 exhibited significant anti-inflammatory activities, with IC50 values of 25.5 and 41.5 μM, respectively, while the IC50 value of indomethacin as a positive control was found to be 42.6 μM. Additionally, compound 9 showed mild activity against 786-O and HL-60 cell lines.

Could molecular effects of Caulerpa racemosa metabolites modulate the impact on fish populations of Diplodus sargus?

The green alga Caulerpa racemosa is a non-native, invasive species in the Mediterranean, and an important stressor for several native organisms. The algal capacity to produce secondary metabolites has been suggested to modulate success of the C. racemosa invasion, although many of potentially involved biological pathways still remain unexplored. In this respect, the aim of the present study was to investigate some molecular and cellular effects in the white seabream Diplodus sargus, an ecologically key species, which included the alien C. racemosa in its diet. Organisms were sampled in 2 seasonal periods from 3 locations of Southern Italy, each characterized by different levels of algal abundance. The level of caulerpin, one of the main secondary algal metabolites, in fish tissues has been used as an indicator of the trophic exposure to the seaweed and related with molecular and cellular responses. Chemical analyses indicated that fish from invaded sites can accumulate caulerpin, with liver concentrations ranging from a few up to hundreds of μg/g. Biomarkers analyses revealed only limited alterations of the main antioxidant defences, such as glutathione reductase and levels of glutathione; on the other hand, increased enzymatic activities of cytochrome P450, glutathione S-transferases and acyl CoA oxidase, as well as enhanced gene transcription for peroxisome proliferator-activated receptor alpha, cytochrome P4501A and vitellogenin 1 were observed in fish more exposed to C. racemosa as indicated by liver concentrations of caulerpin higher than 50 μg/g. Despite a direct molecular relationship with this algal metabolite could not be established, our results suggest that a C. racemosa enriched diet can modulate biotransformation and fatty acids metabolism of D. sargus. Assessing whether similar effects represent short- or long-term effects will be of crucial importance to understand consequences on the general health status and reproductive performance of exposed key fish species in the Mediterranean region.

Monoterpene indole alkaloids from the stem bark of Mitragyna diversifolia and their acetylcholine esterase inhibitory effects

Five monoterpene indole alkaloids, mitradiversifoline, with a unique rearranged skeleton, specionoxeine-N(4)-oxide, 7-hydroxyisopaynantheine, 3-dehydropaynantheine, and 3-isopaynantheine-N(4)-oxide, and 10 known ones, were isolated from Mitragyna diversifolia. All the isolates were evaluated for their inhibition of acetylcholinesterase activities, and four showed moderate activities, with IC50 values of 4.1, 5.2, 10.2, and 10.3 μM, respectively.

Acetylcholinesterase immobilized capillary reactors coupled to protein coated magnetic beads: a new tool for plant extract ligand screening

The use of immobilized capillary enzyme reactors (ICERs) and enzymes coated to magnetic beads ((NT or CT)-MB) for ligand screening has been adopted as a new technique of high throughput screening (HTS). In this work the selected target was the enzyme acetylcholinesterase (AChE), which acts on the central nervous system and is a validated target for the treatment of Alzheimer's disease, as well as for new insecticides. A new approach for the screening of plant extracts was developed based on the ligand fishing experiments and zonal chromatography. For that, the magnetic beads were used for the ligand fishing experiments and capillary bioreactors for the activity assays. The latter was employed also under non-linear conditions to determine the affinity constants of known ligands, for the first time, as well as for the active fished ligand.

Natural products chemistry research 2010's progress in China

This article reviews the progresses made by Chinese scientists in the field of natural products chemistry in 2010. Selected compounds with unique structural features and/or promising bioactivities were described herein on the basis of structural types.

Chemical constituents antioxidant and anticholinesterasic activity of Tabernaemontana catharinensis

The present work aimed to analyze the alkaloid content of the ethanolic extract of Tabernaemontana catharinensis (Apocynaceae family) and its fractions as well as to evaluate their antioxidant and anticholinesterasic activities. The analyses of the ethanolic extract of T. catharinensis by mass spectrometry allowed identifying the presence of the alkaloids 16-epi-affinine, coronaridine-hydroxyindolenine, voachalotine, voacristine-hydroxyindolenine, and 12-methoxy-n-methyl-voachalotine, as well as an alkaloid with m/z 385.21 whose spectrum suggests a derivative of voacristine or voacangine. The extract and its alkaloid rich fractions showed antioxidant activity, especially those that contain the alkaloid m/z 385.21 or 16-epi-affinine with DPPH scavenging activity (IC₅₀) between 37.18 and 74.69 μg/mL. Moreover, the extract and its fractions exhibited anticholinesterasic activity, particularly the fractions characterized by the presence of 12-methoxy-n-methyl-voachalotine, with IC₅₀ = 2.1 to 2.5 μg/mL. Fractions with 16-epi-affinine combined good antioxidant (IC₅₀ = 65.59 to 74.69 μg/mL) and anticholinesterasic (IC₅₀ = 7.7 to 8.3 μg/mL) activities, representing an option for further studies aimed at treating neurodegenerative diseases.

Natural AChE Inhibitors from Plants and their Contribution to Alzheimer's Disease Therapy

As acetylcholinesterase (AChE) inhibitors are an important therapeutic strategy in Alzheimer's disease, efforts are being made in search of new molecules with anti-AChE activity. The fact that naturally-occurring compounds from plants are considered to be a potential source of new inhibitors has led to the discovery of an important number of secondary metabolites and plant extracts with the ability of inhibiting the enzyme AChE, which, according to the cholinergic hypothesis, increases the levels of the neurotransmitter acetylcholine in the brain, thus improving cholinergic functions in patients with Alzheimer's disease and alleviating the symptoms of this neurological disorder. This review summarizes a total of 128 studies which correspond to the most relevant research work published during 2006-2012 (1st semester) on plant-derived compounds, plant extracts and essential oils found to elicit AChE inhibition.

Progress of pharmacological studies on alkaloids from Apocynaceae

Alkaloid was a kind of biological active ingredient. There were various types of alkaloids in Apocynaceae. This paper reviewed the progress on alkaloids from Apocynaceae, which contained origin, structure, and pharmacological activity.

Subtle effects of biological invasions: cellular and physiological responses of fish eating the exotic pest Caulerpa racemosa

The green alga Caulerpa racemosa var. cylindracea has invaded Mediterranean seabed including marine reserves, modifying the structure of habitats and altering the distributional patterns of associated organisms. However, the understanding of how such invasion can potentially affect functional properties of Mediterranean subtidal systems is yet to be determined. In this study, we show that C. racemosa changes foraging habit of the native white seabream, Diplodus sargus. In invaded areas, we found a high frequency of occurrence of C. racemosa in the stomach contents of this omnivorous fish (72.7 and 85.7%), while the alga was not detected in fish from a control area. We also found a significant accumulation of caulerpin, one of the main secondary metabolites of C. racemosa, in fish tissues. The level of caulerpin in fish tissues was used here as an indicator of the trophic exposure to the invasive pest and related with observed cellular and physiological alterations. Such effects included activation of some enzymatic pathways (catalase, glutathione peroxidases, glutathione S-transferases, total glutathione and the total oxyradical scavenging capacity, 7-ethoxy resorufin O-deethylase), the inhibition of others (acetylcholinesterase and acylCoA oxidase), an increase of hepatosomatic index and decrease of gonadosomatic index. The observed alterations might lead to a detrimental health status and altered behaviours, potentially preventing the reproductive success of fish populations. Results of this study revealed that the entering of alien species in subtidal systems can alter trophic webs and can represent an important, indirect mechanism which might contribute to influence fluctuations of fish stocks and, also, the effectiveness of protection regimes.

Mycobacterium tuberculosis and cholinesterase inhibitors from Voacanga globosa

Globospiramine (1), a new spirobisindole alkaloid possessing an Aspidosperma-Aspidosperma skeleton, together with deoxyvobtusine (2), deoxyvobtusine lactone (3), vobtusine lactone (4) and lupeol (5), were isolated and identified from Voacanga globosa through a bioassay-guided purification. The gross structure and absolute stereochemistry of 1 were established by circular dichroism spectroscopy, HR-MS and unambiguous NMR spectroscopic experiments. In addition, a new biogenetic pathway for the formation of the spiro-Aspidosperma-Aspidosperma skeleton is proposed. Alkaloid 1 showed potent antituberculosis activity against Mycobacterium tuberculosis H(37)Rv as evidenced in microplate Alamar blue assay (MIC = 4 μg/mL) and low-oxygen recovery assay (LORA (MIC = 5.2 μg/mL). The bisindole alkaloids also exhibited promising activity against acetylcholinesterase and, especially butyrylcholinesterase, with deoxyvobtusine (2) (IC(50) = 6.2 μM) as the most strongly inhibiting compound. This study extends the variety of alkaloid structural platforms which exhibit antimycobacterial and anticholinesterase activity.