Assessment of acetylcholinesterase activity using indoxylacetate and comparison with the standard Ellman's method

A 3D-Fluorescence Fingerprinting Approach to Detect Physiological Modifications Induced by Pesticide Poisoning in Apis mellifera: A Preliminary Study

The combined use of 3D-fluorescence spectroscopy and independent component analysis using a differential fingerprinting approach has been applied with success to detect physiological effects of dimethoate in honeybees. Biochemical determinations combined with the identification of fluorescence zones that may correspond to proteins, NADH or neurotransmitters/neurohormones (octopamine, dopamine and serotonin) related to the physiological stress caused by the pesticide enabled phenomenological modeling of the physiological response in the honeybee using a simple and rapid method. The signals associated with the fluorophores involved in the response to stress were extracted from the fluorescence spectra using an unsupervised algorithm such as independent component analysis. The signals of different neurotransmitters were isolated on separated factorial components, thus facilitating their biochemical interpretation.

Indoxyl Acetate as a Substrate for Analysis of Lipase Activity

Lipases play a crucial role in metabolism of microbes, fungi, plants, and animals, and in analytical chemistry, they are often used in detection of fats and triglycerides. Determination of lipase activity is also important in toxicology, when lipase activity can be both increased and decreased by organophosphates and other pesticides and in medicine for diagnosis of heart diseases. The standard method for lipase activity determination is based on cleaving ester bonds in lipase buffer containing Tween. Our aim was to find a method with faster and more sensitive response. It is known that acetylcholinesterase belongs to the same group of hydrolases enzymes as lipases and it cleaves indoxyl acetate, so we assume indoxyl acetate could report a similar reaction with lipase. Our method is based on indoxyl acetate as a substrate for lipase, where indoxyl acetate is cleaved by lipase to indoxyl and acetate moiety and blue indigo is created. The method was optimized for different times and amount of enzyme and compared with the standard Tween assay. The calibration curve measured in reaction time 20 minutes with 10 μl of lipase exhibited the best analytical parameters, and it showed Michaelis-Menten response with the Michaelis-Menten constant equal to 8.72 mmol/l. The indoxyl acetate-based method showed faster and more sensitive response than the standard method for lipase activity determination, so it has great potential in biosensor construction and it could be used in industry, medicine, toxicology, and common practice where the activity of lipases is need to be measured.

Assessment of Monopterus albus liver as a source of Cholinesterase for the detection of heavy metals

Heavy metals pollution has now become a serious environmental problem worldwide especially in Malaysia River. As a precaution, continuous environmental monitoring is needed to minimize heavy metal to the ecosystem. Inhibitive enzyme assay based on enzyme including cholinesterase has been introduced as a rapid, cheap and reliable method to assess the level of contamination in the river. In this study, the Asian swamp eel,Monopterus albus, was selected and determined of the sensitivity level towards heavy metals. The liver of M. albus was extracted and purified using ion exchange chromatography of which DEAE sepharose as the matrix of the column. Based on the Ellman assay, cholinesterase was obtained at 4.86 purification fold with the percentage recovery of 30.32 %. The enzyme works optimally at pH 9 (0.1 M Tris-HCl buffer) and 25 °C, while BTC; 369×103U.mg−1was selected as the preferable substrate which shows highest catalytic efficiencies compared to ATC and BTC at 1457 × 103, 1220 × 103and 488 × 103Vmax.Km−1, respectively, Cholinesterase was tested with eight metal ions at the concentration of 5 ppm and the ascending order of inhibition is as followed; arsenic = chromium ⩽ plumbum ⩽ copper ⩽ argentum = nickel < mercury. From this study, the ability of cholinesterase partially purified from the liver tissue ofM. albushas the potential to be an assay for heavy metals.

Mediterranean Cypress “Cupressus sempervirens”: A Review on Phytochemical and Pharmacological Properties

Background:

Cupressus sempervirens (C. sempervirens), commonly known as Mediterranean cypress is native to the eastern Mediterranean region, North America and subtropical Asia at higher altitudes. The crude, semi-purified and purified extracts of C. sempervirens have long been recognized for its pharmacological activities as evidenced by its extensive use by indigenous cultures in herbal medicines, tonics and infusion. Pharmacological properties displayed the prodigious biological activities that could be further explored for development of new herbal formulations or therapeutic agents.

Aims:

This review presents a critical analysis of the current state of knowledge about the ethno medicinal uses, phytochemistry and pharmacological properties of C. sempervirens L and its future applications.

Materials and Methods:

Literature related to C. sempervirens and its synonyms were searched on the available online literature databases such as Google Scholar, PubMed, SciFinder, Scopus, Springer, ScienceDirect, Wiley, ACS, Scielo and Web of Science, thesis, dissertations, books, reports, local herbal encyclopedias and other relevant websites.

Results:

A review of literature showed that decoction of cones and young branches of C. sempervirens gave astonishing effect in the treatment of hemorrhoids and to treat excessive sweating in the feet. Enormous pharmacological properties have been found including antiseptic, anti-inflammatory, antispasmodic, antioxidant, antimicrobial, hepatoprotective, wound-healing, anticoagulant, antihyperlipidemic, anticancer, neurobiological, antidiabetic, and antiosteoporotic. Approximately 109 phytochemical constituents have been searched out as isolates from various parts of this plant comprising mostly diterpenoids and biflavonoids.

Conclusion:

Numerous in vivo and in vitro studies have provided support for the traditional uses of C. sempervirens but further research work is required towards isolating more active constituents and for validating its clinical utilization in the herbal formulations for humans as well as investigating any potential toxicity for future clinical studies.

In Vitro Evaluation of Neutral Aryloximes as Reactivators for Electrophorus eel Acetylcholinesterase Inhibited by Paraoxon

Casualties caused by organophosphorus pesticides are a burden for health systems in developing and poor countries. Such compounds are potent acetylcholinesterase irreversible inhibitors, and share the toxic profile with nerve agents. Pyridinium oximes are the only clinically available antidotes against poisoning by these substances, but their poor penetration into the blood-brain barrier hampers the efficient enzyme reactivation at the central nervous system. In searching for structural factors that may be explored in future SAR studies, we evaluated neutral aryloximes as reactivators for paraoxon-inhibited Electrophorus eel acetylcholinesterase. Our findings may result into lead compounds, useful for development of more active compounds for emergencies and supportive care.

Validation and kinetic of enzymatic method for the detection of organophosphate insecticides based on cholinesterase inhibition

Kinetic and validation of the enzymatic method for the determination of fenitrothion organophosphorus based on cholinesterase inhibition were studied. A Linear relationship was obtained with a determination coefficient R² of 0.9989 suggesting that the noncompetitive inhibition kinetic equation is suitable to represent the enzymatic assay of fenitrothion. The value of the inhibition constant K_I was 0.374 μg/ml/min. The analytical logarithmic curve for the determination of fenitrothion concentration using the percentage of cholinesterase inhibition presented good linear relations at concentrations of 0.05-2 μg/ml (R² = 0.9889). The maximum inhibition 83% was observed at 2.0 μg/ml final assay concentration. The lower inhibition 3.3% was observed at 0.05 μg/ml detection limit. The experimental measurement condition was optimized. The enzymatic method exhibited detection limits (LOD) in the range of 0.05-2.0 μg/ml. The limit of quantification (LOQ) was 0.06 μg/ml with inhibition 13%. The concentration of fenitrothion that inhibited the hydrolysis of substrate by 50% (IC50 value) was 0.4 μg/ml. Standard deviations and coefficients of variation indicate a good precision of the enzymatic method for the detection of organophosphate insecticides at an incubation time of 20 min.

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.

Synthesis and in vitro evaluation of neutral aryloximes as reactivators of Electrophorus eel acetylcholinesterase inhibited by NEMP, a VX surrogate

Casualties caused by nerve agents, potent acetylcholinesterase inhibitors, have attracted attention from media recently. Poisoning with these chemicals may be fatal if not correctly addressed. Therefore, research on novel antidotes is clearly warranted. Pyridinium oximes are the only clinically available compounds, but poor penetration into the blood-brain barrier hampers efficient enzyme reactivation at the central nervous system. In searching for structural factors that may be explored in SAR studies, we synthesized and evaluated neutral aryloximes as reactivators for acetylcholinesterase inhibited by NEMP, a VX surrogate. Although few tested compounds reached comparable reactivation results with clinical standards, they may be considered as leads for further optimization.

Inihibition of mullet (M. liza) brain acetylcholinesterase activity by in vitro polycyclic aromatic hydrocarbon exposure

Polycyclic aromatic hydrocarbons (PAH) have been reported as acetylcholinesterase (AChE) inibitors, although in vitro studies on PAH effects on AChE activity are scarce and have only been performed using electric eel brain extracts. Thus, this study investigated PAH effects on brain AChE activity in a tropical fish species in Southeastern Brazil, mullet (Mugil liza). Mullet specimens were obtained from Guanabara Bay (N = 20), Rio de Janeiro, Brazil. Brain AChE was extracted and exposed to an environmentally relevant concentration of Pyrene, Chrysene, Phenanthrene, and Naphthalene, and PAH metabolites, 2-Naphthol and 1-OH-Pyrene. AChE activity inhibition was observed, although no difference was observed between high- and low- molecular weight PAH. 2-Naphthol was a less potent AChE inhibitor than Naphthalene, albeit non-significantly. Further studies are required, since only one PAH concentration was used herein. Mullet brain extracts seem to be adequate to assess possible neurotoxic PAH effects on fish AChE.

Thiocholine-triggered reaction in personal glucose meters for portable quantitative detection of organophosphorus pesticide

A portable and user-friendly method using personal glucose meters for on-site quantitative detection of organophosphorus pesticide (OP) was developed. The inhibition of organophosphorus compounds on acetylcholinesterase (AChE) leads to reduced yields of thiocholine formed by the enzymatic hydrolysis of acetylthiocholine chloride. Ferricyanide ([Fe(CN)₆]^3-), the mediator used in glucose test strips for electron transfer to the electrode, can be rapidly reduced to ferrocyanide ([Fe(CN)₆]^4-) by thiocholine. This reaction enables direct measurement of thiocholine by personal glucose meters in the same way as measuring the glucose in blood, offering an interesting choice to quantify OP. After incubation of AChE for 30 min and enzymatic reaction of 10 min, the yield of thiocholine was measured by a personal glucose meter, achieving detection limit of 5 μg L^-1 for paraoxon. The proposed method was successfully applied to the detection in apples and cucumbers, presenting promising potential for on-site OP detection in food samples.

Evaluate neuroprotective effect of silibinin using chronic unpredictable stress (cus) model

Chronic unpredictable stressors can produce a situation similar to clinical depression, and such animal models can be used for the preclinical evaluation of antidepressants. Many findings have shown that the levels of proinflammatory cytokines (e.g., TNF-α) and oxidative stress (increased lipid peroxidation, decreased glutathione levels, and endogenous antioxidant enzyme activities) are increased in patients with depression. Silibinin is the major active constituent of silymarin, a standardized extract of the milk thistle seeds, containing a mixture of flavonolignans consisting of silibinin, isosilibinin, silicristin, silidianin and exhibit antioxidant activity. Objectives The present study was designed to investigate the effect of silibinin on unpredictable chronic stressinduce behavioral and biochemical alterations in mice.

METHODS

Mice were subjected to different stress paradigms daily for a period of 45 days to induce depressive like behavior such as memory acquisition, and retention.

RESULTS

Chronic treatment with silibinin significantly reversed the unpredictable chronic stress-induced behavioral (improve memory function), biochemical changes (decreased glutathione levels, superoxide dismutas), and inflammation surge (serum TNF-α IL 1β) in stressed mice.

CONCLUSION

The study revealed that silibinin exerted effects in behavioral despair paradigm in chronically stressed mice, specifically by modulating central oxidative stress and inflammation.

Structural Insights of Stereospecific Inhibition of Human Acetylcholinesterase by VX and Subsequent Reactivation by HI-6

Over 50 years ago, the toxicity of irreversible organophosphate inhibitors targeting human acetylcholinesterase (hAChE) was observed to be stereospecific. The therapeutic reversal of hAChE inhibition by reactivators has also been shown to depend on the stereochemistry of the inhibitor. To gain clarity on the mechanism of stereospecific inhibition, the X-ray crystallographic structures of hAChE inhibited by a racemic mixture of VX (P _R/S) and its enantiomers were obtained. Beyond identifying hAChE structural features that lend themselves to stereospecific inhibition, structures of the reactivator HI-6 bound to hAChE inhibited by VX enantiomers of varying toxicity, or in its uninhibited state, were obtained. Comparison of hAChE in these pre-reactivation and post-reactivation states along with enzymatic data reveals the potential influence of unproductive reactivator poses on the efficacy of these types of therapeutics. The recognition of structural features related to hAChE's stereospecificity toward VX shed light on the molecular influences of toxicity and their effect on reactivators. In addition to providing a better understanding of the innate issues with current reactivators, an avenue for improvement of reactivators is envisioned.

Molecular Modeling and In Vitro Studies of a Neutral Oxime as a Potential Reactivator for Acetylcholinesterase Inhibited by Paraoxon

The present work aimed to compare the small, neutral and monoaromatic oxime, isatin-3-oxime (isatin-O), to the commercial ones, pralidoxime (2-PAM) and obidoxime, in a search for a new potential reactivator for acetylcholinesterase (AChE) inhibited by the pesticide paraoxon (AChE/POX) as well as a novel potential scaffold for further synthetic modifications. The multicriteria decision methods (MCDM) allowed the identification of the best docking poses of those molecules inside AChE/POX for further molecular dynamic (MD) studies, while Ellman's modified method enabled in vitro inhibition and reactivation assays. In corroboration with the theoretical studies, our experimental results showed that isatin-O have a reactivation potential capable of overcoming 2-PAM at the initial moments of the assay. Despite not achieving better results than obidoxime, this molecule is promising for being an active neutral oxime with capacity of crossing the blood⁻brain barrier (BBB), to reactivate AChE/POX inside the central and peripheral nervous systems. Moreover, the fact that isatin-O can also act as anticonvulsant makes this molecule a possible multipotent reactivator. Besides, the MCDM method showed to be an accurate method for the selection of the best docking poses generated in the docking studies.

1-Naphthyl acetate: A chromogenic substrate for the detection of erythrocyte acetylcholinesterase activity

Erythrocyte acetylcholinesterase (AChE) is a preferred biomarker for the detection of organophosphorus poisoning. Acetylthiocholine (ATCh) is the most popular substrate for the detection of AChE activity. However, oximolysis is a prominent feature with ATCh. In this context, we have searched alternative substrates for AChE using in silico tools for screening of a better substrate. The in silico approach was performed to understand the fitness and the Total Interaction Energy (TIE) of substrates for AChE. The alternative substrates for AChE were screened in terms of high Goldscore and favorable TIE in comparison to acetylcholine (ACh)-AChE complex and other relevant esterases. Among the screened substrates, 1-Naphthyl acetate (1-NA) exhibited the most favorable interaction with AChE in terms of highest TIE and corresponding high Goldscore. The Molecular Dynamic (MD) simulation of the 1-NA-AChE complex showed a stable complex formation over a period of 5 ns. The results obtained in the in silico studies were validated in vitro using pure erythrocyte AChE and hemolysate. We observed 1-NA to be a better alternative substrate for AChE than ATCh in terms of lower Km value. Its specificity appeared at least similar to ATCh. Therefore, we propose that 1-NA can be an attractive chromogenic substrate for the measurement of AChE activity, and it possess the potential to detect organophosphorus pesticide (OP) poisoning.

Phoresis and Enhanced Diffusion Compete in Enzyme Chemotaxis

Chemotaxis of enzymes in response to gradients in the concentration of their substrate has been widely reported in recent experiments, but a basic understanding of the process is still lacking. Here, we develop a microscopic theory for chemotaxis that is valid for enzymes and other small molecules. Our theory includes both nonspecific interactions between enzyme and substrate as well as complex formation through specific binding between the enzyme and the substrate. We find that two distinct mechanisms contribute to enzyme chemotaxis: a diffusiophoretic mechanism due to the nonspecific interactions and a new type of mechanism due to binding-induced changes in the diffusion coefficient of the enzyme. The latter chemotactic mechanism points toward lower substrate concentration if the substrate enhances enzyme diffusion and toward higher substrate concentration if the substrate inhibits enzyme diffusion. For a typical enzyme, attractive phoresis and binding-induced enhanced diffusion will compete against each other. We find that phoresis dominates above a critical substrate concentration, whereas binding-induced enhanced diffusion dominates for low substrate concentration. Our results resolve an apparent contradiction regarding the direction of urease chemotaxis observed in experiments and, in general, clarify the relation between the enhanced diffusion and the chemotaxis of enzymes. Finally, we show that the competition between the two distinct chemotactic mechanisms may be used to engineer nanomachines that move toward or away from regions with a specific substrate concentration.

Assessment of Enzyme Inhibition: A Review with Examples from the Development of Monoamine Oxidase and Cholinesterase Inhibitory Drugs

The actions of many drugs involve enzyme inhibition. This is exemplified by the inhibitors of monoamine oxidases (MAO) and the cholinsterases (ChE) that have been used for several pharmacological purposes. This review describes key principles and approaches for the reliable determination of enzyme activities and inhibition as well as some of the methods that are in current use for such studies with these two enzymes. Their applicability and potential pitfalls arising from their inappropriate use are discussed. Since inhibitor potency is frequently assessed in terms of the quantity necessary to give 50% inhibition (the IC50 value), the relationships between this and the mode of inhibition is also considered, in terms of the misleading information that it may provide. Incorporation of more than one functionality into the same molecule to give a multi-target-directed ligands (MTDLs) requires careful assessment to ensure that the specific target effects are not significantly altered and that the kinetic behavior remains as favourable with the MTDL as it does with the individual components. Such factors will be considered in terms of recently developed MTDLs that combine MAO and ChE inhibitory functions.

Sensitive inkjet printing paper-based colormetric strips for acetylcholinesterase inhibitors with indoxyl acetate substrate

A new paper-based biosensing approach has been developed for sensitive and rapid detection of acetylcholinesterase (AChE) inhibitors. The biosensing zone of the paper strip is constructed with an inkjet printing method, and the biomolecule AChE is immobilized into two layers of biocompatible sol-gel-derived silica ink with a "sandwich" form. Indoxyl acetate (IDA) is used as a chromogenic substrate, which is colorless and can be catalytically hydrolyzed into blue-colored indigo dipolymer. When the enzymatic activity of AChE is inhibited after incubation with organophosphate pesticides (OPs), there is a decreased hydrolysis of IDA accompanying with a drop in color intensity. Paraoxon and trichlorfon are used as the representative OPs in the assay. Due to the low solubility and high molar absorption coefficient of the IDA dipolymer product, the paper-based strip can form a neat blue sensing zone and shows obviously improved sensitivity with a limit of detection (LOD) of 0.01ngmL^-1 paraoxon and 0.04ngmL^-1 trichlorfon (S/N=3) and the LODs for visual detection are 0.03ngmL^-1 for paraoxon and 0.1ngmL^-1 for trichlorfon comparing with the previously reported colorimetric methods. The concentrations of paraoxon in apple juice samples are also detected, and the results are in accord well with these results from high-performance liquid chromatography, showing great potential for on-site detection of OPs in practical application. The developed assay can be used to qualitatively and semiquantitatively estimate with naked eyes and quantitatively assess OPs through image analysis.

Acetylcholinesterase-Inhibition and Antibacterial Activity of Mondia whitei Adventitious Roots and Ex vitro-Grown Somatic Embryogenic-Biomass

Mondia whitei (Hook.f.) Skeels is an important endangered medicinal and commercial plant in South Africa. In vitro propagation systems are required for biomass production and bioactivity analysis to supplement wild resources/stocks. Adventitious roots from somatic embryogenic explants using suspension culture and ex vitro-grown plants produced via somatic embryogenesis were established using different plant growth regulator treatments. The adventitious root biomass and different parts of ex vitro-grown and mother plants were used to investigate the potential for acetylcholinesterase (AChE) and antibacterial activities. Adventitious roots derived from 2.5 μM indole-3-acetic acid (IAA) treatments and ex vitro-grown plants derived from meta-topolin riboside and IAA treatments gave the best AChE and antibacterial activities. The in vitro-established M. whitei and ex vitro biomass have comparable ability to function as inhibitors of acetylcholinesterase and antibacterial agents, and can be used as potent bioresources in traditional medicine.

A reversed-phase compatible thin-layer chromatography autography for the detection of acetylcholinesterase inhibitors

A dual readout autographic assay to detect acetylcholinesterase inhibitors present in complex matrices adsorbed on reversed-phase or normal-phase thin-layer chromatography plates is described. Enzyme gel entrapment with an amphiphilic copolymer was used for assay development. The effects of substrate and enzyme concentrations, pH, incubation time, and incubation temperature on the sensitivity and the detection limit of the assay were evaluated. Experimental design and response surface methodology were used to optimize conditions with a minimum number of experiments. The assay allowed the detection of 0.01% w/w of physostigmine in both a spiked Sonchus oleraceus L. extract chromatographed on normal phase and a spiked Pimenta racemosa (Mill.) J.W. Moore leaf essential oil chromatographed on reversed phase. Finally, the reversed-phase thin-layer chromatography assay was applied to reveal the presence of an inhibitor in the Cymbopogon citratus (DC.) Stapf essential oil. The developed assay is able to detect acetylcholinesterase inhibitors present in complex matrixes that were chromatographed in normal phase or reversed-phase thin-layer chromatography. The detection limit for physostigmine on both normal and reversed phase was of 1×10(-4) μg. The results can be read by a change in color and/or a change in fluorescence.

Optimal detection of cholinesterase activity in biological samples: modifications to the standard Ellman's assay

Ellman's assay is the most commonly used method to measure cholinesterase activity. It is cheap, fast, and reliable, but it has limitations when used for biological samples. The problems arise from 5,5-dithiobis(2-nitrobenzoic acid) (DTNB), which is unstable, interacts with free sulfhydryl groups in the sample, and may affect cholinesterase activity. We report that DTNB is more stable in 0.09 M Hepes with 0.05 M sodium phosphate buffer than in 0.1M sodium phosphate buffer, thereby notably reducing background. Using enzyme-linked immunosorbent assay (ELISA) to enrich tissue homogenates for cholinesterase while depleting the sample of sulfhydryl groups eliminates unwanted interactions with DTNB, making it possible to measure low cholinesterase activity in biological samples. To eliminate possible interference of DTNB with enzyme hydrolysis, we introduce a modification of the standard Ellman's assay. First, thioesters are hydrolyzed by cholinesterase to produce thiocholine in the absence of DTNB. Then, the reaction is stopped by a cholinesterase inhibitor and the produced thiocholine is revealed by DTNB and quantified at 412 nm. Indeed, this modification of Ellman's method increases butyrylcholinesterase activity by 20 to 25%. Moreover, high stability of thiocholine enables separation of the two reactions of the Ellman's method into two successive steps that may be convenient for some applications.

Performance Evaluation of Monolith Based Immobilized Acetylcholinesterase Flow-Through Reactor for Copper(II) Determination with Spectrophotometric Detection

A monolith based immobilized acetylcholinesterase (AChE) flow-through reactor has been developed for the determination of copper(II) using flow injection spectrophotometric system. The bioreactor was prepared inside a microcapillary column byin situpolymerization of butyl methacrylate, ethylene dimethacrylate, and 2,2-dimethoxy-1,2-diphynyletane-1-one in the presence of 1-decanol, followed by vinyl azlactone functionalization and AChE immobilization. The behavior of AChE before and after being immobilized on the monolith was evaluated by kinetic parameters from Lineweaver and Burk equation. The detection was based on measuring inhibition effect on the enzymatic activity of AChE by copper(II) using Ellman’s reaction with spectrophotometric detection at 410 nm. The linear range of the calibration graph was obtained over the range of 0.02–3.00 mg L−1. The detection limit, defined as 10% inhibition (I10), was found to be 0.04 mg L−1. The repeatability was 3.35 % (n=5) for 1.00 mg L−1of copper(II). The proposed method was applied to the determination of copper(II) in natural water samples with sampling rate of 4 h−1.

Isolation and characterization of bioactive compounds from plant resources: the role of analysis in the ethnopharmacological approach

The phytochemical research based on ethnopharmacology is considered an effective approach in the discovery of novel chemicals entities with potential as drug leads. Plants/plant extracts/decoctions, used by folklore traditions for treating several diseases, represent a source of chemical entities but no information are available on their nature. Starting from this viewpoint, the aim of this review is to address natural-products chemists to the choice of the best methodologies, which include the combination of extraction/sample preparation tools and analytical techniques, for isolating and characterizing bioactive secondary metabolites from plants, as potential lead compounds in the drug discovery process. The work is distributed according to the different steps involved in the ethnopharmacological approach (extraction, sample preparation, biological screening, etc.), discussing the analytical techniques employed for the isolation and identification of compound/s responsible for the biological activity claimed in the traditional use (separation, spectroscopic, hyphenated techniques, etc.). Particular emphasis will be on herbal medicines applications and developments achieved from 2010 up to date.