Dual electrophoretically-mediated microanalysis in multiple injection mode for the simultaneous determination of acetylcholinesterase and α-glucosidase activity applied to selected polyphenols

A colorimetric sensing strategy based on chitosan-stabilized platinum nanoparticles for quick detection of α-glucosidase activity and inhibitor screening

α-Glucosidase (α-Glu) is implicated in the progression and pathogenesis of type II diabetes (T2D). In this study, we developed a rapid colorimetric technique using platinum nanoparticles stabilized by chitosan (Ch-PtNPs) to detect α-Glu activity and its inhibitor. The Ch-PtNPs facilitate the conversion of 3,3',5,5'-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB) in the presence of dissolved O2. The catalytic hydrolysis of 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) by α-Glu produces ascorbic acid (AA), which reduces oxTMB to TMB, leading to the fading of the blue color. However, the presence of α-Glu inhibitors (AGIs) hinders the generation of AA, allowing Ch-PtNPs to re-oxidize colorless TMB back to blue oxTMB. This unique phenomenon enables the colorimetric detection of α-Glu activity and AGIs. The linear range for α-Glu was found to be 0.1-1.0 U mL-1 and the detection limit was 0.026 U mL-1. Additionally, the half-maximal inhibition value (IC50) for acarbose, an α-Glu inhibitor, was calculated to be 0.4769 mM. Excitingly, this sensing platform successfully detected α-Glu activity in human serum samples and effectively screened AGIs. These promising findings highlight the potential application of the proposed strategy in clinical diabetes diagnosis and drug discovery.

An in-line method for high-throughput screening of protein tyrosine phosphatase receptor type O inhibitors by capillary electrophoresis based on electrophoretically mediated microanalysis

Protein tyrosine phosphatase receptor type O (PTPRO) plays an important role in inflammation-related pathways and has become an emerging drug target. In this study, we developed an in-line capillary electrophoresis (CE) method for the investigation of the enzymatic activity of PTPRO, which was based on electrophoretically mediated microanalysis (EMMA). After a thorough method validation of the optimized conditions, this protocol was successfully employed to determine the kinetics of PTPRO as well as the half-maximal inhibitory concentration (IC50) of two typical PTPRO inhibitors. The final results were consistent with the values obtained through classical ultraviolet-visible (UV-vis) spectrophotometry. Our new method exhibited improved accuracy and reduced consumption, avoiding the disadvantages of traditional methods. This work provides a new strategy for PTPRO enzyme kinetic studies as well as inhibitory activity determination through capillary electrophoresis for the first time.

Two-dimensional metal-organic framework catalyzed chemiluminescent reaction for alpha-glucosidase inhibitor screening

α-Glucosidase inhibitors (AGIs) are oral antidiabetic drugs used in the treatment of type Ⅱ diabetes. It is integral to establish methods for AGIs screening. For the detection of α-glucosidase (α-Glu) activity and screening of AGIs, a chemiluminescence (CL) platform was established based on cascade enzymatic reactions. Firstly, the catalytic activity of a two-dimensional (2D) metal-organic framework (MOF) with iron as central metal atoms and 1,3,5-benzene tricarboxylic acid as a ligand (denoted as 2D Fe-BTC) in the luminol-hydrogen peroxide (H2O2) CL reaction were studied. Mechanism studies showed that the Fe-BTC may react with H2O2 to produce ·OH and act as catalase to facilitate the decomposition of H2O2 to produce O2, thus showing good catalytic activity in the luminol-H2O2 CL reaction. The proposed luminol-H2O2-Fe-BTC CL system exhibited an outstanding response to glucose with the aid of glucose oxidase (GOx). The luminol-GOx-Fe-BTC system showed a detection linear range from 50 nM to 10 μM with a detection limit (LOD) of 3.62 nM for glucose detection. Then, the luminol-H2O2-Fe-BTC CL system was applied to the detection of α-glucosidase (α-Glu) activity and screening of AGIs based on cascade enzymatic reactions using acarbose and voglibose as model drugs. The IC50 of acarbose and voglibose was 7.39 μM and 1.89 mM, respectively.

Immobilized acetylcholinesterase in magnetic nanoparticles for in-line inhibition studies using a capillary electrophoresis system

Enzyme assays can be performed with the capillary electrophoresis technique (CE) in many approaches, such as the immobilized enzyme micro-reactor. Acetylcholinesterase is a promising enzyme to be used when pursuing such a method, as it has already been explored in the proposal of similar methods of miniaturizing enzyme assays. The present work proposes a novel enzyme micro-reactor, based on the anchorage of the enzyme on magnetic nanoparticles of MnFe₂O_4, with chitosan and glutaraldehyde as the cross-linker in the capillary by means of an arrange of neodymium magnets. The calculated K_m of the enzyme evaluated by this method was 1.12 mmol L^-1, comparable to other studies in the literature that utilizes immobilized enzymes. Also, IC₅₀ for neostigmine was assessed in 3 different micro-reactors, with an average of 29.42 ± 3.88 μmol L^-1. In terms of the micro-reactor stability, it was possible to perform at least 25 experiments with assembled micro-reactor. The method was applied to hydroalcoholic extracts of 7 plant species. Plinia cauliflora had the best result, with 42.31 ± 6.81% of enzyme inhibition in a concentration of 100 mg L^-1.

Alternative method for microenzymatic inhibition activities monitoring from Baccharis trimera extracts by CZE-UV

INTRODUCTION

Capillary zone electrophoresis with direct UV detection (CZE-UV) was used to investigate the hypothesis about the extract of Baccharis trimera enzymatic activities as an analytical approach to monitoring the phenomenon.

OBJECTIVE

The aim of this work was to investigate enzymatic bioactivities of the hydroalcoholic and infusion extracts of B. trimera through screening evaluation of the inhibition of the enzymes acetylcholinesterase (AChE) and α-glycosidase (α-GLY).

METHOD

An alternative approach using CZE-UV to hydroalcoholic and infusion extracts of B. trimera monitoring was applied to evaluate the inhibition ability of the enzymes AChE and α-GLY. The result of the reaction of acetylthiocholine (AThCh) with AChE was thiocholine (TCh) and acetic acid, and from the amount of TCh generated, the AChE inhibition was calculated. For the inhibition study of the two enzymes, the reactions of the extracts were optimised to be performed in situ, inside the capillary column, and the introduction of the solutions was performed through ordered sequential plug injections.

RESULTS

Samples extracted with 70% ethanol presented 7.80% inhibition for AChE and 0.51% for α-GLY, while samples extracted with 96% ethanol resulted in 6.89% inhibition for AChE and no inhibition activity for α-GLY.

CONCLUSION

In the present work, the potentialities of CZE-UV for the study of hydroalcoholic and infusion extracts of B. trimera were demonstrated. The experimental results were useful for the calculation of the percentage of the inhibition activities of the AChE and α-GLY enzymes.

Microscale Quantification of the Inhibition of Neuraminidase Using Capillary Nanogel Electrophoresis

Neuraminidase inhibitors modulate infections that involve sialic acids, making quantitative analyses of this inhibitory effect important for selecting and designing potential therapeutics. An automated nanogel capillary electrophoresis system is developed that integrates a 5 nL enzyme inhibition reaction in line with a 5 min separation-based assay of the enzymatic product to quantify inhibition as the half maximal inhibitory concentration (IC50) and inhibitor constant (Ki). A neuraminidase enzyme from Clostridium perfringens is non-covalently immobilized in a thermally tunable nanogel positioned in the thermally controlled region of the capillary by increasing the capillary temperature to 37 °C. Aqueous inhibitor solutions are loaded into the capillary during the nanogel patterning step to surround the enzyme zone. The capillary electrophoresis separation provides a means to distinguish the de-sialylated product, enabling the use of sialyllactose which contains the trisaccharide motif observed on serine/threonine-linked (O-linked) glycans. A universal nanogel patterning scheme is developed that does not require pre-mixing of enzymes with inhibitors when an automated capillary electrophoresis instrument is used, thus reducing the consumption of enzymes and enabling adaption of the method to different inhibitors. The universal approach is successfully applied to two classical neuraminidase inhibitors with different electrophoretic mobilities. The IC50 and Ki values obtained for N-acetyl-2,3-dehydro-2-deoxyneuraminic acid (DANA) are 13 ± 3 and 5.0 ± 0.9 μM, respectively, and 28 ± 3 and 11 ± 1 μM, respectively, for Siastatin B. These values agree with literature reports and reflect the weaker inhibition anticipated for Siastatin B in comparison to DANA.

Bioactive Components from Ampelopsis japonica with Antioxidant, Anti-α-Glucosidase, and Antiacetylcholinesterase Activities

The dried root of Ampelopsis japonica (Thunb.) Makino (A. japonica.) is a traditional medicine used to treat fever, pain, and wound healing. It exhibits anti-inflammatory, antitumor, antityrosinase, and antimelanogenic activities. In this paper, we used different solvent extracts from the root of A. japonica to determine their antioxidant activity. Acetone extract showed relatively strong antioxidant properties by 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH), superoxide radical scavenging activity, and ferric reducing antioxidant power (FRAP) assays. In addition, these extracts also showed significant α-glucosidase and acetylcholinesterase (AChE) inhibitory activities. Acetone extract significantly inhibited α-glucosidase with an IC₅₀ value of 8.30 ± 0.78 μg/mL, and ethanol extract remarkably inhibited AChE with an IC₅₀ value of 37.08 ± 7.67 μg/mL. Using HPLC analysis and comparison with the chemical composition of various solvent extracts, we isolated seven active compounds and assessed their antioxidant, anti-α-glucosidase, and anti-AChE activities. Catechin (1), gallic acid (2), kaempferol (3), quercetin (4), resveratrol (6), and epicatechin (7) were the main antioxidant components in the root of A. japonica. According to the results of DPPH, ABTS, and superoxide radical scavenging assays, these isolates showed stronger antioxidant capacity than butylated hydroxytoluene (BHT). Moreover, 1, 3, 4, euscaphic acid (5), 6, and 7 also expressed stronger anti-α-glucosidase activity than the positive control acarbose, and all the isolated compounds had a good inhibitory effect on AChE. Molecular docking models and hydrophilic interactive modes for AChE assays suggest that 1 and 5 exhibit unique anti-AChE potency. This study indicates that A. japonica and its active extracts and components may be a promising source of natural antioxidants, α-glucosidase, and AChE inhibitors.

Enhanced Sample Throughput Capillary Zone Electrophoresis with UV Detection in Hydrodynamically Closed System for Determination of Ibuprofen

A simple analytical approach based on capillary zone electrophoresis with ultraviolet detection and repeated sample injection strategy (applied in a hydrodynamically closed separation system for the first time) was developed for the determination of ibuprofen (IBU) in commercially available pharmaceutical preparations. The proposed method was characterized by significantly increased sample throughput and favorable validation parameters, highly demanded in routine quality control laboratories. The limit of detection was predicted at the concentration level of 0.31 µg/mL. Intra-day precision expressed as the relative standard deviation of IBU concentration ranged from 1.9 to 5.6%, and corresponding intra-day accuracy expressed as the relative error was in the interval of 87.1–106.5%. Inter-day precision was in the range of 2.6–15.0%, and inter-day accuracy was 94.9–102.7%. The developed method was able to quantify IBU in complex pharmaceutical matrices represented by commercially available tablets and oral suspension. The determined contents of IBU in the tested dosage forms were in good agreement with the manufacturer’s declaration. The analytical performance of the developed method was evaluated according to the innovative RGB Additive Color Model strategy. It was demonstrated that the proposed method is characterized by very good analytical performance parameters, safety and eco-friendliness, and practical effectiveness.

Overview of in-capillary enzymatic reactions using capillary electrophoresis

This review summarizes the research that has recently been performed on in-capillary enzymatic reactions integrated with capillary electrophoresis. The manuscript is subdivided in homogeneous and heterogeneous approaches. The main homogeneous techniques are Electrophoretically Mediated Microanalysis, At-inlet and Transverse Diffusion of Laminar Flow Profiles. The main heterogeneous ones are Immobilized MicroEnzyme Reactors with enzymes grafted on either non-magnetic or magnetic particles. The overview covers the period from 2018 to early 2021. The applications range from drug discovery over natural products to food, beverage and pesticide analysis.

Defatted Seeds of Oenothera biennis as a Potential Functional Food Ingredient for Diabetes

The defatted seeds of Oenothera biennis (DSOB) are a by-product of evening primrose oil production that are currently not effectively used. In this study, α-glucosidase inhibition, aldose reductase inhibition, antioxidant capacity, polyphenol composition, and nutritional value (carbohydrates, proteins, minerals, fat, organic acid, and tocopherols) of DSOB were evaluated using the seeds of Oenothera biennis (SOB) as a reference. DSOB was an excellent inhibitor of α-glucosidase (IC₅₀ = 3.31 μg/mL) and aldose reductase (IC₅₀ = 2.56 μg/mL). DSOB also showed considerable antioxidant capacities (scavenging of 2,2-diphenyl-1-picrylhydrazyl, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid, nitric oxide, peroxynitrite, and hydroxyl radicals). DSOB was a reservoir of polyphenols, and 25 compounds in DSOB were temporarily identified by liquid chromatography coupled with electrospray ionization–quadrupole time of flight–mass spectrometry analysis. Moreover, the carbohydrate, protein, and mineral content of DSOB were increased compared to that of SOB. DSOB contained large amounts of fiber and low levels of sugars, and was rich in calcium and iron. These results imply that DSOB may be a potential functional food ingredient for diabetes, providing excellent economic and environmental benefits.

A colorimetric sensing strategy based on enzyme@metal-organic framework and oxidase-like IrO2/MnO2 nanocomposite for α-glucosidase inhibitor screening

A highly sensitive colorimetric sensing strategy based on enzyme@metal-organic framework (GAA@Cu-MOF) and IrO₂/MnO₂ nanocomposite was exploited innovatively for screening of α-glucosidase (GAA) inhibitors. IrO₂/MnO₂ nanocomposite exhibits excellent oxidase-mimicking activity which can directly catalyze the oxidation of 3,3^,5,5^,-tetramethylbenzidine (TMB) into a blue product with an absorption maximum at 652 nm. And GAA@Cu-MOF can decompose L-ascorbic acid-2-O-α-D-glucopyranosyl (AAG) to ascorbic acid (AA). The produced AA can destroy the IrO₂/MnO₂ nanocomposite and reduce its oxidase-like activity. However, the generation of AA is restricted when GAA inhibitors are added to the system, which allows the oxidase-like activity of the IrO₂/MnO₂ nanocomposite to be maintained. In view of this, a method for screening of GAA inhibitors was developed. In addition to enhancing the stability of GAA, the method can also effectively avoid the potential interference of H₂O₂ in the screening process of GAA inhibitors, which helps to improve the sensitivity of the method. Therefore, highly sensitive determination for acarbose and ascorbic acid are achieved with detection limits of 6.27 nM and 1.23 μM, respectively. The proposed method was successfully applied to screen potential GAA inhibitors from oleanolic acid derivatives. Graphical abstract.