Platinum nanoparticles decorating a biomass porous carbon nanocomposite-modified electrode for the electrocatalytic sensing of luteolin and application

Extraction, detection, bioactivity, and product development of luteolin: A review

Luteolin is a kind of natural flavonoid, widely existing in a variety of plants, has been revealed to have a wide range of biological activities. In recent years, the research results of luteolin are abundant. Here we review the latest research results of luteolin in order to provide new ideas for further research and development of luteolin. In this paper, the focus of the search was published between 2010 and 2024 on the extraction and determination of luteolin, biological activities, and the development and application of luteolin products. A comprehensive search using the keyword "luteolin" was conducted in the PubMed, Web of Science and WIPO databases. Through the collection of related literature, this paper summarized a variety of extraction techniques of luteolin, including immersion extraction, solvent extraction, ultrasonic-assisted extraction, supercritical fluid extraction and so on. The determination methods include: thin layer chromatography (TLC), high performance liquid chromatography (HPLC), capillary electrophoresis (CE), electrochemical method (ED) and so on. In addition, the biological activities of luteolin, including antioxidant, anti-inflammatory, anti-tumor, antibacterial, analgesic and so on, were described. And luteolin as the main component of the product is being gradually developed, and has been used in the field of food, medicine and cosmetics. This paper provides a reference for further study of luteolin.

Monitoring of Specific Phytoestrogens by Dedicated Electrochemical Sensors: A Review

Phytoestrogens are non-steroidal estrogens produced from plants that can bind with the human body's estrogenic receptor site and be used as a substitute for maintaining hormonal balance. They are mainly classified as flavonoids, phenolic acids, lignans, stilbenes, and coumestans; some are resocyclic acids of lactones, which are mycotoxins and not natural phytoestrogen. Phytoestrogens have many beneficial medicinal properties, making them an important part of the daily diet. Electrochemical sensors are widely used analytical tools for analysing various pharmaceuticals, chemicals, pollutants and food items. Electrochemical sensors provide an extensive platform for highly sensitive and rapid analysis. Several reviews have been published on the importance of the biological and medicinal properties of phytoestrogens. However, this review provides an overview of recent work performed through electrochemical measurements with electrochemical sensors and biosensors for all the classes of phytoestrogens done so far since 2019.

Highly sensitive amperometric sensors based on laccase-mimetic nanozymes for the detection of dopamine

The current research presents novel sensors based on laccase-like mimetics for the detection of dopamine (DA). The synthesized laccase-like nanozymes (nAuCu, nPtCu, nCuMnCo, and nCoCuCe) were prepared by a simple hydrothermal method and exhibited an attractive catalytic activity toward DA. The developed amperometric sensors based on laccase nanozymes (nAuCu and nPtCu) are more stable, selective, and revealed a higher sensitivity (6.5-fold than the biosensor based on the natural fungal laccase from Trametes zonata). The amperometric sensors were obtained by modification of the glassy carbon electrodes (GCEs) with AuPt nanoparticles. Functionalization of the electrode surface by AuPt NPs resulted in increased catalytic activity of the laccase-like layer and higher sensitivity. Among studied configurations, the sensor containing nAuCu and nAuPt possesses a wide linear range for dopamine detection (10-170 μM), the lowest limit of detection (20 nM), and the highest sensitivity (10 650 ± 8.3 A M-1 m-2) at a low applied potential (+0.2 V versus Ag/AgCl). The proposed simple and cost-effective sensor electrode was used for the determination of DA in pharmaceuticals.

Electrochemistry of Flavonoids: A Comprehensive Review

Flavonoids represent a large group of aromatic amino acids that are extensively disseminated in plants. More than six thousand different flavonoids have been isolated and identified. They are important components of the human diet, presenting a broad spectrum of health benefits, including antibacterial, antiviral, antimicrobial, antineoplastic, anti-mutagenic, anti-inflammatory, anti-allergic, immunomodulatory, vasodilatory and cardioprotective properties. They are now considered indispensable compounds in the healthcare, food, pharmaceutical, cosmetic and biotechnology industries. All flavonoids are electroactive, and a relationship between their electron-transfer properties and radical-scavenging activity has been highlighted. This review seeks to provide a comprehensive overview concerning the electron-transfer reactions in flavonoids, from the point of view of their in-vitro antioxidant mode of action. Flavonoid redox behavior is related to the oxidation of the phenolic hydroxy groups present in their structures. The fundamental principles concerning the redox behavior of flavonoids will be described, and the phenol moiety oxidation pathways and the effect of substituents and experimental conditions on flavonoid electrochemical behavior will be discussed. The final sections will focus on the electroanalysis of flavonoids in natural products and their identification in highly complex matrixes, such as fruits, vegetables, beverages, food supplements, pharmaceutical compounds and human body fluids, relevant for food quality control, nutrition, and healthcare research.

The Peroxidase-like Nanocomposites as Hydrogen Peroxide-Sensitive Elements in Cholesterol Oxidase-Based Biosensors for Cholesterol Assay

Catalytically active nanomaterials, in particular, nanozymes, are promising candidates for applications in biosensors due to their excellent catalytic activity, stability and cost-effective preparation. Nanozymes with peroxidase-like activities are prospective candidates for applications in biosensors. The purpose of the current work is to develop cholesterol oxidase-based amperometric bionanosensors using novel nanocomposites as peroxidase (HRP) mimetics. To select the most electroactive chemosensor on hydrogen peroxide, a wide range of nanomaterials were synthesized and characterized using cyclic voltammetry (CV) and chronoamperometry. Pt NPs were deposited on the surface of a glassy carbon electrode (GCE) in order to improve the conductivity and sensitivity of the nanocomposites. The most HRP-like active bi-metallic CuFe nanoparticles (nCuFe) were placed on a previously nano-platinized electrode, followed by conjugation of cholesterol oxidase (ChOx) in a cross-linking film formed by cysteamine and glutaraldehyde. The constructed nanostructured bioelectrode ChOx/nCuFe/nPt/GCE was characterized by CV and chronoamperometry in the presence of cholesterol. The bionanosensor (ChOx/nCuFe/nPt/GCE) shows a high sensitivity (3960 A·M^-1·m^-2) for cholesterol, a wide linear range (2-50 µM) and good storage stability at a low working potential (-0.25 V vs. Ag/AgCl/3 M KCl). The constructed bionanosensor was tested on a real serum sample. A detailed comparative analysis of the bioanalytical characteristics of the developed cholesterol bionanosensor and the known analogs is presented.

A boronate-affinity magnetic molecularly imprinted polymer for luteolin recognition

In this study, 3-carboxyphenylboronic acid (CP)-functionalized amino-modified Fe₃O₄ (Fe₃O₄@NH₂-CP, FNC) magnetic molecularly imprinted polymers (FNC@MIPs) were synthesized and applied for the quick identification and selective separation of luteolin (LTL). The structure and morphology were characterized in detail by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and vibrating specimen magnetometry (VSM) methods. The FNC@MIPs had a homogeneous shape, excellent magnetic characteristics, quick binding kinetics, a high adsorption capacity, acceptable selectivity, and stable reusability. The solid-phase extraction parameters and preparation conditions were both optimized. Under optimized conditions, the maximal adsorption capacity was 14.26 mg g^-1 and the imprinting factor was 3.62. Furthermore, the experimental kinetics data were best fitted with the pseudo-first-order model (R² = 0.9877), and the Langmuir model could describe the adsorption process (R² = 0.9979), suggesting a monolayer covering. The practical application of the sorbent for LTL detection in Lonicera japonica Thunb samples showed recoveries in the range of 84.5-108.7%. Therefore, the strategy offers a fresh avenue for the extraction and purification of LTL.

Preparation and Application of Electrochemical Horseradish Peroxidase Sensor Based on a Black Phosphorene and Single-Walled Carbon Nanotubes Nanocomposite

To design a new electrochemical horseradish peroxidase (HRP) biosensor with excellent analytical performance, black phosphorene (BP) nanosheets and single-walled carbon nanotubes (SWCNTs) nanocomposites were used as the modifier, with a carbon ionic liquid electrode (CILE) as the substrate electrode. The SWCNTs-BP nanocomposite was synthesized by a simple in situ mixing procedure and modified on the CILE surface by the direct casting method. Then HRP was immobilized on the modified electrode with Nafion film. The electrocatalysis of this electrochemical HRP biosensor to various targets was further explored. Experimental results indicated that the direct electrochemistry of HRP was realized with a pair of symmetric and quasi-reversible redox peaks appeared, which was due to the presence of SWCNTs-BP on the surface of CILE, exhibiting synergistic effects with high electrical conductivity and good biocompatibility. Excellent electrocatalytic activity to trichloroacetic acid (TCA), sodium nitrite (NaNO₂), and hydrogen peroxide (H₂O₂) were realized, with a wide linear range and a low detection limit. Different real samples, such as a medical facial peel solution, the soak water of pickled vegetables, and a 3% H₂O₂ disinfectant, were further analyzed, with satisfactory results, further proving the potential practical applications for the electrochemical biosensor.

Nanocomposites of boronic acid-functionalized magnetic multi-walled carbon nanotubes with flexible branched polymers as a novel desorption/ionization matrix for the capture and direct detection of cis-diol-flavonoid compounds coupled with MALDI-TOF-MS

Novel boronic acid-functionalized magnetic multi-walled carbon nanotubes with flexible branched polymer (Fe₃O₄@MWCNTs@ε-PL@BA) nanocomposites were fabricated and applied as the desorption/ionization matrix for the MALDI-TOF-MS determination of low molecular weight flavonoids. The prepared nanocomposite was systematically characterized by various techniques. Compared to the traditional organic matrix, the proposed Fe₃O₄@MWCNTs@ε-PL@BA matrix has excellent ionization efficiency and low-background noise interference due to the MWCNTs unique electron-phonon interaction and the high introduction density of boronic acid functional groups. Good sensitivity and ultra-high salt tolerance of the Fe₃O₄@MWCNTs@ε-PL@BA-assisted MALDI-TOF-MS were permitted for the determination and quantification of flavonoids in actual samples. Noticeably, the limits of detection (LODs) for the target flavonoids were in the range 17-33 nM. The relative standard deviations (RSDs) of spot-to-spot and sample-to-sample (n = 10) were ≤ 9.8% and ≤ 10.1%, respectively. Furthermore, the wide linear ranges (0.1 - 500 µg/mL) and satisfactory calibration plot coefficients (R² > 0.99) of flavonoids were achieved by MALDI-TOF-MS with the Fe₃O₄@MWCNTs@ε-PL@BA matrix. Good recoveries (92-105.5%) were achieved for the target flavonoids in practical food samples. Hence, the prepared Fe₃O₄@MWCNTs@ε-PL@BA nanocomposites have applications in the selective and efficient capture of target flavonoids active biomolecules coupled with MALDI-TOF-MS determination in actual samples.

A Comprehensive Review on the Electrochemical Sensing of Flavonoids

Flavonoids are bioactive polyphenolic compounds, widespread in the plant kingdom. Flavonoids possess broad-spectrum pharmacological effects due to their antioxidant, anti-tumor, anti-neoplastic, anti-mutagenic, anti-microbial, anti-inflammatory, anti-allergic, immunomodulatory, and vasodilatory properties. Care must be taken, since excessive consumption of flavonoids may have adverse effects. Therefore, proper identification, quantification and quality evaluations of flavonoids in edible samples are necessary. Electroanalytical approaches have gained much interest for the analysis of redox behavior and quantification of different flavonoids. Compared to various conventional methods, electrochemical techniques for the analysis of flavonoids offer advantages of high sensitivity, selectivity, low cost, simplicity, biocompatibility, easy on-site evaluation, high accuracy, reproducibility, wide linearity of detection, and low detection limits. This review article focuses on the developments in electrochemical sensing of different flavonoids with emphasis on electrode modification strategies to boost the electrocatalytic activity and analytical efficiency.

Analytical determinations of luteolin

Plants, through the photosynthesis process, produce the substances necessary for all the life cycles of nature, which are called "primary metabolites." Moreover, there are some plants that synthesize, in addition to these, other substances with more specific functions, which are known as "secondary metabolites." It is inside this group that flavonoids are located, whose main function is to protect organisms from damage caused by different oxidizing agents. Luteolin (3,4,5,7-tetrahydroxy-flavone) belongs to the sub-class of flavonoids known as flavones and is one of 10,000 flavonoids currently known, being one of the most bio-active flavonoids. Its various beneficial properties for health, together with the increasing reduction in the use of synthetic antioxidants, make the study of luteolin a very active field. Within this, the quantification of this molecule has become a subject of very special interest given that it is transversal to all fields. In this review article, we aim to give the reader a broad and deep vision of this topic, focusing on the events reported in the last 5 years and covering all possible techniques related to analytical determinations. We will discuss in terms of advantages and disadvantages between techniques, selectivity, sensitivity, costs, time consumption, and reagents as well as in the complexity of operations.

A fungus-derived biomass porous carbon-MnO2 nanocomposite-modified electrode for the voltammetric determination of rutin

In this study, we designed a simple procedure for the synthesis of fungus-derived biomass porous carbon (FBPC), which was further used to prepare a MnO₂@FBPC composite by a hydrothermal method. The MnO₂@FBPC nanocomposite showed a porous structure, large specific surface area, and high conductivity, and was modified on the carbon ionic liquid electrode (CILE) to obtain a working electrode for the sensitive voltammetric determination of rutin. The electrochemical response of rutin was studied via cyclic voltammetry with electrochemical parameters calculated. Under the optimal conditions, the linear range for the rutin analysis was obtained by the differential pulse voltammetry from 0.008 to 700.0 μmol L^-1 with the detection limit of 2.67 nmol L^-1 (3σ). This MnO₂@FBPC/CILE was applied to directly detect the rutin concentration in drug and human urine samples with satisfactory results.

Ultrasensitive Electrochemical Sensor for Luteolin Based on Zirconium Metal-Organic Framework UiO-66/Reduced Graphene Oxide Composite Modified Glass Carbon Electrode

Luteolin is a kind of natural flavonoid with many bioactivities purified from a variety of natural herbs, fruits and vegetables. Electrochemical sensing has become an outstanding technology for the detection of luteolin in low concentration due to its fast response, easy operation and low cost. In this study, electroreduced graphene oxide (ErGO) and UiO-66 were successively modified onto a glassy carbon electrode (UiO-66/ErGO/GCE) and applied to the detection of luteolin. A combination of UiO-66 and ErGO showed the highest promotion in the oxidation peak current for luteolin compared with those of a single component. The factors affecting the electrochemical behavior of UiO-66/ErGO/GCE were evaluated and optimized including pH, accumulation potential, accumulation time and scan rate. Under optimum conditions, UiO-66/ErGO/GCE showed satisfactory linearity (from 0.001 μM to 20 μM), reproducibility and storage stability. The detection limit of UiO-66/ErGO/GCE reached 0.75 nM of luteolin and was suitable for testing real samples. Stable detection could be provided at least eight times by one modified electrode, which guaranteed the practicability of the proposed sensor. The fabricated UiO-66/ErGO/GCE showed a rapid electrochemical response and low consumption of materials in the detection of luteolin. It also showed satisfactory accuracy for real samples with good recovery. In conclusion, the modification using MOFs and graphene materials made the electrode advanced property in electrochemical sensing of natural active compounds.

Biosensors and Sensing Systems for Rapid Analysis of Phenolic Compounds from Plants: A Comprehensive Review

Phenolic compounds are secondary metabolites frequently found in plants that exhibit many different effects on human health. Because of the relevant bioactivity, their identification and quantification in agro-food matrices as well as in biological samples are a fundamental issue in the field of quality control of food and food supplements, and clinical analysis. In this review, a critical selection of sensors and biosensors for rapid and selective detection of phenolic compounds is discussed. Sensors based on electrochemistry, photoelectrochemistry, fluorescence, and colorimetry are discussed including devices with or without specific recognition elements, such as biomolecules, enzymes and molecularly imprinted materials. Systems that have been tested on real matrices are prevalently considered but also techniques that show potential development in the field.