Magnetic molecularly imprinted polymers for spectrophotometric quantification of curcumin in food

Rational Design of Molecularly Imprinted Polymers for Curcuminoids Binding: Computational and Experimental Approaches for the Selection of Functional Monomers

Molecularly imprinted polymers (MIPs) have emerged as bespoke materials with versatile molecular applications. In this study, we propose a proof of concept for a methodology employing molecular dynamics (MD) simulations to guide the selection of functional monomers for curcuminoid binding in MIPs. Curcumin, demethoxycurcumin, and bisdemethoxycurcumin are phenolic compounds widely employed as spices, pigments, additives, and therapeutic agents, representing the three main curcuminoids of interest. Through MD simulations, we investigated prepolymerization mixtures composed of various functional monomers, including acrylamide (ACA), acrylic acid (AA), methacrylic acid (MAA), and N-vinylpyrrolidone (NVP), with ethylene glycol dimethacrylate (EGDMA) as the cross-linker and acetonitrile as the solvent. Curcumin was selected as the template molecule due to its structural similarity to the other curcuminoids. Notably, the prepolymerization mixture containing NVP as the functional monomer demonstrated superior molecular recognition capabilities toward curcumin. This observation was supported by higher functional monomer molecules surrounding the template, a lower total nonbonded energy between the template and monomer, and a greater number of hydrogen bonds in the aggregate. These findings suggest a stronger affinity between the functional monomer NVP and the template. We synthesized, characterized, and conducted binding tests on the MIPs to validate the MD simulation results. The experimental binding tests confirmed that the MIP-NVP exhibited higher binding capacity. Consequently, based on MD simulations, our computational methodology effectively guided the selection of the functional monomer, leading to MIPs with binding capacity for curcuminoids. The outcomes of this study provide a valuable reference for the rational design of MIPs through MD simulations, facilitating the selection of components for MIPs. This computational approach holds the potential for extension to other templates, establishing a robust methodology for the rational design of MIPs.

Yellow-emitting carbon dots as fluorescent sensors for the rapid determination of curcumin

The non-standard use of curcumin could cause some adverse drug reactions, such as diarrhea, nausea and skin allergies. Thus, the curcumin determination was fundamental to disease treatment and prevention. Herein, a facile and efficient fluorescent probe was developed based on carbon dots, which was prepared through hydrothermal method (o-phenylenediamine and N-isopropylacrylamide as the reaction raw materials). Characteristics of the as-fabricated carbon dots (NCDs) were studied through some analysis techniques, such as UV-vis absorption spectroscopy, transmission electron microscopy, Fourier transform infrared instrument, X-ray photoelectron spectroscopy and fluorescence spectrophotometer. Fluorescence quenching phenomenon could be observed after addition of curcumin. This as-prepared fluorescent probe displayed a significant response for the determination of curcumin with a satisfactorily lower detection limit of 0.017 μM and a considerable linear range of 0.5-50 μM compared to reported literatures. Because of the preeminent repeatability and anti-jamming capability, the as-developed CDs suggested mighty potentiality for actual applications of curcumin detection in real samples and temperature sensing.

Synthesis and Characteristics of Polymer-Mediated Curcumin Molecular Imprinting for Quantitative Determination of Curcumin in Food Samples

In this study, a molecularly imprinted polymer (MIP)-based extraction process for determining curcumin in food samples was carried out. MIP and NIP were thermally synthesized in acetonitrile solvent (porogen) using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linking agent, azobisisobutyronitrile as an initiator, and curcumin as a template molecule. Parameters affecting the synthesis process, such as temperature, the ratio of the components in the reaction, and the extraction solvent, were investigated. The characteristics of the synthesized material were examined using infrared spectroscopy and scanning electron microscopy. The maximum adsorption capacity of the material was found to be 1.34 mg/g MIP with an adsorption efficiency of 89.96% for MIP and 12.35% for NIP. The MIP material exhibited high selectivity for curcumin compared to other compounds such as quercetin (18.00%), rutin (14.74%), and ketoconazole (0.00%). The analysis method for curcumin using the MIP material was performed with validated parameters including linear range (1 - 25 mg/L, r2 = 0.9997), accuracy (recovery rate of 90.90 %), precision (RSDR = 0.338 %, RSDr = 1.591 %), detection limit (0.051 mg/L), and quantification limit (0.156 mg/L). The validation results indicated that the HPLC-DAD method was entirely suitable for analyzing the curcumin content in food samples.

Molecularly imprinted polymers: A closer look at the template removal and analyte binding

Molecularly imprinted polymers (MIPs), which first appeared over half a century ago, are now attracting considerable attention as artificial receptors, particularly for sensing. MIPs, especially applied to biomedical analysis in biofluids, contribute significantly to patient diagnosis at the point of care, thereby allowing health monitoring. Despite the importance given to MIPs, removal of templates and binding of analytes have received little attention and are currently the least focused steps in MIP development. This critical review is dedicated to a comprehensive analysis and discussion of cutting-edge concepts and methodologies in the removal and binding steps pertaining to various types of analytes, including ions, molecules, epitopes, proteins, viruses, and bacteria. The central objective of this review is to comprehensively examine and discuss a range of removal methods, including soxhlet extraction, immersion, microwave-assisted technique, ultrasonication, electrochemical approach, and proteolytic digestion, among others. Additionally, we will explore various binding methods, such as soaking, drop-casting, and batch sorption, to provide a comprehensive overview of the subject. Furthermore, the current challenges and perspectives in removal and binding are highlighted. Our review, at the interface of chemistry and sensors, will offer a wide range of opportunities for researchers whose interests include MIPs, (bio)sensors, analytical chemistry, and diagnostics.

High-efficiency fluorescent coordination polymer nanoparticles co-doped with Ce3+/Tb3+ ions for curcumin detection

Curcumin (Cur) possesses diverse biological and pharmacologic effects. It is widely used as a food additive and therapeutic medicine. A study to determine a sensitive detection method for Cur is necessary and meaningful. In this work, double rare earth ions co-doped fluorescent coordination polymer nanoparticles (CPNPs) were developed for the Cur detection. The CPNPs were synthesized by using adenosine monophosphate (AMP) as bridge ligands via coordination self-assembly with Ce3+ and Tb3+. The AMP-Ce/Tb CPNPs exhibited the characteristic green fluorescence of Tb3+ and had high luminescence efficiency. Under the optimal conditions, the fluorescence intensity of AMP-Ce/Tb CPNPs could be significantly quenched by Cur. The fluorescence quenching extent at λex/λem of 300 nm/544 nm showed a good linear relationship with the Cur concentration in the range of 10 to 1000 nM. The detection limit was as low as 8.0 nM (S/N = 3). This method was successfully applied to the determination of Cur in real samples with satisfactory results. The luminescence mechanism of AMP-Ce/Tb CPNPs and the fluorescence quenching mechanism of the CPNPs by Cur were both examined.

Synthesis, Characterization, and Evaluation of a Novel Molecularly Imprinted Polymer (MIP) for Selective Quantification of Curcumin in Real Food Sample by UV-Vis Spectrophotometry

Curcumin is the main colorant of the curcuma longa plant, a food with many benefits for human health. This work aims to synthesize a novel molecularly imprinted polymer (MIP) for the selective detection of curcumin in real samples obtained from the local market of Peru. MIPs were synthesized via bulk polymerization using curcumin, acrylamide, ethylene glycol dimethacrylate, ABCV, and acetonitrile. FTIR spectra showed equal spectra for MIP and NIP. N2 physisorption analysis presented a higher value BET surface for the MIP (28.5 m2 g-1) compared to the NIP (18.5 m2 g-1). The adsorption capacity of the MIP was evaluated using UV-vis spectrophotometry in the band around 430 nm. The adsorption kinetics found were of pseudo-second-order and a Qe value of 16.2 mg g-1. Furthermore, the adsorption process resembles the Freundlich adsorption model with a heterogeneity factor of less than 1 (0.61) and Kf greater for MIP (1.97). The selectivity test indicated that MIP is more selective for curcumin (Q = 13.20 mg g-1) than against interferents (Q = 2.19 mg g-1). The specific selectivity factor (S) obtained for the interferents was greater than 1 which indicates a good selectivity. Finally, the application of MIP in real samples using UV-vis spectrophotometry yielded a recovery value greater than 70%.

Electrochemical Investigation of Curcumin-DNA Interaction by Using Hydroxyapatite Nanoparticles-Ionic Liquids Based Composite Electrodes

Hydroxyapatite nanoparticles (HaP) and ionic liquid (IL) modified pencil graphite electrodes (PGEs) are newly developed in this assay. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV) were applied to examine the microscopic and electrochemical characterization of HaP and IL-modified biosensors. The interaction of curcumin with nucleic acids and polymerase chain reaction (PCR) samples was investigated by measuring the changes at the oxidation signals of both curcumin and guanine by differential pulse voltammetry (DPV) technique. The optimization of curcumin concentration, DNA concentration, and the interaction time was performed. The interaction of curcumin with PCR samples was also investigated by gel electrophoresis.

Development of hydrophilic magnetic molecularly imprinted polymers for the dispersive solid-phase extraction of sulfonamides from animal-derived samples before HPLC detection

Highly hydrophilic magnetic molecularly imprinted polymers were prepared through a surface imprinting technique for dispersive solid-phase extraction coupled with high-performance liquid chromatography to detect trace levels of ten sulfonamides in animal-derived samples. The obtained imprinted polymers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and adsorption experiments, which exhibited excellent specific adsorption for template sulfamethazine in aqueous solution. Moreover, the adsorption process could be completed within 25 min. Under the optimum conditions, the method exhibits good linear performance in the range of 5-to 10 mg/L, limits of detection ranging from 0.57 to 1.50 μg/L, and good recoveries of 85.09-110.93% in the spiked samples (chicken, cow milk, and goat milk). The proposed detection method not only avoids the use of organic solvents but also simplifies the pretreatment procedure via excellent magnetic properties. Furthermore, the method shows great potential for the rapid detection of drug residues.

The Synthesis of Molecularly Imprinted Polymers on Microcentrifuge Tube Filters for Solid-Phase Extraction and the HPLC-UV Determination of Andrographolides

Molecular imprinting-based solid-phase extraction has been in the spotlight to improve recognition selectivity and detection sensitivity of andrographolides. The synthesis of molecularly imprinted polymers on micro centrifuge tube filters for the extraction and the determination of andrographolides were investigated. Molecularly imprinted polymers were synthesized using the photo-polymerization method for the preconcentration of andrographolides (AD) template molecule using 2,2-dimethoxy-2-phenylacetophenone as initiators, the mixture of 1-dodecanol and toluene solvent, 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate as functional monomers and cross-linked, respectively. The resultant AD molecularly imprinted polymers (AD-MIPs) were characterized using the Fourier-transform infrared spectrum and scanning electron microscopy. The maximum adsorption of AD-MIPs toward the andrographolides was found to be 85%, and could reach binding equilibrium within 60 min. The sample solution was separated by AD-MIP using solid-phase extraction (SPE). Subsequently, the sample solution was analyzed by the high-performance liquid chromatography (HPLC) method. The AD-MIP could be successfully applied to specifically separate and determine the andrographolides from pharmaceutical products and biological fluid samples with relatively high recoveries (102.01-108.61%). The present method is simple, selective, accurate, and provides a promising alternative to traditional SPE sorbents for the extraction and determination of andrographolides in real samples and biological fluid samples.

Luminescence of Eu (III) complex under near-infrared light excitation for curcumin detection

An intrinsic Eu(III) luminescence phenomenon of Eu(III) complex was found under near-infrared light (NIRL) excitation of xenon lamp, and the maximum excitation wavelength is about twice the excitation wavelength of its Stokes fluorescence. The NIRL excitation fluorescence was mainly originated from second order diffracted light (SODL) excitation. The Eu(III) complex was consist of Eu(III), Gd(III), 2-trifluoroacetylacetone (TTA) and cetyltrimethylammonium bromide (CTAB). Curcumin (Cur) could notably quench the luminescence intensity of the Eu(III) complex. Based on this, a sensitive method for Cur detection was developed. Under optimum conditions, the decrease extent in the fluorescence intensity at 611 nm exhibited a good linear relationship with the Cur concentration in the range of 2.0 × 10^-9 mol/L - 6.0 × 10^-8 mol/L under 746 nm excitation, the limit of detection (LOD, S/N = 3) was 5.2 × 10^-10 mol/L. While, the linear relationship and the LOD of Stokes fluorescence method (λ_ex/λ_em = 360/611 nm) were found to be 1.0 × 10^-8 mol/L - 6.0 × 10^-8 mol/L and 2.6 × 10^-9 mol/L, respectively. The former method is superior to the latter one in Cur detection. Both two methods were successfully applied to determine Cur in real samples. The luminescence mechanism of Eu(III) complex under the NIRL excitation and the quenching mechanism of Cur on the Eu(III) fluorescence was also investigated.

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.

Discrimination between nanocurcumin and free curcumin using graphene quantum dots as a selective fluorescence probe

Accurate-controlled sized graphene quantum dots (GQDs) have been used as an analytical nanoprobe for detecting curcumin as a function of the photoluminescent quenching upon increasing concentrations of the analyte. Regarding the importance of curcumin nanoparticles in nutraceutical food, the analytical method described herein was also proven for the discrimination of curcumin remaining in free solution from that encapsulated into water-soluble nanomicelles of ca. 11 nm. This recognition is based on the displacement of GQD emission when interacting with both curcumin species. Maximum emission wavelength of GQDs suffers a gradual quenching as well as a red-shifting upon increasing concentrations of free curcumin (from 458 to 490 nm, exciting at 356 nm). On the other hand, in the presence of nanocurcumin, GQD photoluminescent response only displays a quenching effect (458/356 nm). The sensitivity of the described method in terms of detection limits was 0.3 and 0.1 μg mL-1 for curcumin and nanocurcumin, respectively. The applicability of the photoluminescent probe for the quantification and discrimination between both curcumin environments was demonstrated in nutraceutical formulations namely functional food capsules and fortified beverages such as ginger tea. Graphical abstract.

Application of aeration-assisted homogeneous liquid-liquid microextraction procedure using Box-Behnken design for determination of curcumin by HPLC

A simple, efficient, and rapid sample preparation method based on aeration-assisted homogeneous liquid-liquid microextraction was developed for determination of curcumin in food samples by high-performance liquid chromatography. The centrifuge step has been eliminated in this procedure. The effects of some variables, such as pH, volume of extraction solvent, extraction time, and salt effect, were studied through a Box-Behnken design method. Under the optimum conditions, calibration curves of curcumin were linear in the range of 0.08-4000 μg/mL with R2  = 0.997. Limit of detection and relative standard deviation were 0.019 μg/mL and 3.01%, respectively. The preconcentration factor achieved was 166. The proposed method was successfully applied to determination of curcumin in various food samples.

Characterization, Classification and Authentication of Turmeric and Curry Samples by Targeted LC-HRMS Polyphenolic and Curcuminoid Profiling and Chemometrics

The importance of monitoring bioactive substances as food features to address sample classification and authentication is increasing. In this work, targeted liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) polyphenolic and curcuminoid profiles were evaluated as chemical descriptors to deal with the characterization and classification of turmeric and curry samples. The profiles corresponding to bioactive substances were obtained by TraceFinder^TM software using accurate mass databases with 53 and 24 polyphenolic and curcuminoid related compounds, respectively. For that purpose, 21 turmeric and 9 curry samples commercially available were analyzed in triplicate by a simple liquid-solid extraction procedure using dimethyl sulfoxide as extracting solvent. The obtained results demonstrate that the proposed profiles were excellent chemical descriptors for sample characterization and classification by principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA), achieving 100% classification rates. Curcuminoids and some specific phenolic acids such as trans-cinnamic, ferulic and sinapic acids, helped on the discrimination of turmeric samples; polyphenols, in general, were responsible for the curry sample distinction. Besides, the combination of both polyphenolic and curcuminoid profiles was necessary for the simultaneous characterization and classification of turmeric and curry samples. Discrimination among turmeric species such as Curcuma longa vs. Curcuma zedoaria, as well as among different Curcuma longa varieties (Alleppey, Madras and Erode) was also accomplished.

Advances in Molecularly Imprinted Systems: Materials, Characterization Methods and Analytical Applications

Introduction:

A molecular imprinting is one of the fascinating modification methods that employ molecules as targets to create geometric cavities for recognition of targets in the polymeric matrix. This method provides a broad versatility to imprint target molecules with different size, three-dimensional structure and physicochemical features. In contrast to the complex and timeconsuming laboratory surface modification procedures, this method offers a rapid, sensitive, inexpensive, easy-to-use, and selective approach for the diagnosis, screening and monitoring disorders. Owing to their unique features such as high selectivity, physical and chemical robustness, high stability, low-cost and reusability of this method, molecularly imprinted polymers have become very attractive materials and been applied in various applications from separation to detection.

Background:

The aims of this review are structured according to the fundamentals of molecularly imprinted polymers involving essential elements, preparation procedures and also the analytical applications platforms. Finally, the future perspectives to increase the development of molecularly imprinted platforms.

Methods:

A molecular imprinting is one of the commonly used modification methods that apply target as a recognition element itself and provide a wide range of versatility to replica other targets with a different structure, size, and physicochemical features. A rapid, easy, cheap and specific recognition approach has become one of the investigation areas on, especially biochemistry, biomedicine and biotechnology. In recent years, several technologies of molecular imprinting method have gained prompt development according to continuous use and improvement of traditional polymerization techniques.

Results:

The molecularly imprinted polymers with excellent performances have been prepared and also more exciting and universal applications have been recognized. In contrast to the conventional methods, the imprinted systems have superior advantages including high stability, relative ease and low cost of preparation, resistance to elevated temperature, and pressure and potential application to various target molecules. In view of these considerations, molecularly imprinted systems have found application in various fields of analytical chemistry including separation, purification, detection and spectrophotometric systems.

Conclusion:

Recent analytical methods are reported to develop the binding kinetics of imprinted systems by using the development of other technologies. The combined platforms are among the most encouraging systems to detect and recognize several molecules. The diversity of molecular imprinting methods was overviewed for different analytical application platforms. There is still a requirement of more knowledge on the molecular features of these polymers. A next step would further be the optimization of different systems with more homogeneous and easily reachable recognition sites to reduce the laborious in the accessibility in the three-dimensional polymeric materials in sufficient recognition features and also better selectivity and sensitivity for a wide range of molecules.

Magnetic molecularly imprinted specific solid-phase extraction for determination of dihydroquercetin from Larix griffithiana using HPLC

The naturally occurring quercetin flavonoid, dihydroquercetin, is widely distributed in plant tissues and has a variety of biological activities. Herein, a magnetic molecularly imprinted solid-phase extraction was tailor made for selective determination of dihydroquercetin in Larix griffithiana using high-performance liquid chromatography. Amino-functionalized core-shell magnetic nanoparticles were prepared and characterized using scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and infrared spectroscopy. The polymer had an average diameter of 250 ± 2.56 nm and exhibited good stability and adsorption for template molecule, which is enriched by hydrogen bonding interaction. Multiple factors for extraction, including loading, washing, elution solvents, and extraction time, were optimized. The limit of detection was 1.23 μg/g. The precision determined at various concentration of dihydroquercetin was less than 4% and the mean recovery was between 74.64 and 101.80%. It has therefore been shown that this protocol can be used as an alternative extraction to quantify dihydroquercetin in L. griffithiana and purify quercetin flavonoid from other complex matrices.

Rapid measurements of curcumin from complex samples coupled with magnetic biocompatibility molecularly imprinted polymer using electrochemical detection

Curcumin widely exists in food, and rapid selective and accurate detection of curcumin have great significance in chemical industry. In this experiment, a new magnetic biocompatibility molecularly imprinted polymer was prepared with nontoxic and biocompatible Zein to adsorb curcumin selectively. The polymer has high biocompatibility, good adsorption capacity, and specific adsorption for curcumin. Combined with portable electrochemical workstations, the polymer can be used to detect curcumin rapidly and cost-effectively. Using curcumin as a template and Zein as the crosslinking agent, the polymers were synthesized on the surface of Fe₃ O₄ particles for solid phase extraction. The experimental results showed that the polymer reached large adsorption capacity (32.12 mg/g) with fast kinetics (20 min). The adsorption characteristic of the polymer followed the Langmuir isotherm and pseudo-second-order kinetic models. Hexacyanoferrate was used as electrochemical probe to generate signals, and the linear range was 5-200 µg/mL for measuring curcumin. The experimental analysis showed that the polymer was an ideal material for selective accumulation of curcumin from complex samples. This approach has been successfully applied to the determination of curcumin in food samples with electrochemical detection, indicating that this is a feasible and practical technique.

Study of solvent effect on the synthesis of magnetic molecularly imprinted polymers based on ultrasound probe: Application for sulfonamide detection

In this work, a comparative study of the effect of various solvents on the synthesis of magnetic molecularly imprinted polymers (MMIPs) based on the use of high-power ultrasound probe is reported for the first time. Dimethylsulfoxide (DMSO), dimethylformamide (DMF), ethanol, acetonitrile and acetone were studied as solvents for the synthesis of MMIPs. Several crucial experimental conditions such as the time of synthesis and the applied amplitude were investigated. DMSO, DMF and ethanol were successfully used for ultrasound-assisted synthesis of MMIPs. However, for the polymerization performed using acetonitrile and acetone, no significant conversion to product was observed. Under optimal conditions for each solvent tested, the synthesized MMIPs were characterized using several techniques such as Scanning/Transmission Electron Microscopy (SEM and STEM modes), X-Ray Diffraction, Fourier Transform Infra-Red Spectroscopy, Thermal Gravimetric Analysis and Vibrating Sample Magnetometer system. The study of adsorption time of MMIPs showed that fast adsorption occurred due to the presence of specific imprinted sites on the surface. Moreover, isotherm study showed that the experimental equilibrium data fitted well with Freundlich model. The results of selectivity study indicated that MMIPs could selectively recognize the target molecule. Due to its high adsorption properties and easiness of preparation, MMIP-DMSO was used successfully as adsorbent material in solid-phase extraction coupled to a colorimetric method for sulfamethoxazole (SMX). After optimizing analytical conditions, a calibration plot was performed in the concentration range from 0.2 to 5 µg·mL^-1 with limits of detection and quantitation of 0.06 and 0.2 µg·mL^-1, respectively. The developed procedure was applied successfully for SMX determination in spiked tap and mineral waters showing satisfactory recoveries. Besides, reusability study demonstrated that MMIP could be reused at least 8 times keeping good binding capacity.

Curcumin: Biological, Pharmaceutical, Nutraceutical, and Analytical Aspects

Turmeric is a curry spice that originated from India, which has attracted great interest in recent decades because it contains bioactive curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin). Curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-hepta-1,6-diene-3,5-dione), a lipophilic polyphenol may work as an anticancer, antibiotic, anti-inflammatory, and anti-aging agent as suggested by several in vitro, in vivo studies and clinical trials. However, poor aqueous solubility, bioavailability, and pharmacokinetic profiles limit curcumin’s therapeutic usage. To address these issues, several curcumin formulations have been developed. However, suboptimal sample preparation and analysis methodologies often hamper the accurate evaluation of bioactivities and their clinical efficacy. This review summarizes recent research on biological, pharmaceutical, and analytical aspects of the curcumin. Various formulation techniques and corresponding clinical trials and in vivo outcomes are discussed. A detailed comparison of different sample preparation (ultrasonic, pressurized liquid extraction, microwave, reflux) and analytical (FT-IR, FT-NIR, FT-Raman, UV, NMR, HPTLC, HPLC, and LC-MS/MS) methodologies used for the extraction and quantification of curcuminoids in different matrices, is presented. Application of optimal sample preparation, chromatographic separation, and detection methodologies will significantly improve the assessment of different formulations and biological activities of curcuminoids.

Anti-inflammatory Action of Curcumin and Its Use in the Treatment of Lifestyle-related Diseases

Chronic inflammation plays a significant role in lifestyle-related diseases, such as cardiovascular diseases and obesity/impaired glucose tolerance. Curcumin is a natural extract that possesses numerous physiological properties, as indicated by its anti-inflammatory action. The mechanisms underlying these effects include the inhibition of nuclear factor-kappaB and Toll-like receptor 4-dependent signalling pathways and the activation of a peroxisome proliferator-activated receptor-gamma pathway. However, the bioavailability of curcumin is very low in humans. To resolve this issue, several drug delivery systems have been developed and a number of clinical trials have reported beneficial effects of curcumin in the management of inflammation-related diseases. It is expected that evidence regarding the clinical application of curcumin in lifestyle-related diseases associated with chronic inflammation will accumulate over time.

Efficient discovery and capture of new neuronal nitric oxide synthase-postsynaptic density protein-95 uncouplers from herbal medicines using magnetic molecularly imprinted polymers as artificial antibodies

In the scope of stroke treatment, new neuronal nitric oxide synthase-postsynaptic density protein-95 uncouplers from herbal medicines were discovered and captured. To do so, highly selective magnetic molecularly imprinted polymers with a core-shell structure were prepared as artificial antibodies. According to the results of computational simulations, we designed and synthesized various polymers with varying amounts and types of template, functional monomer, cross-linker, and solvent. Characterization and performance tests revealed that the most appropriate artificial antibodies showed uniform spherical morphologies, large adsorption capacities, fast-binding kinetics, high selectivity, and quick separation. These artificial antibodies were then used as sorbents for dispersive magnetic solid-phase extraction coupled with high-performance liquid chromatography and mass spectrometry to capture and identify structural analogs to ZL006 from extracts of Scutellariae radix, Psoraleae fructus, and Trifolium pratense. Furthermore, according to the neuroprotective effect and coimmunoprecipitation test, Baicalein, Neobavaisoflavone, Corylifol A, and Biochanin A can be the potential uncouplers of neuronal nitric oxide synthase-postsynaptic density protein-95. Therefore, this present study contributes valuable information for the discovery of neuronal nitric oxide synthase-postsynaptic density protein-95 uncouplers from herbal medicines.

Polyhydric polymer-loaded pyrene composites as powerful adsorbents and fluorescent probes: highly efficient adsorption and test strips-based fluorimetric analysis of curcumin in urine and plant extracts

A polyhydric polymer fluorescent probe was designed for the accumulation and fluorimetric detection of curcumin (Cur).

Thermo-responsive molecularly imprinted polymer containing magnetic nanoparticles: Synthesis, characterization and adsorption properties for curcumin

A novel intelligent thermoresponsive-magnetic molecularly imprinted polymer (TMMIP) nanocomposite based on N-isopropylacrylamide (NIPAM) & Fe₃O₄ was designed for the controlled & sustained release of Curcumin (CUR) with the ability to response external stimulus. The TMMIP nanocomposite was prepared using acryl functionalized β-cyclodextrin (β-CD) and NIPAM as functional monomers and CUR as target molecule. The recognition cavities which caused by host-guest interactions had direct influence to enhanced drug loading and sustained release of CUR. According to in-vitro release experiment in two different temperatures (below & above LCST of NIPAM) the prolonged & controlled release of CUR were observed. The release rate could be controlled by changing the temperature because of the phase transition behavior of NIPAM monomer. Also, the proposed biosensor displayed effective role in separation science, reasonable adsorption capacity (77mgg^-1), fast recognition (10min equilibration), selective extraction toward CUR in the presence of structural analogues and easily separation using external magnetic field. Moreover, the synthesized TMMIP was confirmed by various characterization.

Preparation and evaluation of magnetic molecularly imprinted polymers for the specific enrichment of phloridzin

In present study, magnetic molecularly imprinted polymers (MMIPs) were successfully prepared for specific recognition and selective enrichment of phloridzin from the leaves of Malus doumeri (Bois) A. Chev and rats' plasma. The magnetic Fe₃O₄ were prepared by the solvothermal reaction method and followed by the modification of TEOS and functionalization with APTES. Using functionalized Fe₃O₄ particles as the magnetic cores, phloridzin as template, ethylene glycol dimethacrylate (EGDMA) as cross-linker and 2,2-azobisisobutyonnitrile (AIBN) as initiator, the MMIPs were prepared through APTES to associate the template on the surface of the magnetic substrate. The structural features and morphological characterizations of MMIPs were performed by FT-IR, SEM, TEM, XRD, TGA and VSM. The adsorption experiments revealed that the MMIPs presented high selective recognition property to phloridzin. The selectivity experiment indicated that the adsorption capacity and selectivity of polymers to phloridzin was higher than that of baicalin and 2,3,5,4'-ttrahydroxy stilbene-2-O-β-D-glucoside. Furthermore, the MMIPs were employed as adsorbents for extraction and enrichment of phloridzin from the leaves of M. doumeri and rats' plasma. The recoveries of phloridzin in the leaves of M. doumeri ranged from 81.45% to 90.27%. The maximum concentration (C_max) of phloridzin in rats' plasma was detected as 12.19 ± 0.84μg/mL at about 15min after oral administration of phloridzin (200mg/kg). These results demonstrate that the prepared MMIPs are suitable for the selective adsorption of phloridzin from complex samples such as natural medical plants and biological samples.

Synthesis of curcuminoid-imprinted polymers applied to the solid-phase extraction of curcuminoids from turmeric samples

A molecular imprinting polymer technique was successfully applied to precipitation polymerization by using styrene as a functional monomer, curcuminoids as templates, acetonitrile as a porogenic solvent, benzoyl peroxide as the initiator, and ethylene glycol dimethacrylate as the crosslinker. The effects of interaction on the adsorption capacity of the molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) were investigated. A comparison of the adsorption capacity for MIP and NIP indicated that the NIP had the lowest adsorption capacity. The curcuminoid-imprinted polymer (Cur-MIP) was synthesized from 0.0237 mmol of styrene, 47.0 g of acetonitrile, 1.0238 mmol of ethylene glycol dimethacrylate, 0.0325 mmol of curcuminoids, and 0.2480 mmol of benzoyl peroxide. A high-performance liquid chromatography method with fluorescence detection was developed and validated for various chromatographic conditions for the determination of the curcuminoids in turmeric samples. The sample solution was separated using the Cur-MIP via solid-phase extraction and analyzed on a Brownlee analytical C₁₈ column (150 mm × 6 mm, 5 µm) using an isocratic elution consisting of acetonitrile and 0.1% trichloroacetic acid (40:60, v/v). The flow rate was maintained at 1.5 mL/min. The fluorescence detector was set to monitor at λ_ex = 426 nm and λ_em = 539 nm. The quantification limit values were found to be 16.66, 66.66, and 33.33 µg/L for curcumin, demethoxycurcumin, and bisdemethoxycurcumin, respectively. Thus, we concluded that the Cur-MIP and high-performance liquid chromatographic-fluorescence method could be applied to selective extraction and could be used as a rapid tool for the determination of curcuminoids in medicinal herbal extracts.

"On-off" switchable tool for food sample preparation: merging molecularly imprinting technology with stimuli-responsive blocks. Current status, challenges and highlighted applications

Sample preparation still remains a great challenge in the analytical workflow representing the most time-consuming and laborious step in analytical procedures. Ideally, sample pre-treatment procedures must be more selective, cheap, quick and environmental friendly. Molecular imprinting technology is a powerful tool in the development of highly selective sample preparation methodologies enabling to preconcentrate the analytes from a complex food matrix. Actually, the design and development of molecularly imprinted polymers-based functional materials that merge an enhancement of selectivity with a controllable and switchable mode of action by means of specific stimulus constitutes a hot research topic in the field of food analysis. Thus, combining the stimuli responsive mechanism and imprinting technology a new generation of materials are emerging. The application of these smart materials in sample preparation is in early stage of development, nevertheless new improvements will promote a new driven in the demanding field of food sample preparation. The new trends in the advancement of food sample preparation using these smart materials will be presented in this review and highlighted the most relevant applications in this particular area of knowledge.

Newest applications of molecularly imprinted polymers for extraction of contaminants from environmental and food matrices: A review

This paper presents an overview of the recent applications of molecularly imprinted polymers (MIPs) to sample preparation. The review is thought to cover analytical procedures for extraction of contaminants (mainly illegal/noxious organic compounds) from food and environmental matrices, with a particular focus on the various pre-concentration/cleanup techniques, that is offline and online solid-phase extraction (SPE), dispersive SPE (d-SPE), magnetic SPE (MSPE), solid-phase microextraction (SPME) and stir-bar sorptive extraction (SBSE), applied before instrumental quantification. The selectivity and extraction efficiency of MIP-based sorbent phases are critically discussed, also in relation to the physical-chemical properties resulting from the synthetic procedures. A variety of molecularly imprinted sorbents is presented, including hybrid composites embedding carbon nanomaterials and ionic liquids. The analytical performance of MIP materials in sample preparation is commented as function of the complexity of the matrix, and it is compared to that exhibited by (commercial) aspecific and/or immunosorbent phases.

Curcumin, a Compound from Natural Sources, a True Scientific Challenge - A Review

Curcumin, a plant-derived polyphenolic compound, naturally present in turmeric (Curcuma longa), has been the subject of intensive investigations on account of its various activities. The implementation of safe, beneficial and highly functional compounds from natural sources in human nutrition/prevention/therapy requires some modifications in order to achieve their multi-functionality, improve their bioavailability and delivery strategies, with the main aim to enhance their effectiveness. The low aqueous solubility of curcumin, its rapid metabolism and elimination from the body, and consequently, poor bioavailability, constitute major obstacles to its application. The main objectives of this review are related to reported strategies to overcome these limitations and, thereby, improve the solubility, stability and bioavailability of curcumin. The effectiveness of curcumin could be greatly improved by using nanoparticle-based carriers. The significance of the quality of a substance delivery system is reflected in the fact that carrying curcumin as a food additive/nutrition also means carrying the active biological product/drug. This review summarizes the state of the art, and highlights some examples and the most significant advances in the field of curcumin research.

A simple and sensitive sensor based on a molecularly imprinted polymer-modified carbon paste electrode for the determination of curcumin in foods

A highly sensitive and selective molecularly imprinted polymer-modified carbon paste electrode (MIP-CPE) was designed.