Preparation, characterization and usage of molecularly imprinted polymer for the isolation of quercetin from hydrolyzed nettle extract

Cell-Penetrating Drug Carrier by Molecular Recognition of Sphingomyelin on Plasma Membranes

Plasma membranes not only maintain the intracellular microenvironment through their phospholipid bilayer but also eliminate exogenous compounds outside the cell membranes. Most drugs especially with high polarity are prevented from entering into cells to exert their effects. Therefore, it is of great significance to design effective drug carriers with a penetrating ability toward plasma membranes. In this study, a dual-templated MIP (dt-MIPs) carrier with controllable microstructure and high drug loading capacity was prepared using highly expressed sphingomyelin on the plasma membrane and tenofovir (TFV), a first-line drug for HIV and chronic hepatitis B, as template molecules. The drug release experiments performed in vitro under simulated physiological conditions demonstrated that sustained and stable adsorption of TFV on dt-MIPs was more than 80% over 50 h. By a combination of flow cytometry and confocal microscopy, dt-MIPs were found to have efficient cell permeability. Furthermore, mass-spectrometry-based intracellular pharmacokinetic studies demonstrated that TFV was delivered completely into cells within 30 min with the delivery of dt-MIPs. The study presented above suggested that dt-MIPs are expected to be alternative nanoscale drug carriers for enhanced drug permeability and controlled release.

Preparation and application of caffeic acid imprinted polymer

In the present study, molecularly imprinted polymers were synthesized using caffeic acid (CA) as a template molecule and then used for the extraction of CA and chlorogenic acid (CLA) from complex matrices. Syntheses were carried out in tetrahydrofuran as porogenic solvent using 4-vinyl pyridine, methacrylic acid, acrylamide, and 1-vinyl imidazole as monomers, ethylene glycol dimethacrylate as crosslinker and 2,2'-azobisisobutyronitrile as initiator. In polymerization processes, different ratios of the template:monomer:crosslinker (T:M:CrL) were used to obtain the most suitable polymer. Caffeic acid:4-vinylpiridine:ethylene glycol dimethacrylate's 1:4:16 mole ratio of MIP was determined as the most convenient polymer for CA recognition. In addition, nonimprinted polymers (NIPs) without templates were prepared. Dynamic and static adsorption tests were applied to determine the absorption features of the NIPs and CA-MIPs. Separation and purification studies of CA and CLA were performed with molecular imprinted solid phase extraction (MISPE) application. All steps of MISPE (loading, washing, elution) were optimized by HPLC analysis.

Advances in Molecular Imprinting Technology for the Extraction and Detection of Quercetin in Plants

Quercetin is a kind of flavonoid compound, which has antioxidative, anti-aging and anti-cancer effects, so it is of great importance to study the efficient extraction and highly sensitive detection of quercetin. Molecular imprinting technology has remarkable selectivity and resistance to complex matrix interference, which is often used for extracting quercetin. The methods of molecular imprinted solid phase extraction, molecularly imprinted microsphere extraction, molecularly imprinted electrochemical sensor recognition and molecularly imprinted composite material extraction of quercetin from plant samples were discussed in detail. This review provides valuable information on efficient and sensitive methods for separating and purifying quercetin in plants. It also provides a technical reference for further investigation of the separation and analysis of active ingredients in natural products.

Preparation and optimization of a molecularly imprinted polymers - solid phase extraction system for the extraction of bioactive sesquiterpene lactones of Ambrosia maritima plant

A solid phase extraction (SPE) system for sesquiterpene lactones of damsissa was developed utilising molecularly imprinted polymers (MIPs). The prepared MIPs had a mesoporous structure and particle size of ≈2.65 µm with 3.99 nm pore size. Additionally, MIPs exhibited high thermal stability with degradation temperature between 209 and 459 °C. Optimized MIP-SPE protocol conditions were set at loading step: 1 mL ethanol; washing step: 1 mL water; eluting step: 4 mL methanol. Developed MIP-SPE system showed a binding capacity of 66.66 mg/g based on Langmuir isotherm which was selected as the best fitting model isotherm. Good selectivity coefficients were observed for neoambrosin of 2.37, 1.31 and 1.14 against umbelliferone, quercetin glucoside and p-coumaric acid, respectively. Furthermore, the proposed MIP-SPE protocol displayed some potential in the isolation of sesquiterpene lactones from damsissa plant extract and laid a foundation for the development of more selective MIPs to nonpolar natural products.

A flower-like ionic molecularly imprinted membrane for the deglycosylation of rutin

A kind of molecularly imprinted polymer based on ionic liquids (MIPIL) with flower-like shape was developed for the adsorption of rutin and its deglycosylated product. The MIPIL film was characterized by scanning electron microscope (SEM) and X-ray photo-electron spectroscopy (XPS). The adsorption capacity of quercetin on the proposed imprinted cavity of rutin in the presence of glucose and rhamnose was 3.7 ± 0.017 times as much as that in the absence of glucose and rhamnose. And the adsorption capacity of quercetin varied with the concentration of glucose and rhamnose changing. Thus, the proposed MIPIL film coupled with HPLC was used to explore the deglycosylation of rutin by tracking rutin and quercetin, which confirmed to the pseudo-first-order reaction kinetic with the constant of 0.044 ± 1.5 × 10^-4 min^-1 at 35 °C. The rutin and quercetin were quantified using the above MIPIL film in the two Ginkgo leaves extracted by pure water and pure ethanol, respectively. Because of lower solubility in water, the content of rutin in ethanol extraction solution was higher than in water solution. On the contrary, the content of quercetin in water extraction solution was higher than in ethanol solution, which resulted from the higher solubility of glucose and rhamnose in water. The RSD ranged from 2.8 to 4.5%, and the recovery rate ranged from 91.9 to 105.3%.

Application of Molecularly Imprinted Polymers for the Detection of Volatile and Off-Odor Compounds in Food Matrices

Molecularly imprinted polymers (MIPs) are synthetic receptors having specific cavities intended for a template molecule with a retention mechanism that depends on molecular recognition of the targeted constituent. They were initially established for the detection of minor molecules including drugs, pesticides, or pollutants. One of the most remarkable areas where MIPs have potential utilization is in food analysis, especially in terms of volatile compounds which are found in very low concentrations in foods but play a crucial role for consumer preference and acceptance. In recent years, these polymers have been used extensively for sensing volatile organic and off-odor compounds in terms of food quality for selective high-extraction purposes. This review first summarizes the basic principles and production processes of MIPs. Second, their recent applications in the separation, identification, and quantification of volatile and off-odor compounds in food samples are elucidated.

Simple and Efficient Detection Approach of Quercetin from Biological Matrix by Novel Surface Imprinted Polymer Based Magnetic Halloysite Nanotubes Prepared by a Sol-Gel Method

Molecular imprinted polymers coated magnetic halloysite nanotubes (MHNTs-MIPs) were prepared through sol-gel method by using quercetin (Que), APTES and TEOS as template, monomer and cross-linker agent, respectively. The synthesized MHNTs-MIPs were characterized by fourier transform infrared, scanning electron microscope, transmission electron microscope, XRD and vibrating sample magnetometer. Various parameters influencing the binding capacity of the MHNTs-MIPs were investigated with the help of response surface methodology. Selectivity experiments showed that the MHNTs-MIPs exhibited the maximum selective rebinding to Que. Therefore, the MHNTs-MIPs was applied as a solid-phase extraction adsorbent for the extraction and preconcentration of quercetin and luteolin in serum and urine samples. The limits of detection for quercetin and luteolin range from 0.51 to 1.32 ng mL-1 in serum and from 0.23 to 1.05 ng mL-1 in urine, the recoveries are between 95.20 and 103.73% with the RSD less than 5.77%. While the recovery hardly decreased after several cycles. The designed MHNTs-MIP with high affinity, sensitivity and maximum selectivity toward Que in SPE might recommend a novel method for the extraction of flavonoids in other samples like natural products.

Ultrasound-assisted solid phase microextraction-HPLC method based on Fe3O4@SiO2-NH2-molecularly imprinted polymer magnetic nano-sorbent for rapid and efficient extraction of harmaline from Peganum harmala extract

In the present study, a magnetic molecularly imprinted polymer (MMIP) was synthesized for the extraction of harmaline from Peganum harmala by dispersive solid-phase microextraction (DSPME). The MMIP for selective and intelligent extraction of harmaline with excellent functionality and high selectivity was synthesized using the sol-gel method with functionalized superparamagnetic core-shell nanoparticles, ethylene glycol dimethacrylate (EDMA) as a cross-linker, methacrylic acid (MAA) as a functional monomer, and 2,2-azobisisobutyronitrile (AIBN) as a porogen. To study the properties and morphology of the coated polymer, FT-IR spectroscopy, FESEM, TEM images, and VSM were used. The DSPME-HPLC-UV equipment was used to quantify and analyze the data obtained from harmaline extraction. In this research, the efficiency of the synthesized polymer in harmaline extraction was modeled and optimized using the response surface methodology based on central composite design (RSM-CCD). In addition, for modeling the isotherm of harmaline sorption by the MMIP, Langmuir and Freundlich isotherm equations were used. The obtained results showed that the extraction of harmaline with the MMIP was well described with Freundlich isotherm. The results of the validation of the method showed that the measurement of harmaline in the concentration range of 1.0-4000 ng mL^-1 followed a linear relationship (R² = 9986.0). Moreover, the accuracy or repeatability index (% RSD) was determined to be < 10, and the LOQ and LOD values were 0.526 and 0.158 ng mL^-1, respectively. The results of this study showed that the DSPME technique by using the synthesized MMIP as an effective sorbent with high efficiency and capacity could be utilized for pre-concentration and extraction of harmaline from real and complex samples.

Molecularly imprinted polymer as solid phase extraction phase for condensed tannin determination from Brazilian natural sources

This study proposed the developed of a molecularly imprinted polymer for the extraction and determination of condensed tannins from the barks of Red Angico (Anadenanthera macrocarpa), Jabuticaba (Myrciaria jabuticaba) and Umbu (Spondias tuberosa). The polymer was synthesized using the condensed tannin extracted from the Red Angico bark as the template molecule, as well as, catechin standard solution. Selectivity and characterization tests for the molecularly imprinted polymers and a non-imprinted polymer were performed. The polymers were employed as extraction phase for the solid-phase extraction of condensed tannins from the studied samples. A higher imprinting coefficient was obtained for MIP synthesized from catechin standard solution as template. The intrinsic solid-phase extraction variables were evaluated and optimized. The developed methodology showed inter- and intra-day precisions of 6.7-10.1 and 4.6-8.4, respectively, and recovery values ranging from 101.9 to 105.5. The obtained limits of detection and quantification were 10 mg L^-1 and 40 mg L^-1, respectively. It is important to highlight that the developed methodology here was applied to common waste and tailings from Brazilian food industry. The results indicate that the polymers were capable to extract tannins from the evaluated samples, reducing method cost and time.

Valorization of Red Onion Peels for Quercetin Recovery Using Quercetin-Imprinted Polymer

Quercetin (QC) is one of the most prominent dietary antioxidants present in vegetables/fruits, specifically in onions that rank second in consumption following tomato. QC with proven health benefits is now largely utilized as a nutritional supplement. In this work that aims to isolate QC from red onion peels forming a huge agricultural waste, a QC-molecularly imprinted polymer (QC-MIP) in a molar ratio of 1:4:20 (QC:4-vinylpyridine:ethylene glycol dimethacrylate) was prepared thermally through bulk polymerization. Molecularly imprinted solid phase extraction (MISPE) procedures were applied for the selective pre-concentration and purification of QC from both red onion peel methanolic extract with 58% recovery and from the extract hydrolyzate with 86% recovery. The hydrolysis process increased both the QC amount as expected and the recovery yield due to changing matrix components. The results demonstrated that onion peel can easily and efficiently be converted to a valuable product, QC, using QC-MIP as SPE sorbent.

Ordered macroporous molecularly imprinted polymers prepared by a surface imprinting method and their applications to the direct extraction of flavonoids from Gingko leaves

In this work, to improve the availability of the recognition sites of molecularly imprinted polymers (MIPs), ordered macroporous molecularly imprinted polymers (OMMIPs) were facilely prepared by grafting a quercetin-MIPs layer on the pore walls of the ordered macroporous thiol group functionalized silica. The pore structures were characterized by FTIR, Raman, SEM, BET and TGA measurements. The results indicated that OMMIPs possessed a nanoscale polymer layer, a more regular macroporous structure and a greater porosity compared with the traditional bulk MIPs (TBMIPs). The polymer content of OMMIPs was about 49.7%. Kinetic and isothermal adsorption experiments indicated that OMMIPs exhibited higher affinity and selectivity towards quercetin than its structural analogues. Moreover, OMMIPs could improve the intra-particle adsorption and thus provide a significant improvement in recognition sites availability over TBMIPs. Using the quercetin-OMMIPs as SPE sorbent, quercetin was directly extracted from the crude Gingko leaves extract with a satisfying selectivity and elution recovery.

Application of Molecularly Imprinted Polymers (MIP) and Magnetic Molecularly Imprinted Polymers (mag-MIP) to Selective Analysis of Quercetin in Flowing Atmospheric-Pressure Afterglow Mass Spectrometry (FAPA-MS) and in Electrospray Ionization Mass Spectrometry (ESI-MS)

Molecularly imprinted polymer (MIP) and magnetic molecularly imprinted polymer (mag-MIP) for solid extraction and pre-concentration of quercetin have been successfully prepared by thermal polymerization method using quercetin (Q) as a template, acrylamide (AA) as a functional monomer, and ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent. The MIP and mag-MIP were successfully applied in analysis of quercetin by mass spectrometry (MS) methods. To perform ambient plasma ionization experiments, a setup consisting of the heated crucible, a flowing atmospheric-pressure afterglow (FAPA) plasma ion source, and amaZon SL ion trap (Bruker, Bremen, Germany) was used. The heated crucible with programmable temperature allowed desorption of the analytes from MIPs structure which resulted in their direct introduction into the ion stream. The results of Q-MIP/Q-mag-MIP and FAPA-MS measurements were compared with those of the analysis of quercetin by the ESI-MS method without extractions and pre-concentration of analytes on polymers. Limits of detection (LOD) for quercetin solutions in both positive and negative ESI-MS were established at 10⁻⁸ M and 10⁻⁷ M, respectively. The linearity (R² = 0.9999) of the proposed analytical procedure for quercetin determination in positive ions was provided in the range between 10⁻⁴ M and 10⁻⁷ M. Moreover, the same parameters were established for FAPA-MS in positive ions, reaching LOD at 0.005 mg/gMIP and the linearity of the method in the range of 0.015–0.075 mg/gMIP with the correlation coefficient value R² = 0.9850.

Preparation of novel molecularly imprinted magnetic graphene oxide and their application for quercetin determination

In this work, quercetin (Que) molecular imprinted polymer (MIP) material decorated on magnetic graphene oxide (MGO) with high performance was prepared for the first time using a surface-imprinting technique. Magnetic graphene oxide was synthesized using the solvothermal route. Methacrylic acid (MAA) was used as functional monomer, ethylene glycol dimethyl acrylate (EGDMA) as cross-linker; Que. was used as template, for the decoration with MIP. The prepared nanocomposite was examined by different characterization methods including fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM). The adsorption performance was investigated. MGO-MIP was found to have high loading (369 mg g^-1) and selective capacity making the nanomaterial more performant than previous similar reported nanomaterials. The determination of Que. was carried out by mean of magnetic solid phase extraction method coupled with high-performance liquid chromatography (HPLC) and the extraction conditions studies were also performed out. Under the optimized conditions, MGO-MIP showed great performance for the extraction, separation and determination of Que. in green tea and serum samples, compared to the flavonoid analogs luteolin (Lut) and rutin (Rut) in the same matrix samples.

Fabrication of a magnetic metal–organic framework molecularly imprinted polymer for extraction of anti-malaria agent hydroxychloroquine

A new magnetic metal–organic framework molecularly imprinted polymer was synthesized by the sol–gel method for the determination of hydroxychloroquine sulfate.

Selective detection of chloramphenicol based on molecularly imprinted solid-phase extraction in seawater from Jiaozhou Bay, China

This study highlights an efficient sample pre-treatment method for preconcentration and detection of chloramphenicol in marine water using molecularly imprinted solid-phase extraction (MISPE). Chloramphenicol molecularly imprinted microspheres were prepared and evaluated on the base of morphology, capacity and selectivity. The imprinted microspheres exhibited specific recognition and high retention capability to chloramphenicol and were applied as special solid-phase extraction adsorbents. An off-line MISPE protocol has been optimized and a creative analytical method coupled to HPLC-DAD was successfully developed for the cleanup and determination of chloramphenicol in seawater samples. Method performance was satisfactory with recoveries ranging from 81 to 90% and relative standard deviation (RSD) was <4.93% (n = 3). Accuracy of the method was assessed at three spiking concentration levels and the limit of detection was 5 ng L^-1. Finally, five seawater samples from Jiaozhou Bay of China were determined and the results showed that there was no chloramphenicol detected.

Extraction approaches used for the determination of biologically active compounds (cyclitols, polyphenols and saponins) isolated from plant material

Based on the bioactive properties of certain compounds, such as antioxidant and anti-inflammatory activities, an interesting subject of research are natural substances present in various parts of plants. The choice of the most appropriate method for separation and quantification of biologically active compounds from plants and natural products is a crucial step of any analytical procedure. The aim of this review article is to present an overview of a comprehensive literature study from the last 10 years (2007-2017), where relevant articles exposed the latest trends and the most appropriate methods applicable for separation and quantification of biologically active compounds from plant material and natural products. Consequently, various extraction methods have been discussed, together with the available procedures for purification and pre-concentration and dedicated methods used for analysis.