"Two-dimensional" molecularly imprinted solid-phase extraction coupled with crystallization and high performance liquid chromatography for fast semi-preparative purification of tannins from pomegranate husk extract.

In this study, "two dimensional" molecularly imprinted solid-phase extraction (2D-MIP-SPE) of semi-preparative grade was constructed to fast purify ellagitannins in pomegranate husk extract with the help of crystallization and reverse-phase liquid chromatgoraphy (RPLC). Ellagic acid and punicalagin imprinted polymers were synthesized in batch mode and two semi-preparative MIP-SPE columns were individually packed. After investigaing "functional complementation", 2D-MIP-SPE was constructed using ellagic acid MIP and punicalagin MIP-SPE as the first and second dimension, respectively. Then, pomegranate husk extract was fast divided into four fractions individually enriching in ellagic acid, granatin A, punicalagin and ellagic acid glucoside by 2D-MIP-SPE. With the aid of crystallization and RPLC, ellagic acid (13.5mg) and punicalagin (53.4mg) were fast obtained in 30min. Ellagic acid glucoside was purified to the purity near 100% with a recovery of 86.1%. Granatin A (92%) was directly obtained by 2D-MIP-SPE with the recovery of 81.8%. All above indicated that 2D-MIP-SPE was highly efficient in natural product purification. The concept of "functional complementation" was expected to be a useful tool in the construction of 2D-MIP-SPE.

On-line restricted access molecularly imprinted solid phase extraction of ivermectin in meat samples followed by HPLC-UV analysis.

A new restricted access molecularly imprinted polymer coated with bovine serum albumin (RAMIP-BSA) was synthesized, characterized and used for direct analysis of ivermectin from bovine meat samples, in a two-dimensional liquid chromatography system with UV detection. Ivermectin, 4-vynilpiridine and ethylene glycol dimethacrylate were employed as template, functional monomer and cross-linker, respectively. A BSA layer was cross-linked around the polymer, resulting in a biocompatible chemical barrier able to eliminate about 100% of protein from the samples. Ivermectin was extracted from the minced meat samples through a solvent extraction using methanol:water (70:30, v:v), and the extracts were directly injected into the two-dimensional liquid chromatography system, without any other treatment. Samples, fortified with ivermectin from 50 to 500 µg kg(-1), were used to build the analytical calibration curve (r=0.996). The limit of quantification was 50 µg kg(-1). Precision and accuracy presented variation coefficients, as well as relative errors lower than 17.0% and within -18.5% and 22.0%, respectively.

Synthesis of water-compatible imprinted polymers of in situ produced fructosazine and 2,5-deoxyfructosazine.

Fructosazine and 2,5-deoxyfructosazine are two natural chemicals with various applications as flavoring agents in food and tobacco industry; the 2,5-deoxyfructosazine has also anti-diabetic and anti-inflammatory activities. In order to quantify these compounds in natural samples such as plant or food, we have developed a selective technique based on a water-compatible molecularly imprinted polymer (MIP). MIPs are prepared with a covalent approach from 2,5-deoxyfructosazine as template formed in situ by the self-condensation of glucosamine with vinylphenyl boronic acid, taken as catalyst and covalent monomer during the pre-complexation step. Acrylamide and polyethylene glycol diacrylate are used as supplementary non-covalent functional monomer and cross-linker, respectively. For the first time, a highly cross-linked but highly polar imprinted polymer of fructosazine and deoxyfructosazine is obtained as a solid material and not a gel. Amount of monomers is optimized to obtain high selectivity for both molecules. Results show that the MIPs prepared have a significant imprinting effect with a resulting imprinting factor of 3 for both templates. Molecularly imprinted solid-phase extraction is then performed and could be used in routine analysis to extract 2,5-deoxyfructosazine and fructosazine from soy sauce.

Syntheses of molecularly imprinted polymers: Molecular recognition of cyproheptadine using original print molecules and azatadine as dummy templates.

The use of custom-made polymeric materials with high selectivities as target molecules in solid-phase extraction (SPE), known as molecularly imprinted solid-phase extraction (MISPE), is becoming an increasingly important sample preparation technique. However, the potential risk of leakage of the imprinting molecules during the desorption phase has limited application. The use of a mimicking template, called a dummy molecular imprinting polymer (DMIP), that bears the structure of a related molecule and acts as a putative imprinting molecule may provide a useful solution to this problem. In the current study, cyproheptadine (CPH) and azatadine (AZA) were used as templates in the development of an MIP and DMIP for acrylic acid and methacrylic acid monomers. Our results indicate that DMIPs have equal recognition of CPH, avoiding the problem of leakage of original template during the desorption phase relative to MIPs synthesized in presence of the print molecule CPH. Examination of the surface structure of the two polymer products by SEM shows appreciable differences in structural morphology and function of the monomers employed. These results are well supplemented by data obtained for swelling ratios and solvent uptake. Molecular modelling of CPH and AZA suggests that both substrates are similar in shape and volume.