Publicação
Development of amphiphilic adsorbents for the stimulated uptake and release of polyphenols
| Resumo: | This work was devoted to the development of amphiphilic molecularly imprinted polymers (MIPs) to target the stimulated uptake and release of polyphenols. MIP particles were synthetized through a free radical precipitation polymerization process with a hydrophobic crosslinker and different hydrophilic functional monomers. Polydatin was selected as the template polyphenol and anionic, cationic and neutral adsorbent particles were thus produced The formation of microparticles e g with size in the order of 1 μm was evidenced by SEM. The incorporation of crosslinker and functional monomer in the final polymer networks was observed using FTIR. The adsorption capabilities of the materials synthetized were evaluated using solid phase extraction (SPE) with solvents of different amphiphilic character. Besides the individual retention, the competitive adsorption of a mixture of polydatin + resveratrol + gallic acid was also studied through HPLC (an Ascentis® C18 column was used). Some selectivity of the materials towards the different molecules was observed but the most relevant result obtained was the ability of the produced cationic networks to retain huge amounts of gallic acid. MIPs were also packed in HPLC columns and a continuous process with recycling was conceived through the use of an HPLC pump. Dynamics for the saturation and the release processes were thus measured and the role of the hydrophobic interactions in the different polyphenols adsorption/desorption was highlighted. These issues were further enhanced through the analysis of the retention and release of phenolic compounds in a sequence of two MIPs. A solvent gradient scheme was used and these ideas were applied to a created mixture containing gallic acid, tannic acid, polydatin and resveratrol. Portuguese Douro Region red wine was considered as a source of phenolic compounds and an extract from chestnut shell was also evaluated. The extract from chestnut shell was obtained through supercritical extraction with CO2, using Bragança region fruits. Supercritical extraction with CO2 was performed at T=50 °C and P=150 bar Results obtained evidenced that optimized MIPs can be undoubtedly used to separate and concentrate polyphenols present in red wine, such as resveratrol or polydatin. These findings were further enhanced through the adsorption and release of the gallic acid + tannic acid + polydatin + resveratrol in the series of MIPs. Measurements for the shell chestnut extract obtained with supercritical conditions showed that phenolic compounds should not be present in an appreciable amount (in contrast with the red wine extract). Different extraction techniques (e.g. extraction at alkaline supercritical conditions) and chestnut plant components (leaves, burs, stalks, etc) should be considered in future researches to light this issue. At last, the synthesis of improved amphiphilic adsorbents through the RAFT grafting of functional brushes in the MIP particles surface was addressed. Preliminary results obtained seem to show that the grafted hydrophilic polymer brushes modify the pH/temperature triggered retention/release of polyphenols. However, future studies are needed to clarify these complex issues. |
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| Autores principais: | Sadoyan, Gayane |
| Assunto: | Polyphenols Molecular imprinting Amphiphilic adsorbents Supercritical extraction |
| Ano: | 2017 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Instituto Politécnico de Bragança |
| Idioma: | inglês |
| Origem: | Biblioteca Digital do IPB |
| Resumo: | This work was devoted to the development of amphiphilic molecularly imprinted polymers (MIPs) to target the stimulated uptake and release of polyphenols. MIP particles were synthetized through a free radical precipitation polymerization process with a hydrophobic crosslinker and different hydrophilic functional monomers. Polydatin was selected as the template polyphenol and anionic, cationic and neutral adsorbent particles were thus produced The formation of microparticles e g with size in the order of 1 μm was evidenced by SEM. The incorporation of crosslinker and functional monomer in the final polymer networks was observed using FTIR. The adsorption capabilities of the materials synthetized were evaluated using solid phase extraction (SPE) with solvents of different amphiphilic character. Besides the individual retention, the competitive adsorption of a mixture of polydatin + resveratrol + gallic acid was also studied through HPLC (an Ascentis® C18 column was used). Some selectivity of the materials towards the different molecules was observed but the most relevant result obtained was the ability of the produced cationic networks to retain huge amounts of gallic acid. MIPs were also packed in HPLC columns and a continuous process with recycling was conceived through the use of an HPLC pump. Dynamics for the saturation and the release processes were thus measured and the role of the hydrophobic interactions in the different polyphenols adsorption/desorption was highlighted. These issues were further enhanced through the analysis of the retention and release of phenolic compounds in a sequence of two MIPs. A solvent gradient scheme was used and these ideas were applied to a created mixture containing gallic acid, tannic acid, polydatin and resveratrol. Portuguese Douro Region red wine was considered as a source of phenolic compounds and an extract from chestnut shell was also evaluated. The extract from chestnut shell was obtained through supercritical extraction with CO2, using Bragança region fruits. Supercritical extraction with CO2 was performed at T=50 °C and P=150 bar Results obtained evidenced that optimized MIPs can be undoubtedly used to separate and concentrate polyphenols present in red wine, such as resveratrol or polydatin. These findings were further enhanced through the adsorption and release of the gallic acid + tannic acid + polydatin + resveratrol in the series of MIPs. Measurements for the shell chestnut extract obtained with supercritical conditions showed that phenolic compounds should not be present in an appreciable amount (in contrast with the red wine extract). Different extraction techniques (e.g. extraction at alkaline supercritical conditions) and chestnut plant components (leaves, burs, stalks, etc) should be considered in future researches to light this issue. At last, the synthesis of improved amphiphilic adsorbents through the RAFT grafting of functional brushes in the MIP particles surface was addressed. Preliminary results obtained seem to show that the grafted hydrophilic polymer brushes modify the pH/temperature triggered retention/release of polyphenols. However, future studies are needed to clarify these complex issues. |
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