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- Competitive Adsorption of Phenolic Acids, Secoiridoids, and Flavonoids in Quercetin Molecularly Imprinted Polymers and Application for Fractionation of Olive Leaf ExtractsPublication . Almeida, Ayssata Patrícia da Costa Leocádia Vaz; Martins, Ana Filipa; Dias, Rolando; Costa, Mário RuiThe competitive adsorption of phenolic acids, secoiridoids, and flavonoids in a molecularly imprinted polymer (MIP) functionalized with 4-vinylpiridine (4VP) moieties is analyzed here considering vanillic acid, oleuropein, and quercetin as reference molecules. Measured adsorption isotherms highlight a much stronger binding capacity of the quercetin-MIP particles toward quercetin as compared with vanillic acid and oleuropein. The acquired data were used to design and scale-up sorption/desorption processes aiming at the fractionation of olive leaf extracts. We show that a simple adsorption process, avoiding many pre-preparation steps, is possible when working at a high extract concentration due to the strong binding capacity of the MIP for flavonoids, even when using aqueous mixtures with a large alcoholic content. Solvent-gradient/temperature-swing desorption led to a sequence of fractions with enrichment of non-flavonoids at low alcoholic content while glycosylated flavonoids were enriched in fractions with 40% < alcohol content < 80%. Enrichment factors of 13 and 12 were measured for luteolin-7-O-glucoside and apigenin-7-O-glucoside, respectively. Flavonoid aglycones were enriched in fractions with alcohol content >80% (enrichment factors >20 for luteolin and quercetin). The findings reported here demonstrate the usefulness of the developed materials and sorption/desorption conditions for agricultural residue valorization and circular bioeconomy.
- Chemical characterization, antioxidant and antimicrobial activities of winemaking industry by-productsPublication . Duarte, Cristina Nogueira; Dias, Maria Inês; Heleno, Sandrina A.; Santos-Buelga, Celestino; Dias, Rolando; Barros, Lillian; Amaral, Joana S.The exploitation of bioactive compounds trom agri-food by-products has been attracting an increasing interest from different industries within a circular economy context since several of compounds may have health properties or be used as natural colorants or preservatives. So far, several studies have been developed on the characterization of red wine grape pomace and its components (seeds, skins, and stems). However, less attention has been paid to other by-products, such as grape pomace from white wine, the residues after distillation, wine lees, and diatomaceous earth, the latter used in the filtration of wine and corresponding to about 250 tons/year of waste in Portugal. In this work, samples of these by-products were evaluated for their chemical composition by HPLC-DAD-ESI-Msn and bioactivities (antioxidant activity by TBARS, DPPH, and reducing power assays, and antimicrobial activity against eight bacteria and two fungi). Fifteen non-anthocyanin phenolic compounds were found, including 5 phenolic acids, 4 flavan-3-0Is, 2 0- glycosylated flavanols, 3 flavanol aglycones, and one unknown. In the red wine byproducts 12 anthocyanins were detected, most being malvidin derivatives. Wine lees and white grape pomace before distillation presented the highest contents of phenolic compounds. Ali samples showed antibacterial and antifunga! activity against most of the tested microorganisms, with red and white grape pomace and diatomaceous earth having the best bacteriostatic activity, while the lees stood out against fungi. Ali samples showed promising antioxidant capacity, with very good results obtained on TBARS for the white pomace after distillation and diatomaceous earth. Overall, the results show that besides grape pomace other wine industry byproducts are also good sources of bioactive compounds with high potential for exploitation.
- Fractionation of flavonols and anthocyanins in winemaking residues using molecularly imprinted cellulose‐synthetic hybrid particles with pyridyl active surfacePublication . Gomes, Catarina P.; Dias, Rolando; Costa, Mário RuiHybrid cellulose-synthetic particles with surface active pyridyl moieties and molecularly imprinted cavities for quercetin were prepared via atom transfer radical polymerization. The functionalization of the materials with pyridyl groups was confirmed by FTIR and the SEM micrographs of the hybrid particles demonstrate a clear surface modification compared with the pristine cellulose. Competitive sorption/desorption testing of the imprinted and non-imprinted particles with standard polyphenols show the achievement of an imprinting factor IF similar to 8. Moreover, it was also confirmed the high retention capability of the hybrid materials for polyphenols, due to their strong binding with the surface pyridyl moieties, even when using hydroalcoholic solvents of high ethanol content (e.g., ethanol/water 80/20 v/v). The sorption capabilities of the synthesized materials for polyphenols were explored with the fractionation of flavonols and anthocyanins in winemaking residues. High concentration and enrichment factors were achieved for high-added value compounds, namely five times for quercetin and 12 for quercetin-3-O-glucuronide with a diatomaceous earth extract and up to 4 for flavonols in a grape pomace (e.g. myricetin and quercetin glucosides). This research demonstrates de feasibility for the combination between the development of engineered materials addressing sustainability with their application to the valorization of agro-industrial wastes.
- Separation of Bioactive Compounds in Olive Leaf with a Pyridyl-Functionalized Adsorbent and Hydroalcoholic SolventsPublication . Bilalov, Elchin; Martins, Cláudia Filipa; Costa, Mário Rui; Dias, RolandoThe separation of different types of bioactive compounds in olive leaf is demonstrated with a tailored adsorbent functionalized with pyridyl moieties and sorption−desorption processes developed to use only hydroalcoholic solvents. The competitive binding isotherms of mixtures of vanillic acid, oleuropein, quercetin, maslinic, and oleanolic acids in water/ethanol solvents, with the composition ranging from 50/50 up to 100% ethanol, prove the feasibility of the separation of such different classes of molecules. The bioactive compounds in two industrial olive leaf extracts with different crude compositions were separated with the pyridyl-based polymer particles in packed columns, employing multicycle sorption/desorption processes. A polyphenol-rich extract was subjected to separation, resulting in the isolation of fractions containing varying concentrations of specific compounds. For example, a fraction enriched with oleuropein exhibited a concentration of approximately 80% (an enrichment factor of ∼4 in comparison with the crude extract), while glycosylated flavonoids were present at a concentration of around 60% in another fraction (an enrichment factor of ∼12). Additionally, aglycone flavonoids were present in fractions at a concentration of approximately 83% (an enrichment factor of ∼49). On the other hand, the separation of polyphenols and triterpene acids in an olive leaf extract with a high triterpene content was also demonstrated, with a ratio of flavonoids to triterpenoids of approximately 23 in isolated fractions, as compared to approximately 1 observed in the crude extract. The developed approach yielded luteolin with an enrichment factor of approximately 7. These novel achievements are intended to contribute to sustainability and a circular bioeconomy through the efficient industrial valorization of agricultural by products.
- Molecular imprinting of 5-fluorouracil in particles with surface RAFT grafted functional brushesPublication . Oliveira, Daniela; Dias, Rolando; Costa, Mário RuiMolecularly imprinted particles with surface grafted functional polymer brusheswere synthesized and evaluated aiming at the targeting of 5-fluorouracil (5-FU). A molecular imprinting material for 5-FU was prepared through precipitation crosslinking polymerization, in the presence of a RAFT agent, and choosing either methacrylic acid (MAA) or 2-hydroxyethyl methacrylate (HEMA) as functional monomers. In a later step, different kinds of functional polymer brushes, namely poly(methacrylic acid), poly(2-hydroxyethyl methacrylate) and poly(Nisopropylacrylamide) were grafted in the particles through a “grafting from” process starting on the RAFT groups present in their surface. The accomplishment of 5-FU imprinting was proven through comparative drug uptake measurements with imprinted/non-imprinted materials. Enhancement of 5-FU release in alkaline conditions comparatively to acidic environmentswas shown for particleswith different combinations of molecular imprinting and grafted functional brushes. TheMAA imprinting systemwith PMAA grafted functional brushes shows the highest improvement in 5-FU release triggered by a pH change from 2 to 10. Furthermore, for particles with PNIPA grafted brushes, a boost in drug release was also shown at T = 20 °C as compared to 40 °C. The novel achievements reported here put into evidence the combined benefits of molecularly imprinted particles with surface grafted functional polymer brushes concerning molecular recognition and stimulated 5-FU release.
- Development of high performance and facile to pack molecularly imprinted particles for aqueous applicationsPublication . Oliveira, Daniela; Freitas, Filipa; Kadhirvel, Porkodi; Dias, Rolando; Costa, Mário RuiDifferent kinds of molecularly imprinted particles were synthesized and compared, aiming at the development of materials combining high molecular recognition capabilities and facile use as column packing materials for chromatographic aqueous applications. Solution, inverse-suspension and precipitation polymerization were considered and two different model molecules (5-fluorouracil and caffeine) were used to highlight the effect of the interaction between the template molecule and the functional monomer on imprinting efficiency. Particles synthesized through the proposed inverse-suspension process exhibit facile use for packing columns, allow the stable running of chromatographic systems and present a high performance in drug uptake and release in aqueous media. Frontal analysis measurements highlight these key features of the synthesized particles. Drug sorption capabilities of 0.890 mol/g and 5.774 mol/g were measured for 5-fluorouracil and caffeine, respectively, using frontal analysis with eluents containing the target molecules at concentration 0.1 mM. Due to the lower amount of solvent required than with precipitation polymerization, the developed inverse-suspension process presents high synthesis yields, which can be exploited for the large-scale manufacture and commercialization of molecularly imprinted materials. The combined features of the particles makes possible their direct use in bioseparations or in the development of assays and pharmacokinetic studies concerning the presence of drugs in biological fluids.
- Impressão molecular de polifenóis em partículas de polímero sensíveis a estímulosPublication . Gomes, Catarina; Dias, Rolando; Costa, Mário RuiPolifenóis como o frans-resveratrol, catequina, ácido elágico, ete, apresentam aplicações importantes na indústria farmacêutica, cosmética ou em medicina devido às suas propriedades antioxidantes. Estes compostos estSo presentes em diversas fontes vegetais e existe um elevado interesse no desenvolvimento de técnicas e processos de extracção, purificação e concentração que permitam a sua utilização de forma eficiente. Por outro lado, muitos polifenóis (ex. resveratrol) têm baixa bndisponibilidade por administração oral devido a múltiplos factores como a fraca solubilidade em melo aquoso e a sua elevada taxa de metabolizaçâo e excreção pelo organismo. Desta forma, é também vantajoso o desenvolvimento de veículos para a sua retenção e libertação controlada. A técnica de impressão molecular tem como objectivo criar numa rede de polímero cavidades com tamanho molecular que apresentem elevada afinidade e especificidade com uma molécula alvo (T). Idealmente, o material molecularmente impresso deve ser capaz de reconhecer essa molécula em sucessivos ciclos de retençSo/Iibertaçao.
- Preparation of molecularly imprinted adsorbents with improved retention capability of polyphenols and their application in continuous separation processesPublication . Gomes, Catarina; Dias, Rolando; Costa, Mário RuiThis research explores the use of molecularly imprinted polymers (MIPs) in continuous adsorption processes to target polyphenols present in plant extracts. Different kinds of MIPs were prepared and tested in individual and competitive adsorption/ desorption assays. High polyphenol retention was shown to be possible, even when solvents of low water content are used. A lower impact of hydrophobic interactions is observed with MIPs, namely in comparison with commercial synthetic resins, and so, despite the absence of a perfect selectivity, molecular imprinting was congenial in the functionalization and improved binding site accessibility. Moreover, the potential usefulness of the prepared MIPs to improve downstream processing of polyphenols is also demonstrated through their application in chromatographic separation processes. The direct use of plant extracts of high alcoholic content, avoiding the need for solvent change and water addition, the suppression of energetic costs associated to water evaporation and the possibility to work in a wide range of polyphenols solubility are possible advantages of the developed MIP adsorbents in such kinds of biorefining processes. The development of simulation tools to aid the design and optimization of the involved continuous adsorption/desorption is also here addressed. In this work, MIPs were tested with cork and chestnut shell extracts, a supercritical CO2 olive leaf extract and red wine. Results here obtained show the successful isolation of ellagic acid with cork and chestnut shell extracts, oleuropein with the olive leaf extract and the clear simplification of the red wine extract, enabling the identification/quantification of resveratrol, quercetin, kaempferol and other polyphenols.
- Chemical composition and biological activity of different residues obtained from the wine industryPublication . Duarte, Cristina Nogueira; Dias, Maria Inês; Heleno, Sandrina A.; Santos-Buelga, Celestino; Dias, Rolando; Barros, Lillian; Amaral, Joana S.In recent years, the bioactive compounds present in agri-food sub-products have attracted increased attention due to their health benefits and advantages within a circular economy context. Annually, wine production is responsible for the production of large amounts of phytotoxic waste, which elimination is considered challenging since these residues can be hazardous to the environment when used as fertilizers or just discarded. Phenolic compounds are secondary metabolites processed by plants that have shown several health benefits, acting as antioxidants, antimicrobials, anticarcinogenic, or antidiabetics, among others. Bioactive phenolic molecules have attracted considerable attention from the pharmaceutical, cosmetic, and food industries. So far, several studies have been developed on the characterization of grape pomace and its components (seeds, skins, and stems), especially directed to the residues of red varieties.1 However, less attention has been paid to other by-products generated during winemaking, such as waste from the production of white wine, wine lees and diatomaceous earth. The latter is used in the filtration of wine and constitutes about 250 tons/year of waste from the wine sector in Portugal alone, making it a very pertinent residue with still scarce information being found in the literature. In this context, within the framework of the BacchusTech project that seeks to develop new innovative processes, comprising the extraction, purification, and concentration of bioactive compounds present in winemaking residues, different residues including pomace, lees and diatomaceous earth were evaluated for their chemical composition and bioactivities. Residues were extracted using an hydroalcoholic solvent (80%, v/v), total phenolic compounds were estimated using the Folin- Ciocalteu reagent and individual phenolic compounds were identified and quantified by liquid chromatography coupled to mass spectrophotometry (HPLC-DAD-ESI-MSn). Additionally, the biological activity was assessed through TBARS, DPPH, and reducing power assays to determine the antioxidant activity, and the antimicrobial activity was evaluated by broth microdilution against eight bacteria and two fungi. The phenolic composition was in accordance with the previously reported in red wines.2,3 Fifteen non-anthocyanin phenolic compounds were found, five phenolic acids (gallic acid and derivatives, p-hydroxybenzoic and p-coumaric acid), four flavan-3-ols (procyanidin dimers), two O-glycosylated flavanols (isorhamnetin and quercetin derivatives), three flavanol aglycones (quercetin, kaempferol, and myricetin), and one unknown compound. Regarding anthocyanins, five compounds were found, namely malvidin derivatives linked to acyl groups. Wine lees and white grape pomace before distillation presented the highest contents of phenolic compounds; however, only diatomaceous earth sample reveal the presence of O-glycosylated flavonoids. All samples showed antibacterial and antifungal activity against most of the tested microorganisms. The best bacteriostatic activity was evidenced by the red and white grape pomace before distillation and diatomaceous earth, while the wine lees stood out for their fungistatic activity. In general, all samples showed promising antioxidant capacity, with very good results being obtained on TBARS assay, particularly for the white pomace after distillation (EC50 = 0.016±0.002 mg/mL), diatomaceous earth (EC50 = 0.063±0.001 mg/mL) and red pomace before distillation (EC50 = 0.08±0.04 mg/mL). Overall, the results obtained showed that the residues analyzed are good sources of bioactive compounds, namely anthocyanins and other phenolic compounds, which can be used as raw materials for the steps of concentration, purification and/or isolation of compounds of added value.
- Prediction of mean square radius of gyration of tree-like polymers by a general kinetic approachPublication . Costa, Mário Rui; Dias, RolandoThis paper describes a kinetic method to predict the z-average molecular mean square radius of gyration of tree-like polymers formed by irreversible reactions, assuming Gaussian chains. It is based on the population balance equations for the two-sided molecular distributions of pendant chains associated with every chemically distinguishable kind of bonds. An automated method for the solution of those equations is valid both before as well as after gelation for complex kinetic schemes. Examples of its use are presented with polycondensation systems leading to hyperbranched polymers, the anionic polymerization of mono- and divinyl monomers and a radical polymerization with terminal branching and transfer to polymer.