Results

The composition and structure of phenolic compounds present in three natural matrices was evaluated, as well as their bioactivity in several dimensions. The initial selection of solvents was performed by measuring the solubility of model phenolic compounds (flavonoids and phenolic acids) in conventional organic solvents and in eutectic solvents. Afterwards, the most promising solvents were used in the extraction step and the operating conditions were optimized. The bioactivity of extracts with higher polyphenol content was characterized. The extraction yield of phenolic compounds obtained with the selected eutectic solvents was similar to that obtained with conventional volatile organic solvents, with the advantage that they can be incorporated directly into dermocosmetic formulations, without solvent separation. Thus, extracts with better bioactivity were incorporated into commercial dermocosmetic formulations. In parallel, fundamental studies were carried out on the physical properties of eutectic solvents as well as on hydrotropy phenomena associated with their use in aqueous solutions. Strategies were also developed for the recovery of phenolic compounds from the non-volatile DES extract. It is also important to highlight that the methodologies developed could be extended to other biomass residues.

The main results obtained can be found in the following scientific publications in international SCI journals:

(1) Teixeira, G.; Abranches, D. O.; Silva, L. P.; Vilas-Boas, S. M.; Pinho, S. P.; Ferreira, A. I. M. C. L.; Santos, L. M. N. B. F.; Ferreira, O.; Coutinho, J. A. P. Liquefying Flavonoids with Terpenoids through Deep Eutectic Solvent Formation. Molecules 2022, 27 (9), 2649. https://doi.org/10.3390/molecules27092649.

(2) Lobo Ferreira, A. I. M. C.; Vilas-Boas, S. M.; Silva, R. M. A.; Martins, M. A. R.; Abranches, Dinis. O.; Soares-Santos, P. C. R.; Almeida Paz, F. A.; Ferreira, O.; Pinho, S. P.; Santos, L. M. N. B. F.; Coutinho, J. A. P. Extensive Characterization of Choline Chloride and Its Solid–Liquid Equilibrium with Water. Physical Chemistry Chemical Physics 2022, 24 (24), 14886–14897. https://doi.org/10.1039/D2CP00377E.

(3) Besrour, N.; Oludemi, T.; Mandim, F.; Pereira, C.; Dias, M. I.; Sokovic, M.; Stojkovic, D.; Ferreira, O.; Ferreira, I. C. F. R.; Barros, L. Article Valorization of Juglans Regia Leaves as Cosmeceutical Ingredients: Bioactivity Evaluation and Final Formulation Development. Antioxidants 2022, 11 (4). https://doi.org/10.3390/antiox11040677.

(4) Vilas-Boas, S. M.; Cordova, I. W.; Kurnia, K. A.; Almeida, H. H. S.; Gaschi, P. S.; Coutinho, J. A. P.; Pinho, S. P.; Ferreira, O. Comparison of Two Computational Methods for Solvent Screening in Countercurrent and Centrifugal Partition Chromatography. Journal of Chromatography A 2022, 1666. https://doi.org/10.1016/j.chroma.2022.462859.

(5) Añibarro-Ortega, M.; Pinela, J.; ciric, A.; Lopes, E.; Molina, A. K.; Calhelha, R. C.; Sokovic, M.; Ferreira, O.; Ferreira, I. C. F. R.; Barros, L. Extraction of Aloesin from Aloe vera Rind Using Alternative Green Solvents: Process Optimization and Biological Activity Assessment. Biology (Basel) 2021, 10 (10). https://doi.org/10.3390/biology10100951.

(6) Abranches, D. O.; Benfica, J.; Soares, B. P.; Ferreira, A. M.; Sintra, T. E.; Shimizu, S.; Coutinho, J. A. P. The Impact of the Counterion in the Performance of Ionic Hydrotropes. Chemical Communications 2021, 57 (23), 2951–2954. https://doi.org/10.1039/D0CC08092F.

(7) Abranches, D. O.; Benfica, J.; Shimizu, S.; Coutinho, J. A. P. The Perspective of Cooperative Hydrotropy on the Solubility in Aqueous Solutions of Cyrene. Industrial & Engineering Chemistry Research 2020, 59 (41), 18649–18658. https://doi.org/10.1021/acs.iecr.0c02346.

(8) Abranches, D. O.; Benfica, J.; Shimizu, S.; Coutinho, J. A. P. Solubility Enhancement of Hydrophobic Substances in Water/Cyrene Mixtures: A Computational Study. Industrial & Engineering Chemistry Research 2020, 59 (40), 18247–18253. https://doi.org/10.1021/acs.iecr.0c03155.

(9) Vilas-Boas, S. M.; Alves, R. S.; Brandão, P.; Campos, L. M. A.; Coutinho, J. A. P.; Pinho, S. P.; Ferreira, O. Solid-Liquid Phase Equilibrium of trans-Cinnamic Acid, p-Coumaric Acid and Ferulic Acid in Water and Organic Solvents: Experimental and Modelling Studies. Fluid Phase Equilibria 2020, 521. https://doi.org/10.1016/j.fluid.2020.112747.

(10) Vieira, V.; Calhelha, R. C.; Barros, L.; Coutinho, J. A. P.; Ferreira, I. C. F. R.; Ferreira, O. Insights on the Extraction Performance of Alkanediols and Glycerol: Using Juglans Regia L. Leaves as a Source of Bioactive Compounds. Molecules 2020, 25 (11). https://doi.org/10.3390/molecules25112497.

(11) Vieira, V.; Pereira, C.; Abreu, R. M. V.; Calhelha, R. C.; Alves, M. J.; Coutinho, J. A. P.; Ferreira, O.; Barros, L.; Ferreira, I. C. F. R. Hydroethanolic Extract of Juglans Regia L. Green Husks: A Source of Bioactive Phytochemicals. Food and Chemical Toxicology 2020, 137. https://doi.org/10.1016/j.fct.2020.111189.

(12) Vilas-Boas, S. M.; Abranches, D. O.; Crespo, E. A.; Ferreira, O.; Coutinho, J. A. P.; Pinho, S. P. Experimental Solubility and Density Studies on Aqueous Solutions of Quaternary Ammonium Halides,and Thermodynamic Modelling for Melting Enthalpy Estimations. Journal of Molecular Liquids 2020, 300. https://doi.org/10.1016/j.molliq.2019.112281.

(13) Finimundy, T. C.; Pereira, C.; Dias, M. I.; Caleja, C.; Calhelha, R. C.; Sokovic, M.; Stojkovic, D.; Carvalho, A. M.; Rosa, E.; Barros, L.; Ferreira, I. C. F. R. Infusions of Herbal Blends as Promising Sources of Phenolic Compounds and Bioactive Properties. Molecules 2020, 25 (9). https://doi.org/10.3390/molecules25092151.

(14) Añibarro-Ortega, M.; Pinela, J.; Barros, L.; ciric, A.; Silva, S. P.; Coelho, E.; Mocan, A.; Calhelha, R. C.; Sokovic, M.; Coimbra, M. A.; Ferreira, I. C. F. R. Compositional Features and Bioactive Properties of Aloe vera Leaf (Fillet, Mucilage, and Rind) and Flower. Antioxidants 2019, 8 (10). https://doi.org/10.3390/antiox8100444.

(15) Vilas-Boas, S. M.; Vieira, V.; Brandão, P.; Alves, R. S.; Coutinho, J. A. P.; Pinho, S. P.; Ferreira, O. Solvent and Temperature Effects on the Solubility of Syringic, Vanillic or Veratric Acids: Experimental, Modeling and Solid Phase Studies. Journal of Molecular Liquids 2019, 289. https://doi.org/10.1016/j.molliq.2019.111089.

(16) Vieira, V.; Pereira, C.; Pires, T. C. S. P.; Calhelha, R. C.; Alves, M. J.; Ferreira, O.; Barros, L.; Ferreira, I. C. F. R. Phenolic Profile, Antioxidant and Antibacterial Properties of Juglans Regia L. (Walnut) Leaves from the Northeast of Portugal. Industrial Crops and Products 2019, 134, 347–355. https://doi.org/10.1016/j.indcrop.2019.04.020.

(17) Vilas-Boas, S. M.; Brandão, P.; Martins, M. A. R.; Silva, L. P.; Schreiner, T. B.; Fernandes, L.; Ferreira, O.; Pinho, S. P. Solubility and Solid Phase Studies of Isomeric Phenolic Acids in Pure Solvents. Journal of Molecular Liquids 2018, 272, 1048–1057. https://doi.org/10.1016/j.molliq.2018.10.108.