Percorrer por autor "Mattedi, Silvana"
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- Enhanced Antimalarial Activity of Extracts of Artemisia annua L. Achieved with Aqueous Solutions of Salicylate Salts and Ionic LiquidsPublication . Ferreira, Ana M.; Sales, Isabela; Santos, Sónia A.O.; Santos, Tiago; Nogueira, Fátima; Mattedi, Silvana; Pinho, Simão; Coutinho, João A.P.; Freire, Mara G.Artemisinin, a drug used to treat malaria, can be chemically synthesized or extracted from Artemisia annua L. However, the extraction method for artemisinin from biomass needs to be more sustainable while maintaining or enhancing its bioactivity. This work investigates the use of aqueous solutions of salts and ionic liquids with hydrotropic properties as alternative solvents for artemisinin extraction from Artemisia annua L. Among the investigated solvents, aqueous solutions of cholinium salicylate and sodium salicylate were found to be the most promising. To optimize the extraction process, a response surface method was further applied, in which the extraction time, hydrotrope concentration, and temperature were optimized. The optimized conditions resulted in extraction yields of up to 6.50 and 6.44 mg·g-1, obtained with aqueous solutions of sodium salicylate and cholinium salicylate, respectively. The extracts obtained were tested for their antimalarial activity, showing a higher efficacy against the Plasmodium falciparum strain compared with pure (synthetic) artemisinin or extracts obtained with conventional organic solvents. Characterization of the extracts revealed the presence of artemisinin together with other compounds, such as artemitin, chrysosplenol D, arteannuin B, and arteannuin J. These compounds act synergistically with artemisinin and enhance the antimalarial activity of the obtained extracts. Given the growing concern about artemisinin resistance, the results here obtained pave the way for the development of sustainable and biobased antimalarial drugs. © 2024 The Authors. Co-published by Zhejiang University and American Chemical Society.
- Enhancing artemisinin solubility in aqueous solutions: searching for hydrotropes based on ionic liquidsPublication . Sales, Isabela; Abranches, Dinis O.; Costa, Pedro; Sintra, Tânia E.; Ventura, Sónia P.M.; Mattedi, Silvana; Coutinho, João A.P.; Freire, Mara G.; Pinho, SimãoArtemisinin is a sesquiterpenoid lactone peroxide, known for its potent antimalarial activity that can be extracted from Artemisia annua L. This compound is only sparingly soluble in water, making its extraction using environmental-friendly and non-toxic aqueous solvents difficult. In the attempt to overcome this limitation, hydrotropes, which are a class of compounds that can assist in increasing the solubility of hydrophobic solutes in water, were investigated in this work. In particular, the hydrotropic capability of ionic liquids (ILs) on the aqueous solubility of artemisinin was studied. The effects of IL concentration and anion nature of 1-butyl-3-methylimidazolium-based ILs on the solubility of artemisinin at 303.2 K in water were evaluated. It is here shown the excellent capacity of ILs containing thiocyanate or dicyanamide anions to enhance the solubility of artemisinin in aqueous media, with a magnitude comparable to that obtained with the best organic solvents. Furthermore, solvatochromic parameters of the ILs aqueous solutions were also measured and combined with COSMO-RS and the cooperative hydrotropy model to establish relations between the artemisinin solubility enhancement and the solvent characteristics. The solubility enhancement of artemisinin is favored by the apolarity of the medium and the lower hydrogen-bond acceptor character of the hydrotrope.
- Selection of hydrotropes for enhancing the solubility of artemisinin in aqueous solutionsPublication . Sales, Isabela; Abranches, Dinis O.; Sintra, Tânia E.; Mattedi, Silvana; Freire, Mara G.; Coutinho, João A.P.; Pinho, SimãoArtemisinin is an antimalarial substance very sparingly soluble in water. In the attempt to identify environmental-friendly and non-toxic aqueous-based solvents to extract it from Artemisia annua L., the solubility of artemisinin in aqueous solutions of different hydrotropes was measured at 303.2 K, for hydrotrope concentrations up to 5 M. The ability of the studied hydrotropes for enhancing the artemisinin solubility increases in the following order: Na[N(CN)2] < Na[SCN] < [Chol][Van] < [Chol][Gal] < [N4,4,4,4]Cl < [Chol][Sal] < [P4,4,4,4]Cl < Na[Sal], with Na[Sal] allowing an increase in the solubility of 750 fold compared to pure water. The COSMO-RS model and experimental Kamlet-Taft solvatochromic parameters were applied to connect the solubility enhancement with solvent properties. At low hydrotrope concentration, the solubility increases with the decreasing of the difference between the Apolar Factors of the hydrotrope and artemisinin, while for higher hydrotrope concentration, the hydrogen-bond acceptor character of the hydrotrope seems to have an impact on the solubility enhancement. Even if some mechanistic understanding is still to unfold, quantitatively the empirical correlations of solubility enhancement with the hydrotrope concentration and the solvatochromic parameters show very high accuracy. In particular, 93% of the change on the artemisinin solubility enhancement could be explained using the hydrotrope concentration and two combined solvatochromic parameters (αβ and π∗2) as explaining variables.