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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.
- Extraction of phenolic compounds from Juglans regia L. leaves using aqueous solutions of eutectic solventsPublication . Cordova, Isabella Weber; Oludemi, Taofiq; Vieira, Vanessa; Pires, Tânia C.S.P.; Pinho, Simão; Barros, Lillian; Ferreira, OlgaThe leaves of Juglans regia L. (walnut tree) are a rich source of bioactive phenolic compounds, particularly flavonoids and phenolic acids, which can be used in cosmetic applications due to their antioxidant properties. Conventionally, these compounds are extracted using volatile organic solvents. This study focuses on a more sustainable approach by designing a heat-assisted extraction process using aqueous solutions of eutectic solvents (ES) composed of cosmetic-compatible ingredients aiming for direct incorporation into cream formulations. In this context, aqueous solutions of the ES betaine + urea and betaine + 1,3-propanediol (PPD) were selected, considering their potential as cosmetic ingredients. The screening process targeted the maximum extraction yield of phenolic compounds (phenolic acids and flavonoids), quantified by HPLC-DAD. The selected variables were water content (25, 50 and 75 % in weight) and the molar proportion of the ES components. For comparison purposes, pure water was used as a reference solvent. The total phenolic content ranged between 5.5 and 14.6 mg/g of dry plant. Betaine:urea (2:1), betaine:PPD (1:2), betaine, and PPD, all with 50 % water mass percentage, were among those resulting in higher extraction yields and were further selected for bioactivity analysis. The system containing betaine presented the best antioxidant capacity, analysed through ferric reducing power, DPPH radical scavenging, and TBARS assays. The extracts obtained with PPD presented the highest antimicrobial activity against gram-positive and gram-negative bacteria, and yeast. The results show the potential of using binary aqueous mixtures of betaine, or 1,3-propanediol, which are simple ingredients in cosmetics formulations, to efficiently extract phenolic compounds from a natural matrix. Moreover, the bioactivity results, particularly in the antioxidant dimension, support using J. regia leaves as a source of natural antioxidants.
- Experimental and theoretical studies on water activity: aqueous solutions of amino acids with electrolytesPublication . Fernandes, Isa Cristiana Moreira; Vilarinho, Mário F.; Pinho, SimãoIn the recent past a considerable body of work has been published on the measurement of activity coefficients and solubility data in aqueous amino acid solutions containing electrolytes [1]. However, no information on water activity in this type of system has yet been published [2]. In this work water activity (aw) in DL-alanine, glycine or L-serine aqueous systems with ammonium sulfate, at 298.15 K, was measured. The LabMASTER-aw water activity instrument (Novasina, Switzerland) was used to perform the measurements. The instrument, with a controlled chamber temperature (± 0.2 K), shows high precision (± 0.001 aw units). The new experimental data was used to test different theoretical schemes such as Zdanovskii-Stokes-Robinson (ZSR) model [3] and its extension, or the Clegg-Seinfeld-Brimblecombe (CSB) approach [4], in the calculation of amino acid and electrolyte activity coefficients in those solutions. Comparisons between the different approaches are given.
- Insights into the chloride versus bromide effecton the formation of urea quaternary ammonium eutectic solventsPublication . Martins, Mónia A.R.; Abranches, Dinis O.; Silva, Liliana P.; Pinho, Simão; Coutinho, João A.P.The intermolecular interactions of urea and quaternary ammonium salts relevant to their thermodynamic nonideality were here investigated by measuring the solid-liquid equilibria of their binary mixtures. The experimental data revealed that the anion transfer between the quaternary ammonium salt and urea increases with increasing alkyl chain lengths, leading to negative deviations from ideality in the urea-rich side for [N4,4,4,4]- based systems. However, the use of bromides instead of chlorides dampens the nonideality of urea because of larger size and lower electronegativity of the anion. The behavior of urea when mixed with ChCl or ChBr was found to be remarkably different, indicating that its nonideality in the ChCl/urea eutectic solvent is governed by urea-chloride rather than hydroxyethyl-urea interactions. The conclusions presented highlight the contribution of charge delocalization in the formation of deep eutectic solvents of type III.
- Erratum: Solubilities of biologically active phenolic compounds: Measurements and modelingPublication . Queimada, António; Mota, Fátima L.; Pinho, Simão; Macedo, Eugénia A.
- Representation of salt solubility in mixed solvents: a comparison of thermodynamic modelsPublication . Pinho, Simão; Macedo, Eugénia A.A simple and accurate apparatus for the measurement of salt solubilities in mixed solvents by an analytical method is presented. Salt solubility data have been measured for the systems water/methanol/NaCl, water/methanol/KCl at 298.15 and 323.15 K and for the system water/ethanol/NaCl at 298.15, 323.15 and 348.15K.
- Partial molar volumes of glycine and dl-alanine in aqueous ammonium sulfate solutions at 278.15, 288.15, 298.15 and 308.15 KPublication . Martins, Mónia A.R.; Ferreira, Olga; Hnědkovský, Lubomír; Cibulka, Ivan; Pinho, SimãoIn this work, the partial molar volumes of glycine and DL-alanine in aqueous solutions of ammonium sulfate at 0.0, 0.1, 0.3, 0.7, and 1.0 mol.kg(-1) are determined between 278.15 and 308.15 K. Transfer volumes were obtained, which are larger for glycine than DL-alanine. On the contrary, the hydration numbers are higher for DL-alanine than glycine, and dehydration of the amino acids is observed with increasing temperature or salt molality. The data suggest that interactions between ion and charged/hydrophilic groups are predominant and, by applying the methodology proposed by Friedman and Krishnan, it was concluded that they are mainly pairwise. A group-contribution scheme has been successfully applied to the pairwise volumetric interaction coefficient. Finally, the dehydration effect on glycine, alanine and serine in the presence of different electrolytes has been rationalized in terms of the charge density and a parameter accounting for the cation's hydration.
- Exploring the bioactive potential of Artemisia annua L. hydroethanolic extracts obtained by microwave-assisted extractionPublication . Calhelha, Ricardo C.; Alves, Maria José; Barros, Lillian; Pinho, Simão; Ayuso, ManuelArtemisia annua L. is known for producing artemisinin, a sesquiterpene lactone compound, which is applied to treat of malaria [1]. Its pharmacodynamic and pharmacokinetic characteristics, as well as its strong capacity for Plasmodium elimination, have raised many expectations for this new class of antimalarial drugs [2]. However, this plant has been also used in traditional Chinese medicine to treat of various diseases since ancient times. Recent studies have focused on its extensive biological activities, which makes this plant an excellent candidate to be used in clinical therapies. Thus, this work aimed to evaluate different bioactivities from a hydroethanolic extract of Artemisia annua. The plant extract in ethanol:water (80:20 v/v) was obtained by microwave-assisted extraction. The antioxidant activity was determined by thiobarbituric acid reactive substances (TBARS) assay, showing a potent activity with an IC50 of 10.3 ± 1.0 μg/mL. A. annua L. extract also exhibited antibacterial and antifungal properties, with concentrations ranging from 2.5 to 10 mg/mL. The ethanolic extract was very effective against the four tumor cell lines, presenting GI50 ranging from 21 to 61 μg/mL and excellent anti-inflammatory activity (38 μg/mL). However, it was also cytotoxic against the two normal cells tested (50 and 19 μg/mL). Concluding, despite the excellent biological activities exhibited by A. annua L. extract, it was also demonstrated to be cytotoxic against normal cells. Therefore, further studies are necessary to study how the cytotoxicity of this extract could be reduced without affecting its bioactive properties.
- CPA EoS modeling of multifunctional associating fluidsPublication . Queimada, António; Mota, Fátima L.; Pinho, Simão; Macedo, Eugénia A.
- Solubility studies of trans-cinnamic acid in mixed solventsPublication . Soares, Bruna de Paula; Ferreira, Olga; Leite, Priscilla G.; Pinho, SimãoPhenolic acids are a subclass of phenolic compounds with chemical and biological properties of interest in the pharmaceutical and food industries. The design of their extraction and separation processes includes the knowledge of their thermophysical properties as well as multicomponent solid-liquid equilibria data. For these compounds, even essential solubility data in pure organic solvents and water are scarce. Therefore, in this work, trans-cinnamic acid was chosen as a model compound for which only a few solubility data in pure water and alcohols can be found in the literature [1-3]. The solubility of trans-cinnamic acid in the mixed solvents water + ethanol, and water + methanol was measured, at 298.15 K, using the isothermal shake-flask method and quantitative analysis either by gravimetry or UV spectrophotometry. As can be seen in Fig. 1, the solubility of the acid can significantly increase with the addition of the alcohol, with a more pronounced effect induced by ethanol. In a complementary approach and aiming to search for other methods to increase the aqueous solubility of trans-cinnamic acid, the phase-solubility diagram was determined for systems containing α-cyclodextrin. References [1] J. Li, Z. Zeng, L. Sun, W. Xue, H. Wang, Journal of Chemical and Engineering Data, 61 (2016) 1192−1198. [2] F. Mota, A. Queimada,, S. Pinho, E. Macedo, Industrial and Engineering Chemistry Research, 47 (2008) 5182-5189. [3] Solubilities of Organic Compounds in Organic Solvents, J. Bradley, C. Neylon, R. Guha, A. Williams, B. Hooker, A. Lang, B. Friesen, Open Notebook Science, 2009.