Institute of Molecular Sciences

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Publications

Unravelling the structure of peroxides with antiparasitic activity: the relative impact of a trioxolane or a tetraoxane pharmacophore on the overall molecular structure

Publication . Amado, Patrícia; Jesus, A. J. Lopes; Paixão, José A.; Fausto, Rui; Cristiano, Maria De Lurdes

Plasmodium falciparum artemisinin-resistance boosted the quest for novel plasmodial "fast killers," uncovering antimalarial candidates OZ439 and E209, whose peroxide precursors are 1,2,4-trioxolane (1) and 1,2,4,5-tetraoxane (2), differing solely in the pharmacophore (trioxolane or tetraoxane). Combining X-ray crystallography and vibrational spectroscopy, along with Hirsh-feld surface analysis and calculations (CE-B3LYP/6-31G(d,p)) of pairwise interaction energies of intermolecular contacts existing in the crystal structure, may deepen the understanding of relative reactivity and properties of these endoperoxides classes. In the crystal, the tetraoxane ring in 2 and the trioxolane-adamantyl fragment in 1 are disordered, with molecules 1 and 2 existing as two distinct, stable conformations. Whereas the dominant C-H center dot center dot center dot O H-bonds in 1 connect an adamantyl C-H and O1 or O2 of the trioxolane ring, in 2 they involve the carbonyl oxygen, acting as a double acceptor from phenyl ring C-H groups. C-H center dot center dot center dot O and C-H center dot center dot center dot pi H-bonds define the molecular packing of 2, while C-H center dot center dot center dot H-C van der Waals interactions determine the packing of 1. The dispersive component dominates the interaction energies calculated for the most representative molecular pairs.

2022Journal article

Restricted access

Tunning processes for organic matter removal from slaughterhouse wastewater treated by immediate one-step lime precipitation and atmospheric carbonation

Publication . Simão Madeira, Luís Miguel; Almeida, Adelaide; Rosa Da Costa, Ana; Mestre, Ana S.; Carvalho, Fátima; Ribau Teixeira, Margarida

Adsorption using unmodified/modified commercial activated carbons and constructed wetlands (CW) planted with Vetiveria zizanioides were evaluated as tuning processes for lowering chemical oxygen demand (COD) from slaughterhouse wastewater pretreated by the integrated process of immediate one-step lime precipitation and atmospheric carbonation. Powdered and granular activated carbons (PAC and GAC), and PAC and GAC incorporated with iron oxide nanoparticles (PACMAG and GACMAG) were used. COD removal using different adsorbent separation methods (i.e., sedimentation, filtration, or magnetic separation) was also evaluated. The adsorption results indicated that the best adsorbent doses and contact times of the studied adsorbents were 70 g L-1 and 5 min for PAC and PACMAG, and 60 g L-1 and 60 min for GAC and GACMAG. Under optimized conditions, GAC (75.7 +/- 1.0%) and GACMAG (73.5 +/- 2.1%) were more efficient than PAC (59.7 +/- 1.0%) and PACMAG (59.0 +/- 0.0%) in removing COD. The incorporation of iron oxide nanoparticles in GAC and PAC did not affect the adsorption of COD. The Temkin model was the best isotherm model found for PAC and PACMAG, while for GAC and GACMAG was the BET model. Pseudo-order n kinetic model was the best kinetic model found for all the adsorbents tested. There were no significant differences in the removal of COD between filtration and magnetic separations. Phytoremediation results indicated that increased COD removal efficiency occurred when the applied COD mass load decreased or when the bed depth was increased. Maximum COD removals of around 89.9-95.0% were achieved. Vetiveria zizanioides showed no signs of toxicity throughout the trials.

2023-10Journal article

Open access

Ethylene removal by Ag-based ZSM-5 adsorbents for the preservation of climacteric fruits

Publication . Ferreira, R.; Lopes, H.; Lourenço, J. P.; Silva, J. M.; João, I. M.; Ribeiro, M. F.; Fernandes, A.

Ethylene removal is crucial for fruits and vegetables preservation because even a very low concentration (<0.1ppm) can induce ripening during storage and transportation. Ag+ exchanged ZSM-5 zeolites were investigated as adsorbents for the efficient removal of ethylene. Two ZSM-5 materials (Si/Al ratios of 15 and 40), with different amounts of Ag (up to 6 % by weight) and two compensating cations, Na+ and H+, were used for this purpose. The adsorbents were characterized by X-ray Diffraction, diffuse reflectance spectroscopy and H2- TPR experiments. Their performance in ethylene adsorption was determined by the means of breakthrough curves experiments, mimicking the atmospheric conditions of industrial fruits cold storage chambers, particularly the high relative humidity levels. Results show that adsorbents are highly efficient in removing ethylene (max. 500 µmol.g-1 in the absence of water). Monovalent Ag+ species have been identified as the main contributors to the excellent performance of the different adsorbents, as they can easily interact with ethylene through strong π interaction. Moreover, statistical analysis (ANOVA) results confirmed that, in the presence of water, Ag-based ZSM-5 materials with a higher Si/Al ratio and Na+ as the charge balancing cation, i.e., those with a higher hydrophobic character, are the best adsorbents for ethylene removal.

2024-02Journal article

Open access

NaCl elicitation enhances metabolite accumulation and stress resilience in Inula crithmoides L. shoot cultures: implications for its nutritional and medicinal value

Publication . Rodrigues, Maria João; Neng, Nuno; Custódio, Luísa

This study explored the impact of sodium chloride (NaCl) elicitation on the accumulation of primary and secondary metabolites and the oxidative stress responses of Inula crithmoides L. (golden samphire) in vitro shoot cultures. Elicitation involved applying different concentrations of NaCl (0, 50, 100, and 200 mM) for 4 weeks. This was followed by assessing its impact on plant growth, physiological parameters (pigments, hydrogen peroxide content, total soluble sugars and proteins, and proline), and secondary metabolism (phenylalanine ammonia-lyase activity, shikimic acid, phenolics, flavonoids, and hydroxycinnamic acids) in the shoots. The extracts were also analysed using high-performance liquid chromatography (HPLC). The NaCl elicitation did not affect shoot growth but increased physiological functions such as photosynthesis and oxidative stress management under moderate salinity levels. In addition, NaCl treatments increased the synthesis of soluble sugars and proteins, particularly proline, as well as bioactive phenolics such as gentisic acid, chlorogenic acid, 4-hydroxybenzoic acid, luteolin-7-O-glucoside, and naringenin-7-O-glucoside. The NaCl elicitation in golden samphire shoot cultures offers a significant method for enhancing the production of important nutritional and bioactive compounds. This underscores the species' potential for cultivation in saline environments and provides valuable prospects for its utilization in the health and nutrition sectors.

2024-04Journal article

Open access

Contamination analysis of Arctic ice samples as planetary field analogs and implications for future life-detection missions to Europa and Enceladus

Publication . Coelho, Lígia F.; Blais, Marie-Amélie; Matveev, Alex; Keller-Costa, Tina; Vincent, Warwick F.; Da Silva Costa, Rodrigo; Martins, Zita; Canário, João

Missions to detect extraterrestrial life are being designed to visit Europa and Enceladus in the next decades. The contact between the mission payload and the habitable subsurface of these satellites involves significant risk of forward contamination. The standardization of protocols to decontaminate ice cores from planetary field analogs of icy moons, and monitor the contamination in downstream analysis, has a direct application for developing clean approaches crucial to life detection missions in these satellites. Here we developed a comprehensive protocol that can be used to monitor and minimize the contamination of Arctic ice cores in processing and downstream analysis. We physically removed the exterior layers of ice cores to minimize bioburden from sampling. To monitor contamination, we constructed artificial controls and applied culture-dependent and culture-independent techniques such as 16S rRNA amplicon sequencing. We identified 13 bacterial contaminants, including a radioresistant species. This protocol decreases the contamination risk, provides quantitative and qualitative information about contamination agents, and allows validation of the results obtained. This study highlights the importance of decreasing and evaluating prokaryotic contamination in the processing of polar ice cores, including in their use as analogs of Europa and Enceladus.

2022Journal article

Open access