Browsing by Author "Millan, Daniela "

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    A ternary eutectic solvent for cellulose nanocrystal production: exploring the recyclability and pre-pilot scale-up
    (2023) Mariño, Mayra A. ; Paredes Gutierrez, Maria Gabriela; Martinez Ahumada, Natalia del Pilar; Millan, Daniela ; Tapia, Ricardo A. ; Ruiz, Domingo ; Isaacs Casanova, Mauricio Alejandro; Pavez Guerrero, Paulina Isabel
    Deep eutectic solvents (DES) formed using choline chloride (ChCl), p-toluenesulfonic acid (pTSA) of stoichiometry ChCl: pTSA (1:1) and (1:2), and its ternary eutectic mixtures with phosphoric acid (PA) 85% as an additive (ChCl: pTSA: PA) were evaluated for cellulose nanocrystal (CNC) isolation. Initially, the hydrolytic efficiency to produce CNC of each DES was compared before and after adding phosphoric acid by Hammett acidity parameters and the Gutmann acceptor number. Moreover, different DES molar ratios and reaction time were studied at 80°C for CNC optimization. The nanomaterial characteristics were analyzed by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The ternary eutectic mixture ChCl: pTSA: PA molar ratio (1:1:1.35) was chosen as a suitable recyclable ternary system at the laboratory scale. A CNC yield of about 80% was obtained from the hydrolysis of commercial cellulose in five cycles of recovery, but it dropped to 35% in pre-pilot scaling. However, no variation in the average size of the resulting CNC was observed (132 ± 50 nm x 23 ± 4 nm), which presented high thermal stability (Tmax 362°C) and high crystallinity of about 80% after 3 h of reaction time.
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    Design of benzimidazoles, benzoxazoles, benzothiazoles and thiazolopyridines as leukotriene A4 hydrolase inhibitors through 3D-QSAR, docking and molecular dynamics
    (2023) Lorca, Marcos; Faundez, Mario; Pessoa-Mahana, C. David; Recabarren-Gajardo, Gonzalo; Diethelm-Varela, Benjamin; Millan, Daniela; Celik, Ismail; Mellado, Marco; Araque, Ileana; Mella, Jaime; Romero-Parra, Javier
    Human leukotriene A4 hydrolase enzyme (LTA4H) catalyses the biotransformation of the inactive precursor leukotriene A4 (LTA4) to the bioactive Leukotriene B4 (LTB4), which causes many inflammatory responses in the human body. Therefore, the selective inhibition of this enzyme becomes a useful strategy for the treatment of several illnesses such as asthma, allergic rhinitis, cardiovascular diseases, and cancer. Herein we report a 3D-QSAR/ /CoMFA and CoMSIA study on a series of 47 benzimidazoles, benzoxazoles, benzothiazoles and thiazolopyridines reported as potent LTA4H inhibitors. Good statistical parameters were obtained for the best model (q2 = 0.568, r2 ncv = 0.891 and r2 test = 0.851). A new series of 10 compounds capable of inhibiting leukotriene A4 hydrolase with high potency was presented. All designed inhibitors showed low IC50 in nano- and sub-nanomolar ranges, when they were evaluated in 3D-QSAR models. Subsequently, the designed molecules, as well as the least and most active compounds were subjected to docking and molecular dynamics studies into LTA4H. In conclusion, we summarised a thorough structure-activity relationship (SAR) of LTA4H inhibitors of heterocyclic structure. These models can be used for the rational proposal of new inhibitors.
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    Ionic liquids: anion effect on the reaction of O,O-diethyl O-(2,4-dinitrophenyl) phosphate triester with piperidine
    (2015) Pavez, Paulina; Millan, Daniela; Cocq, Cristian; Santos, Jose G.; Nome, Faruk
    The reactions of O,O-diethyl 2,4-dinitrophenylphosphate triester (1) with piperidine in ionic liquids and four conventional organic solvents (COS) were subjected to kinetic and product studies. Analytical techniques (UV-vis and NMR) identified two pathways: nucleophilic attack at the phosphoryl center and at the C-1 aromatic carbon. The nucleophilic rate constants (k(N)(T)) for these parallel reactions were separated into two terms: k(N)(P) and k(N)(Ar) for the corresponding electrophilic centers. Both the rate and the selectivities of the reactions are strongly dependent on the nature of the ionic liquid used, and a good correlation with the solvent acceptor capacity to form hydrogen bonds (beta) was observed. Remarkably, an exclusive attack at the phosphoryl center was found using [Bmim] DCA, [Bmpyrr] DCA and [Bmpy] DCA as the reaction solvents. In contrast, with [Bmim]PF6 as the reaction solvent, attack at the C-1 aromatic was the main path (94%). These results suggest that ionic liquids can be considered to be designer solvents because by an appropriate choice of the anion it is possible to steer the selectivity of this reaction.
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    Solvatochromism and electrophilicity
    (ELSEVIER SCIENCE BV, 2011) Caroli Rezende, Marcos; Dominguez, Moises; Aracena, Andres; Millan, Daniela
    Solvatochromic dyes that exhibit a negative or a positive behaviour may be distinguished and their solvatochromism predicted with the aid of DFT-based indices, such as their electrophilicity omega, hardness eta and by the Fukui electrophilic functions f(G)(+) of the donor and acceptor moieties of the molecule, calculated in the gas-phase and in solvents treated as polarised continua. The protocol was successfully applied to 10 examples of phenolate betaines from the literature, five of them exhibiting a negative and five a positive solvatochromism. (C) 2011 Elsevier B.V. All rights reserved.
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    Theoretical Substituent Electrophilicities
    (SOC BRASILEIRA QUIMICA, 2011) Caroli Rezende, Marcos; Millan, Daniela
    A Hammett-like equation, relating theoretical global and substituent electrophilicities, is derived for substituted ethylenes and benzoic acids, allowing the calculation of electrophilic substituent constants a.. Correlations are given between the theoretical a, constants and kinetic or thermodynamic parameters of various chemical processes from the literature. Though electrophilic substituent constants are formally similar to the Hammett constants, they are derived from entirely different theoretical postulates. The similarities and differences between the two sets of constants are discussed and rationalized in terms of the definition of the electrophilic power of a chemical species.