Browsing by Author "Tapia, Ricardo A. "
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- ItemA 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 IsabelDeep 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.
- ItemMicrowave-Assisted Reaction of 2,3-Dichloronaphthoquinone with Aminopyridines(SOC BRASILEIRA QUIMICA, 2009) Tapia, Ricardo A.; Cantuarias, Lorena; Cuellar, Mauricio; Villena, JoanThe synthesis of pyridylaminonaphthoquinones by microwave-assisted reaction of 2,3-dichloro1,4-naphthoquinone with aminopyridines is described. The use of microwave irradiation diminished the reaction times and improved the yields substantially in all these reactions. The compounds were tested for their cytotoxic activities against MCF-7 breast cancer cell line.
- ItemNew Approaches to 6-Oxoisoaporphine and Tetrahydroisoquinoline Derivatives(WILEY-BLACKWELL, 2010) Sobarzo Sanchez, Eduardo; Uriarte, Eugenio; Santana, Lourdes; Tapia, Ricardo A.; Perez Lourido, Paulo2,3-Dihydro-6-hydroxy-5-methoxy-7H-dibenzo[de,h]quinolin-7-one, 6-hydroxy-5-methoxy-7H-dibenzo[de,h]quinolin-7-one, and 2-(6,7-dimethoxy-3,4-dihydroisoquinolin-l-yl)benzyl benzoate, easily available by a Bischler-Napieralski cyclization, were used as starting materials to afford 6-oxoisoaporphine and 2,3-dimethoxy-5,6,8,12b-tetrahydroisoindolo[1,2-a]isoquinoline as the main products. However, the catalytic hydrogenation of the benzyl benzoate derivative afforded, under mild conditions, 1,2,3,4-tetrahydro-6.7-dimethoxy-1 -(2-methylphenyl)isoquinoline.
- ItemNL MIND-BEST: A web server for ligands and proteins discovery-Theoretic-experimental study of proteins of Giardia lamblia and new compounds active against Plasmodium falciparum(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2011) Gonzalez Diaz, Humberto; Prado Prado, Francisco; Sobarzo Sanchez, Eduardo; Haddad, Mohamed; Chevalley, Severine Maurel; Valentin, Alexis; Quetin Leclercq, Joelle; Dea Ayuela, Maria A.; Teresa Gomez Munos, Maria; Munteanu, Cristian R.; Jose Torres Labandeira, Juan; Garcia Mera, Xerardo; Tapia, Ricardo A.; Ubeira, Florencio M.There are many protein ligands and/or drugs described with very different affinity to a large number of target proteins or receptors. In this work, we selected Ligands or Drug-target pairs (DTPs/nDTPs) of drugs with high affinity/non-affinity for different targets. Quantitative Structure-Activity Relationships (QSAR) models become a very useful tool in this context to substantially reduce time and resources consuming experiments. Unfortunately most QSAR models predict activity against only one protein target and/or have not been implemented in the form of public web server freely accessible online to the scientific community. To solve this problem, we developed here a multi-target QSAR (mt-QSAR) classifier using the MARCH-INSIDE technique to calculate structural parameters of drug and target plus one Artificial Neuronal Network (ANN) to seek the model. The best ANN model found is a Multi-Layer Perceptron (MLP) with profile MLP 20:20-15-1:1. This MLP classifies correctly 611 out of 678 DTPs (sensitivity=90.12%) and 3083 out of 3408 nDTPs (specificity=90.46%), corresponding to training accuracy=90.41%. The validation of the model was carried out by means of external predicting series. The model classifies correctly 310 out of 338 DTPs (sensitivity=91.72%) and 1527 out of 1674 nDTP (specificity = 91.22%) in validation series, corresponding to total accuracy = 91.30% for validation series (predictability). This model favorably compares with other ANN models developed in this work and Machine Learning classifiers published before to address the same problem in different aspects. We implemented the present model at web portal Bio-AIMS in the form of an online server called: Non-Linear MARCH-INSIDE Nested Drug-Bank Exploration & Screening Tool (NL MIND-BEST), which is located at URL: http://miaja.tic.udc.es/Bio-AIMS/NL-MIND-BEST.php. This online tool is based on PHP/HTML/Python and MARCH-INSIDE routines. Finally we illustrated two practical uses of this server with two different experiments. In experiment 1, we report by first time Quantum QSAR study, synthesis, characterization, and experimental assay of antiplasmodial and cytotoxic activities of oxoisoaporphine alkaloids derivatives as well as NL MIND-BEST prediction of potential target proteins. In experiment 2, we report sampling, parasite culture, sample preparation, 2-DE, MALDI-TOF, and -TOF/TOF MS, MASCOT search, MM/MD 3D structure modeling, and NL MIND-BEST prediction for different peptides a new protein of the found in the proteome of the human parasite Giardia lamblia, which is promising for anti-parasite drug-targets discovery. (c) 2011 Elsevier Ltd. All rights reserved.
- ItemPhenoxy- and Phenylamino-Heterocyclic Quinones: Synthesis and Preliminary Anti-Pancreatic Cancer Activity(WILEY-V C H VERLAG GMBH, 2022) Sanchez, Patricio; Salas, Cristian O.; Gallardo-Fuentes, Sebastian; Villegas, Alondra; Veloso, Nicolas; Honores, Jessica; Inman, Martyn; Isaacs, Mauricio; Contreras, Renato; Moody, Christopher J.; Cisterna, Jonathan; Brito, Ivan; Tapia, Ricardo A.The successful application of fragment-based drug discovery strategy for the efficient synthesis of phenoxy- or phenylamino-2-phenyl-benzofuran, -benzoxazole and -benzothiazole quinones is described. Interestingly, in the final step of the synthesis of the target compounds, unusual results were observed on the regiochemistry of the reaction of bromoquinones with phenol and aniline. A theoretical study was carried out for better understanding the factors that control the regiochemistry of these reactions. The substituted heterocyclic quinones were evaluated in vitro to determine their cytotoxicity by the MTT method in three pancreatic cancer cell lines (MIA-PaCa-2, BxPC-3, and AsPC-1). Phenoxy benzothiazole quinone 26a showed potent cytotoxic activity against BxPC-3 cell lines, while phenylamino benzoxazole quinone 20 was the most potent on MIA-PaCa-2 cells. Finally, electrochemical properties of these quinones were determined to correlate with a potential mechanism of action. All these results, indicate that the phenoxy quinone fragment led to compounds with increased activity against pancreatic cancer cells.
- ItemTrypanosoma cruzi: Activities of lapachol and alpha- and beta-lapachone derivatives against epimastigote and trypomastigote forms(PERGAMON-ELSEVIER SCIENCE LTD, 2008) Salas, Cristian; Tapia, Ricardo A.; Ciudad, Karina; Armstrong, Veronica; Orellana, Myriam; Kemmerling, Ulrike; Ferreira, Jorge; Maya, Juan Diego; Morello, AntonioDerivatives of natural quinones with biological activities, such as lapachol, alpha- and beta-lapachones, have been synthesized and their trypanocidal activity evaluated in vitro in Trypanosoma cruzi cells. All tested compounds inhibited epimastigote growth and trypomastigote viability. Several compounds showed similar or higher activity as compared with current trypanocidal drugs, nifurtimox and benznidazole. The results presented here show that the anti-T Cruzi activity of the alpha-lapachone derivatives can be increased by the replacement of the benzene ring by a pyridine moiety. Free radical production and consequently oxidative stress through redox cycling or production of electrophilic metabolites are the potential biological mechanism of action for these synthetic quinones. (c) 2007 Elsevier Ltd. All rights reserved.