DSpace Angular :: Browsing by Author "Valderrama, Jaime A."

Browsing by Author "Valderrama, Jaime A."

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Biological evaluation of donor-acceptor aminonaphthoquinones as antitumor agents
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2010) Benites, Julio; Valderrama, Jaime A.; Bettega, Karina; Pedrosa, Rozangela Curi; Buc Calderon, Pedro; Verrax, Julien
Several members of the phenylamino-1,4-naphthoquinone series were prepared in order to investigate structure-activity relationships (SAR) and to explore the antitumor effects associated with this scaffold. The cytotoxic effects of the aminoquinones (EC50) against a panel of cancer cell lines (MCF7, DU145 and T24 cells) and healthy fibroblasts (BALB/3T3) were assessed in vitro using the MTT reduction assay 48 h after drug exposure. SAR analysis of the aminonaphthoquinone series showed that insertion of a chlorine atom in the acceptor quinone nucleus and/or insertion of a methyl group at the nitrogen atom of the donor phenylamino group induced significant changes in cytotoxic activity. Quinones 7 and 9, which exhibited the highest selective indexes (5.73 and 6.29, respectively), were further characterized using the following assays: Colony formation, caspase-3 activity, and ATP content. The results showed that aminoquinone 7 strongly influenced ATP levels and impaired the proliferative capacity of T24 cells without activating caspase-3. (C) 2010 Elsevier Masson SAS. All rights reserved.
Design and synthesis of angucyclinone 5-aza analogues
(GEORG THIEME VERLAG KG, 2006) Valderrama, Jaime A.; Gonzalez, M. Florencia; Colonelli, Pamela; Vasquez, David
A highly efficient one-pot procedure for the synthesis of phenanthridine-1,7,10-triones from acylbenzoquinones and cyclic enaminones is reported. The cycloaddition reactions of these quinones with 1-trimethylsilyloxybutadiene followed by hydrolysis and oxidative processes provide entry to a variety of angucyclinone 5-aza analogues.
Design and synthesis of angucyclinone AB-pyrido[2,3-d] pyrimidine analogues
(PERGAMON-ELSEVIER SCIENCE LTD, 2008) Valderrama, Jaime A.; Vasquez, David
The preparation of two pyrimido[4,5-c]isoquinoline-7, 10-quinones from acylhydroquinones and 1,3-dimethyl-5-aminouracil and their cycloadditions with 1-trimethylsilyloxybutadiene and 1-dimethylamino-3-methyl-1-azabutadiene is described. The remarkable regio-control of these cycloadditions that yield stable 1:1 cycloadducts is discussed on the basis of steric interactions into the pyrimido[4,5-c]isoquinoline-7,10-quinones. The access to angucyclinone AB-pyridopyrimidine analogues from Diels-Alder adducts and preliminar evidences on their antitumour activities are also reported. (c) 2007 Elsevier Ltd. All rights reserved.
Gastroprotective Effect and Cytotoxicity of Labdeneamides with Amino Acids
(GEORG THIEME VERLAG KG, 2011) Schmeda Hirschmann, Guillermo; Rodriguez, Jaime A.; Theoduloz, Cristina; Valderrama, Jaime A.
Semisynthetic aromatic amides from Araucaria araucana diterpene acids have been shown to display a relevant gastroprotective effect with low cytotoxicity. The aim of this work was to assess the gastroprotective effect of amino acid amides from imbricatolic acid and its 8(9)-en isomer in the ethanol/HCl-induced gastric lesions model in mice as well as to determine the cytotoxicity of the obtained compounds on the following human cell lines: normal lung fibroblasts (MRC-5), gastric adenocarcinoma (AGS), and liver hepatocellular carcinoma (Hep G2). The diterpenes 15-acetoxyimbricatolic acid, its 8(9)-en isomer, 15-hydroxyimbricatolic acid, and the 8(9)-en derivative, bearing a COOH function at C-19, were used as starting compounds. New amides with C-protected amino acids were prepared. The study reports the effect of a single oral administration of either compound 50 min before the induction of gastric lesions by ethanol/HCl. Some 20 amino acid monoamides were obtained. Dose-response experiments on the glycyl derivatives showed that at a single oral dose of 100 mg/kg, the compounds presented an effect comparable to the reference drug lansoprazole at 20 mg/kg and at 50 mg/kg reduced gastric lesions by about 50%. All derivatives obtained in amounts >30 mg were compared at a single oral dose of 50 mg/kg. The best gastroprotective effect was observed for the exomethylene derivatives bearing a valine residue at C-19 either with an acetoxy or free hydroxy group at C-15. The tryptophanyl derivative from the acetate belonging to the 8,9-en series presented selective cytotoxicity against hepatocytes. The glycyl amide of 15-acetoxyimbricatolic acid was the most cytotoxic and less selective compound with IC50 values between 47 and 103 mu M for the studied cell lines. This is the first report on the obtention of semisynthetic amino acid amides from labdane diterpenes.
Inhibition of human topoisomerase I and activation of caspase-3 by aza-angucyclinones and arylaminopyrimido[4,5-c]isoquinoline-7,10-quinones
(SPANDIDOS PUBL LTD, 2012) Monsalve, Francisco A.; Valderrama, Jaime A.; Vasquez, David; Ibacache, Andrea; Rodriguez, Jaime A.; Gonzalez, Daniel R.; Leiva, Elba; Gonzalez, Enrique
Cancer is the second cause of death in the world after cardiovascular diseases. Cancer cells acquire capacities not present in normal cells, such as self-sufficiency, resistance to antiproliferative stimuli, evasion of apoptosis, unlimited replication, invasiveness and metastasis. Consequently, it is of major interest to explore and develop molecules with anticancer activity directed to specific targets. In this study, we aimed to evaluate two series of polycyclic quinones: aza-angucyclinone and arylaminopyrimido[4,5-c]isoquinoline-7,10-quinones, in their capacity to inhibit human topoisomerase I (TOP1) and to trigger apoptosis through activation of caspase-3. We evaluated the capacity of the two series of polycyclic quinones to inhibit TOP1, using a DNA supercoiled relaxation assay and their capacity to induce apoptosis through the activation of caspase-3 in HL60 cells. Both series of quinones inhibited TOP1 activity over 50%. When we evaluated the pro-apoptotic capacity of both series of quinones, at therapeutically relevant concentrations, the arylaminoquinones ADPA-ICC (methyl 7-(4-methoxyphenyl)amino-1,3-dimethyl-5,8-dioxo-5,8-dihydroisoquinoline-4-carboxylate), P4 (9-phenylamino-3,4-dihydrophenanthridine-1,7,10(2H)-trione) and the aza-angucyclinone OH-6H (8-hydroxy-2,4-dimethyl-2H,4H-benzo[g]pyrimido[4,5-c]isoquinoline-1,3,7,12-tetraone) increased the caspase-3 activity by approximately 2-fold over the control. The series of the arylaminoquinones and aza-angucyclinones showed differential antiproliferative capacity. We further identified a group of them that showed antiproliferative capacity possibly through inhibition of TOP1 and by activation of caspase-3. This group of molecules may represent a potential pharmacological tool in treatment against cancer.
Part 1: Effect of vitamin C on the biological activity of two euryfurylbenzoquinones on TLT, a murine hepatoma cell line
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2008) Benites, Julio; Rojo, Leonel; Valderrama, Jaime A.; Taper, Henryk; Calderon, Pedro Buc
2-Euryfuryl- and 2-euryfuryl-3-nitro-1,4-benzoquinone Q2 and Q3, prepared via oxidative coupling reactions of sesquiterpene euryfuran 1 to 2-nitro-1,4-benzoquinone and 1,4-benzoquinone, were tested for their cytotoxicity towards TLT cells (a murine hepatoma cell line) in the absence and in the presence of vitamin C. Their cytotoxic profile was completely different. In cells incubated with Q2 (from 1 to 50 mu g/ml), cell survival was not modified, both GSH and ATP were depleted to about 50% of control values (at 50 mu g/ml); and caspase-3 was activated in a dose-dependent manner. These effects were observed whatever cells were incubated or not in the presence of vitamin C. In the case of Q3, the cytotoxicity was rather unrelated to its concentration but the association of vitamin C plus the highest Q3 concentration (50 mu g/ml) results in a strong cell death (more than 60%). At such a concentration, a complete lack of caspase-3 activity was observed, probably due to cell lysis. At lower concentrations of Q3 (1 and 10 mu g/ml), caspase-3 activity was lower than that observed in the absence of vitamin C or even under control conditions. Both GSH and ATP were kept fairly constant as compared to control values but in the presence of vitamin C and Q3, at 50 mu g/ml, a decrease in their amounts was observed. (C) 2007 Elsevier Masson SAS. All rights reserved.
Redox-Active Quinones and Ascorbate: An Innovative Cancer Therapy That Exploits the Vulnerability of Cancer Cells to Oxidative Stress
(BENTHAM SCIENCE PUBL LTD, 2011) Verrax, Julien; Beck, Raphael; Dejeans, Nicolas; Glorieux, Christophe; Sid, Brice; Pedrosa, Rozangela C.; Benites, Julio; Vasquez, David; Valderrama, Jaime A.; Buc Calderon, Pedro
Cancer cells are particularly vulnerable to treatments impairing redox homeostasis. Reactive oxygen species (ROS) can indeed play an important role in the initiation and progression of cancer, and advanced stage tumors frequently exhibit high basal levels of ROS that stimulate cell proliferation and promote genetic instability. In addition, an inverse correlation between histological grade and antioxidant enzyme activities is frequently observed in human tumors, further supporting the existence of a redox dysregulation in cancer cells. This biochemical property can be exploited by using redox-modulating compounds, which represent an interesting approach to induce cancer cell death. Thus, we have developed a new strategy based on the use of pharmacologic concentrations of ascorbate and redox-active quinones. Ascorbate-driven quinone redox cycling leads to ROS formation and provokes an oxidative stress that preferentially kills cancer cells and spares healthy tissues. Cancer cell death occurs through necrosis and the underlying mechanism implies an energetic impairment (ATP depletion) that is likely due to glycolysis inhibition. Additional mechanisms that participate to cell death include calcium equilibrium impairment and oxidative cleavage of protein chaperone Hsp90. Given the low systemic toxicity of ascorbate and the impairment of crucial survival pathways when associated with redox-active quinones, these combinations could represent an original approach that could be combined to standard cancer therapy.
Regiochemical control in the amination reaction of phenanthridine-7,10-quinones
(PERGAMON-ELSEVIER SCIENCE LTD, 2009) Valderrama, Jaime A.; Andrea Ibacache, J.
The reaction of substituted phenanthridine-7,10-quinones with amines to construct novel aminophenanthridinequinone derivatives as antitumor agents is described. The regiochemistry of the amination reaction is discussed in terms of inductive and steric effects of remote substituents to the quinone ring, which Control the direction of the conjugate addition of the amines across the quinone double bond. Evidences on the significant in vitro antitumor activities of some of the obtained aminoquinones, are reported. (C) 2009 Elsevier Ltd. All rights Reserved.
Studies on quinones. Part 42: Synthesis of furylquinone and hydroquinones with antiproliferative activity against human tumor cell lines
(PERGAMON-ELSEVIER SCIENCE LTD, 2008) Benites, Julio; Valderrama, Jaime A.; Rivera, Felipe; Rojo, Leonel; Campos, Nair; Pedro, Madalena; Jose Nascimento, Maria Saeo
The preparation of furyl-1,4-quinone and hydroquinones by reaction of 2-furaldehyde N,N-dimethylhydrazone with benzo- and naphthoquinones is reported. Access to furylnaphthoquinones from unactivated quinones requires acid-induced conditions, however oxidative coupling reactions of activated quinones proceed under neutral conditions. The in vitro cytotoxic activity of the prepared compounds against a panel of three human cancer cell lines has been studied. Most of the furyl-1,4-quinones exhibited good antiproliferative activity (GI(50) = 6.5-33.5 mu m) against the MCF-7, NCI-H460, and SF-268 (CNS cancer) cell lines chosen for testing. (C) 2007 Elsevier Ltd. All rights reserved.
Studies on quinones. Part 43: Synthesis and cytotoxic evaluation of polyoxyethylene-containing 1,4-naphthoquinones
(PERGAMON-ELSEVIER SCIENCE LTD, 2008) Valderrama, Jaime A.; Leiva, Hilda; Rodriguez, Jaime A.; Theoduloz, Cristina; Schmeda Hirshmann, Guillermo
A series of naphthoquinones 2,3-disubstituted with chlorine and oxyethylene groups have been prepared from 2,3-dichloro- and 2,3-dimethoxy-1,4-naphthoquinone. The members of these series were tested on normal human. broblasts and on a panel of four human cancer cell lines. Antitumor activities, which were in the range of IC50 1.3-89.5 mu M, discussed in terms of LUMO energy, lipophilicity and size of the polyoxyethylene moiety. (C) 2008 Elsevier Ltd. All rights reserved.
Studies on quinones. Part 44: Novel angucyclinone N-heterocyclic analogues endowed with antitumoral activity
(PERGAMON-ELSEVIER SCIENCE LTD, 2008) Valderrama, Jaime A.; Colonelli, Pamela; Vasquez, David; Florencia Gonzalez, M.; Rodriguez, Jaime A.; Theoduloz, Cristina
In the search for new potentially anticancer drugs, series of angucyclinone aza-analogues containing pyridine and pyridopyridazine rings have been designed and synthesized by a highly efficient sequence involving a one-pot step for the synthesis of tricyclic quinone intermediate and highly regiocontrolled cycloaddition reactions with polarized 1,3-dienes. The new N-heterocyclic angular quinones were evaluated in vitro on normal human. broblasts and on a panel of four distinct human cancer cell lines. All tested compounds showed high to moderate antitumor activity. Among the compounds, those with one and two pyridine moieties fused to the quinone system have shown the best effect. Structure-activity relationships established the main structural requirement for the activity of the new potential anticancer drugs. (C) 2008 Elsevier Ltd. All rights reserved.
Studies on quinones. Part 46. Synthesis and in vitro antitumor evaluation of aminopyrimidoisoquinolinequinones
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2010) Vasquez, David; Rodriguez, Jaime A.; Theoduloz, Cristina; Calderon, Pedro Buc; Valderrama, Jaime A.
In the search of structure-activity relationship studies and to explore the antitumor effect associated with the pyrimidoisoquinolinequinone scaffold, several diversily substituted 8-aminopyrimido[4,5-c] isoquinolinequinones were regioselectively synthesized. Variation in the structure of the nitrogen substituent bonded to the 8-position of the pyrimidoisoquinolinequinone system led to a set of alkylamino-, phenylamino- and alkyphenylamino derivatives. The cytotoxic activity of the aminoquinone derivatives was evaluated in vitro using the MTT colorimetric method against one normal cell line (MRCS lung fibroblasts) and four human cancer cell lines (AGS human gastric adenocarcinoma; SK-MES-1 human lung cancer cells, and J82 human bladder carcinoma; HL-60 human leukemia) in 72-h drug exposure assays. Among the series, five compounds exhibited interesting antitumor activity against AGS human gastric adenocarcinoma and human lung cancer cells. The SAR studies revealed that both the nature of the nitrogen substituent into the quinone ring and the methyl group at the 6-position play key roles in the antitumor activity. (C) 2010 Elsevier Masson SAS. All rights reserved.
Studies on quinones. Part 47. Synthesis of novel phenylaminophenanthridinequinones as potential antitumor agents
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2011) Valderrama, Jaime A.; Ibacache, Andrea; Rodriguez, Jaime A.; Theoduloz, Cristina; Benites, Julio
In our search for potential anticancer agents, a series of 8- and 9-phenylamino-3,4-tetrahydro-phenanthridine-1,7,10(2H)-triones with substituent variations at 6-, 8- and 9-positions were prepared using a highly efficient sequence involving: a) solar photoacylation reactions of benzoquinone with arylaldehydes, b) one-pot procedure for the synthesis of 3,4-dihydrophenanthridine-1,7,10(2H)-trione intermediates from acylhydroquinones and c) highly regiocontrolled acid-induced amination reaction of phenanthridinequinones with phenylamines. The members of this series were in vitro evaluated using the KIT colorimetric method against one normal cell line and three human cancer cell lines. The SAR analysis indicates that the location of nitrogen substituents on the quinone nucleus, the presence of methyl, phenyl, furyl and thienyl groups at the 6-position and the aromatization of the angular cyclo-aliphatic ring of the phenylamino-3,4-tetrahydrophenanthridine-1,7,10(2H)-trione pharmacophore play key roles in the antitumor activity. (C) 2011 Elsevier Masson SAS. All rights reserved.
Synthesis and Antitumor Evaluation of 6-Aryl-substituted benzo[j]phenanthridine- and Benzo[g]pyrimido[4,5-c]isoquinolinequinones
(MDPI, 2012) Iribarra, Jennyfer; Vasquez, David; Theoduloz, Cristina; Benites, Julio; Rios, David; Valderrama, Jaime A.
A variety of novel 6-arylsubstituted benzo[j]phenanthridine-and benzo[g]pyrimido[4,5-c]isoquinolinequinones were synthesized from 1,4-naphthoquinone, aryl-aldehydes and enaminones via a two-step synthetic approach. The cytotoxic activity of the aminoquinone derivatives was evaluated in vitro against one normal cell line (MRC-5 lung fibroblasts) and three human cancer cell lines (AGS human gastric adenocarcinoma; SK-MES-1 human lung cancer cells, and J82 human bladder carcinoma) in 72-h drug exposure assays using the MTT colorimetric method. Structure-activity relationships within the series of angular quinones reveal that the insertion of pyrrol-2-yl and furan-2-yl groups at the 6-position is more significant for the increase of the potency and selectivity index of the pharmacophores.
Synthesis and antitumor evaluation of 8-phenylaminopyrimido[4,5-c]isoquinolinequinones
(PERGAMON-ELSEVIER SCIENCE LTD, 2009) Vasquez, David; Rodriguez, Jaime A.; Theoduloz, Cristina; Verrax, Julien; Calderon, Pedro Buc; Valderrama, Jaime A.
A series of 8-phenylaminopyrimido[4,5-c]isoquinoline-7,10-quinone derivatives were prepared by regioselective amination reaction of pyrimido[4,5-c] isoquinoline-7,10-quinones with arylamines in the presence of a Lewis acid catalyst. Preliminary evaluation of the members of the series against cancer cell lines and assays of activation of their cytotoxic activity on K562 cells with ascorbic acid are reported. (C) 2009 Elsevier Ltd. All rights reserved.
Synthesis and Antitumor Evaluation of Thiophene Analogs of Kigelinone
(BENTHAM SCIENCE PUBL LTD, 2009) Valderrama, Jaime A.; Espinoza, Omar; Rodriguez, Jaime; Theoduloz, Cristina
The synthesis of kigelinone thiophene analogs and related naphtho[2,3-b] thiophene-4,9-quinones from 2-substituted 4,7-dimethoxybenzo[b]thiophenes via an oxidative deprotection, Diels-Alder, and oxidative aromatization reaction sequence is reported. The 2-substituted naphtho[2,3-b] thiophene-4,9-quinones display significant antitumor activity in the range IC50 1.1-47 mu M on a panel of four distinct human cancer cell lines.
The solar-chemical photo-Friedel-Crafts heteroacylation of 1,4-quinones
(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Benites, Julio; Rios, David; Diaz, Pilar; Valderrama, Jaime A.
Photochemical reactions between 1,4-benzo- and 1,4-naphthoquinone and several heteroaromatic carbaldehydes were investigated under solar irradiation conditions. These reactions gave the corresponding heteroacylated hydroquinones in the range 71%-92% yield. (C) 2010 Elsevier Ltd. All rights reserved.

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