Browsing by Author "Taper, Henryk"

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    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.
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    Part 2: Influence of 2-Euryfuryl-1,4-naphthoquinone and Its peri-Hydroxy Derivatives on Both Cell Death and Metabolism of TLT Cells, a Murine Hepatoma Cell Line. Modulation of Cytotoxicity by Vitamin C
    (PHARMACEUTICAL SOC JAPAN, 2009) Benites, Julio; Adolfo Valderrama, Jaime; Taper, Henryk; Calderon, Pedro Buc
    2-Euryfuryl-1,4-naphthoquinone C-1 and its 5- and 5,8-hydroxy derivatives C-2 and C-3, were tested for their cytotoxicity towards transplantable liver tumor (TLT) cells (a murine hepatoma cell line) in the absence and in the presence of vitamin C. Cell death, caspase-3 activity and two metabolic end-points, namely the intracellular content of ATP and glutathione (GSH), were employed to evaluate their cytotoxicity. In a range of concentration from 0 to 10 mu g/ml C-1 and C-3 were non toxic against TLT cells, while compound C-2 killed about 50% of cells by necrosis. Interestingly, the presence of vitamin C did not enhance the cytolysis of C-2, but its addition exacerbated the effects of the three compounds on both ATP and GSH contents, the two metabolic end points selected in our study. Our assumption is that the electron donor effect of the peri-hydroxyl substituents on euryfurylnaphthoquinones and the hydrogen bond between the peri-hydroxy and quinone carbonyl groups influence the electron-acceptor capability of the quinone nucleus and thus modifies the electron transfer from ascorbate to the electroactive quinone nucleus. The combination of euryfurylnaphthoquinones with vitamin C may he of potential clinical interest, because cancer cells accumulate vitamin C, they are sensitive to an oxidant insult and they depend on glycolysis (ATP formation) for their survival.