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BY-NC-ND 3.0 license Open Access Published by De Gruyter June 2, 2014

Redox Properties of Novel Antioxidant 5,8-Dihydroxycoumarin: Implications for its Prooxidant Cytotoxicity

Aušra Nemeikaitė-Čėnienė, Audronė Marozienė, Audrius Pukalskas, Petras Rimantas Venskutonis and Narimantas Čėnasb

The aim of this work was to characterize the redox properties of the new antioxidant 5,8- dihydroxycoumarin (5,8-DHC), isolated from sweet grass (Hierochloë odorata L.), and to determine its impact on its cytotoxic action. Reversible electrochemical oxidation of 5,8- DHC at pH 7.0 was characterized by the midpoint potential (Ep/2) of 0.23 V vs. the normal hydrogen electrode. 5,8-DHC was slowly autoxidized at pH 7.0, and it was active as a substrate for peroxidase (POD, EC 1.11.1.7) and tyrosinase (TYR, EC 1.14.18.1). Oxidation of 5,8-DHC by POD/H2O2 yielded the product(s) which reacted with reduced glutathione and supported the oxidation of NADPH by ferredoxin:NADP+ reductase (FNR, EC 1.18.1.2) and NAD(P)H:quinone oxidoreductase (NQO1, DT-diaphorase, EC 1.6.99.2). The concentration of 5,8-DHC for 50% survival of bovine leukemia virus-transformed lamb kidney fibroblasts (line FLK) during a 24-h incubation was (60 ± 5.5) μm. Cytotoxicity of 5,8-DHC was decreased by desferrioxamine, catalase, the antioxidant N,N’-diphenyl-p-phenylene diamine, and potentiated by 1,3-bis-(2-chloroethyl)-1-nitrosourea and dicumarol, an inhibitor of NQO1. This shows that 5,8-DHC possesses the oxidative stress-type cytotoxicity, evidently due to the action of quinodal oxidation product(s). The protective effect of isoniazide, an inhibitor of cytochrome P-450 2E1, points to hydroxylation of 5,8-DHC as additional toxification route, whereas the potentiating effect of 3,5-dinitrocatechol, an inhibitor of catechol-omethyltransferase (COMT, EC 2.1.1.6), points to the o-methylation of hydroxylation products as the detoxification route.

Published Online: 2014-6-2
Published in Print: 2005-12-1

© 1946 – 2014: Verlag der Zeitschrift für Naturforschung

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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