Simultaneous detection of pro- and antioxidative effects in the variants of the deoxyribose degradation assay

Abstract

Interest in the redox properties of natural products has led to the development of various assays for the detection of antioxidant activities and ROS-scavenging properties. Here, additional modifications of the 2-deoxy-d-ribose degradation assay are introduced that specifically allow the determination of interactions of the test compound with the autoxidation of ascorbic acid and the autoxidation of the test compound itself. To illustrate this, juglone and quercetin were used as examples. The modified assay systems provide insights into their specific antioxidative and pro-oxidative properties. In additional, an extensive characterization of the redox properties of their complex with iron is possible, if iron ions are added in the free form or complexed with EDTA. The juglone-iron complex proved to be pro-oxidative in a wider range of milieus than the quercetin-iron complex.

Figure 1

Chemical structures of juglone (1) and quercetin (2).

Figure 2

Chelates of juglone and quercetin with ions of transition metals.

Figure 3

Activities of juglone and quercetin in various systems of the deoxyribose degradation assay, quantified in % malonyldialdehyde, an oxidative decomposition product of 2-deoxy-d-ribose; bars are means; error bars, standard deviation; N = 3, letters indicate different levels of significance (95% probability, Duncan’s multiple range test).

Figure 4

Selected possible one electron and two electron redox reactions of phenolic and quinone groups of juglone. AA, ascorbic acid; DAA, dehydroascorbic acid.

Figure 5

Selected possible one electron redox reactions of quinone and semiquinone groups of juglone.

Figure 6

Reduction of the iron(III)−juglone complex by trihydroxynaphthalene or juglone.

Figure 7

Selected possible one electron redox reactions of quercetin.

Figure 8

Selected possible two electron redox reactions of quercetin.