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. 2023 Jul 7;28(13):5265.
doi: 10.3390/molecules28135265.

Characterization of the Synergistic Antioxidant Activity of Epigallocatechin Gallate (EGCG) and Kaempferol

Qiang Zhang  1 , Junkun Pan  1 , Hui Liu  1 , Zhonggao Jiao  1
Affiliations

Characterization of the Synergistic Antioxidant Activity of Epigallocatechin Gallate (EGCG) and Kaempferol

Qiang Zhang et al. Molecules. .

Abstract

Epigallocatechin gallate (EGCG) and kaempferol exhibit cellular antioxidant activity; however, their interactive effects in terms of antioxidant actions and underlying mechanisms remain unclear. In this study, their cytoprotective effects were examined against 2,2-azobis (2-amidinopropane) dihydrochloride solution (ABAP)-induced oxidative stress in HepG2 cells. The results showed that the median effective dose (EC50) of the EGCG and kaempferol (6:1.5, c/c) combination was 3.4 ± 0.1 μg/mL, with a combination index (CIavg) value of 0.54, which represented a significant synergistic effect. Further experiments proved that the combined pretreatment with EGCG and kaempferol exerted protective effects by suppressing reactive oxygen species (ROS) generation, upregulating cellular antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px)) in a dose-dependent manner. The mechanism of synergistic antioxidant effects of EGCG combined with kaempferol may be due to the up-regulation of higher antioxidant enzyme activities that improve the antioxidant capacities and balance the cell oxidative stress. The synergistic antioxidant effect of EGCG and kaempferol can provide a theoretical basis for the development of formulas of functional food ingredients.

Keywords: EGCG; antioxidant enzymes; cellular antioxidant activity; kaempferol; synergistic effect.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structure of EGCG (A) and kaempferol (B).
Figure 2
Figure 2
Cell viabilities of HepG2 cells treated with various concentrations of EGCG (A), kaempferol (B), and EGCG + kaempferol combination (C). Data are shown as the mean ± SD from four independent experiments. Different letters represent significant differences at p < 0.05.
Figure 3
Figure 3
Kinetic curves of ABAP-induced DCF fluorescence and the inhibition of oxidation by the EGCG and kaempferol (6:1.5) combination (A) on the fluorescence in HepG2 cells with PBS wash. The EC50 of EGCG, kaempferol, and EGCG + kaempferol combinations (B). Different letters represent significant differences at p < 0.05.
Figure 4
Figure 4
The CAA values of EGCG, kaempferol, and EGCG + kaempferol combinations at different proportions (A–C); (D) the Fa–CI plot of EGCG + kaempferol (6:1.5). * p < 0.05.
Figure 5
Figure 5
The possible mechanisms of EGCG and kaempferol combination antioxidant activities in HepG2 cells. The red arrow represent the activities of SOD, CAT, AND GSH-Px increase.
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