Evaluation of antioxidant properties of a new compound, pyrogallol-phloroglucinol-6,6'-bieckol isolated from brown algae, Ecklonia cava

Abstract

In this study, antioxidant and free radical scavenging activities of the natural antioxidative compound, pyrogallol-phloroglucinol-6,6'-bieckol (PPB) isolated from brown algae, Ecklonia cava was assessed in vitro by measuring the radical scavenging activities (DPPH, alkyl, hydroxyl, and superoxide) using electron spin resonance (ESR) spectrometry, intracellular reactive oxygen species (ROS) scavenging activity, and DNA damage assay. According to the results of these experiments, the scavenging activity PPB against difference radicals was in the following order: DPPH, alkyl, hydroxyl, and superoxide radicals (IC(50); 0.90, 2.54, 62.93 and 109.05 µM). The antioxidant activities of PPB were higher than that of the commercial antioxidant, ascorbic acid. Furthermore, PPB effectively inhibited DNA damage induced by H(2)O(2). These results suggest that the natural antioxidative compound, PPB, can be used by the natural food industry.

Keywords: Ecklonia cava; antioxidant; brown algae; pyrogallol-phloroglucinol-6,6'-bieckol.

Fig. 1

Schematic of the isolation and purification of the active compound from Ecklonia cava

Fig. 2

MS spectroscopic and chemical structure of the active compound isolated from E. cava. The spectra were generated in negative ionization mode (A). Chemical structure and HMBC correlation of the active compound isolated from E. cava (B).

Fig. 3

Free radical scavenging activities of PPB measured using an ESR spectrometer. (A) DPPH radical; (B) Alkyl radical; (C) Hydroxyl radical; (D) Superoxide radical. Experiments were conducted in triplicate and the data were expressed as the means ± SE. Values with different alphabets are significantly different at P < 0.05 as analyzed by Duncan's multiple range test (DMRT).

Fig. 4

The cytotoxic effect of the PPB isolated from E. cava at different concentrations. The viability of Vero cells was determined using the MTT assay. Experiments were conducted in triplicate and the data are expressed as the means ± SE. Values with different alphabets are significantly different at P < 0.05 as analyzed by Duncan's multiple range test (DMRT).

Fig. 5

Effect of the PPB on scavenging intracellular reactive oxygen species. The intracellular reactive oxygen species generated were detected via the DCFH-DA method. Experiments were conducted in triplicate and the data were expressed as the means ± SE. Values with different alphabets are significantly different at P < 0.05 as analyzed by Duncan's multiple range test (DMRT).

Fig. 6

Protective effect of different concentrations of the PPB on H₂O₂-induced DNA damage using the comet assay. Photomicrographs of DNA damage and migration observed under PPB. (A) Control; (B) 100 µM H₂O₂; (C) 25 µg/mL of PPB + 100 µM H₂O₂; (D) 50 µg/mL of PPB + 100 %M H₂O₂. The cells damaged by H₂O₂-treatment were assessed via the comet assay. Experiments were conducted in triplicate and the data were expressed as the means ± SE. Values with different alphabets are significantly different at P < 0.05 as analyzed by Duncan's multiple range test (DMRT).