Characterizing Eckol as a Therapeutic Aid: A Systematic Review

Manandhar, Bandana; Paudel, Pradeep; Seong, Su Hui; Jung, Hyun Ah; Choi, Jae Sue

The desirability of developing effective chemo-preventive agents against UVB-induced skin cancer in humans has led to an assessment of the chemo-preventive efficacy of brown algae polyphenols (2-O-(2,4,6-trihydroxyphenyl)-6,6´-bieckol, 6,6´-bieckol, 8,8´-bieckol, 7-phloroeckol, 2-phloroeckol, eckol, dieckol, phlorofucofuroeckol, phlorotannin A, fucofuroeckol A, and various minor homologues) against photo carcinogenesis in the SKH-1 hairless mouse skin model. A decrease in tumor incidence was seen when brown algal polyphenols were administered through diet (79%) and skin (94%) with moderate protection against skin carcinogenesis induced by UV-B radiation in mice. The propagation of tumor decreased from 8.54 ± 0.75 to 4.73 ± 0.74 (p < 0.005) and 3.75 ± 0.54 (p < 0.001) when treated with 0.1% and 0.5% brown polyphenols through diet, in tumors/tumor-bearing mice, exhibiting a 45% and 56% inhibition. On the other hand, topical administration of 3 and 6 mg of these compounds reduced tumor multiplicity from 8.45 ± 1.23 to 3.42 ± 0.56 (p < 0.001) and 4.56 ± 0.56 (p < 0.005), respectively, in tumors/tumor-bearing mice. They also suppressed the gene expression of cyclooxygenase (COX)-2, decreased PGE 2 levels in the skin, inhibited the amount of COX-2 protein, and reduced the rate of proliferating cells in the epidermis. In summary, eckol exerts protective effects against skin carcinogenesis induced by UVB radiation [59] . Also in another study, the photo-protective effects of phlorotannins on the cell damage caused by UVB radiation was demonstrated. The E. cava-isolated phlorotannins (phloroglucinol, eckol, and dieckol) and polyphenol were examined for their protective effect against UVB-induced photo-oxidative stress in human fibroblast cells. Eckol exhibited slightly low activity against UVB radiation-mediated ROS (174.4% ROS at 250 µM) as compared to dieckol (100.7% ROS at 250 µM) when the level of ROS was recorded as 234.1% in UVB-irradiated cells (positive control). Eckol showed cell survival rates of 45%, 50%, and 56% at concentrations of 5, 50, and 100 µM, respectively. The comet assay was performed to evaluate whether phlorotannins protected against DNA damage and revealed that eckol had about 21%, 43%, and 53% inhibitory activity at concentrations of 0.5, 5, and 50 µM, respectively [60].