Inhibitory phlorotannins from the edible brown alga Ecklonia stolonifera on total reactive oxygen species (ROS) generation

Reactive oxygen species (ROS) play an important role in the pathogenesis of many human degenerative diseases such as cancer, aging, arteriosclerosis, and rheumatism. Much attention has been focused on the development of safe and effective antioxidants. To discover sources of antioxidative activity in marine algae, extracts from 17 kinds of seaweed were screened for their inhibitory effect on total ROS generation in kidney homogenate using 2′,7′- dichlorofluorescein diacetate (DCFH-DA). ROS inhibition was seen in three species: Ulva pertusa, Symphyocladia latiuscula, and Ecklonia stolonifera. At a final concentration of 25 μg/mL, U. pertusa inhibited 85.65±20.28% of total ROS generation, S. latiscula caused 50.63±0.09% inhibitory, and the Ecklonia species was 44.30±7.33% inhibition. E. stolonifera OKAMURA (Laminariaceae), which belongs to the brown algae, has been further investigated because it is commonly used as a foodstuff in Korea. Five compounds, phloroglucinol (1), eckstolonol (2), eckol (3), phlorofucofuroeckol A (4), and dieckol (5), isolated from the ethyl acetate soluble fraction of the methanolic extract of E. stolonifera inhibited total ROS generation.