Abstract
The composition and antioxidative properties of crude phlorotannins isolated from Japanese Eisenia and Ecklonia species including cultured E. kurome were analyzed. As a result of liquid chromatography mass spectrometry analysis, it was suggested that the phlorotannins were composed of compounds containing 3 - 7 phloroglucinol units for Eisenia species and 3 - 8 phloroglucinol units for Ecklonia species. The antioxidant properties of phlorotannins were evaluated using the hydrophilic oxygen radical absorbance capacity (H-ORAC) assay, the measurements of superoxide anion radical scavenging activity (SOSA) with electron spin resonance method, and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and reducing power assay. It was clarified that the phlorotannins contained H-ORAC values of 8.9 × 103 - 1.0 × 104 μmol-Trolox equivalents (TE)/g, SOSA of 1.5 × 104 - 2.9 × 104 superoxide dismutase units/g, DPPH radical scavenging activity of 4.7 × 103 - 5.5 × 103 μmol-TE/g, and reducing power of 6.5 × 102 - 7.0 × 102 mg-ascorbic acid equivalents/g, and had excellent antioxidative properties.
Highlights
Many researchers are paying attention to the physiology of non-nutritive compounds included in botanical materials, especially the antioxidative properties and therapeutic effects of polyphenols
Ahn et al [9] showed that phloroglucinol, eckol, and dieckol isolated from the brown alga Ecklonia cava had scavenging effects against alkyl and hydroxyl radicals
The main objective of this study is to evaluate the antioxidative properties of crude phlorotannins prepared from Japanese Eisenia species (Eisenia bicyclis and Eisenia arborea) and Ecklonia species (Ecklonia cava and Ecklonia kurome)
Summary
Many researchers are paying attention to the physiology of non-nutritive compounds included in botanical materials, especially the antioxidative properties and therapeutic effects of polyphenols. We isolate phloroglucinol and eckols: eckol (phloroglucinol trimer), phlorofucofuroeckol A (a pentamer), dieckol and 8,8’-bieckol (hexamers) from the Eisenia and Ecklonia species, and report their inhibition of phospholipid peroxidation in the liposome system and scavenging activities of these phlorotannins against the superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals [8]. From the comparison of the 50% effective concentration value of tested samples, the scavenging activities of the eckols, including phlorofucofuroeckol A, dieckol and 8,8’-bieckol on DPPH and superoxide anion radicals are found to be around 2 - 10 times higher than those of catechin, ascorbic acid, and α-tocopherol [8]. Ahn et al [9] showed that phloroglucinol, eckol, and dieckol isolated from the brown alga Ecklonia cava had scavenging effects against alkyl and hydroxyl radicals. It can be concluded that the individual phlorotannin compounds from the Eisenia and Ecklonia species have prominent antioxidant properties as antioxidant polyphenols, as with the polyphenols of terrestrial plants
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