Isolation and Structural Determination of Two Novel Phlorotannins from the Brown Alga Ecklonia kurome Okamura, and Their Radical Scavenging Activities

Abstract

Two novel phlorotannins with a molecular weight of 974, temporarily named 974-A and 974-B, were isolated from the polyphenol powder prepared from the edible marine brown alga Ecklonia kurome Okamura, and their chemical structures were determined by spectroscopic method. The isolated yield of the total of 974-A and 974-B was approximately 4% (w/w) from the polyphenol powder. In 974-A, the carbon at the C2′ position in the A ring of phlorofucofuroeckol-A forms a C–C bond with the carbon at the C2″ position of the C ring of triphloretol-B, while in 974-B, phlorofucofuroeckol-B and triphloretol-B form a C–C bond in the same manner as in 974-A. These structures were supported by high resolution-MS/MS data. To evaluate the antioxidant activities, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and intracellular radical scavenging assay, using 2′,7′-dichlorofluorescin diacetate (DCFH-DA), were performed for 974-A, 974-B, and four known phlorotannins. The results of the DPPH assay showed that the IC50 values of 974-A, 974-B, phlorofucofuroeckol-A, and dieckol were significantly smaller than those of phlorofucofuroeckol-B, phloroglucinol, α-tocopherol, and ascorbic acid. Furthermore, the DCFH-DA assay suggested that 974-A, 974-B, and dieckol reduce intracellular reactive oxygen species most strongly among the tested compounds.

Brown Algae <i>Himantothallus grandifolius</i> (Desmarestiales, Phaeophyceae) Suppresses Proliferation and Promotes Apoptosis-Mediated Cell Death in Tumor Cells

“…Phlorotannins purified from others brown algae such as Ecklonia sp. has shown cytocompatible effects to human fetal lung fibroblasts cell line (MRC-5) [28] and macrophage-like form cell (THP-1 cell) [15]. A recent report using dieckol, an isolated compound from Ecklonia stolonifera Okamura algae extracts, also presented more selective effects to Hek-293 compared to a tumor cell line Hep3B [29].…”

“…Cytotoxic studies using total extract obtained from a variety of algae have demonstrated that brown algae are a potential source of compounds presenting biological activities on tumor cells [15] 50 showed greater IC 50 (>1000 μg/mL) [25]. A study with red algae Gracilaria tenuistipitata C.F.…”

“…Marine algal polyphenol compounds, known as phlorotannins, are highly hydrophilic molecules found especially in brown algae [2] [17]. Several bioactivities have been reported for phlorotannins, such as antimicrobial, antiallergic, promoter of angiogenesis, tyrosinase inhibitory, anti-inflammatory, antioxidant and antitumor [15].…”

Laminaria japonica Aresch. and Ecklonia Kurome Okam. 昆布 (Kunbu, Kelp)

“…Recently, YotsuYamashita M and his partner isolated and determined two novel phlorotannins 974-A (9) and 974-B (10) from E. kurome with radical scavenging activities (shown in Fig. 86.3) [7].…”

Feeding the Abalone Haliotis discus hannai with the Seaweed Eisenia bicyclis Allows the Accumulation of Phlorotannins

“…Infra red (IR) spectra were measured on a Perkin-Elmer (Wellesley, MA) spectrophotometer. Each compound was identified by comparison with previously published spectral data Yotsu-Yamashita et al, 2013).…”