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Mar. Drugs 2013, 11(1), 165-183; doi:10.3390/md11010165

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

1
Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
2
Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
3
Beauty Care Products Division, Nagase & Co., Ltd., Kobe 651-2241, Japan
*
Author to whom correspondence should be addressed.
Received: 12 November 2012 / Revised: 11 December 2012 / Accepted: 4 January 2013 / Published: 18 January 2013
(This article belongs to the Special Issue Marine Algae)
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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. View Full-Text
Keywords: phlorotannins; Ecklonia kurome; structural determination; NMR; radical scavenging activity phlorotannins; Ecklonia kurome; structural determination; NMR; radical scavenging activity
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Yotsu-Yamashita, M.; Kondo, S.; Segawa, S.; Lin, Y.-C.; Toyohara, H.; Ito, H.; Konoki, K.; Cho, Y.; Uchida, T. Isolation and Structural Determination of Two Novel Phlorotannins from the Brown Alga Ecklonia kurome Okamura, and Their Radical Scavenging Activities. Mar. Drugs 2013, 11, 165-183.

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