Phlorotannins of the edible brown seaweed Ecklonia cava Kjellman induce sleep via positive allosteric modulation of gamma-aminobutyric acid type A-benzodiazepine receptor: A novel neurological activity of seaweed polyphenols

Suengmok Cho, Hyejin Yang, You Jin Jeon, C. Justin Lee, Young Ho Jin, Nam In Baek, Dongsoo Kim, Sung Myung Kang, Minseok Yoon, Heim Yong, Makoto Shimizu, Daeseok Han

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

The primary objective was to investigate whether seaweeds have hypnotic activity. Methanol extracts of 30 seaweeds were screened for their binding activity at the GABA type A-benzodiazepine (GABA A-BZD) receptor, a well-characterised molecular target for sedative-hypnotics. The most active seaweed was Ecklonia cava Kjellman (ECK). An ethanol extract of ECK (ECK-E) significantly potentiated pentobarbital-induced sleep in mice. In four solvent fractions separated from ECK-E, hypnotic activity was proportional to contents of total phenols and total phlorotannins, known as seaweed polyphenols. Major phlorotannins of the ethyl acetate (EtOAc) fraction with the highest activity were eckol, eckstolonol, dieckol, and triphlorethol-A, and their K i (binding affinity, μM) values for [ 3H]-flumazenil binding were 1.070, 1.491, 3.072, and 4.419, respectively. Hypnotic effects of ECK-E and the EtOAc fraction were fully inhibited by flumazenil, a specific GABA A-BZD receptor antagonist. These results imply that phlorotannins of ECK induce sleep by positive allosteric modulation of the GABA A-BZD receptor.

Original languageEnglish
Pages (from-to)1133-1142
Number of pages10
JournalFood Chemistry
Volume132
Issue number3
DOIs
Publication statusPublished - 2012 Jun 1

Keywords

  • Ecklonia cava Kjellman
  • Edible seaweeds
  • GABA type A-benzodiazepine receptor
  • Hypnotic activity
  • Phlorotannin

ASJC Scopus subject areas

  • Analytical Chemistry
  • Food Science

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