Antimicrobial effect of phlorotannins from marine brown algae
Antimicrobial effect of phlorotannins from marine brown algae
Sung-Hwan Eom , Young-Mog Kim Se-Kwon Kim
a Marine Bioprocess Research Center, Pukyong National University, Busan 608-737, Republic of Koreab Department of Food Science and Technology, Pukyong National University, Busan 608-737, Republic of Koreac Marine Biochemistry Laboratory, Department of Chemistry, Pukyong National University, Busan 608-737, Republic of Korea
Marine organisms exhibit a rich chemical content that possess unique structural features as compared to
terrestrial metabolites. Among marine resources, marine algae are a rich source of chemically diverse
compounds with the possibility of their potential use as a novel class of artificial food ingredients and
antimicrobial agents. The objective of this brief review is to identify new candidate drugs for antimicro-bial activity against food-borne pathogenic bacteria. Bioactive compounds derived from brown algae are
discussed, namely phlorotannins, that have anti-microbial effects and therefore may be useful to explore
as potential antimicrobial agents for the food and pharmaceutical industries.
Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3251
Phlorotannins from marine brown algae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3253
Antibacterial effect of phlorotannins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3253
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3254
Conflict of Interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3254Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3254References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3254
the marine biodiversity of the ocean can be expected to yieldnew therapeutic agents (
Since the 1970s, more than 21,855 structurally diverse, bioac-
Increasing resistance of clinically important bacteria to existing
tive natural products with an astounding array of biological activ-
antibiotics is a major problem throughout the world
ities have been discovered from marine microbes, algae and
). Over the past 20 years, investigators from virtually
invertebrates Even though, the ocean covers
every corner of the world have documented that increasing pro-
more than 70% of the earth’s surface, we only use less than 10%
portions of Staphylococcus aureus are resistant to penicillin and
of the total ocean area (In particular, many marine
other antibiotics. As a result, the majority of S. aureus are swamped
organisms live in complex habitats exposed to extreme conditions
with methicillin-resistant S. aureus (MRSA). In spite of the available
and in adapting to new environment surroundings, they produce a
effective treatments against serious infections due to MRSA, high
wide variety of secondary metabolites which cannot be found in
mortality rates are still a major concern. There are a few new
other organisms. Moreover, considering its great taxonomic diver-
agents in development that can be expected to benefit the situa-
sity, investigations related to the search for new bioactive com-
tion in the next decade ). Over the past 50 years,
pounds from the marine environment can be seen as an almost
S. aureus has become resistant to most antibiotics except vancomy-
unlimited field. In addition, since the biological productivity of ter-
cin and other glycopeptides. Recently, these antibiotics have been
restrial ecosystems has also perhaps reached what it can achieve;
the mainstay of treatment for the multi drug-resistant S. aureusand therefore the possibility that vancomycin resistance mighttransfer from vancomycin-resistant enterococci to multi drug-
⇑ Corresponding author. Tel.: +82 516297094; fax: +82 516297099.
resistant S. aureus has been extremely worrying
0278-6915/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
S.-H. Eom et al. / Food and Chemical Toxicology 50 (2012) 3251–3255
). Moreover, the emergence of several newly discovered MRSA
terrestrial metabolites (). In the marine environ-
showed antibiotic resistance to vancomycin and teicoplanin
ment, where all surfaces are constantly exposed to the threat of
(As an alternative to vancomycin for treatment of
surface colonisation, sessile organisms remain relatively free from
S. aureus infection, the new antimicrobial agents such as linezolid,
biofouling Furthermore, the chemical com-
quinupristin/dalfopristin, daptomycin, tigecycline, and fidaxomicin
pounds produced by marine organisms are less well known than
are being used for the most severe infections ).
those of their terrestrial counterparts. Among marine organisms,
One of the ways of preventing antibiotic resistance is by using
edible seaweeds have been identified as an under-exploited plant
new compounds which are not based on the existing synthetic
resource and a source of functional foods. It is believed that the
antimicrobial agents. Thus, the search for novel natural sources
physiological and genetic characteristics of seaweeds differ com-
from marine ecosystems could lead to the isolation of new antibi-
pared to those of terrestrial plants. They are extensively used in
otics ). Many organisms produce marine natural
food and medicine The ability of seaweeds to pro-
products that possess unique structural features as compared to
duce secondary metabolites of antimicrobial value, such as volatile
Fig. 1. Structures phlorotannins derived from marine algae [ phloroglucinol (1), eckol (2), fucofuroeckol-A (3), phlorofucofuroeckol-A (4), dioxinodehydroeckol (5), 8,80-bieckol(6), 7-phloroeckol (7), & dieckol (8)].
S.-H. Eom et al. / Food and Chemical Toxicology 50 (2012) 3251–3255
phlorotannin compounds such as eckol, phlorofucofuroeckol A
and dieckol, and 8,80-bieckol have been isolated from E. kurome
and E. bicyclis Phlorotannins in E. Arborea
possess a strong anti-allergic effect and their structures were elu-
cidated as eckol, 6,60-bieckol, 6,80-bieckol, 8,80-bieckol, phlorofu-
phlorotannins as polyphenolic secondary metabolites are found
cofuroeckol-A, and phlorofucofuroeckol-B ().
Moreover, 6,60-Bieckol diphlorethohydroxycarmalol, and phloro-
Thus, the screen for antimicrobial agents as safe alternatives
glucinol have been isolated from brown algae I. okamurae (
and secondary metabolites from marine algae is attracting atten-
Collectively, phlorotannins can be used functional
tion in the food industry. This review focuses on phlorotannins de-
ingredients in the food and pharmaceutical industries.
rived from marine algae and presents their potential application asantimicrobial agents.
Some synthetic preservatives and additives used in the food
industry have been evaluated as toxic to various cells and organs,
Marine algae have become an important source of pharmaco-
mutagens and tumor promoters over long-term use (
logically active metabolites. Also, they are widely distributed and
Therefore, recently there has been a great
abundant throughout the coastal areas of many countries. In addi-
deal of interest in searching for novel natural antibiotics and these
tion, they are a source of useful secondary metabolites such as
studies have shown that phlorotannins in brown algae can act as
agar, carragenean and alginate with interesting pharmaceutical
potential antimicrobial agents that may be useful in the food
properties Among marine algae, brown algae
have been reported to contain higher phlorotannin contents as
marine phenolic compounds (). Phlorotannins
The isolated and characterized phlorotannins (1–8) from brown
consist of polymers of phloroglucinol (1,3,5-tryhydroxybenzene)
algae with antimicrobial activity are presented in such as
units and are formed in the acetate–malonate pathway in marine
phloroglucinol (1), eckol (2), fucofuroeckol-A (3), phlorofucofuroec-
algae. Furthermore these phlorotannins are highly hydrophilic
kol-A (4), dioxinodehydroeckol (5), 8,80-bieckol (6), 7-phloroeckol
components with a wide range of molecular sizes (126–650 kDa)
(7), and dieckol (8). In addition, triphloroethol A, 6,60-bieckol and
8,4000-dieckol have been reported. These isolated phlorotannins have
Several phlorotannins purified from brown seaweeds such as
been shown to have antimicrobial effect against food-borne
Ecklonia cava, E. kurome, E. stolonifera, Eisenia aborea, Eisenia
pathogenic bacteria, antibiotic resistance bacteria, and human tinea
bicyclis, Ishige okamurae, Pelvetia siliquosa have medicinal and phar-
maceutical benefits and have shown strong anti-oxidant, anti-
Dieckol purified from E. cava has fungicidal activity (
inflammatory, anti-viral, anti-tumor, anti-diabetes and anti-cancer
It has shown a potent antifungal activity against Trichophy-
ton rubrum associated with dermatophytic nail infections in hu-
mans. In addition, it has shown a potent inhibition of cell
Eckol, dieckol, and phloroglucinol from E. cava have shown po-
membrane integrity as well as cell metabolism against T. rubrum.
tential for skin whitening effect () and anti-hyper-
The MIC (minimum inhibitory concentration) values for eckol from
tensive effect E. cava also contains other
E. cava indicates potent antimicrobial activity against methicillin-
phlorotannins including 6,60-bieckol, 8,80-bieckol, 8,4000-dieckol,
resistant S. aureus (MRSA) in the range of 125–250 lg/mL
dioxinodehydroeckol, fucodiphlorethol G, phlorofucofuroeckol-A,
Dieckol isolated from E. stolonifera may possess stron-
ger anti-MRSA activity than eckol and the MICs of dieckol were in
Table 1Phlorotannin compounds with antibacterial effect.
Inhibition of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA)
dieckol (8)dioxinodehydroeckol(5)fucofuroeckol-A (3)7-phloroeckol (7)Phlorofucofuroeckol-A (4)
Inhibition of S. aureus, MRSA, Salmonella sp.
. Inhibition of Campylobacter jejuni, Escherichia coli, Salmonella enteritidis, Salmonella
Inhibition of S. aureus and MRSA, bacillus subtilis.
Inhibition of Acinetobacter sp. Klebsiella pneumonia,
Legionella birminghamensis, Salmonella typhimurium, Shigella flexneri
a IC50: concentration of a compound required for 50% inhibition in vitro.
MIC: minimum inhibitory concentration. à MBC: minimum bactericidal concentration.
S.-H. Eom et al. / Food and Chemical Toxicology 50 (2012) 3251–3255
the ranges of 32–64 lg/mL ). Although the current
methicillin-resistant Staphylococcus aureus and Salmonella spp. Food borne
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