Exploiting biological activities of brown seaweed Ecklonia cava for potential industrial applications: a review

Seaweeds are rich in vitamins, minerals, dietary fibres, proteins, polysaccharides and various functional polyphenols. Many researchers have focused on brown algae as a potential source of bioactive materials in the past few decades. Ecklonia cava is a brown seaweed that is abundant in the subtidal regions of Jeju Island in the Republic of Korea. This seaweed attracted extensive interest due to its multiple biological activities. E. cava has been identified as a potential producer of wide spectrum of natural substances such as carotenoids, fucoidans and phlorotannins showing different biological activities in vital industrial applications including pharmaceutical, nutraceutical, cosmeceutical and functional food. This review focuses on biological activities of the brown seaweed E. cava based on latest research results, including antioxidant, anticoagulative, antimicrobial, antihuman immunodeficiency virus, anti-inflammatory, immunomodulatory, antimutagenic, antitumour and anticancer effects. The facts summarized here may provide novel insights into the functions of E. cava and its derivatives and potentially enable their use as functional ingredients in potential industrial applications.     

鼠尾藻多酚及其各组分的抗凝血活性筛选

目的筛选鼠尾藻多酚及其各组分的抗凝血活性。方法采用膜分离方法对鼠尾藻多酚进行分级;采用毛细管法测定小鼠凝血时间;采用剪尾法测定小鼠出血时间;采用试管法测定新西兰兔激活部分凝血活酶时间、血浆凝血酶原时间和血浆凝血酶时间。结果高相对分子质量(Mr)鼠尾藻多酚分级级分极显著地延长小鼠凝血时间、出血时间、新西兰兔激活部分凝血活酶时间,且其延长程度与多酚Mr成正相关关系,Mr大于1.0×105的组分体内体外抗凝血活性与阿司匹林相近。结论高Mr鼠尾藻多酚具有极显著的体内、体外抗凝血活性。     

Effect of phlorotannins isolated from Ecklonia cava on angiotensin I-converting enzyme (ACE) inhibitory activity

Inhibition of angiotensin I-converting enzyme (ACE) activity is the most common mechanism underlying the lowering of blood pressure. In the present study, five organic extracts of a marine brown seaweed Ecklonia cava were prepared by using ethanol, ethyl acetate, chloroform, hexane, and diethyl ether as solvents, which were then tested for their potential ACE inhibitory activities. Ethanol extract showed the strongest ACE inhibitory activity with an IC₅₀ value of 0.96 mg/ml. Five kinds of phlorotannins, phloroglucinol, triphlorethol-A, eckol, dieckol, and eckstolonol, were isolated from ethanol extract of E. cava, which exhibited potential ACE inhibition. Dieckol was the most potent ACE inhibitor and was found to be a non-competitive inhibitor against ACE according to Lineweaver-Burk plots. Dieckol had an inducible effect on the production of NO in EAhy926 cells without having cytotoxic effect. The results of this study indicate that E. cava could be a potential source of phlorotannins with ACE inhibitory activity for utilization in production of functional foods.     

Pancreatic Lipase Inhibitory Activity of Phlorotannins Isolated from Eisenia bicyclis

Pancreatic lipase is a potential therapeutic target for the treatment of diet‐induced obesity in humans. In an ongoing search for new pancreatic lipase inhibitors from natural sources, a methanolic extract of marine brown algae, Eisenia bicyclis, showed a significant inhibitory effect against pancreatic lipase. Bioassay‐guided isolation of this methanolic extract using a pancreatic lipase inhibitory assay led to the isolation and identification of six known phlorotannins: eckol (1), fucofuroeckol A (2), 7‐phloroeckol (3), dioxindehydroeckol (4), phlorofucofuroeckol A (5), and dieckol (6). The structures were established on the basis of nuclear magnetic resonance and mass spectrometry spectroscopic data interpretation. Among the isolated phloroglucinol polymers, compounds 2 and 3 showed potent inhibitory effects on pancreatic lipase with IC₅₀ values ranging from 37.2 ± 2.3 to 12.7 ± 1.0 μM, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

In Vitro Antibacterial Activity and Synergistic Antibiotic Effects of Phlorotannins Isolated from Eisenia bicyclis Against Methicillin‐Resistant Staphylococcus aureus

Six phlorotannins, isolated from Eisenia bicyclis, were evaluated for antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MIC) of the compounds were in the range 32 to 64 µg/mL. Phlorofucofuroeckol‐A (PFF) exhibited the highest anti‐MRSA activity, with an MIC of 32 µg/mL. An investigation of the interaction between these compounds and the β‐lactam antibiotics ampicillin, penicillin, and oxacillin revealed synergistic action against MRSA in combination with compound PFF. To our knowledge, this is the first report on the anti‐MRSA activity of phlorotannins from E. bicyclis. The results obtained in this study suggest that the compounds derived from E. bicyclis can be a good source of natural antibacterial agents against MRSA. Copyright © 2012 John Wiley & Sons, Ltd.     

海黍子多酚对亚油酸甲酯氧化的抑制作用

本文采用萃取硅胶注层析分离技术,从海黏子（Sargassum kjllmanianum）中分离获得4种海藻多酚类物质,用油溶性自由基引发剂（AMVN）引发氧化亚油酸甲酯（Methyl linolenate,ML）,用HPLC测定亚油酸甲酯氢过氧化物（ML－OOH）含量,以BHT和VE为对照,评价了海黍子多酚类物质的抗氧化能力。结果表明：在自由基引发剂（AMVN）作用下,获得的海藻多酚（buylated hyohoxytoluene）（0．2％）对ML氧化的抑制作用均比BHT（0．02％）好,但不如VE（0．2％）的效果好。各种海藻多酚所表现出的抗氧化能力相近。     

New insights into seaweed polyphenols on glucose homeostasis

Abstract

Context: Polyphenol-rich marine macroalgae are gaining dietary importance due to their influence over diabetes mellitus and the role as a vital source of high-value nutraceuticals. Their assorted beneficial effects on human health include competitive inhibition of digestive enzymes, varying the activity of hepatic glucose-metabolizing enzymes, lowering the plasma glucose levels, and lipid peroxidation, delaying the aging process.

Objective: In this paper, we review the health beneficial effects of polyphenols and phlorotannins from brown seaweeds with special emphasis on their inhibitory effects on carbohydrate-metabolizing enzymes.

Methods: A survey of literature from databases such as Sciencedirect, Scopus, Pubmed, Springerlink, and Google Scholar from the year 1973 to 2013 was done to bring together the information relating to drug discovery from brown seaweeds as a source for diabetes treatment.

Results: Over the past two decades, 20 different bioactive polyphenols/phlorotannins have been isolated and studied from 10 different brown algae. Discussion of the positive effect on the inhibition of enzymes metabolizing carbohydrates in both in vitro and in vivo experiments are included.

Conclusion: Despite the recent advancements in isolating bioactive compounds from seaweeds with potential health benefit or pharmaceutical behavior, studies on the polyphenol effectiveness on glucose homeostasis in human beings are very few in response to their functional characterization. Added research in this area is required to confirm the close connection of polyphenol rich seaweed-based diet consumption with glucose homeostasis and the exciting possibility of prescribing polyphenols to treat the diabetes pandemic.     

Fabrication and characterization of phlorotannins/poly (vinyl alcohol) hydrogel for wound healing application

Abstract

Phlorotannins (PH) derived from brown algae have been shown to have biological effects. However, the application of PH in biomedical materials has not been investigated. Here, we investigated the effects of PH on normal human dermal fibroblast (NHDF) proliferation and fabricated a composite hydrogel consisting PH and poly (vinyl alcohol) (PVA) (PVA/PH) by a freezing-thawing method for wound healing applications. Cell proliferation was significantly higher in the PH-treated (0.01 and 0.02%) cells than in non-treated cells. Based on the mechanical properties, the PVA/PH hydrogel had a significantly increased swelling ratio and ultimate strain compared to the PVA hydrogel, but the ultimate tensile strength and tensile modulus were decreased. Additionally, cell attachment and proliferation on the composites were evaluated using NHDFs. The results showed that after 1 and 5 days, cell attachment and proliferation were significantly increased on the PVA/PH hydrogel compared with that on the PVA hydrogel. The findings from this study suggest that the PVA/PH hydrogel may be a candidate biomedical material for wound healing applications.     

Evaluation of Toxicity of Crude Phlorotannins and Phloroglucinol Using Different Model Organisms

Phlorotannins have been proven to contain numerous bioactive compounds that have potential to be applied in variety industries, including cosmetics, functional foods, nutraceuticals, environmental management, and medicine. The larvicidal and growth-inhibiting properties of phlorotannins have been extensively studied in various organisms. However, the toxicity of the phloroglucinol oligomer of phlorotannin is unclear, especially in Artemia salina, Daphnia magna, Lactuca sativa, and Chlorella vulgaris, which are commonly used in many bioassays. Therefore, research using these four organisms should be designed to provide basic information about the toxic effects of phlorotannins and phloroglucinol. This study aimed to evaluate the larvicidal and inhibitory properties of phlorotannins and phloroglucinol on A. salina, D. magna, L. sativa, and C. vulgaris. Phlorotannin extract and phloroglucinol were administered at various concentrations to each test organism. The survival rate of A. salina nauplii and D. magna neonates was observed every 24 h to 72 h, whereas the L. sativa seed germination and inhibition rate of C. vulgaris were observed up to 96 h. The results showed that the 24 h LC50 of phlorotannin on A. salina and D. magna were 10.67 and 1.32 mg/mL, respectively. The germination inhibition of L. sativa was 53.3% with a seed growth of less than 4 mm after 96 h upon exposure to 1 mg/mL of phlorotannin. Freshwater and seawater C. vulgaris experienced yield inhibition of 39.47 and 43.46%, respectively, when 2 mg/mL of phlorotanin was added. These results indicate that phlorotannin affects the survival and growth of the test organisms, so its use as a pesticide, herbicide, and algaecide agent for environmental and aquaculture applications can be further studied.