Seung-Hong Lee

Dieckol isolated from Ecklonia cava inhibits α-glucosidase and α-amylase in vitro and alleviates postprandial hyperglycemia in streptozotocin-induced diabetic mice.

This study was designed to investigate whether dieckol may inhibit α-glucosidase and alpha-amylase activities, and alleviate postprandial hyperglycemia in streptozotocin-induced diabetic mice. Dieckol isolated from Ecklonia cava, brown algae, evidenced prominent inhibitory effect against alpha-glucosidase and alpha-amylase. The IC(50) values of dieckol against alpha-glucosidase and alpha-amylase were 0.24 and 0.66 mM, respectively, which evidenced the higher activities than that of acarbose. Dieckol did not exert any cytotoxic effect in human umbilical vein endothelial cells (HUVECs) at various concentrations (from 0.33 to 2.69 mM). The increase of postprandial blood glucose levels were significantly suppressed in the dieckol administered group than those in the streptozotocin-induced diabetic or normal mice. Moreover, the area under curve (AUC) was significantly reduced via dieckol administration (259 versus 483 mmol min/l) in the diabetic mice as well as it delays absorption of dietary carbohydrates. Therefore, these result indicated that dieckol might be a potent inhibitor for α-glucosidase and α-amylase.

Protective effects of dieckol isolated from Ecklonia cava against high glucose-induced oxidative stress in human umbilical vein endothelial cells

The effect of dieckol, one of phlorotannin polyphenol compound purified from Ecklonia cava (E. cava) against high glucose-induced oxidative stress was investigated using human umbilical vein endothelial cells (HUVECs), which is susceptible to oxidative stress. High glucose (30mM) treatment induced HUVECs cell death, but dieckol, at concentration 10 or 50microg/ml, significantly inhibited the high glucose-induced cytotoxicity. Furthermore, treatment with dieckol dose-dependently decreased thiobarbituric acid reactive substances (TBARS), intracellular reactive oxygen species (ROS) generation and nitric oxide level increased by high glucose. In addition, high glucose levels induced the overexpressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and nuclear factor-kappa B (NF-kB) proteins in HUVECs, but dieckol treatment reduced the overexpressions of these proteins. These findings indicate that dieckol is a potential therapeutic agent that will reduce the damage caused by hyperglycemia-induced oxidative stress associated with diabetes.

Anti-diabetic effects of brown algae derived phlorotannins, marine polyphenols through diverse mechanisms.

Marine algae are popular and abundant food ingredients mainly in Asian countries, and also well known for their health beneficial effects due to the presence of biologically active components. The marine algae have been studied for biologically active components and phlorotannins, marine polyphenols are among them. Among marine algae, brown algae have extensively studied for their potential anti-diabetic activities. Majority of the investigations on phlorotannins derived from brown algae have exhibited their various anti-diabetic mechanisms such as α-glucosidase and α-amylase inhibitory effect, glucose uptake effect in skeletal muscle, protein tyrosine phosphatase 1B (PTP 1B) enzyme inhibition, improvement of insulin sensitivity in type 2 diabetic db/db mice, and protective effect against diabetes complication. In this review, we have made an attempt to discuss the various anti-diabetic mechanisms associated with phlorotannins from brown algae that are confined to in vitro and in vivo.

In vitro and in vivo antioxidant activities of polysaccharide purified from aloe vera (Aloe barbadensis) gel

The in vitro and in vivo antioxidant potentials of a polysaccharide isolated from aloe vera gel were investigated. Enzymatic extracts were prepared from aloe vera gel by using ten digestive enzymes including five carbohydrases and five proteases. Among them, the highest yield was obtained with the Viscozyme extract and the same extract showed the best radical scavenging activity. An active polysaccharide was purified from the Viscozyme extract using ethanol-added separation and anion exchange chromatography. Purified aloe vera polysaccharide (APS) strongly scavenged radicals including DPPH, hydroxyl and alkyl radicals. In addition, APS showed a protective effect against AAPH-induced oxidative stress and cell death in Vero cells as well as in the in vivo zebrafish model. In this study, it is proved that both the in vitro and in vivo antioxidant potentials of APS could be further utilized in relevant industrial applications.

Dieckol isolated from brown seaweed Ecklonia cava attenuates type ІІ diabetes in db/db mouse model.

In the present study, the attenuation of type ІІ diabetes by dieckol, a phlorotannin derivative isolated from brown seaweed, Ecklonia cava was investigated in C57BL/KsJ-db/db, a type ІІ diabetes mouse model. Dieckol was administered intraperitoneal injection at doses of 10 and 20 mg/kg body weight diabetes mice for 14 days. The blood glucose level, serum insulin level and body weight were significantly reduced in the dieckol administered group, compared to that of the saline administered group. Furthermore, reduced thiobarbituric acid reactive substraces (TBARS), as well as increased activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-px) in liver tissues were observed in the dieckol administered group. In addition, increased levels of the phosphorylation of AMPK and Akt were observed in the muscle tissues of the dieckol administered group in a Western blotting analysis. According to the findings of this study, it could be suggested that, dieckol can be developed as a therapeutic agent for type ІІ diabetes.

Inhibitory effect of diphlorethohydroxycarmalol on melanogenesis and its protective effect against UV-B radiation-induced cell damage

In this study, potential inhibitory effect of 21 species of marine algae on melanogenesis was assessed via tyrosinase inhibitory effect. The Ishige okamurae extract tested herein evidenced profound tyrosinase inhibitory effect, compared to that exhibited by other marine algae extracts. Thus, I. okamurae was selected for use in further experiments, and was partitioned with different organic solvents. Profound tyrosinase inhibitory effect was detected in the ethyl acetate fraction, and the active compound was identified as the carmalol derivative, diphlorethohydroxycarmalol (DPHC), which evidenced higher levels of activity than that of commercial whitening agent. Intracellular reactive oxygen species (ROS) induced by ultraviolet (UV)-B radiation was reduced by the addition of DPHC and cell viability was dose-dependently increased. Moreover, DPHC demonstrated strong protective properties against UV-B radiation via damaged DNA tail length and morphological changes in fibroblast. Hence, these results indicate that DPHC isolated from I. okamurae has potential whitening effects and prominent protective effects on UV-B radiation-induced cell damages which might be used in pharmaceutical and cosmeceutical industries.

Anti-inflammatory effect of fucoidan extracted from Ecklonia cava in zebrafish model.

Fucoidan extracted from Ecklonia cava had strong anti-inflammatory activities. However, the direct effects of fucoidan of E. cava on anti-inflammatory activities in vivo model remained to be determined. Therefore, the present study was designed to assess in vivo anti-inflammatory effect of fucoidan extracted from E. cava (ECF) using tail-cutting-induced and lipopolysaccharide (LPS)-stimulated zebrafish model. Treating zebrafish model with tail-cutting and LPS-treatment significantly increased the ROS and NO level. However, ECF inhibited this tail-cutting-induced and LPS-stimulated ROS and NO generation. These results show that ECF alleviated inflammation by inhibiting the ROS and NO generation induced by tail-cutting and LPS-treatment. In addition, ECF has a protective effect against the toxicity induced by LPS exposure in zebrafish embryos. This outcome could explain the potential anti-inflammatory activity of ECF, which might have a beneficial effect during the treatment of inflammatory diseases.

Effects of brown alga, Ecklonia cava on glucose and lipid metabolism in C57BL/KsJ-db/db mice, a model of type 2 diabetes mellitus.

Recently, there has been a growing interest in alternative therapies of marine algae for diabetes. Therefore, the anti-diabetic effects of brown alga, Ecklonia cava was investigated in type 2 diabetic animal. Male C57BL/KsJ-db/db (db/db) mice were divided into control, dieckol rich extract of E. cava (AG-dieckol), or rosiglitazone (RG) groups. The blood glucose, blood glycosylated hemoglobin levels, and plasma insulin levels were significantly lower in the AG-dieckol and RG groups than in the control db/db mice group, while glucose tolerance was significantly improved in the AG-dieckol group. AG-dieckol markedly lowered plasma and hepatic lipids concentration compared to the control db/db mice group. The antioxidant enzyme activities were significantly higher in the AG-dieckol group than in the control db/db mice group, yet its TBARS level was markedly lower compared to the RG group. With regard to hepatic glucose regulating enzyme activities, glucokinase activity was enhanced in the AG-dieckol group mice, while glucose-6-phosphatase and phosphoenolpyruvate carboxykinase activities in the AG-dieckol group mice were significantly lowered than those in the control db/db mice group. These results suggest that AG-dieckol exert an anti-diabetic effect in type 2 diabetic mice by improving the glucose and lipid metabolism and antioxidant enzymes.

Molecular characteristics and anti-inflammatory activity of the fucoidan extracted from Ecklonia cava

Enzymatic extraction has been successfully used for extracting numerous biologically active compounds from a wide variety of seaweeds. In this study, we found that enzymatic extraction of the fucoidan from Ecklonia cava may be more advantageous than water extraction. Therefore, we studied the E. cava fucoidans extracted by the enzymatic extraction technique and used ion-exchange chromatography to determine their molecular characteristics and anti-inflammatory activities. The crude and fractionated fucoidans (F1, F2, and F3) consisted mostly of carbohydrates (47.1-57.1%), uronic acids (9.0-15.8%), and sulfates (16.5-39.1%), as well as varying levels of proteins (1.3-8.7%). The monosaccharide levels significantly differed, and the composition included fucose (53.1-77.9%) and galactose (10.1-32.8%), with a small amount of rhamnose (2.3-4.5%), xylose (4.0-8.2%), and glucose (0.8-2.2%). These fucoidans contained one or two subfractions with an average molecular weight (Mw) ranging from 18 to 359×10(3)g/mol. These fucoidans significantly inhibited NO production in lipopolysaccharide (LPS)-induced Raw 264.7 macrophage cells by down-regulating the expression of iNOS, COX-2, and pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β. Thus, the present results suggest that E. cava fucoidan may be a potentially useful therapeutic approach for various inflammatory diseases.

Protective effect of marine algae phlorotannins against AAPH-induced oxidative stress in zebrafish embryo

In this study the protective effect of phlorotannins, including phloroglucinol, eckol, dieckol, eckstolonol and triphloroethol A, isolated from brown algae Ecklonia cava was investigated against AAPH-induced oxidative stress toxicity in zebrafish embryos. Zebrafish embryos were exposed to AAPH and compared with other groups that were co-exposed with phlorotannins until 2-days post-fertilisation. All phlorotannins scavenged intracellular ROS and prevented lipid peroxidation and reduced AAPH-induced cell death in zebrafish embryos. Negative changes in morphological phenomena, such as pericardial oedema, yolk sac oedema, and growth retardation in zebrafish embryos exposed to AAPH were not observed in groups exposed to phlorotannins. These results clearly indicate that phlorotannins possess prominent antioxidant activity against AAPH-mediated toxicity and might be potential therapeutic agents for treating or preventing several diseases implicated with oxidative stress. This study provides a useful tool for examining the protective effect of antioxidants against AAPH-induced oxidative stress in an alternative in vivo model.