Seok-Chun Ko

Effect of phlorotannins isolated from Ecklonia cava on melanogenesis and their protective effect against photo-oxidative stress induced by UV-B radiation.

In the present study, three kinds of phlorotannins, marine algal polyphenol, were isolated from a brown alga Ecklonia cava, and their inhibitory effect on melanogenesis as well as the protective effect against photo-oxidative stress induced by UV-B radiation was investigated. The effect on melanogenesis was evaluated via the inhibitory effects of tyrosinase and melanin synthesis. Among the phlorotannins, dieckol showed higher effect than that of the other phlorotannins in the both assays; especially the value of dieckol in the tyrosinase inhibition assay was relatively higher than that of a commercial tyrosinase inhibitor (kojic acid). The UV-B protection effect was evaluated via DCFH-DA, MTT, comet assays, and morphological changes in fibroblast. Intracellular ROS induced by UV-B radiation was reduced by the addition of phlorotannins and cell viability was dose-dependently increased. Moreover, dieckol demonstrated strong protective properties against UV-B radiation-induced DNA damage via damaged tail intensity and morphological changes in fibroblast. Hence, these results indicated that dieckol isolated from E. cava has potential whitening effects and prominent protective effects on UV-B radiation-induced cell damages, which might be used in pharmaceutical and cosmeceutical industries.

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.

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.

Protective effect of a novel antioxidative peptide purified from a marine Chlorella ellipsoidea protein against free radical-induced oxidative stress

Protein derived the marine Chlorella ellipsoidea was hydrolyzed using different proteases (papain, trypsin, pepsin and α-chymotrypsin) for production of antioxidative peptide, and the antioxidant activities of their hydrolysates were investigated using free radical scavenging assay by electron spin resonance spin-trapping technique. Among the hydrolysates, the peptic hydrolysate exhibited the highest antioxidant activity compared to other hydrolysates. To identify antioxidant peptide, the peptic hydrolysate was purified using consecutive chromatographic methods, and the antioxidant peptide was identified to be Leu-Asn-Gly-Asp-Val-Trp (702.2 Da) by Q-TOF ESI mass spectroscopy. The antioxidant peptide scavenged peroxyl, DPPH and hydroxyl radicals at the IC(50) values of 0.02, 0.92 and 1.42 mM, respectively. The purified peptide enhanced cell viability against AAPH-induced cytotoxicity on normal cells. Furthermore, the purified peptide reduced the proportion of apoptotic and necrotic cells induced by AAPH, as demonstrated by decreased sub-G(1) hypodiploid cells and decreased apoptotic body formation by flow cytometry.

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.

Octaphlorethol A, a novel phenolic compound isolated from a brown alga, Ishige foliacea, increases glucose transporter 4-mediated glucose uptake in skeletal muscle cells

Skeletal muscle is the major site of glucose disposal. Promoting glucose uptake into this tissue may attenuate the insulin resistance that precedes type 2 diabetes. However, the anti-diabetic effect of marine algae on glucose uptake and metabolism in skeletal muscle remains poorly understood. Here, we report the glucose uptake effects of octaphlorethol A (OPA), a novel phenolic compound isolated from Ishige foliacea, on skeletal muscle cells. OPA increased glucose uptake in differentiated L6 rat myoblast cells in a dose-dependent manner relative to the control. In addition, we found that OPA increased glucose transporter 4 (Glut4) translocation to the plasma membrane. Furthermore, we also demonstrated these OPA effects essentially depended on the protein kinase B (Akt) and AMP-activated protein kinase (AMPK) activation. In summary, PI3-K/Akt and AMPK activation were involved in mediating the effects of OPA on glucose transport activation and insulin sensitivity. OPA can be further developed as a potential anti-diabetic therapy.

Dieckol, a phlorotannin isolated from a brown seaweed, Ecklonia cava, inhibits adipogenesis through AMP-activated protein kinase (AMPK) activation in 3T3-L1 preadipocytes.

In this study, we assessed the potential inhibitory effect of 5 species of brown seaweeds on adipogenesis the differentiation of 3T3-L1 preadipocytes into mature adipocytes by measuring Oil-Red O staining. The Ecklonia cava extract tested herein evidenced profound adipogenesis inhibitory effect, compared to that exhibited by the other four brown seaweed extracts. Thus, E. cava was selected for isolation of active compounds and finally the three polyphenol compounds of phlorotannins were obtained and their inhibitory effect on adipogenesis was observed. Among the phlorotannins, dieckol exhibited greatest potential adipogenesis inhibition and down-regulated the expression of peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer-binding proteins (C/EBPα), sterol regulatory element-binding protein 1 (SREBP1) and fatty acid binding protein 4 (FABP4) in a dose-dependent manner. The specific mechanism mediating the effects of dieckol was confirmed by AMP-activated protein kinase (AMPK) activation. These results demonstrate inhibitory effect of dieckol compound on adipogenesis through the activation of the AMPK signal pathway.

Marine-derived biological macromolecule-based biomaterials for wound healing and skin tissue regeneration.

Wound healing is a complex biological process that depends on the wound condition, the patients health, and the physicochemical support given through external materials. The development of bioactive molecules and engineered tissue substitutes to provide physiochemical support to enhance the wound healing process plays a key role in advancing wound-care management. Thus, identification of ideal molecules in wound treatment is still in progress. The discovery of natural products that contain ideal molecules for skin tissue regeneration has been greatly advanced by exploration of the marine bioenvironment. Consequently, tremendously diverse marine organisms have become a great source of numerous biological macromolecules that can be used to develop tissue-engineered substitutes with wound healing properties. This review summarizes the wound healing process, the properties of macromolecules from marine organisms, and the involvement of these molecules in skin tissue regeneration applications.

Hepatoprotective effects of dieckol-rich phlorotannins from Ecklonia cava, a brown seaweed, against ethanol induced liver damage in BALB/c mice

Alcoholic liver disease, which is one of the most serious liver disorders, has been known to cause by ethanol intake. In the present study, in vivo hepatoprotective effects of dieckol-rich phlorotannins (DRP) from Ecklonia cava, a brown seaweed, on ethanol induced hepatic damage in BALB/c mice liver were investigated. After administration of 5 and 25mg/kg mouse of DRP and 4 g/kg mice ethanol, the body weights and survival rates were increased as compared to the control, which is ethanol-treated group without DRP. The glutamic oxaloacetic transaminase and glutamic pyruvic transaminase levels in the serum were lower than those of the control. DRP exhibited a reduction of the total cholesterol. The lower levels of SOD enzyme and a reduction of the formation of malondialdehyde were occurred in mice fed with 5 and 25mg/kg mouse of DRP. Finally the effect on improvement of fatty liver induced by ethanol was observed by taking out the liver immediately after dissecting the mouse. However, no significant difference was observed on hepatic histopathological changes. In conclusion, this study indicated that DRP could protect liver injury induced by ethanol in vivo. It suggested that DRP possesses the beneficial effect to human against ethanol-induced liver injury.