Sung-Myung Kang

Evaluation of anti-inflammatory effect of fucoxanthin isolated from brown algae in lipopolysaccharide-stimulated RAW 264.7 macrophages.

In this study, potential anti-inflammatory effect of fucoxanthin isolated from brown algae was assessed via inhibitory effect of nitric oxide (NO) production in lipopolysaccharide (LPS) induced RAW 264.7 macrophage cells. The Myagropsis myagroides was selected for further experiments due to its profound NO inhibitory effect, and was partitioned with different organic solvents. Highest NO inhibitory effect was detected in the chloroform fraction, and the active compound was identified as fucoxanthin, a kind of carotenoid available in brown algae evidenced high correlation with the inhibitory effect of NO production (r(2)=0.9511). Though, fucoxanthin significantly inhibited the NO production, it slightly reduced the prostaglandin E(2) (PGE(2)) production. The inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) protein expressions were inhibited by fucoxanthin. Further, RT-PCR analysis indicated that the iNOS and COX-2 mRNA expressions were suppressed by fucoxanthin. Moreover, the release of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6), and the mRNA expression levels of those cytokines were reduced by the addition of fucoxanthin in a dose-dependent manner. Hence, these results suggest that the use of fucoxanthin may be a useful therapeutic approach for the various inflammatory diseases.

Fucoxanthin inhibits the inflammatory response by suppressing the activation of NF-κB and MAPKs in lipopolysaccharide-induced RAW 264.7 macrophages

It has been previously determined that pro-inflammatory mediators including nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β and IL-6 contribute to the courses of a variety of inflammatory diseases. In this study, we evaluated the anti-inflammatory effects of fucoxanthin (FX), a natural biologically active substance isolated from Ishige okamurae, by determining its inhibitory effects on pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated murine macrophage RAW 264.7 cells. FX induced dose-dependent reductions in the levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins and concomitant reductions in the production of NO and PGE₂. Additionally, FX was shown to suppress the production of inflammatory cytokines including IL-1β, TNF-α, and IL-6. Furthermore, FX inhibited the cytoplasmic degradation of inhibitors of B (IκB)-α and the nuclear translocation of p50 and p65 proteins, resulting in lower levels of nuclear factor (NF)-κB transactivation. Additionally, FX was shown to induce a dose-dependent inhibition of the phosphorylation of mitogen-activated protein kinases (MAPKs; JNK, ERK and p38). Collectively, the results of this study demonstrate that FX reduces the levels of pro-inflammatory mediators including NO, PGE₂, IL-1β, TNF-α, and IL-6 via the inhibition of NF-κB activation and the suppression of MAPK phosphorylation in RAW 264.7 cells. These findings reveal, in part, the molecular basis underlying the anti-inflammatory properties of FX.

Fucoxanthin induces apoptosis in human leukemia HL-60 cells through a ROS-mediated Bcl-xL pathway.

Fucoxanthin, a natural biologically active substance isolated from Ishige okamurae, evidences antitumor activity in human leukemia cell HL-60 cells via the induction of apoptosis. However, the mechanism underlying fucoxanthin-induced apoptosis in HL-60 cells remains unclear. In this study, we focused on the effect of fucoxanthin induction on the accumulation of reactive oxygen species (ROS), and on the triggering of Bcl-xL signaling pathway in HL-60 cells. We determined that ROS are generated during fucoxanthin-induced cytotoxicity and apoptosis in HL-60 cells, and that N-acetylcysteine (NAC), a ROS scavenger, suppressed fucoxanthin-induced cytotoxicity and apoptosis. Moreover, fucoxanthin-induced the cleavage of caspases -3 and -7, and poly-ADP-ribose polymerase (PARP) and a decrease of Bcl-xL levels, whereas NAC pre-treatment significantly inhibited caspase-3, -7, and PARP cleavage and the reduction in Bcl-xL levels. In this study, it was demonstrated for the first time that fucoxanthin generated ROS and that the accumulation of ROS performed a crucial role in the fucoxanthin-induced Bcl-xL signaling pathway.

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.

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.

Inhibition of tumor growth in vitro and in vivo by fucoxanthin against melanoma B16F10 cells.

The present study was designed to evaluate the molecular mechanisms of fucoxanthin against melanoma cell lines (B16F10 cells). Fucoxanthin reduced the proliferation of B16F10 cells in a dose-dependent manner accompanied by the induction of cell cycle arrest during the G(0)/G(1) phase and apoptosis. Fucoxanthin-induced G(0)/G(1) arrest was associated with a marked decrease in the protein expressions of phosphorylated-Rb (retinoblastoma protein), cyclin D (1 and 2) and cyclin-dependent kinase (CDK) 4 and up-regulation of the protein levels of p15(INK4B) and p27(Kip1). Fucoxanthin-induced apoptosis was accompanied with the down-regulation of the protein levels of Bcl-xL, an inhibitor of apoptosis proteins (IAPs), resulting in a sequential activation of caspase-9, caspase-3, and PARP. Furthermore, the anti-tumor effect of fucoxanthin was assessed in vivo in Balb/c mice. Intraperitoneal administration of fucoxanthin significantly inhibited the growth of tumor mass in B16F10 cells implanted mice.

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.

Molecular docking studies of a phlorotannin, dieckol isolated from Ecklonia cava with tyrosinase inhibitory activity

In this study, the phlorotannin dieckol, which was isolated from the brown alga Ecklonia cava, was examined for its inhibitory effects on melanin synthesis. Tyrosinase inhibitors are important agents for cosmetic products. We therefore examined the inhibitory effects of dieckol on mushroom tyrosinase and melanin synthesis, and analyzed its binding modes using the crystal structure of Bacillus megaterium tyrosinase (PDB ID: 3NM8). Dieckol inhibited mushroom tyrosinase with an IC(50) of 20μM and was more effective as a cellular tyrosinase having melanin reducing activities than the commercial inhibitor, arbutin, in B16F10 melanoma cells, and without apparent cytotoxicity. It was found that dieckol behaved as a non-competitive inhibitor with l-tyrosine substrates. For further insight, we predicted the 3D structure of tyrosinase and used a docking algorithm to simulate binding between tyrosinase and dieckol. These molecular modeling studies were successful (calculated binding energy value: -126.12kcal/mol), and indicated that dieckol interacts with His208, Met215, and Gly46. These results suggest that dieckol has great potential to be further developed as a pharmaceutical or cosmetic agent for use in dermatological disorders associated with melanin.

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.