Byong-Tae Jeon

Reactive Oxygen Scavenging Effect of Enzymatic Extracts from Sargassum thunbergii

The free radical scavenging activity of water soluble natural antioxidants from Sargassum thunbergii, which is a brown marine alga, was evaluated by examining the radical scavenging activities of the extracts of hydrolyzates from S. thunbergii on hydroxyl, 1,1-diphenyl-2-picrylhydrazyl (DPPH), and alkyl radicals. A spin-trapping electron spin resonance (ESR) spectrometer was employed, and the results were compared for their ESR signal intensity. S. thunbergii was enzymatically hydrolyzed to prepare water soluble extracts by five carbohydrases (AMG, Celluclast, Termamyl, Ultraflo, and Viscozyme) and proteases (Alcalase, Flavorzyme, Kojizyme, Neutrase, and Protamex). The scavenging activity of the radicals increased with increased concentrations of the extracts. The scavenging results were higher for hydroxyl and alkyl radicals and lower for DPPH radical as compared with vitamin C as a reference. The hydrogen peroxide scavenging activity of the extracts was also investigated; the Alcalase extract showed the highest scavenging activity among the extracts prepared with the five proteases and five carbohydrates. In addition, the DNA damage was determined by using the comet assay with alkaline electrophoresis and was quantified by measuring the tail length. The preventive effect of Alcalase extract from S. thunbergii against DNA damage increased with increments of concentration of the enzymatic extracts.

Chitooligosaccharide and Its Derivatives: Preparation and Biological Applications

Chitin is a natural polysaccharide of major importance. This biopolymer is synthesized by an enormous number of living organisms; considering the amount of chitin produced annually in the world, it is the most abundant polymer after cellulose. The most important derivative of chitin is chitosan, obtained by partial deacetylation of chitin under alkaline conditions or by enzymatic hydrolysis. Chitin and chitosan are known to have important functional activities but poor solubility makes them difficult to use in food and biomedicinal applications. Chitooligosaccharides (COS) are the degraded products of chitosan or chitin prepared by enzymatic or chemical hydrolysis of chitosan. The greater solubility and low viscosity of COS have attracted the interest of many researchers to utilize COS and their derivatives for various biomedical applications. In light of the recent interest in the biomedical applications of chitin, chitosan, and their derivatives, this review focuses on the preparation and biological activities of chitin, chitosan, COS, and their derivatives.

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.

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.

Purification and characterization of a nitric oxide inhibitory peptide from Ruditapes philippinarum

Ruditapes philippinarum (R. philippinarum) were hydrolyzed using 8 proteases to produce an anti-inflammatory peptide of the various hydrolysates produced, the Alcalase hydrolysate exhibited the highest nitric oxide (NO) inhibitory activity. The derived peptide was purified using high performance liquid chromatography (HPLC) and NO-inhibitory activity of the purified compound was evaluated. The sequence of the NO-inhibitory peptide obtained was composed of 10 amino acid residues, Gln-Cys-Gln-Gln-Ala-Val-Gln-Ser-Ala-Val at N-terminal position. In addition, we investigated the inhibitory effect of the purified peptide from R. philippinarum on NO production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. In this analysis the purified peptide from R. philippinarum was shown to inhibit LPS-induced NO production in RAW264.7 cells. The present results indicate that the purified peptide displayed potent anti-inflammation activity in RAW264.7 cells.

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.

Isolation and identification of an antioxidant flavonoid compound from citrus-processing by-product

BACKGROUND Large amounts of citrus by-products are released from juice-processing plants every year. Most bioactive compounds are found in the peel and inner white pulp. Flavonoids are a widely distributed group of bioactive compounds. The methanolic extract of citrus peel powder has been shown to possess strong antioxidant activity. Therefore the aim of this study was to isolate the major antioxidant flavonoid compound from Citrus unshiu (satsuma) peel as citrus by-product and evaluate its antioxidant activity. RESULTS The major flavonoid isolated from C. unshiu peel was identified as quercetagetin. The structure of the compound was determined by tandem mass spectrometry and ultraviolet spectroscopy. Its antioxidant activity was assessed by assays of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, hydroxyl radical and intracellular reactive oxygen species (ROS) scavenging and DNA damage inhibition. Quercetagetin showed strong DPPH radical-scavenging activity (IC₅₀ 7.89 µmol L⁻¹) but much lower hydroxyl radical-scavenging activity (IC₅₀ 203.82 µmol L⁻¹). Furthermore, it significantly reduced ROS in Vero cells and showed a strong protective effect against hydrogen peroxide-induced DNA damage. CONCLUSION The results of this study suggest that quercetagetin could be used in the functional food, cosmetic and pharmaceutical industries.

Chitooligosaccharides decreases plasma lipid levels in healthy men

Chitosan, which is derived from chitin, has drawn much attention due to its low toxicity and potential use in medical and pharmaceutical applications. The biological activities of chitosan have been shown to depend on its molecular weight (MW) and degree of deacetylation. In this study, we investigated whether oral chitooligosaccharides, which are easily absorbed into the body, can reduce the plasma level of lipid in smokers and non-smokers because smoking is a high-risk factor for cardiovascular diseases. All healthy men (11 smokers and 8 non-smokers) consumed 500 mg of chitooligosaccharides in water twice daily before a meal (breakfast and dinner) over a 6-week period. Total cholesterol and low-density lipoprotein cholesterol levels were significantly decreased in both the smoker group and non-smoker group when compared with baseline. These results suggest that low MW chitooligosaccharides would be an effective dietary supplement for lowering cholesterol level.

Dieckol Isolated from Ecklonia cava Protects against High-Glucose Induced Damage to Rat Insulinoma Cells by Reducing Oxidative Stress and Apoptosis

Pancreatic β cells are very sensitive to oxidative stress and this might play an important role in β cell death with diabetes. The protective effect of dieckol, one of the phlorotannin polyphenol compounds purified from Ecklonia cava (E. cava), against high glucose-induced oxidative stress was investigated by using rat insulinoma cells. A high-glucose (30 mM) treatment induced the death of rat insulinoma cells, but dieckol, at a concentration 17.5 or 70 µM, significantly inhibited the high-glucose induced glucotoxicity. Treatment with dieckol also dose-dependently reduced thiobarbituric acid reactive substances (TBARS), the generation of intracellular reactive oxygen species (ROS), and the nitric oxide level increased by a high glucose concentration. In addition, the dieckol treatment increased the activities of antioxidative enzymes including catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) in high glucose-pretreated rat insulinoma cells. Dieckol protected rat insulinoma cells damage under high glucose conditions. These effects were mediated by suppressing apoptosis and were associated with increased anti-apoptotic Bcl-2 expression, and reduced pro-apoptotic cleaved caspase-3 expression. These findings indicate that dieckol might be useful as a potential pharmaceutical agent to protect against the glucotoxicity caused by hyperglycemia-induced oxidative stress associated with diabetes.

Sulfated Chitosan Oligosaccharides Suppress LPS-Induced NO Production via JNK and NF-κB Inactivation

Various biological effects have been reported for sulfated chitosan oligosaccharides, but the molecular mechanisms of action of their anti-inflammatory effects are still unknown. This study aimed to evaluate the anti-inflammatory effects of sulfated chitosan oligosaccharides and to elucidate the possible mechanisms of action. The results showed that pretreated low molecular weight sulfated chitosan oligosaccharides inhibited the production of nitric oxide (NO) and inflammatory cytokines such as IL-6 and TNF-α in lipopolysaccharide (LPS)-activated RAW264.7 cells. The sulfated chitosan oligosaccharides also suppressed inducible nitric oxide synthase (iNOS), phosphorylation of JNK and translocation of p65, a subunit of NF-κB, into the nucleus by inhibiting degradation of IκB-α. Our investigation suggests sulfated chitosan oligosaccharides inhibit IL-6/TNF-α in LPS-induced macrophages, regulated by mitogen-activated protein kinases (MAPKs) pathways dependent on NF-κB activation.