Yong-Ki Hong

Pukyong National University, Busan, Busan, South Korea

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Publications (97)141.15 Total impact

  • Sang-Bum Lee · Sung-Koo Kim · Yong-Ki Hong · Gwi-Taek Jeong
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    ABSTRACT: In this study, the platform-chemicals and sugar production from the macro-algae, Kappaphycus alvarezii, were investigated. The production of glucose, galactose, levulinic acid (LA), and 5-hydroxymethylfurfural (5-HMF) was evaluated by dilute-acid-catalyzed hydrothermal reaction. By this approach, the respective optimal yields (and reaction conditions) were as follows: glucose 2.15 g/L (reaction temperature: 160 °C, catalyst amount: 1.09%, reaction time: 20 min), galactose 14.47 g/L (160.3 °C, 1.02%, 20.3 min), LA 11.69 g/L (178.2 °C, 2.87%, 39.3 min) and 5-HMF 3.02 g/L (160.6 °C, 1%, 20.1 min).
    No preview · Article · Jan 2016 · Algal Research
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    ABSTRACT: Neurodegenerative disorders, which affect memory, cognition, and social functions, can be treated using neurotrophic agents to support neuronal development and protect mature neurons from atrophy. We screened 34 tropical seaweed species collected from Indonesian coastal areas for their neurite-outgrowth-promoting activity (NOPA) in fetal rat hippocampal neurons in vitro. Based on the number and total length of primary neurites, red seaweeds had greater NOPA than green and brown seaweeds. The red seaweed Kappaphycus alvarezii showed the highest NOPA. Addition of the ethanol extract to the culture (1 μg mL−1) significantly accelerated initial neuronal maturation from stage I to stage II (70 %; P < 0.05) within 24 h and increased the number of neurites that developed multipolar characteristics (48 %; P < 0.05). These results indicate that the aquaculturable carrageenan producer K. alvarezii might be a promising source of neurotrophic compounds to enhance memory and learning.
    No preview · Article · Jan 2016 · Journal of Applied Phycology
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    ABSTRACT: The hot water extract of leather carp (Cyprinus carpio nudus) has been used as a nourishing tonic soup and as an aid for recovery from physical fatigue. In this study, we investigated the effect of leather carp extract on exercise performance in mice. Swimming endurance and forelimb grip strength were assessed following oral administration of the extract (once per day for 7 days) at a dose of 0.5 mg/10 μL/g body weight. After 7 days, mice given the leather carp extract had significantly greater swimming endurance [105±18 s (P<0.05); 52% longer than day 0] and forelimb grip strength [1.18±0.05 Newton (P<0.01); 17% greater than day 0]. The extract increased muscle mass, but had little effect on body weight. Following the swimming exercise, blood glucose, glutathione peroxidase, and superoxide dismutase levels in extract-fed mice were significantly higher (145%, 131%, and 106%, respectively) than in the saline control group. Blood levels of high-density lipoprotein cholesterol were also significantly increased (128%) in mice given the extract compared to the controls. These results suggest that leather carp extract can improve physical exercise performance and prevent oxidative stress caused by exhaustive workouts.
    No preview · Article · Jan 2016 · Preventive Nutrition and Food Science
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    ABSTRACT: We describe robustly anchored triblock copolymers that adopt loop conformations on surfaces and endow them with unprecedented lubricating and antifouling properties. The triblocks have two end-blocks with catechol-anchoring groups and a looping polyethyleneoxide (PEO) midblock. The loops mediate strong steric repulsion between two mica surfaces. When sheared at constant speeds of ~2.5 μm/s, the surfaces exhibit an extremely low friction coefficient of ~0.002-0.004 without any signs of damage up to pressures of ~ 2-3 MPa that are close to most biological bearing systems. Moreover, the polymer loops enhance inhibition of cell adhesion and proliferation compared to polymers in the random coil or brush conformations. These results demonstrate that strongly anchored polymer loops are effective for high lubrication and low cell adhesion and represent a promising candidate for the development of specialized high performance biomedical coatings.
    No preview · Article · Dec 2015 · ACS Nano
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    ABSTRACT: The stoloniferous hydrozoan Obelia geniculata frequently colonizes late harvested blade of the aquacultured brown seaweed Saccharina japonica. To understand harmful effects of the hydrozoans, we measured the tissue viability, proximate compositions, amino acid and fatty acid profiles, and metal contents of healthy blades, colonized blades, and hydrozoans isolated from the seaweed. Hydrozoans contained high amount of zinc (1.7 g/kg dry weight), which is 23% against the provisional tolerable weekly intake, at levels higher than the recommended range in food. In seaweed blades beneath the colony, after the removal of hydrozoans, levels of selenium, iodine, and docosahexaenoic acid increased, while copper, cadmium, nickel, chromium, and erucic acid levels decreased compared to healthy tissues. As evaluated for food or fodder, hydrozoans deteriorate the quality of seaweed, thus the epiphytic hydrozoans must be removed from the seaweed blade prior to its use. © 2015, Korean Society of Environmental Risk Assessment and Health Science and Springer Science+Business Media Dordrecht.
    No preview · Article · Sep 2015 · Toxicology and Environmental Health Sciences
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    Full-text · Dataset · Aug 2015
  • Issa Bangoura · Yong-Ki Hong

    No preview · Article · Jul 2015
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    ABSTRACT: Abalone containing phlorotannins is produced by feeding the phlorotannin-rich brown seaweed Eisenia bicyclis after 4 days of starvation. Reverse-phase high-performance liquid chromatography (RP-HPLC) was used to isolate and quantify phlorotannins, which were identified by mass spectrometry and [ 1 H]-nuclear magnetic resonance to be the P1 compound, 7-phloroeckol, and eckol. When E. bicyclis was used as feed, P1 compound accumulated to an average of 1.60 mg/g dry weight of abalone muscle tissue after 18 d, 7-phloroeckolol to 0.21 mg/g after 16 d, and eckol to 0.22 mg/g after 12 d. Saccharina japonica was used as a control feed, and the abalone showed little or no accumulation of phlorotannins in muscle tissue. Feed consumption and growth rate were very similar when either E. bicyclis or S. japonica was fed for 20 d. Half-maximal reductions in the levels of P1 compound, 7-phloroeckol, and eckol accumulation were attained in 1.5, 1.9, and 3.4 days, respectively, after the feed was switched from E. bicyclis to S. japonica. Value-added abalone containing bioactive phlorotannins can be produced by simply changing the feed to the phlorotannin-rich E. bicyclis 18 d prior to harvesting.
    Full-text · Article · Jul 2015 · Fisheries and Aquatic Science
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    ABSTRACT: Age-related neurological disorders are of growing concern among the elderly, and natural products with neuroprotective properties have been attracting increasing attention as candidates for the prevention or treatment of neurological disorders induced by oxidative stress. In an effort to explore natural resources, we collected some common marine seaweed from the Korean peninsula and Indonesia and screened them for neuroprotective activity against hypoxia/reoxygenation (H/R)-induced oxidative stress. Of the 23 seaweeds examined, the ethanol extract of Gracilariopsis chorda (GCE) provided maximum neuroprotection at an optimum concentration of 15 μg/mL, followed by Undaria pinnatifida. GCE increased cell viability after H/R, decreased the formation of reactive oxygen species (measured by 2',7'-dichlorodihydrofluorescein diacetate [DCF-DA] staining), and inhibited the double-stranded DNA breaks (measured by H2AX immunocytochemistry), apoptosis (measured by Annexin V/propidium iodide staining), internucleosomal DNA fragmentation (measured by DNA laddering), and dissipation of mitochondrial membrane potential (measured by JC-1 staining). Using reverse-phase high-pressure liquid chromatography, we quantitated the arachidonic acid (AA) in GCE, which provides neuroprotection against H/R-induced oxidative stress. This neuroprotective effect of AA was comparable to that of GCE. These findings suggest that the neuroprotective effect of GCE against H/R-induced neuronal death is due, at least in part, to the AA content that suppresses neuronal apoptosis.
    No preview · Article · Jun 2015 · Journal of medicinal food
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    ABSTRACT: Freshwater softshell turtle (Trionyx sinensis) extract has been used traditionally as a tonic soup, and to recover from physical fatigue. To support these claims, the forelimb grip strength of mice was measured after feeding a soft-shell turtle extract for 7 days. The T. sinensis extract significantly increased the grip strength to 1.25±0.07 N (P<0.01), which is 16.8% higher than the force on day 0. After exercising, the blood glucose levels in extract-fed mice were 202% higher and urea levels were 73% lower, which were both significantly different than the levels observed after control treatment. Lactate dehydrogenase was significantly higher by 314%, and glutathione peroxidase increased by 165%. In addition, the obesity markers, serum triglyceride and cholesterol, decreased to 62% and 49%, respectively, after mice were fed the extract. These data show that the T. sinensis extract provided more energy for forelimb exercise, prevented protein catabolism and muscle fatigue, and decreased the oxidative stress caused by an exhaustive workout.
    Full-text · Article · Jun 2015 · Preventive Nutrition and Food Science
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    ABSTRACT: The encrusting bryozoan Membranipora membranacea frequently colonizes late-harvested blades of the cultured Saccharina japonica. We measured the proximate compositions, amino acid and fatty acid profiles and metal contents of bryozoans, colonized blades and healthy blades. Bryozoans contained high levels of crude ash (657 g kg-1 dry weight) and arsenic (As; 49 mg kg-1 dry weight) contents, exceeding the recommended range for human food, and had relatively low levels of essential amino acids. The content of inorganic As in bryozoans was 31% of the provisional tolerable weekly intake for inorganic As established by the World Health Organization. Hence, bryozoans decrease the food and fodder quality of the seaweed product. After removing the bryozoans, we found that the seaweed blade tissues beneath the colonies had elevated levels of potassium, iodine and docosahexaenoic acid and reduced levels of copper, chromium and cadmium compared to healthy tissues. Thus, lacy crust bryozoans must be removed from the surface of seaweed prior to its use as food or fodder.
    Full-text · Article · Jan 2015 · Botanica Marina
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    ABSTRACT: Gelidium latifolium was selected as a potential resource for bioethanol production among 25 tropical red seaweed species candidates due to its high carbohydrate content. This report shows a catalytic efficiency comparison between sulfuric (H2SO4) and hydrochloric acid (HCl) as feasible catalysts, which are used for the hydrolysis of G. latifolium. H2SO4 showed better hydrolysis compared to HCl based on sugar production, catalytic efficiency, and ethanol production. These results are important for future applications of bioethanol production on an industrial scale.
    No preview · Article · Dec 2014 · Journal of Industrial and Engineering Chemistry
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    ABSTRACT: Undaria pinnatifida (Harvey) Suringar and Saccharina japonica Areschoug are two common seaweeds, and both are known to have numerous pharmacological properties that include neuroprotective effects. In a previous study, we found that the ethanol extracts of U. pinnatifida (UPE) and S. japonica (SJE) had neurite promoting activities on developing hippocampal neurons. In the present study, we studied and compared the effects of UPE and SJE on neuronal maturation. Both UPE and SJE promoted neurite outgrowth in a dose-dependent manner with optimal concentrations of 5 and 15 μg/mL, respectively. Initial neuronal differentiation was significantly promoted by UPE and SJE. Subsequently, treatment with both increased indices of axonal and dendritic cytoarchitecture, such as, the numbers and lengths of primary processes, although only UPE had a significant effect on branching frequencies. In addition, UPE and SJE showed no evidence of cytotoxicity, rather they protected neurons from naturally occurring death in vitro. These results indicate that UPE and SJE promote axodendritic maturation and neuronal survival and suggest that these algal extracts, especially UPE, have beneficial effects on the nervous system.
    Full-text · Article · Nov 2014 · The American Journal of Chinese Medicine
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    ABSTRACT: The acute-phase response (APR) is an important systemic reaction that occurs within hours of an inflammatory signal caused by physical bodily injury or microbial infection. To investigate the APR of the olive flounder (Paralichthys olivaceus) following infection with a pathogen, we established an expressed sequence tag (EST)-based cDNA microarray chip composed of 13,061 PCR-amplified cDNAs encoding unique genes selected from an olive flounder EST analysis. Microarray analyses showed that the set of genes involved in the APR was strongly up-regulated in the liver of the olive flounder after infection with Edwardsiella tarda. Among the up-regulated genes, catechol-O-methyltransferase domain-containing protein 1, six-transmembrane prostate protein, haptoglobin precursor, and toll-like receptor 5 soluble form were particularly strongly up-regulated. Interestingly, the toll-like receptor 5 soluble form, which has not yet been detected in mammals, was up-regulated as much as 250-fold upon E. tarda infection. These results suggest that the APR mechanism of fish may be regulated differently from that of mammals. The data described here contribute toward our collective understanding of APR, especially in fish.
    Full-text · Article · Sep 2014 · Veterinary Immunology and Immunopathology
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    ABSTRACT: Se conoce que el extracto de metanol del alga parda marina Ecklonia cava presenta actividad antimicrobiana contra Propionibacterium acnes. Para identificar los compuestos que confieren esta actividad antimicrobiana se fraccionó el extracto de metanol, usando cromatografía en columna de sílica gel, mediante el aumento de la polaridad del disolvente. La actividad antimicrobiana de cada fracción se determinó en términos de la concentración mínima inhibitoria. Las fracciones de hexano, éter dietílico, acetona, acetato de etilo, acetonitrilo, metanol y agua fueron producidas. La fracción de acetona presentó la mayor actividad antibacteriana (concentración mínima inhibitoria = 156 μg/mL). Con base en este resultado, la fracción de acetona se purificó por cromatografía en columna en LH-20 Sephadex y HPLC de fase inversa usando una columna Alltima C18 con un gradiente lineal de H2O-MeOH de 30 a 100%. Dos picos se eluyeron a 18.1 (P1) y 23.8 (P2) min, ambos tuvieron actividad antibacteriana marcada (concentración mínima inhibitoria = 39 μg/mL para ambos). La estructura de estos compuestos se determinó sobre la base de 1H y 13C de resonancia magnética nuclear y, mediante la comparación con valores publicados, éstos pueden ser derivados de floroglucinol diecol (P1) y florofucofuroecol-A (P2). Los resultados sugieren que florotaninos derivados de E. cava tienen actividad antimicrobiana frente a P. acnes, y por lo tanto, pueden ser útiles como aditivos naturales en los cosméticos anti-acné ylos productos farmacéuticos.
    Preview · Article · Aug 2014 · Botanical Sciences
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    ABSTRACT: In this study, the recovery of algal oil from Enteromorpha intestinalis based on an acidic-hydrothermal reaction was investigated. Overall, the algal oil yield after the acidic-hydrothermal reaction was increased under the conditions of high reaction temperature, high catalyst concentration, and long reaction time within the tested ranges. Significantly, catalyst concentration, compared with reaction temperature and time, less affected algal oil recovery. The optimal acidic-hydrothermal reaction conditions for production of algal oil from E. intestinalis were as follows-200 °C reaction temperature, 2.92 % catalyst concentration, 54 min reaction time. Under these conditions, an 18.6 % algal oil yield was obtained. By increasing the combined severity factor, the algae oil recovery yield linearly increased.
    No preview · Article · Jul 2014 · Applied Biochemistry and Biotechnology
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    ABSTRACT: This study employed a statistical methodology to investigate the optimization of conversion conditions and evaluate the reciprocal interaction of reaction factors related to the process of red-algae Gracilaria verrucosa conversion to sugars (glucose, galactose), levulinic acid and 5-hydroxymethylfurfural (5-HMF) by acidic hydrolysis. Overall, the conditions optimized for glucose formation included a higher catalyst concentration than did those for galactose, and these conditions for galactose were similar to those for 5-HMF. Levulinic acid production, meanwhile, was optimized at a higher reaction temperature, a higher catalyst concentration, and a longer reaction time than was glucose, galactose or 5-HMF production. By this approach, the optimal yields (and reaction conditions) for glucose, galactose, levulinic acid, and 5-HMF were as follows: glucose 5.29 g/L (8.46 wt%) (reaction temperature 160 °C, catalyst concentration 1.92 %, reaction time 20 min), galactose 18.38 g/L (29.4 wt%) (160 °C, 1.03 %, 20 min), levulinic acid 14.65 g/L (18.64 wt%) (180.9 °C, 2.85 %, 50 min), and 5-HMF 3.74 g/L (5.98 wt%) (160.5 °C, 1 %, 20 min).
    Full-text · Article · Jul 2014 · Bioprocess and Biosystems Engineering
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    ABSTRACT: Phlorotannins are polyphenols of marine algae, particularly brown seaweed, having multiple biological activities. A reverse phase-high performance liquid chromatography method was developed for rapid and routine quantification of two major phlorotannins, dieckol and phlorofucofuroeckol-A (PFE-A), from boiling water- and organic solvent-extracts of brown seaweeds Ecklonia cava, E. stolonifera and Eisenia bicyclis. The regression equations for dieckol and PFE-A were as follows: the concentration (mg ml(-1)) = 16.56 x peak height (cm) + 0.44, and the concentration = 20.60 x peak height (cm) + 0.11, with correlation coefficients of 0.996 and 0.999, respectively. Compared to organic solvent extraction, the recovery yield of dieckol from boiling water extracts of E. cava, E. stolonifera and E. bicyclis was 86%, 93%, and 98%, respectively. The recovery yield of PFE-A was 74%, 86% and 62%, respectively. Antioxidant activity was detected in each E. bicyclis water extract (91%), followed by E. stolonifera (90%) and E. cava (74%). Dieckol and PFE-A showed almost 9- and 7-fold stronger antioxidant activity than the standard butylhydroxytoluene, and 6-and 4-fold greater than L-ascorbic acid in molar concentration, respectively.
    Full-text · Article · Jul 2014 · Journal of Environmental Biology
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    ABSTRACT: Coralline algae, the algal whitening phenomenon-causing seaweeds, are characterized by calcareous deposits in the cell wall. The viability of the coralline algae Lithophyllum yessoense and Corallina pilulifera was quantitated using a triphenyltetrazolium chloride assay and eight calcification inhibitors. Among these inhibitors, ferric citrate showed the strongest inhibition of coralline algae viability. The concentrations of ferric citrate conferring 50% inhibition were 1.7 and 3.8 mM for L. yessoense and C. pilulifera, respectively. Thus, at a specific concentration and in a localized area, ferric citrate may be used to prevent the blooming of coralline algae.
    No preview · Article · Jun 2014 · Fisheries and Aquatic Science

  • No preview · Article · May 2014