Masakuni Tako

Gelation mechanism of agarose

Abstract The non-Newtonian behavior and dynamic viscoelasticity of a series of aqueous solutions of agarose were measured with a rheogoniometer. The flow curve, at 25°, of agarose solution approximated to plastic behavior at 0.1, 0.13, and 0.15% concentrations. Gelation occurred at concentration of 0.13% at low temperature (0°). The dynamic modulus of agarose showed a very high value at low temperature, and increased with an increase in temperature, showing a maximum value at 30°, then it decreased. In the presence of NaCl, KCl, CaCl 2 , and MgCl 2 for a solution of agarose at 0.08% concentration, the transition temperature, at which dynamic modulus decreased rapidly, was observed at 60°. Gelation was also observed at low temperature (0°) in acid and alkaline range after reaching pH values of 2.3 and 9.5, respectively, by addition of 100m m HCl, H 2 SO 4 , NaOH, and Ca(OH) 2 to a 0.08% agarose solution. A possible mode of intra- and inter-molecular hydrogen bonding within and between the agarose molecules in aqueous solution is proposed.

Antioxidant flavonoid glycosides from the leaves of Ficus pumila L.

The Okinawan folks in Japan use Ficus pumila L. as a beverage or herbal medicine to treat diabetes and high blood pressure. Four flavonoid glycosides were isolated and identified as rutin (1 and 3), apigenin 6-neohesperidose (2), kaempferol 3-robinobioside (4) and kaempferol 3-rutinoside (5). Among these compounds, rutin exhibited the strongest antioxidant activity in DPPH radical scavenging assay and superoxide radical inhibition assay. The preparation of Ooitabi leaves in water provide sufficient amount of flavonoid glycosides to the Okinawan although 50% of aqueous ethanol extracted these flavonoid glycosides more effectively. These results show the potential of Ooitabi leaves as a natural source of antioxidant for health management.

Synergistic interaction between xanthan and guar gum

Abstract The non-Newtonian behavior and dynamic viscoelasticity of a series of aqueous mixtures of xanthan and guar gum were measured with a rheogoniometer. At a concentration of 0.2% of total gums, gelation did not occur at room temperature but occurred at a low temperature (0°). A much stronger interaction was observed with a mixture of deacetylated xanthan than that with native xanthan. The maximum dynamic modulus was obtained when the ratio of xanthan to guar gum was 2:1. The transition temperatures of dynamic viscoelasticity for mixtures with native and deacetylated xanthan were observed at 25 and 30°, respectively. It was concluded that the side chains of the guar gum molecular prevent an intermolecular interaction with the side chains of the xanthan molecule. An intermolecular interaction between xanthan and guar gum at low temperature might be promoted between the periphery of the side chains of the xanthan molecule and the backbone of the guar gum molecule and dissociation takes place at the transition temperature.

Synergistic interaction between xanthan and tara-bean gum

Abstract The non-Newtonian behaviour and dynamic viscoelasticity of a series of aqueous mixtures of xanthan and tara-bean gum were measured with a rheogoniometer. At a concentration of 0·2% of total gum, gelation did not occur at room temperature, but at a low temperature (0°C). A much stronger interaction was observed with mixtures containing deacetylated, deacylated, or native xanthan than with depyruvated xanthan. The maximum dynamic modulus was obtained when the ratio of xanthan to tara-bean gum was 1:2. The dynamic viscoelastic parameters for mixtures with deacetylated and deacylated xanthan decreased rapidly at temperatures above 25 and 20°C, respectively. It was concluded that the side chains of the tara-bean gum molecule prevent an intermolecular interaction between xanthan and tara-bean gum. The results obtained support the interaction mechanism between xanthan and locust-bean gum previously proposed.

Synergistic Interaction Between Deacylated Xanthan and Galactomannan

ABSTRACT The dynamic modulus and optical rotation of a mixed solution of denatured xanthan (depyruvated and deacylated) and galactomannan (locust-bean gum and guar gum) were measured with a rheogoniometer and a polarimeter. Gelation occurred in a mixture of native xanthan with locust-bean gum at a concentration of 0.2% total gums at room temperature, but not with guar gum. A mixture of deacylated xanthan and locust-bean gum showed the highest dynamic modulus, about three times as strong ast that of a mixture with depyruvated xanthan. The dynamic modulus of a mixture of deacylated xanthan and locust-bean gum stayed at very small value in the presence of CaCl2 (6.8 mM) and urea (4.0 M). Possible binding sites between deacylated xanthan and locust-bean gum molecules are proposed.

Indicative evidence for a conformational transition in ι-carrageenan

Abstract The non-Newtonian behavior and dynamic viscoelasticity of ι-carrageenan solutions were measured with a rheogoniometer. The K salt of ι-carrageenan showed Newtonian behavior 1.5%, whereas the Ca salt of ι-carrageenan showed plastic behavior even at 0.3%. A gelation occurred in polysaccharide concentrations >1.5 and 0.5% for K and Ca salt of ι-carrageenan upon cooling, respectively. The transition temperature, at which dynamic viscoelasticity decreased rapidly, was observed at 45 or 50° at various concentrations of the Ca salt of ι-carrageenan. The dynamic modulus of the Na and K salts forms of ι-carrageenan showed a very high value at low temperature, and increased with an increase in temperature, showing a maximum value at 5°, then it decreased at 0.2% in the presence of CaCl 2 . However, in the presence of KCl, the K salt form of ι-carrageenan showed a very low dynamic modulus upon cooling. The rheological characteristics of the Ca salt of the ι-carrageenan molecule might be essentially attributed to an intramolecular association, contributed by sulfate groups of adjacent 3,6-anhydro- d -galactose and d -galactose residues through Ca 2+ ions with ionic forces.

Structural characteristics and in vitro macrophage activation of acetyl fucoidan from Cladosiphon okamuranus

We investigated a structural characteristics of acetyl fucoidan (CAF) isolated from commercially cultured Cladosiphon okamuranus. The CAF-induced macrophage activation and its signaling pathways in murine macrophage cell line, RAW 264.7 were also investigated. From the results of methylation analysis, CAF consisted of α-1→3 linked l-fucosyl residues and substituted sulfate and acetyl groups at C-4 on the main chain. CAF induced production of nitric oxide (NO), tumor necrosis factor-α and interleukin-6 in RAW 264.7 cells. Sulfate and acetyl groups of CAF involved in CAF-induced NO production. Neutralizing anti-Toll-like receptor 4 (TLR4), anti-CD14 and anti-scavenger receptor class A (SRA) but not anti-complement receptor type 3 monoclonal antibodies decreased CAF-induced NO production. The results of immunoblot analysis indicated that CAF activated mitogen-activated protein kinases (MAPKs) such as p38 MAPK, extracellular signal-regulated kinase (ERK)1/2 and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). SB203580 (p38 MAPK inhibitor) and SP600125 (SAPK/JNK inhibitor), but not U0126 (MAPK/ERK kinase 1/2 inhibitor) decreased CAF-induced NO production. The results suggested that CAF induced macrophage activation through membrane receptors TLR4, CD14 and SRA, and MAPK signaling pathways.

D-Mannose-specific interaction between xanthan and D-galacto-D-mannan

A gelation occurred in a mixed solution of xanthan and locust‐bean gum at room temperature; in contrast, gelation did not occur in a solution of xanthan and guar gum. The maximum dynamic modulus was obtained when the mixing ratio of xanthan and locust‐bean gum was 1:2 at 0.2% total gums. A mixture of deacetylated xanthan and locust‐bean gum showed the highest dynamic modulus, about twice that of the mixture of native xanthan. We concluded that the intermolecular interaction between xanthan and locustbean gum might occur between the side chains of the former and back‐bone of the latter molecules in a lock‐and‐key arrangement.

Chemical Characterization of Fucoidan from Commercially Cultured Nemacystus decipiens (Itomozuku).

Fucoidan was isolated from Nemacystus decipiens KUCKUCK which is commercially cultured at the rate of about 2,000 t/year in fields of the Okinawa Islands, in Japan. The yield of fucoidan extracted by 0.1 M HCl was 0.5% (W/W) based on the wet algae. The total carbohydrate, sulfuric acid, ash, and moisture in fucoidan was 65.8, 30.8, 22.3, and 3.8%, respectively. Fucose and galactose were identified by liquid chromatography. The molar ratio of the sugar residues in the fucoidan was estimated to be L-fucose:D-galactose:sulfuric acid=1.0:0.05:1.0. The optical rotation of the fucoidan (0.4%) showed a value of -0.315° at 60°C, then it decreased a little with decreasing temperature. The infrared spectrum of isolated fucoidan is in agreement with that of standard fucoidan. The molecular mass of fucoidan was estimated to be 2.4×10(5). The (1)H- and (13)C-NMR spectral data suggest that fucoidan is mainly composed of L-fucopyranose, 2-mono-O-sulfo-L-fucopyranose, 4-mono-O-sulfo-L-fucopyranose, and 2,4-di-O-sulfo-L-fucopyranose.

Gelatinization Mechanism of Rice Starch

ABSTRACT The non-Newtonian behavior and dynamic viscoelasticity of rice starch (Nihonbare; amylose content, 15.8%) solutions were measured with a rheogoniometer. A gelatinization of Nihonbare starch occurred above 3.0% after heating at 100 °C for 30 min. The Nihonbare starch showed shear-thinning behavior at a concentration of 2.0%, but plastic behavior above 3.0% at 25 °C. The viscosity of Nihonbare starch at a concentration of 2.0% solution decreased gradually with increase in temperature from 10 to 55 °C, then it stayed at a constant value with further increase in the temperature. However, for 4.0% solution, rapid decrease in the viscosity was observed after the temperature reached 25 °C up to 50 °C, then it stayed at a constant value. The dynamic modulus of Nihonbare starch stayed at a constant value during increase in the temperature at 4%. The tan δ of the starch showed low values, 0.28, at low temperature range and stayed at a constant up to 30 °C, then it increased a little with increasing tempera...