Chitosan, a polysaccharide made up of b-1,4-linked D-glucosamine residues, is produced by deacetylation of chitin obtained from crab and prawn shells. This polysaccharide is not specifically hydrolyzed by mammalian digestive enzymes, and only limited hydrolysis may occur by the action of enzymes produced by bacterial flora. In recent years, chitosan has attracted much attention as a new biomedical material owing to its unique antibacterial, 1,2) hypoglycemic, [3][4][5] wound-healing, 6,7) and hypocholesterolemic [8][9][10] activities as well as others.11) Even though chitosan has various biologically important properties, its high molecular weight and insolubility in the neutral pH region may restrict its use in vivo. In addition, although the toxicity of chitosan is known to be low, 11) some adverse effects have been reported, including excessive excretion of essential fatty acids 12) and decreased absorption of fat-soluble vitamins and minerals. 13) We consider that it is worthwhile to study the functional properties of the oligosaccharides made from chitosan, because these oligosaccharides, as distinct from chitosan itself, have lower viscosity and are soluble in neutral aqueous solutions. In addition, their toxicity is very low. The biological activities of each of the chitooligosaccharides, however, remain to be studied further.In the present paper, the antioxidant activities of several chitooligosaccharides, especially chitobiose and chitotriose, were studied in different in vitro systems. MATERIALS AND METHODS MaterialsPhenazine methosulfate, nitro blue tetrazolium, pyridoxamine dihydrochloride, D-glucosamine hydrochloride, Trolox (2-carboxy-2,5,7,8-tetramethyl-6-chromanol, a water-soluble a-tocopherol analogue), aminoguanidine hydrochloride, and horseradish peroxidase (Type XII) were obtained from Sigma-Aldrich (St. Louis, MO, U.S.A.). A series of chitooligosaccharide hydrochlorides, di-N-acetylchitobiose, and tri-N-acetylchitotriose were purchased from Seikagaku (Tokyo, Japan). Chelex-100 was obtained from Nippon Bio-Rad (Yokohama, Japan).Inhibition of H 2 O 2 -Induced Hydroxylation of Benzoate Hydroxylation of benzoate by H 2 O 2 was measured by the method of Giardino et al. 22) except that CuSO 4 was supplemented to the reaction mixture. Briefly, 100 mM sodium phosphate buffer (pH 7.4) containing 30 mM sodium benzoate, 10 mM H 2 O 2 , and 0.1 mM CuSO 4 was incubated for 16 h at 37°C in the presence and absence of a test compound. Then the amount of salicylate formed by the reaction was determined by HPLC with a TSK gel ODS-80TM column (150ϫ4.6 mm, 5 mm; Tosoh, Tokyo, Japan). The mobile phase was 10% (v/v) acetonitrile containing 20 mM potassium dihydrogen phosphate, and chromatography was performed at a flow rate of 1.0 ml/min and at a column temperature of 37°C. Salicylate was monitored by measuring fluorescence at excitation and emission wavelengths of 308 and 410 nm, respectively. Scavenging of Hydroxyl Radicals Produced by Photolysis of Zinc OxideThe hydroxyl radical-scavenging activities of tes...

D-mannose is an essential monosaccharide constituent of glycoproteins and glycolipids. However, it is unknown how plasma mannose is supplied. The aim of this study was to explore the source of plasma mannose. Oral administration of glucose resulted in a significant decrease of plasma mannose concentration after 20 min in fasted normal rats. However, in fasted type 2 diabetes model rats, plasma mannose concentrations that were higher compared with normal rats did not change after the administration of glucose. When insulin was administered intravenously to fed rats, it took longer for plasma mannose concentrations to decrease significantly in diabetic rats than in normal rats (20 and 5 min, respectively). Intravenous administration of epinephrine to fed normal rats increased the plasma mannose concentration, but this effect was negated by fasting or by administration of a glycogen phosphorylase inhibitor. Epinephrine increased mannose output from the perfused liver of fed rats, but this effect was negated in the presence of a glucose-6-phosphatase inhibitor. Epinephrine also increased the hepatic levels of hexose 6-phosphates, including mannose 6-phosphate. When either lactate alone or lactate plus alanine were administered as gluconeogenic substrates to fasted rats, the concentration of plasma mannose did not increase. When lactate was used to perfuse the liver of fasted rats, a decrease, rather than an increase, in mannose output was observed. These findings indicate that hepatic glycogen is a source of plasma mannose.

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Bloodstain age could be estimated from the ratio of oxyhemoglobin/total hemoglobin (fractional oxyhemoglobin) in the bloodstain by this present method, if the temperature at which the bloodstain had been kept was known. The oxyhemoglobin was determined with an oxygen electrode immersed in water in which the oxygen had been depleted, and the total hemoglobin was determined by conventional colorimetry (cyanomethemoglobin method). Ages of prepared bloodstain samples (within 24 h after bleeding) were estimated by this present method, which requires only 20 microliters of bloodstain and only 5 min for the whole analysis.