Low molecular weight polymannuronate

Details Low molecular weight polymannuronate Low molecular weight polymannuronate

2001-10-02

2004-06-08

Wilson, James O. (Department: 1623)

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Carbohydrate doai

C514S779000, C514S866000, C514S911000, C536S003000, C426S575000

Reexamination Certificate

active

06747015

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to low molecular weight polymannuronate, and more particularly, the present invention relates to an isolated low molecular weight polymannuronate composition, and a process for preparing thereof from high molecular weight alginate. Further, the present invention pertains to a nutritional composition and a pharmaceutical composition comprising the composition, and a method of treatment of certain conditions using thereof.
2. Description of the Related Art
The incidence of many cardiovascular diseases that are hard to treat such as hypertension, arteriosclerosis, angina pectoris, myocardial infarction and cerebral thrombosis, as well as obesity and diabetes, are increasing due to excessively nutritional diet which includes high fat and high protein, and lack of exercise. There are increasing interests in the prevention and treatment of such diseases. It is preferable to prevent and/or treat these diseases or conditions with dietary foods supplemented with extracts from natural sources rather than with artificially synthesized products because such natural products are normally considered safe and more desirable by the consumer.
Reflecting such trends, there have been much research and development focusing on dietary fibers. Certain dietary fibers were known to have favorable effects on the prevention of constipation and obesity as well as the prevention of geriatric diseases such as thrombosis, arteriosclerosis and hyperlipidemia. J. Ame. Clin. Nutr. 48:748-753, 1988; J. Ame. Clin. Nutr. 52:495-499, 1990; J. Ame. Clin. Nutr. 124:78-83, 1994.
Among dietary fibers, high molecular weight alginate, a dietary fiber component constituting 20-30% of the cell-wall polysaccharides in marine algae (e.g. brown seaweed, sea tangle, gulfweed, hiziki), was known as having effects on lowering cholesterol levels in vivo and repressing obesity. J. Jap. Nutr. 26(3):78-83, 1974; J. Jap. Nutr. 33(6):273-281, 1974; Jap. J. Fisheries 59(5):879-884, 1993.
At present, many alginate-containing products are being manufactured and sold. However, the alginates contained in the products are produced by simple extraction and processing from raw seaweed materials, and are of high molecular weight, which is more than about 4 million daltons. High molecular weight alginate is a block polymer of mannuronate (M) and guluronate (G) monomers. The alginate in its high molecular weight form has high viscosity and low solubility in water. With the high viscosity and low water solubility, it is not easy to add the high molecular form of alginate to foods (especially into beverages) in high concentrations.
Japanese Laid-Open Patent Publication Hei 6-7093 discloses a use of low molecularized alginate as supplement to functional drinks. The term “low molecularized alginate” as used herein refers to the state in which polyguluronate and polymannuronate of Mw. 10-900 kDa are mixed. Compared with high molecular weight alginate, low molecularized alginate is known to have lower viscosity and higher solubility, and to have increased beneficial effects on cholesterol levels.
Conventional methods used to prepare low molecularized alginate from high molecular forms include acid-alkali hydrolysis method [Haug, A., Larsen, B. and Smidsrod, O., Acta Chem. Scand., 20(1):183-190, 1966; Hirst, E. and Rees, D. A. J. Chem. Soc., 9:1182-1187, 1965; Hirst, E. L., Percival, E. and Wold, J. K. J. Chem. Soc., 8:1493-1499, 1964], hydrolysis under heat and pressure [Japanese Patent Laid-Open Publication Hei 6-7093, 1994; Kimura, Y., Watanabe, K. and Okuda, H., J. Ethnopharmacology 54:47-54,1996] and hydrolysis by enzymes [Doubet, R. S. and Quatrano, R. S., Appl. Environ. Microbiol. 47(4):699-703, 1984; Dunne, W. M. and Buckmire, F. L. A., Appl. Environ. Microbiol. 50(1):562-567, 1985; Hansen, J. B. and Nakamura, L. K. Appl. Environ. Microbiol. 49(4):1019-1021, 1985; Haug, A. and Larsen, B., Carbohydr. Res. 17:297-308, 1971; Romeo, T. and Preston, J. F., Biochemistry 25(26):8385-8391, 1986; Yonemoto, Y., Murata, K., Kimura, A., Yamaguchi, H. and Okayama, K., J. of Fermen. and Bioengin. 72(3):152-157, 1991].
The acid-alkali hydrolysis method is difficult to adapt to industrial scale due to deterioration of product quality, corrosion of reactors, need for a substantial amount of neutralizing agents and troublesome handling of strong acids. The second method for preparing low molecularized alginate by heating alginate at 100-200° C. under pressure, also has defects, in that the reaction takes a long time and is costly because the process is carried out at high temperatures of more than 100° C. under high pressure. The enzyme-hydrolysis method is not appropriate for industrialization due to long reaction time.
As mentioned above, compared with high molecular weight alginate, low-molecularized alginate has increased effects on decreasing cholesterol levels and has improved physical properties such as solubility. Thus, the low molecularized alginate is expected to be useful for health-aid foods.
The low-molecularized alginate is a mixture including polymannuronate, polyguluronate, and some copolymers of the mannuronate and guluronate. However, polymannuronate in an isolated form is not known. Nor is it known what effects it will have on decreasing cholesterol levels. Polymannuronate is only known in its calcium salt as a material for controlling the levels of toxic elements in patients with chronic uremia (Kulbe et al., U.S. Pat. No. 4,689,322), or as a cell- or tissue-coating material to protect transplanted cells or tissue following transplantation (Dorian et al., U.S. Pat. No.5,656,468).
SUMMARY OF THE INVENTION
One aspect of the present invention provides a method of preparing a polymannuronate composition. The method comprises: providing alginate; hydrolyzing the alginate to form a mixture comprising polymannuronate and polyguluronate, wherein the polymannuronate has a molecular weight ranged from about 4,000 to about 500,000; and isolating the polymannuronate from the mixture.
In the method, the provision of the alginate comprises extracting the alginate from marine algae. The alginate has a molecular weight from about 2,000,000 to about 4,000,000. The hydrolysis is carried out for about 20 minutes to about 3 hours. Alternatively, the hydrolysis is carried out for about 40 minutes to about 2 hours, or for about 1 hour to about 1.5 hours. The hydrolysis comprises adding one or more acids to the alginate and heating the mixture of the alginate and the acid. A representative group of organic acid is selected from the group consisting of citric acid, malic acid, oxalic acid, lactic acid, succinic acid, tartaric acid and acetic acid. Preferably, the organic acid is acetic acid. The concentration of the organic acid is preferably from about 0.2 M to about 0.6 M. The acids at 0.4 M concentration have pH from about 3.2 to about 4.0, preferably from about 3.4 to about 3.8. Preferably, the acids are organic acids. Following hydrolysis, the isolation of polymannuronate comprises adjusting pH of the mixture to a range from about 2.5 to about 3.5. Preferably, the pH of the mixture is adjusted to a range from about 2.8 to about 3.0. The isolation of polymannuronate further comprises forming a precipitate in the mixture and collecting a supernatant, in which the polymannuronate is dissolved, and further comprises precipitating the polymannuronate from the collected supernatant.
A further aspect of the present invention provides a polymannuronate composition prepared by the method. The polymannuronate prepared by the method has a molecular weight from about 4,000 to about 500,000. Preferably, the molecular weight is from about 10,000 to about 100,000, and more preferably from about 25,000 to about 80,000, furthermore preferably from about 40,000 to about 50,000. The polymannuronate composition has a purity from about 70 wt. % to about 98 wt. %. Preferably, the purity is from about 80 wt. % to about 97 wt. %, more preferably from about 90 wt. % to a

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