Chemistry: natural resins or derivatives; peptides or proteins; – Lignins or derivatives
Reexamination Certificate
2003-04-02
2004-10-19
Nutter, Nathan M. (Department: 1711)
Chemistry: natural resins or derivatives; peptides or proteins;
Lignins or derivatives
C530S507000
Reexamination Certificate
active
06806356
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an improved process for the extraction, isolation, and purification of secoisolariciresinol diglycoside (SDG) from de-fatted flaxseed.
Flaxseed is presently grown for its oil content, used primarily as an industrial oil. The scientific literature contains an abundance of reports on the chemistry and physical properties of various components derived from de-fatted flaxseed. Recently, considerable interest has been demonstrated in a class of minor compounds contained in flaxseed collectively referred to as lignans.
Lignans are generally dimers containing a dibenzylbutane skeleton. When part of the human diet, these compounds are believed to be converted into the mammalian lignans known as enterolactone and enterodiol. (Thompson et al. “Mammalian Lignan Production from Various Goods”,
Nutr. Cancer
16:43-52, (1991).) The principal lignan found in flaxseed is secoisolariciresinol diglucoside, referred to hereinafter as SDG.
Flaxseed typically contains 40% by weight fat (“linseed oil”). De-fatted (hexane-extracted) flax seed contains a residue of about 2% by wt. fat, with the remainder comprising: 46% by wt. fiber (both water-soluble fiber or “mucilage,” acidic heterogeneous polysaccharides that contain galacturonic acid, galactose, rhamnose, and xylose, comprising 30-40% of the total fiber present, and water-insoluble fiber, which comprises 60-70% of the total fiber present); 10% total other carbohydrates, including lignans; 35% by wt. protein; 6-7% ash.
Appreciable amounts of free SDG do not occur in the de-fatted flaxseed. This compound must be liberated by alkaline hydrolysis of various ester-linked polymers. According to the literature, the available SDG in de-fatted flaxseed ranges from 0.9% to 3.0% by wt. (Thompson et al. “Mammalian Lignan Production from Various Goods”,
Nutr. Cancer
16:43-52, (1991).)
There is considerable published evidence indicating that lignans as a class of compounds exhibit a broad spectrum of biological activities, including anti-tumor, anti-mitotic, anti-oxidant, anti-viral, weak estrogenic and anti-estrogenic activities. Studies conducted by the chemotherapy program of the National Cancer Institute indicate that some lignans prevent the growth of tumors. (Thompson et al, “Anticarcinogenic Effect of a Mammalian Lignan Precursor from Flaxseed”,
Proc
. 55
th
Flax Institute of U.S.A
., Fargo, N. Dak., 46-50 (1194).)
Even though there would appear to be very significant commercial uses for lignans like SDG in food supplements, nutraceuticals, and medicines, SDG has remained a laboratory curiosity, principally because it is available in only very limited quantities. To date, only one commercial process has been developed for the extraction and isolation of SDG from flaxseed. Disclosed herein is an improved process for extracting and isolating SDG from de-fatted flaxseed in order to make the compound available less expensively not only in large quantities, but at a purity suitable for use as a nutritional supplement or nutraceutical.
In 1956 Bakke and Klosterman described a laboratory process for extracting SDG from defatted flaxseed using equal parts of 95% ethanol and 1,4-dioxane. (Bakke and Klosterman, “A New Diglucoside from Flaxseed”,
Proceedings of the N. Dakota Academy of Science
10:18-22 (1956).)
Prior publications also refer to methanolysis of complexed SDG (i.e. the ester-linked polymers) and to the use of a sodium or barium methoxide for methanolysis to release non-complexed SDG.
U.S. Pat. No. 5,705,618 issued to Wescott et al, entitled “Process for Extracting Lignans from Flaxseed,” teaches a process for extracting and isolating SDG from de-fatted flaxseed that employs the following sequence of operations:
1.) De-fatted flaxseed meal is contacted with an “aliphatic alcohol solvent” (i.e. mixtures of methanol, ethanol, isopropanol, or butanol with water) to extract the SDG-containing lignan precursor.
2.) Residual solids are separated from the lignan-rich alcohol-water solvent and the lignan-containing extract is then concentrated by removing solvent by distillation until a syrup is obtained.
3.) SDG is liberated from its lignan precursor compounds by hydrolysis of the syrup at an elevated pH.
4.) The hydrolyzed aqueous concentrate is subjected to a liquid/liquid partition to further enrich the SDG. The preferred embodiment calls for the use of ethyl acetate to remove impurities that include the methyl esters of cinnamic acids and other cinnamic acid derivatives. Alternatively, the SDG-containing aqueous phase may be subjected to contact with an anion exchange resin to remove impurities.
5.) The aqueous hydrolysate is subjected to chromatographic separation using reverse-phase high-pressure liquid chromatography (“HPLC”) to isolate SDG.
U.S. Pat. No. 5,705,618 teaches the use of mixtures of aliphatic alcohols and water as the extraction solvent, with preference for alcohol-to-water ratios ranging from 1.85:1 to 3:1.
SUMMARY OF THE INVENTION
The present invention employs mixtures of acetone and water instead of aliphatic alcohols and water as the extraction solvent to extract SDG from de-fatted flaxseed.
In accordance with one aspect of the invention, a process for extracting secoisolariciresinol diglycoside (SDG) from de-fatted flaxseed is described. The process comprises contacting defatted flaxseed with an extraction solvent of acetone and water, extracting the de-fatted flaxseed with the extraction solvent to extract SDG-containing compounds, removal of solvents, followed by alkaline hydrolysis of the extract to liberate free SDG or its salts.
In accordance with another aspect of the present invention, a process for preparing a secoisolariciresinol diglycoside (SDG) concentrate from de-fatted flaxseed is disclosed. The process involves extracting defatted flaxseed with an extraction solvent of acetone and water to obtain an SDG-containing extract, separating residual solids from the SDG-containing extract, removing acetone to provide an acetone stripped extract, lowering the pH of the acetone stripped extract to precipitate SDG, separating precipitated SDG from the acetone stripped extract, subjecting the precipitated SDG in an aqueous slurry to hydrolysis to liberate free SDG and recovering the free SDG from the aqueous slurry.
In accordance with particular aspects of the invention, the precipitated SDG in the extract solution is subjected to hydrolysis to free the SDG from polymeric lignan precursor compounds. In accordance with particularly useful embodiments of the present invention, calcium hydroxide is used to liberate free SDG. The resulting SDG concentrates obtained using calcium hydroxide are non-hygroscopic and easily separated from insoluble calcium salts to provide a product of relatively high purity.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an improved process for the extraction, isolation, and purification of secoisolariciresinol diglycoside (SDG) from de-fatted flaxseed. The process of the invention utilizes an extraction solvent comprising acetone and water to extract SDG from de-fatted flaxseed. The acetone-water solvent increases efficiency and selectivity of the extraction. Furthermore, the acetone can be easily removed after extraction and reused, thereby minimizing solvent usage.
The proportion of acetone to water will typically range from about 35% acetone/65% water by weight to about 65% acetone/35% water by weight. In accordance with one embodiment, the solvent contains about 45% acetone/55% water by weight.
The acetone-water solvent will typically be employed in a ratio of about 6 or more parts by weight solvent mixture to about 1 part by weight de-fatted flaxseed. Preferably, the solvent to feedstock ratio is in the range of about 12:1 to 16:1.
Although the extraction may be performed over a wide range of temperatures for various periods of time, in accordance with one embodiment, it is performed at acetone reflux for about 90 minutes with vigorous agitation.
The mixture is then filtered or centrifuged to remove the undissolv
Dobbins Thomas A.
Wiley David B.
Nutter Nathan M.
Thompson Hine LLP
Wiley Organics, Inc.
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