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What is Secoisolariciresinol glucoside (SDG)?
Secoisolariciresinol diglycoside, or SDG, is a plant lignan most notably
found in flaxseed (linseed). SDG is classified as a phytoestrogen since it is a
plant-derived, nonsteroid compound that possesses estrogen-like activity. SDG has
weak estrogenic activity.
Lignans are one of the two major classes of phytoestrogens; the other class is
the isoflavones. Plant lignans are polyphenolic substances derived from phenylalanine via dimerization of
substituted cinnamic alcohols. Mammalian lignans are lignans derived from plant lignans.
For example, following ingestion, SDG is converted to the aglycone secoisolariciresinol, which
is then metabolized to the mammalian lignans enterolactone and enterodiol. Most of the effects of oral SDG are mediated
by enterolactone and enterodiol.
The molecular formula of SDG is C32H46O16, and its molecular weight is 686.71 daltons. The aglycone of SDG is also known as 2, 3-bis
(3-methoxy-4-hydroxybenzyl) butane-1, 4-diol. Enterolactone is also known as trans-2, 3-bis [(3-hydroxylphenyl) methyl]-butyrolactone. It is represented
by the following structural formula:
ACTIONS AND PHARMACOLOGY
SDG has estrogenic and antioxidant activities. It may also have antiestrogenic,
anticarcinogenic, antiatherogenic and antidiabetic activities.
MECHANISM OF ACTION
SDG, as well as its mammalian lignan metabolites, enterolactone (EL) and enterodiol (ED), have
weak estrogenic activity as measured in in vivo and in vitro assays.
SDG, EL and ED have a number of antioxidant activities, including inhibition of lipid
peroxidation and scavenging of hydroxy radicals. SDG also has anti-platelet-activation factor (PAF) activity. PAF can
induce the release of reactive oxygen species from neutrophils. SDG, via its metabolite EL, has been found to inhibit
estrogen synthase (aromatase) and to stimulate the synthesis of sex hormone binding globulin (SHBG). Both of these actions could account for the possible
anti-estrogen activity of SDG.
The possible anticarcinogenic, antiatherogenic and antidiabetic activities of SDG are thought to be
due, in large part, to the antioxidant activities of its metabolites EL and ED.
SDG, following ingestion, is transported to the large intestine, where it is hydrolyzed by
friendly bacteria to the aglycone secoisolariciresinol. Secoisolariciresinol, in turn, is
metabolized by friendly bacteria in the large intestine to the mammalian lignans
EL and ED. EL and ED are absorbed from the large intestine. Little is known about the distribution of EL and ED to the various tissues of the body. It is known that
ED and EL undergo conjugation in the liver with glucuronate and sulfate. The glucuronate and sulfate conjugates of ED
and EL are excreted in the urine and in the bile.
There appears to be considerable individual variation in the absorption and metabolism of the SDG metabolites ED and EL.
INDICATIONS AND USAGE
There is evidence in in vitro and animal research that SDG may have some
ability to reduce cholesterol levels and protect against atherosclerosis; it may also have some anticancer and antidiabetic
Rabbits fed a high-cholesterol diet supplemented with flaxseed had 46% less atherosclerotic development than rabbits fed the same diet without flaxseed. Still
better results were obtained (73% reduction in atherosclerosis) when the diet was supplemented with SDG
instead of flaxseed. These effects were associated with reduced serum levels of cholesterol and LDL-cholesterol and increased levels of HDL-cholesterol.
SDG has exhibited a number of anticancer effects in in vitro and animal studies. SDG-treated rats were significantly
protected against experimentally induced mammary cancer in one experiment. Subsequently, it was demonstrated that SDG significantly inhibited
experimentally induced mammary tumor multiplicity in a dose-dependent fashion in rats, with more inhibition at higher doses. Flaxseed alone did not significantly affect tumor
size, multiplicity or incidence in this study, but both flaxseed and SDG delayed progression of tumorigenesis. In another recent animal study, supplemental SDG
decreased metastatic pulmonary melanoma tumor size in a dose-dependent fashion, compared with controls. Research continues.
In an animal model of human type 1 diabetes, SDG was said to significantly prevent this form of diabetes.
Prevention was associated with a decrease in the serum and pancreatic lipid peroxidation product malondialdehyde. The researcher concluded
that IDDM is mediated through oxidative stress and that SDG reduces this stress and thus helps prevent development of diabetes. In another experiment, SDG
significantly prevented the development of streptozotocin-induced diabetes in rats. Clinical trials are needed.
CONTRAINDICATIONS, PRECAUTIONS, ADVERSE REACTIONS
SDG is contraindicated in those who are hypersensitive to any component of an SDG-containing product.
Pregnant women and nursing mothers should avoid the use of SDG supplementation.
Women with estrogen receptor-positive tumors should discuss the advisability of the use of SDG-containing
products with their physicians before deciding to use them.
There are no reports of overdosage.
DOSAGE AND ADMINISTRATION
SDG nutritional supplements are currently being developed, and there are no dosage recommendations at present.
SDG is present in flaxseed at levels of 0.6% to 1.8% and in much smaller amounts in flaxseed oil.
Kitts DD, Yuan YV, Wijewickreme AN, Thompson LU. Antioxidant activity of the flaxseed lignan secoisolariciresinol diglycoside and its mammalian lignan metabolites enterodiol and enterolactone. Mol Cell Biochem. 1999; 202:91-100.
Li D, Yee JA, Thompson LU, Yan L. Dietary supplementation with secoisolariciresinol diglycoside (SDG) reduces experimental metastasis of melanoma cells in mice. Cancer Letters. 1999; 142:91-96.
Pool-Zobel BL, Adlercreutz H, Glei M, et al. Isoflavonoids and lignans have different potentials to modulate oxidative genetic damage in human colon cells. Carcinogenesis. 2000; 21:1247-1252.
Prasad K. Hydroxyl radical-scavenging property of secoisolariciresinol diglucoside isolated from flax-seed. Mol Cell Biochem. 1997; 168:117-123.
Prasad K. Oxidative stress as a mechanism of diabetes in diabetic BB prone rats: effect of secoisolariciresinol diglucoside (SDG). Mol Cell Biochem. 2000; 209:89-96.
Prasad K. Reduction of serum cholesterol and hypercholesterolemic atherosclerosis in rabbits by secoisolariciresinol diglucoside isolated from flaxseed. Circulation. 1999; 99:1355-1362.
Prasad K, Mantha SV, Muir AD, Westcott ND. Protective effect of secoisolariciresinol diglucoside against streptozotocin-induced diabetes and its mechanism. Mol Cell Biochem. 2000; 206:141-150.
Schottner M, Spiteller G. Lignans interfering with 5alpha-dihydrotestosterone binding to human sex hormone-binding globulin. J Nat Prod. 1998; 61:119-121.
Thompson LU, Seidl MM, Rickard SE, et al. Antitumorigenic effect of a mammalian lignan precursor from flaxseed. Nutr Cancer. 1996; 26:159-165.
See below for an image of a Flax Hulls jar
Each jar contains 150gm of concentrated
natural organic flax hulls
The above information is provided for general
educational purposes only. It is not intended to replace competent
health care advice received from a knowledgeable healthcare professional.
You are urged to seek healthcare advice for the treatment of any
illness or disease.
Health Canada and the FDA (USA) have not evaluated these
statements. This product is not intended to diagnose, treat, cure, or prevent