Flaxseed Lignan Extract Capsules (SDG)

Flax lignans are not flax oil, and the distinction matters on the purchase order more than anywhere else in this category. This product is a defatted extract of the hull, or seed coat, of Linum usitatissimum L. — the fraction where the seed concentrates its lignans — while the alpha-linolenic acid sits in the cotyledon and is pressed out separately as linseed oil under an entirely different tariff heading. The extract is standardised on secoisolariciresinol diglucoside (SDG), C32H46O16, molecular weight 686.7, CAS 158932-33-3; some reference-standard suppliers catalogue the identical compound as 148244-82-0, so check which number a competitor's certificate of analysis is quoting before assuming a mismatch. SDG does not occur free in the seed. In the hull it is esterified into a lignan macromolecule joined through 3-hydroxy-3-methylglutaric acid, which is why assay methods hydrolyse the extract under alkaline conditions before HPLC, and why two laboratories can report meaningfully different numbers on the same drum if their hydrolysis steps differ. Always buy the specification together with the method. Standard grades are 20%, 35% and 40% SDG; a 250 to 500 mg fill in a size 0 or size 1 capsule therefore delivers roughly 50 to 200 mg SDG per unit, which is the range brands normally build their serving size around. Two contaminants deserve specific attention on flax. It is a documented cadmium accumulator — Regulation (EU) 2023/915 permits 0.50 mg/kg in linseed against 0.10 mg/kg for most other oilseeds — and the seed carries the cyanogenic glycosides linustatin and neolinustatin, for which the same regulation sets 250 mg/kg hydrocyanic acid in unprocessed linseed not placed on the market for the final consumer and 150 mg/kg in retail linseed. Both are tested batch by batch and reported on the certificate of analysis; those regulatory figures apply to the seed as a raw material, and the finished extract is controlled to a tighter internal limit. On allergens, the extract carries no milk, egg, soy, fish, crustacean or tree nut input; flax is not a gluten-bearing cereal, but because it is grown in rotation with wheat and barley we test for gluten cross-contact rather than assume the absence. With the standard HPMC shell the finished capsule is vegan and vegetarian; a gelatin shell would make it bovine and must be declared.