Flaxseeds are from the Linum usitatissimum L. plant.
Flaxseeds occur in two basic varieties/colors: brown or yellow (golden linseeds).
Flaxseeds have lignan contents several times higher than other dietary sources.
Flaxseeds are principally the richest known source of lignans (9–30 mg/g (approximately 301 mg/100 g), with lignan production at 75–800 times that of cereals, legumes, other oil seeds, vegetables and fruit. The principal dietary lignan present in flaxseeds is secoisolariciresinol (2,3-bis (3-methoxy-4-hydroxybenzyl) butane-1,4-115 diol) which is stored as the conjugate SDG that occurs as a component of a linear ester-linked complex in the plant.[1:1]
Whole flaxseeds are chemically stable, but ground flaxseed meal, because of oxidation, may go rancid when left exposed to air at room temperature in as little as one week.
Flaxseeds produce a vegetable oil known as flaxseed oil or linseed oil, which is one of the oldest commercial oils.
Title: The what and who of dietary lignans in human health: Special focus on prooxidant and antioxidant effects
Publication: Trends in Food Science & Technology
Date: October 2020
Study Type: Review
Author(s): Samaneh Soleymani, Solomon Habtemariam, Roja Rahimi, Seyed Mohammad Nabavi
Institution(s): Department of Traditional Pharmacy, School of Persian Medicine, Tehran University of Medical Sciences, Tehran, Iran; Pharmacognosy Research Laboratories and Herbal Analysis Services UK, University of Greenwich, Chatham-Maritime, Kent ME4 4TB, UK; Evidence-based Evaluation of Cost-Effectiveness and Clinical Outcomes Group, The Institute of Pharmaceutical Sciences (TIPS), Tehran University of Medical Sciences, Tehran, Iran; Applied Biotechnology Research Center, Baqiyatallah University Medical Sciences, Tehran, Iran; Division of Translational Medicine, Baqiyatallah Hospital, Baqiyatallah University of Medical Sciences, Tehran, Iran
Abstract: Background: Lignans are large group of polyphenols that are formed by the coupling of two coniferyl alcohol residues. Based on their origin, lignans are broadly grouped into plant lignans such as isolariciresinol, secoisolariciresinol diglucoside, lariciresinol, and matairesinol; and mammalian lignans such as enterodiol and enterolactone. Based on the oxidation level of the lignan skeleton, they are also categorized into numerous groups such as dibenzylfuran, dibenzylbutyrolactol, dihydroxybenzylbutane, arylnaphtalene and aryltetraline lactone derivatives. Depending on structural type and concentration, numerous dietary lignans have been shown to possess biological activities including protective effect against diseases such as hormone-dependent tumors and cardiovascular diseases. Also, they display antioxidant properties in tissues and organs including the liver and the brain, lignans are found in most fiber-rich seeds such as sesame and pumpkin, and grains including barley, wheat, oats and rye. Scope and approach: This paper focus on the metabolism in humans, and recent studies on the antioxidant and possible prooxidant effects of lignans at three levels: in vitro, in vivo in animals and clinical studies. Key Findings and Conclusions: Most of the studies investigating the antioxidant effect of lignans were in vitro and animal models and only five clinical trials were found; one evaluating the effect of enterolactone on Low-density lipoprotein (LDL) peroxidation and four investigating the effects of plant lignans including flaxseed lignan components, secoisolariciresinol and sesamin on lipid peroxidation. So, lignans seem to be a valuable source for identifying new molecules for preventing various diseases especially cardiovascular disorders. Since most of studies are preclinical, however, further clinical trials are required to achieve more conclusive results.