Flaxseed Lignans: Source, Biosynthesis, Metabolism, Antioxidant Activity, Bio-Active

Lignans are compounds found in a variety of plant materials including flaxseed, pumpkin seed, sesame seed, soybean, broccoli, and some berries. The major lignan in flaxseed is called secoisolariciresinol diglucoside (SDG).Once ingested, SDGis converted in the colon into active mammalian lignans, enterodiol, and entero-lactone, which have shown promise in reducing growth of cancerous tumors, especially hormone-sensitive ones such as those of the breast, endometrium, and prostate. Known for their hydrogen-donating antioxidant activity as well as their ability to complex divalent transition metal cations, lignans are propitious to human health. The extraction methods vary from simple to complex depending on extraction, separation, fractionation, identification, and detection of the analytes. Flax lignan is also a source of useful biologically active components found in plant foods, such as phytochemicals, and it is considered a functional food. The safety issues in flaxseed are also briefly discussed. Flax is rich in alpha-linolenic acid (ALA), the essential omega-3 fatty acid, and phytochemicals such as lignans. Flaxseed has been the focus of increased interest in the field of diet and disease research due to the potential health benefits associated with its biologically active components. this article provides a review of the health benefits of the flaxseed lignan secoisolariciresinol diglycoside (SDG). Among the reported potential health benefits associated with flaxseed (FS) and/or low oil meal (FLM) are decreased risk of cardiovascular disease,  decreased risk of cancer, particularly of the mammary and prostate gland; anti-inflammatory activity; laxative effect; and alleviation of menopausal symptoms and osteoporosis. Phytoestrogen supplementation with flaxseed have been reported to increase vaginal cell maturation, an indication of estrogen activity in postmenopausal women, and to significantly reduce menopause symptom scores, particularly hot flashes and vaginal dryness. Also research has demonstrated the ability of SDG to scavenge hydroxyl radicals and shown that SDG have potent antioxidant activity.  Lignans act as either estrogen agonists or antagonists and are natural antioxidants with potential health benefits. This review provides an overview of the flaxseed antioxidant activities and suggests that flaxseed lignans may be used as natural
antioxidants. More in vivo studies are needed to ascertain the overall health effects of lignans. (Editor's Comments)