A comprehensive review of flaxseed ( Linum usitatissimum L.): health-affecting compounds, mechanism of toxicity, detoxification, anticancer and potential risk

Omega-6 (n-6) polyunsaturated fatty acids (PUFA) (e.g., arachidonic acid (AA)) and omega-3 (n-3) PUFA (e.g., eicosapentaenoic acid (EPA)) are precursors to potent lipid mediator signalling molecules, termed “eicosanoids,” which have important roles in the regulation of inflammation. In general, eicosanoids derived from n-6 PUFA are proinflammatory while eicosanoids derived from n-3 PUFA are anti-inflammatory. Dietary changes over the past few decades in the intake of n-6 and n-3 PUFA show striking increases in the (n-6) to (n-3) ratio (~15 : 1), which are associated with greater metabolism of the n-6 PUFA compared with n-3 PUFA. Coinciding with this increase in the ratio of (n-6) : (n-3) PUFA are increases in chronic inflammatory diseases such as nonalcoholic fatty liver disease (NAFLD), cardiovascular disease, obesity, inflammatory bowel disease (IBD), rheumatoid arthritis, and Alzheimer's disease (AD). By increasing the ratio of (n-3) : (n-6) PUFA in the Western diet, reductions may be achieved in the incidence of these chronic inflammatory diseases.

Apoptosis of mammalian cells is accompanied by various morphological changes including nuclear condensation, DNA fragmentation and cell surface changes. Methods developed over the past few years have focused on detection of DNA-associated changes that occur rather late in apoptosis. However, detection of apoptosis at early stages, before gross morphological changes, is critical for understanding the pathways of programmed cell death. In this report, we describe a rapid and reliable assay for detecting early stages of apoptosis. This assay is based on the observation that soon after initiating apoptosis, most mammalian cell types translocate phosphatidylserine (PS) from the inner face of the plasma membrane to the cell surface. Once on the cell surface, PS can be specifically detected by staining with fluorescein isothiocyanate (FITC)-labeled annexin V (annexin V-FITC), a protein with a strong, natural affinity for PS. Using this assay, we have detected apoptotic cells in culture, in real time, using fluorescence microscopy and flow cytometry. In combination with vital dye staining, the progressive stages of apoptosis were observed. PS redistribution occurs earlier than DNA-associated changes and membrane leakage. In addition, PS externalization occurs during apoptosis induced by a variety of stimuli. Therefore, the annexin V binding assay provides an excellent indicator for the early stages of apoptosis.

  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, SDG is 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.