Lignan

The lignans are a large group of polyphenols found in plants. Some examples of lignans are enterolignans, enterodiol and enterolactone. The lignans are a large group of polyphenols found in plants. Some examples of lignans are enterolignans, enterodiol and enterolactone. From lign- (Latin, 'wood') + -an (chemical suffix). Plant lignans are polyphenolic substances derived from phenylalanine via dimerization of substituted cinnamic alcohols (see cinnamic acid), known as monolignols, to a dibenzylbutane skeleton 2. This reaction is catalysed by oxidative enzymes and is often controlled by dirigent proteins. Many natural products, known as phenylpropanoids, are built up of C6C3 units (n-propylbenzene skeleton 1) derived from cinnamyl units just as terpene chemistry builds on isoprene units. Structure 3 is a neolignan, a structure formed by joining the two propylbenzene residues at other than the β-carbon atom of the propyl side chain. When a part of the human diet, some plant lignans are metabolized by intestinal bacteria to mammalian lignans enterodiol (1) and enterolactone (2). Lignans that can be metabolized to mammalian lignans are pinoresinol, lariciresinol, secoisolariciresinol, matairesinol, hydroxymatairesinol, syringaresinol and sesamin.Lignans are one of the major classes of phytoestrogens, which are estrogen-like chemicals and also act as antioxidants. The other classes of phytoestrogens are isoflavones and coumestans. Flax seed and sesame seed contain higher levels of lignans than most other foods. The principal lignan precursor found in flaxseed is secoisolariciresinol diglucoside. Other sources of lignans include cereals (rye, wheat, oat and barley - rye being the richest source), soybeans, cruciferous vegetables such as broccoli and cabbage, and some fruit, particularly apricots and strawberries. Secoisolariciresinol and matairesinol were the first plant lignans identified in foods. Typically, lariciresinol and pinoresinol contribute about 75% to the total lignan intake whereas secoisolariciresinol and matairesinol contribute only about 25%. Lignans are some of the secondary metabolites present in Cannabis sativa. Sources of lignans: A 2007 study shows the complexity of mammalian lignan precursors in the diet. In the table below are a few examples of the 22 analyzed species and the 24 lignans identified in this study.