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Idealized structure of lignin from a softwood Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. [ 1 ] Lignins are particularly important in the formation of cell walls , especially in wood and bark , because they lend rigidity and do not rot easily.
The inclusion of lignin makes the secondary cell wall less flexible and less permeable to water than the primary cell wall. [4] In addition to making the walls more resistant to degradation, the hydrophobic nature of lignin within these tissues is essential for containing water within the vascular tissues that carry it throughout the plant.
Flax seeds and sesame seeds contain high levels of lignans. [1] [8] The principal lignan precursor found in flaxseeds is secoisolariciresinol diglucoside.[1] [8] Other foods containing lignans include cereals (rye, wheat, oat and barley), soybeans, tofu, cruciferous vegetables, such as broccoli and cabbage, and some fruits, particularly apricots and strawberries. [1]
Lignin is a polymer with an inert nature that forms the structures of woody plants. The ratio of the three monolignols as well as their linkages varies depending on the plant species. For example, Norway spruce lignin is almost entirely derived from coniferyl alcohol , whereas paracoumaryl alcohol is the main monomer of lignin in grasses . [ 4 ]
A cell wall is a structural layer that surrounds some cell types, found immediately outside the cell membrane.It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, and functions as a selective barrier. [1]
Suberins and lignins are considered covalently linked to lipids and carbohydrates, respectively, and lignin is covalently linked to suberin, and to a lesser extent, to cutin. [1] [2] [3] Suberin is a major constituent of cork, and is named after the cork oak, Quercus suber. Its main function is as a barrier to movement of water and solutes.
The name derives from the Ancient Greek word πολύς (polus, meaning "many, much") and the word ‘phenol’ which refers to a chemical structure formed by attachment of an aromatic benzenoid ring to a hydroxyl (-OH) group (hence the -ol suffix). The term "polyphenol" has been in use at least since 1894.
Lignin confers structural integrity to plants. Lignin is so heterogeneous and so recalcitrant that its value is almost exclusively measured as a fuel. hemicellulose is composed of branched polysaccharides. A particular problem is that hemicellulose is covalently linked to lignin, usually through ferulic acid component of the
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