Lignan 1831262 221600545 2008-06-25T06:31:26Z 99.153.37.50 Normalize units in flax seed table. {{distinguish|Lignin}} The '''lignans''' are a group of [[chemical compound]]s found in [[plant]]s, particularly in flax seed. 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 the [[isoflavones]], and [[coumestan]]s. Plant lignans are poly[[phenol]]ic substances derived from [[phenylalanine]] via [[dimerization]] of substituted cinnamic alcohols (see [[cinnamic acid]]), known as [[monolignol]]s, to a [[dibenzylbutane]] skeleton '''2'''. This reaction is [[catalysis|catalysed]] by [[oxidative enzyme]]s and is often controlled by [[dirigent protein]]s. [[Image:Lignan.svg|center|300px]] Many natural products, known as [[phenylpropanoid]]s, are built up of C6C3 units (a propylbenzene skeleton '''1''') derived from cinnamyl units just as [[terpene]] chemistry builds on [[isoprene]] units. Structure '''3''' is a neolignan. Some examples of lignans are [[pinoresinol]], [[podophyllotoxin]], and [[steganacin]]. When part of the human diet, some lignans are metabolized to form mammalian lignans known as [[enterodiol]] ('''1''') and [[enterolactone]] ('''2''') by intestinal [[bacteria]]. Lignans that can be metabolized to form mammalian lignans are [[pinoresinol]], [[lariciresinol]], [[secoisolariciresinol]], [[matairesinol]], [[hydroxymatairesinol]], [[syringaresinol]] and [[sesamin]]. [[Image:Enterolactone2.svg|center|250px]] ==Food sources== [[Flax seed]] and [[sesame seed]] are among the highest known sources of lignans. The principal lignan precursor found in flaxseed is [[secoisolariciresinol diglucoside]]. Other sources of lignans include cereals ([[rye]], [[wheat]], [[oat]], [[barley]]), [[pumpkin]] seeds, [[soybean]]s, [[broccoli]], beans, and some berries. Secoisolariciresinol and matairesinol were the first plant lignans identified in foods. Pinoresinol and lariciresinol are more recently identified plant lignans that contribute substantially to the total dietary lignan intakes. Typically, Lariciresinol and pinoresinol contribute about 75% to the total lignan intake whereas secoisolariciresinol and matairesinol contribute only about 25%.<ref>[http://lpi.oregonstate.edu/infocenter/phytochemicals/lignans Linus Pauling Institute at Oregon State University<!-- Bot generated title -->]</ref> This distribution may change as the contributions of syringaresinol and hydroxymatairesinol have not properly been quantified in foods. Sources of lignans:<ref>{{cite journal |author=Milder IE, Arts IC, van de Putte B, Venema DP, Hollman PC |title=Lignan contents of Dutch plant foods: a database including lariciresinol, pinoresinol, secoisolariciresinol and matairesinol |journal=Br. J. Nutr. |volume=93 |issue=3 |pages=393–402 |year=2005 |pmid=15877880 |doi=10.1079/BJN20051371}}</ref> {|class="wikitable" |- !Source!!Amount per 100 g |- |Flaxseed||300,000 µg (0.3 g) |- |Sesame seed||29,000 µg (29 mg) |- |[[Brassica]] vegetables||185 - 2321 µg |- |Grains||7-764 µg |- |Red wine||91 µg |- |Cola||0 |} A recent study<ref>{{cite journal |author=Smeds AI, et al.|title=Quantification of a Broad Spectrum of Lignans in Cereals, Oilseeds, and Nuts|journal=J.Agric. Food. Chem. |volume=55 |pages=1337–1346 |year=2007 |pmid=17261017|doi=10.1021/jf0629134}}</ref> 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. Mammalian lignan precursors as aglycones (µg / 100 g). Major compound(s) in bold. {|class="wikitable" |- !Foodstuff!!Pinoresinol||Syringaresinol||Sesamin||Lariciresinol||Secoisolariciresinol||Matairesinol||Hydroxymatairesinol |- |Flaxseed||871||48||not detected||1780||'''165759'''||529||35 |- |Sesame seed||'''47136'''||205||'''62724'''||13060||240||1137||7209 |- |Rye bran||'''1547'''||'''3540'''||not detected||'''1503'''||462||729||1017 |- |Wheat bran||138||882||not detected||672||868||410||'''2787''' |- |Oat bran||'''567'''||297||not detected||'''766'''||90||440||'''712''' |- |Barley bran||71||140||not detected||133||42||42||'''541''' |} == References == ===Footnotes=== <references/> ===General references=== * [http://www.chem.qmul.ac.uk/iupac/lignan/LG0n1.html#p11 IUPAC lignan nomenclature] ==External links== *[http://www.dietaryfiberfood.com/lignan.php Lignan content in food] *[http://www.grouppekurosawa.com/nutrition.htm Flax meal and oil and the prevention/treatment of cancer] {{Phenylpropanoids}} [[Category:Phytochemicals]] [[Category:Phenylpropanoids]] [[de:Lignane]] [[es:Lignano]] [[fr:Lignane]] [[nl:Lignaan]]