{{short description|Group of polyphenols in plant matter}} {{about|the phytoestrogen|the wood polymer|Lignin|the wine and table grape|Lignan (grape)|the town in Italy|Lignano Sabbiadoro|the commune in Hérault|Lignan-sur-Orb}} {{confuse|text = Lingnan, a geographic area in China}}

The '''lignans''' are a large group of low molecular weight polyphenols found in plants, particularly seeds, whole grains, and vegetables.<ref name="lpi.oregonstate">{{cite web|url=http://lpi.oregonstate.edu/infocenter/phytochemicals/lignans|title=Lignans|publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University|date=2010|access-date=31 July 2017}}</ref> The name derives from the Latin word for "wood".<ref>From ''lign-'' (Latin, "wood") + ''-an'' (chemical suffix).</ref> Lignans are precursors to phytoestrogens.<ref name=lpi.oregonstate/><ref>{{Cite journal | pmid = 21762105 | year = 2011 | last1 = Korkina | first1 = L | title = Plant phenylpropanoids as emerging anti-inflammatory agents | journal = Mini Reviews in Medicinal Chemistry | volume = 11 | issue = 10 | pages = 823–35 | last2 = Kostyuk | first2 = V | last3 = De Luca | first3 = C | last4 = Pastore | first4 = S | doi=10.2174/138955711796575489 }}</ref> They may play a role as antifeedants in the defense of seeds and plants against herbivores.<ref>{{cite journal |doi=10.1039/B514045P|title=An update on bioactive plant lignans|year=2005|last1=Saleem|first1=Muhammad|last2=Kim|first2=Hyoung Ja|last3=Ali|first3=Muhammad Shaiq|last4=Lee|first4=Yong Sup|journal=Natural Product Reports|volume=22|issue=6|pages=696–716|pmid=16311631}}</ref>

==Biosynthesis and metabolism== {{Gallery | title = Structures of some lignans | align = center | footer = | style = | state = | height = | width = | captionstyle = | File:Matairesinol.png | alt1= | Matairesinol, illustrating the dibenzylbutyrolactone motif | File:Secoisolariciresinol Structural Formula V.1.svg | alt2= | Secoisolariciresinol, illustrating the 9,9'-dihydroxydibenzylbutane motif | File:Justicidin A.svg | alt3= | Justicidin A, illustrating the arylnaphthalene motif | File:Pinoresinol.svg | alt4= | Pinoresinol, illustrating the furanofuran motif | File:Steganacin.svg | alt5= | Steganacin, illustrating the dibenzocyclooctadienelactone motif | File:Podophyllotoxin2DCSD.svg | alt6= | Podophyllotoxin, illustrating the aryltetralin motif }} Lignans and lignin differ in their molecular weight, the former being small and soluble in water, the latter being high polymers that are undigestable. Both are polyphenolic substances derived by oxidative coupling of monolignols. Thus, most lignans feature a C<sub>18</sub> cores, resulting from the dimerization of C<sub>9</sub> precursors. The coupling of the lignols occurs at C8. Eight classes of lignans are: "furofuran, furan, dibenzylbutane, dibenzylbutyrolactone, aryltetralin, arylnaphthalene, dibenzocyclooctadiene, and dibenzylbutyrolactol."<ref>{{cite journal |doi=10.1023/B:PHYT.0000045487.02836.32|title=Diversity in lignan biosynthesis|year=2003|last1=Umezawa|first1=Toshiaki|journal=Phytochemistry Reviews|volume=2|issue=3|pages=371–90|s2cid=6276953}}</ref>

Many lignans are metabolized by mammalian gut microflora, producing so-called enterolignans.<ref>{{cite journal |doi=10.1080/10408360701612942|title=Lignans and Human Health|year=2007|last1=Adlercreutz|first1=Herman|journal=Critical Reviews in Clinical Laboratory Sciences|volume=44|issue=5–6|pages=483–525|pmid=17943494|s2cid=31753060}}</ref><ref>{{Cite journal | pmid = 11453749 | year = 2001 | last1 = Heinonen | first1 = S | title = In vitro metabolism of plant lignans: New precursors of mammalian lignans enterolactone and enterodiol | journal = Journal of Agricultural and Food Chemistry | volume = 49 | issue = 7 | pages = 3178–86 | last2 = Nurmi | first2 = T | last3 = Liukkonen | first3 = K | last4 = Poutanen | first4 = K | last5 = Wähälä | first5 = K | last6 = Deyama | first6 = T | last7 = Nishibe | first7 = S | last8 = Adlercreutz | first8 = H | doi=10.1021/jf010038a }}</ref>

==Food sources== Flax seeds and sesame seeds contain high levels of lignans.<ref name=lpi.oregonstate/><ref name= "Landete">{{cite journal |last1= Landete |first1= José |date= 2012 |title= Plant and mammalian lignans: A review of source, intake, metabolism, intestinal bacteria and health |url= https://www.sciencedirect.com/science/article/abs/pii/S0963996912000087 |journal= Food Research International |volume= 46 |issue= 1 |pages= 410–24 |doi= 10.1016/j.foodres.2011.12.023|url-access= subscription }}</ref> The principal lignan precursor found in flaxseeds is secoisolariciresinol diglucoside.<ref name=lpi.oregonstate/><ref name= "Landete">{{cite journal |last1= Landete |first1= José |date= 2012 |title= Plant and mammalian lignans: A review of source, intake, metabolism, intestinal bacteria and health |url= https://www.sciencedirect.com/science/article/abs/pii/S0963996912000087 |journal= Food Research International |volume= 46 |issue= 1 |pages= 410–24 |doi= 10.1016/j.foodres.2011.12.023|url-access= subscription }}</ref> 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).<ref name=lpi.oregonstate/> Lignans are not present in seed oil, and their contents in whole or ground seeds may vary according to geographic location, climate, and maturity of the seed crop, and the duration of seed storage.<ref name=lpi.oregonstate/>

Secoisolariciresinol and matairesinol were the first plant lignans identified in foods.<ref name=lpi.oregonstate/> Typically, lariciresinol and pinoresinol contribute about 75% to the total lignan intake, whereas secoisolariciresinol and matairesinol contribute only about 25%.<ref name="lpi.oregonstate" />

Foods containing lignans:<ref name="lpi.oregonstate" /><ref name="Milder">{{cite journal |vauthors=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=British Journal of Nutrition |volume=93 |issue=3 |pages=393–402 |year=2005 |pmid=15877880 |doi=10.1079/BJN20051371|doi-access=free }}</ref> {|class="wikitable" |- !Source!!Lignan amount |- |Flaxseeds||85.5&nbsp;mg per oz (28.35 g) |- |Sesame seeds||11.2&nbsp;mg per oz |- |''Brassica'' vegetables||0.3-0.8 &nbsp;mg per half cup (125 ml) |- |Strawberries||0.2&nbsp;mg per half cup |}

==Prevalence and health effects==

Lignans are the principal source of dietary phytoestrogens in typical Western diets, even though most research on phytoestrogen-rich diets has focused on soy isoflavones. Lignan's enterolignan products enterodiol and enterolactone have weak estrogenic activity, but they may also exert biological effects through non-estrogenic means.<ref name="lpi.oregonstate"/>

A 2021 review found that lignans have a positive effect on lipid profiles of patients with dyslipidemia related diseases.<ref>{{cite journal|author=Yang, C., Xia, H., Wan, M.|year=2021|title=Comparisons of the effects of different flaxseed products consumption on lipid profiles, inflammatory cytokines and anthropometric indices in patients with dyslipidemia related diseases: systematic review and a dose–response meta-analysis of randomized controlled trials|journal=Nutrition & Metabolism|volume=18|issue=1|pages=91|doi=10.1186/s12986-021-00619-3|pmid=34635132|pmc=8504108 |doi-access=free }}</ref> {{As of|2022}}, there is limited evidence that dietary intake of lignans is associated with a reduced cancer and cardiovascular disease risk.<ref name="lpi.oregonstate"/>

==See also== {{div col|colwidth=30|small=yes}} * Herbalism * Pharmacognosy * Flavonolignan {{div col end}}

==References== {{reflist}}

==External links== * [https://web.archive.org/web/20120414191253/http://www.chem.qmul.ac.uk/iupac/lignan/LG0n1.html#p11 IUPAC lignan nomenclature]

{{Xenoestrogens}} {{Phenylpropanoids}} {{Lignan}}

Category:Lignans Category:Wood extracts