Thelignans are a large group of low molecular weightpolyphenols found inplants, particularlyseeds,whole grains, and vegetables.[1] The name derives from theLatin word for "wood".[2] Lignans are precursors tophytoestrogens.[1][3] They may play a role asantifeedants in the defense of seeds and plants againstherbivores.[4]
Lignans andlignin differ in their molecular weight, the former being small and soluble in water, the latter being high polymers that are undigestable. Both arepolyphenolic substances derived by oxidative coupling ofmonolignols. Thus, most lignans feature a C18 cores, resulting from the dimerization of C9 precursors. The coupling of the lignols occurs at C8. Eight classes of lignans are: "furofuran, furan, dibenzylbutane, dibenzylbutyrolactone,aryltetralin, arylnaphthalene, dibenzocyclooctadiene, and dibenzylbutyrolactol."[5]
Many lignans are metabolized by mammalian gut microflora, producing so-calledenterolignans.[6][7]
Flax seeds andsesame seeds contain high levels of lignans.[1][8] The principal lignan precursor found in flaxseeds issecoisolariciresinol diglucoside.[1][8] Other foods containing lignans include cereals (rye,wheat,oat andbarley),soybeans,tofu,cruciferous vegetables (such asbroccoli andcabbage), and some fruits (particularlyapricots andstrawberries).[1] Lignans are not present inseed oil, and their contents in whole orground seeds may vary according to geographic location, climate, and maturity of the seed crop, and the duration of seed storage.[1]
Secoisolariciresinol and matairesinol were the first plant lignans identified in foods.[1] Typically, lariciresinol and pinoresinol contribute about 75% to the total lignan intake, whereas secoisolariciresinol and matairesinol contribute only about 25%.[1]
Foods containing lignans:[1][9]
| Source | Lignan amount |
|---|---|
| Flaxseeds | 85.5 mg per oz (28.35 g) |
| Sesame seeds | 11.2 mg per oz |
| Brassica vegetables | 0.3-0.8 mg per halfcup (125 ml) |
| Strawberries | 0.2 mg per half cup |
Lignans are the principal source of dietaryphytoestrogens in typicalWestern diets, even though most research on phytoestrogen-rich diets has focused onsoyisoflavones. Lignan'senterolignan productsenterodiol andenterolactone have weakestrogenic activity, but they may also exert biological effects through non-estrogenic means.[1]
A 2021 review found that lignans have a positive effect on lipid profiles of patients withdyslipidemia related diseases.[10] As of 2022 there is limited evidence that dietary intake of lignans is associated with a reduced cancer and cardiovascular disease risk.[1]
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