This article is about the phytoestrogen. For the wood polymer, see Lignin. For the wine and table grape, see Lignan (grape). For the town in Italy, see Lignano Sabbiadoro.
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 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-called enterolignans.[6][7]
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]
A 2021 review found that lignans have a positive effect on lipid profiles of patients with dyslipidemia 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]