The lignans are a large group of low molecular weight
polyphenols found in
plants, particularly
seeds
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm pl ...
,
whole grains, and vegetables.
The name derives from the
Latin word for "wood". Lignans are precursors to
phytoestrogens.
[ They may play a role as antifeedants in the defense of seeds and plants against ]herbivore
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
s.
Biosynthesis and metabolism
Lignans and lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
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."
Many lignans are metabolized by mammalian gut microflora, producing so-called enterolignans.
Food sources
Flax seeds and sesame seeds contain high levels of lignans.rye
Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to both wheat (''Triticum'') and barley (genus ''Hordeum''). Rye grain is u ...
, wheat, oat and barley), soybeans, tofu, cruciferous vegetables, such as broccoli and cabbage
Cabbage, comprising several cultivars of ''Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.&nb ...
, and some fruits, particularly apricot
An apricot (, ) is a fruit, or the tree that bears the fruit, of several species in the genus ''Prunus''.
Usually, an apricot is from the species '' P. armeniaca'', but the fruits of the other species in ''Prunus'' sect. ''Armeniaca'' are also ...
s and strawberries
The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...
.[ Lignans are not present in seed oil, and their contents in whole or ]ground
Ground may refer to:
Geology
* Land, the surface of the Earth not covered by water
* Soil, a mixture of clay, sand and organic matter present on the surface of the Earth
Electricity
* Ground (electricity), the reference point in an electrical c ...
seeds may vary according to geographic location, climate, and maturity of the seed crop, and the duration of seed storage.[
Secoisolariciresinol and matairesinol were the first plant lignans identified in foods.][ Typically, lariciresinol and pinoresinol contribute about 75% to the total lignan intake, whereas secoisolariciresinol and matairesinol contribute only about 25%.]
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 Isoflavones are substituted derivatives of isoflavone, a type of naturally occurring isoflavonoids, many of which act as phytoestrogens in mammals. Isoflavones are produced almost exclusively by the members of the bean family, Fabaceae (Leguminosae) ...
. Lignan's enterolignan products enterodiol and enterolactone have weak estrogenic
Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal activ ...
activity, but they may also exert biological effects through non-estrogenic means.
See also
* Herbalism
* Pharmacognosy
Pharmacognosy is the study of medicinal plants and other natural substances as sources of drugs. The American Society of Pharmacognosy defines pharmacognosy as "the study of the physical, chemical, biochemical, and biological properties of drug ...
* Flavonolignan
References
External links
IUPAC lignan nomenclature
{{Lignan