Lignans are a diverse class of polyphenolic secondary metabolites found in plants, biosynthesized via dimerization of two phenylpropanoid units (typically coniferyl alcohol) to form a characteristic 2,3-dibenzylbutane or related skeleton. Subclasses include dibenzylbutyrolactones, furofurans, arylnaphthalenes, and aryltetralins. They exhibit antioxidant, anti-inflammatory, and weak phytoestrogenic activities, contributing to potential health benefits in cardiovascular and hormonal regulation. Abundant in flaxseeds (secoisolariciresinol diglucoside), sesame, grains, and berries. Properties vary widely by specific structure but the class is generally lipophilic with low volatility and moderate stability under processing conditions.