Lignans and Lignin

Davin, L. B., and Lewis, N. G., 2000, Dirigent proteins and dirigent sites explain the mystery of specificity of radical precursor coupling in lignan and lignin biosynthesis, Plant Physiol. 123 453-461. 

Lewis, N.G. and Davin, L.B. (1998) The biochemical control of monolignol coupling and structure during lignan and lignin biosynthesis. ACS Symp. Sen, 697, 334—61. 

It has been noted that the chemical diversity of plant phenolics is as vast as the plant diversity itself. Most plant phenolics are derived directly from the shikimic acid (simple benzoic acids), shikimate (phenylpropanoid) pathway, or a combination of shikimate and acetate (phenylpropanoid-acetate) pathways. Products of each of these pathways undergo additional structural elaborations that result in a vast array of plant phenolics such as simple benzoic acid and ciimamic acid derivatives, monolig-nols, lignans and lignin, phenylpropenes, coumarins, stilbenes, flavonoids, anthocyanidins, and isollavonoids. 

Polyphenols are a widespread group of secondary metabolites found in plants derived from phenylalanine and tyrosine, and they are characterized by the presence of several phenol groups (i.e., aromatic rings with hydroxyls) [1]. Plant phenolics include simple phenols, phenolic acids (benzoic and cinnamic acid derivatives), coumarins, flavonoids, stilbenes, hydrolysable and condensed tannins, lignans, and lignins [2, 3]. 

Lignans and lignins are both composed of the hydroxy cinnamic alcohols (monohgnols) />-cotmiaryl alcohol, coniferyl alcohol, and... 

Phenolic compounds present in natural products include simple phenols, phenolic acids, tocopherols, stilbenes, coumarins, flavonoids (flavonol, flavones, flavanols, antho-cyanidins, proanthocyanidins), tannins, lignans, and lignins (Naczk and Shahidi, 2006 Folmer et ah, 2014). Phenolic compounds are secondary plant metabolites that are synthesized in response to stress conditions, such as UV irradiation, nutrient deficiencies, infection, and wounding (Naczk and Shahidi, 2006 Ramakrishna and Ravishankar, 2011). 

Monolignol—phytochemicals acting as source materials for biosynthesis of both lignans and lignin. 

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