Lignans and related compounds

Phenolics and their functional derivatives are widely found throughout the plant kingdom. One defining characteristic of these compounds is that their aromatic ring usually contains at least one hydroxyl substituent. In a broad sense, phenolics, which are classified according to their structural skeleton, are basically derivatives from simple phenols and phenolic acids, phenylpropanoids including coumarins and lignans, flavonoids and related compounds, and stilbenes. Some of these compounds which show anti-inflammatory activity are reviewed in this section. 

Two new dibenzocyclooctadiene type lignans called heteroclitins F and G and related compounds isolated from the stems of Kadsura heteroclita inhibited lipid peroxidation in the rat liver homogenate stimulated by Fe2+ ascorbic acid, CCI4, NADPH and ADP-NADPH [271],... 

At the moment, such generalisations are without scientific foundation, but remain tempting when one examines lignans such as the justicidins and related compounds, which are simple arylnaphthalenes with no stereochemical complications (Fig. 8). The tests on these closely related compounds have been carried out in different laboratories mainly on the basis of folk medicine. 

Ward RS (1995) Lignans, neolignans, and related compounds. Nat Prod Rep 12 183-205... 

There are several ways in which phenols have been categorized. Harbome and Simmonds categorized polyphenols based on the number of carbon atoms, which includes simple phenols (Ce) phenolic acids and related compounds (Ce—Ci) acetophenones and phenyl acetic acids (Cg—C2) cinnamic acids, cinamyl aldehydes, and alcohols (Cg—C3) coumarins, isocoumarins, and chromones (Cg—C3) flavonoids (C15) biflavonyls (C30) stilbenes (Cg—C2—Cg) benzophenones and xanthones (Cg—C2—Cg) quinones (Cg, Cio, Cm) betacyanins (Cjg) and lignans, lignins, tannins, and phlobaphenes (which are dimmers, oligomers, or polymers) [19]. Polyphenols have also been categorized by some researchers based on their... 

Two classes of a-hydroxylated lignans have been enantioselectively prepared a) wikstromol (3) [10, 38] and related natural products [39] and b) gomisin A (1) and congeners [40, 41]. In both cases, chiral, non-racemic ita-conic acid derivatives have been synthesized as key compounds for the preparation of -benzyl-y-butyrolactones (either by resolution (g [32]) or by asymmetric hydrogenation (h [25])). 

Sesame oil, which contains a relatively large quantity of 43 and related lignans, has also been used for improvement of health and longevity. Compound 43 showed a significant protective effect against the accumulation of fat droplets and an ability to improve liver functions [143]. 

In this chapter, the origin of cinnamic and p-coumaric acids and their simple derivatives will be discussed initially, as these intermediate substances are precursors to most other groups of related compounds. Various other modified C6-C3 compounds, such as simple phenylpropanoids, lignans, neolignans, lignin, and hydroxybenzoic acids, will then be covered. 

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