Isoflavonoids, occurrence

While fiavonoids have the 2-phenylchromen-4-one backbone, isoflavonoids (Fig. 8) have the 3-phenylchromen-4-one backbone, with no hydroxyl substitution at position 2 in the case of isofiavones. In contrast with the parent class of fiavonoids, the distribution of the isoflavonoid class in the plant kingdom is relatively limited, probably owing to the sporadic occurrence of isoflavone synthase. Isoflavonoids... 

In contrast to the almost ubiquitous occurrence of the flavonoids in higher plants, the isoflavonoids have a very limited taxonomic distribution. They are in general confined to one group of plants - the sub-family Lotoideae of the Leguminosae [390, 391 ]. Occasionally they occur in a few other families [326], The overall biological properties also differ from those of the flavonoids flavonoids on the whole are innocuous substances [392], but isoflavonoids usually have oestrogenic, insecticidal, piscicidal and/or antifungal activities. 

Flavonoids are ubiquitous in all terrestrial plants (except the Anthoceropsidae) but the distribution of isoflavonoids among plants is relatively sparse, probably owing to the sporadic occurrence of the enzyme isoflavone synthasa that stabilises, by an aryl migration, the isoflavonoid skeleton. Accordingly, most of the isoflavonoids have been isolated from leguminous plants [3]. 

Bearing these taxonomic conclusions in mind, an overview of likely biosynthetic relationships between the isoflavonoids discussed in this chapter was proposed [6] and is represented in Fig. (4). This emphasises those compounds whose occurrence is restricted to the 3 species in the proposed series Pinnatifida (C. bijugum, C. judaicum and C. pinnatifidum) and attempted to address the biosynthesis of these compounds, most notably arybenzofurans which are still missing from the latest versions of the isoflavonoid biosynthesis schemes because of the lack of persuasive biogenetic evidence. A 2 -hydroxyisoflavanol, the immediate precursor of isoflav-3-enes and pterocarpans, is shown as the first intermediate. Its... 

There are reports on the presence of isoflavonoids in numerous families of the plant kingdom inclusive 49 angiosperm families (Mackova et al. 2006). The most famous example is their occurrence in the Fabaceae. Isoflavones are formed by structural... 

Symbols indicating compound occurrence ( ) common, ( ) uncommon, and (o) rarely reported. See Section 2.2.2 for isoflavonoid reports from C and M. 

Isoflavonoids are a group of flavonoid compounds exhibiting different biological effects. The occurrence of about 200 known... 

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