Flavanones isoflavones

Depending on their aglycone structure, at least five different groups of 4-oxo-flavonoids are distinguishable flavonols, flavones, flavanones, isoflavones and chalcones. 

Structure-activity relationship. The endothelium-independent vasodilator effects showed by flavonoids are related to the structure of the compound tested. Structure- activity relationships have been studied to flavonoids selected from five groups flavonols, flavones, flavanones, isoflavones, and flavanols in rat isolated aorta on the contractions induced by noradrenaline, KC1 and the phorbol ester derivative PMA, as well as the interactions of these flavonoids with isoprenaline and sodium nitroprusside, Table (2). 

Flavanones - Isoflavones. Although Koser s reagent (1) is known to effect a-tosyloxylation of ketones,1 the reaction with flavanones (2) results in an oxidative 1,2-aryl shift to provide isoflavones (3) in 74-80% yield.2 This conversion has been effected previously with thallium salts. 

Flavonoids isolated firom Astragalus spp. belong to the following classes of constituents flavones, flavonols, flavanones, isoflavones and isoflavans, all as aglycones than glycosides, and pterocarpans (Table 5). 

A wide variety of flavonoid compounds have been isolated from hardwoods, including flavones, flavanols, flavanones, isoflavones, and chalcones, most of whieh are highly hydroxylated, and which vary in hydroxylation pattern. Two of the many compounds present are shown in Figure 2.17 robinetin is the 3-hydroxy-flavone extracted from Robinia and Intsia sp. while the chalcone, okanin, is found in Cyclodiscus sp. 

Flavonoids can be classified according to the degree of oxidation of the three-carbon central segment. From lower to higher degree of oxidation, flavonoids are usually classified as catechins, chalcones, flavanones, isoflavones, flavan-3, 4-diols, flavones, aurones, flavonols and anthocyanins (Fig. (2)) [5],... 

The majority of the plant pigments hitherto isolated from woods in pure form are the flavonoids, such as flavone, flavanone, isoflavone, isoflavanone, pterocar-pane, and chalcone derivatives, along with the phenols stilbene and xanthone, which are almost white or yellow in color. Other flavonoids such as aurone and neoflavone derivatives (orange pigments) have a limited distribution and sometimes occur as wood extractives in species of the Anacardiaceae and Leguminosae (4, 7). The presence of the typical anthocyanin derivatives of flowers and fruits is extremely rare in wood, but their leuco-compounds such as flavan-3-ol and flavan-3,4-diol have been found to occur in the wood of a considerable number of tree species (14). Besides anthocyanidin, the few other deep-colored (red, purple, or blue) pigments from woods usually possess a quinone structure. 

Flavanones, isoflavones Erythrina vogelii On-flow H 500 MHz, 60 p.E cell MeCN-D20 low flow 229 0 Q. 

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