Total isoflavonoids

Using RP-HPLC interfaced with ESI to an MS, it is possible to obtain a mass/ intensity map of all isoflavone metabolites in a single 20 min analysis. Analysis of isoflavonoid conjugate in serum/plasma samples requires initial extraction, but the conjugates can be measured intact either by capillary RP-HPLC-ESI-MS or on regular RP columns by HPLC-HN-APCI-MS. When it is only necessary to measure the total isoflavonoids and their metabofites in blood, hydrolysis can be performed directly in semm/plasma samples and flavonoids recovered by ether or ethyl acetate solvent extraction (Barnes et al., 1998). 

In three of the volumes of The Flavonoids, Advances in Research, published between 1975 and 1993, flavanones and dihydroflavonols were part of the chapter on Minor Flavonoids, expertly written by Professor Bruce Bohm. These Minor Flavonoid chapters also included chalcones, dihydrochalcones, and aurones. The term Minor Flavonoids was first used by Harborne in 1967 to encompass not only flavanones, chalcones, and aurones, but also isoflavonoids, biflavonyls, and leucoanthocyanidins, because so few compounds belonging to each of these flavonoid classes were known at that time. For example, only about 30 flavanone and dihydroflavonol aglycones, 19 chalcones, and 7 aurones were known in 1967. The number of known minor flavonoids increased considerably in the next two decades, so that when the checklist for The Flavonoids, Advances in Research Since 1980 was published in 1988, 429 known flavanones and dihydroflavonols (including glycosides) were listed, 268 chalcones and dihydrochalcones, and 29 aurones. In the last 15 years, the total number of known compounds in these flavonoid classes has more than doubled, so that the term minor flavonoids is no longer appropriate. Consequently, it has been decided that separate chapters should be devoted to the flavanones and dihydroflavonols (this chapter), and chalcones, dihydrochalcones, and aurones (Chapter 16). 

Almost half of the isoflavonoids identified from the Leguminosae, in which prenylated isoflavones constitute >50% of the total (pterocarpanoids, rotenoids, isoflavanones, isoflavans, coumestans, 3-arylcoumarins, and coumaronochromones), exhibit a high degree of structural diversity and complexity of prenylation.8,86"148 More than half of the isoflavones are monoprenylated, whereas 40% are diprenylated, and very few are triprenyl derivatives, with prenylation at positions 6>8>3 5 >6,>2 and O-methylation at 4 >7=6=2 =3 >5 =5>8. A number of novel isoflavonoid structures with rare skeletons, as well as complex isoflavone O- and C-glycosides have recently been reported.8,148... 

In 1980, a group of Department of Plant Biology, The University of Hull, UK examined their antibacterial activity against total 15 species of 8 Gramnegative bacteria and 7 Gram-positive bacteria on two isoflavonoid phytoalexins such as phaseolin [(-)-phaseollin, 39] and kievitone (40) from their hypocotyl lesions of French bean or the rotting of cowpea infected by the Rhizoctonia solani Kiihn infection. 

A summary of studies where some isoflavones and their metabolites have been analyzed from blood samples of sheep and cattle fed red clover is presented in Table 9.1. The concentrations of isoflavonoids seem to be at the same level in both sheep and cattle. Conjugated or total equol concentration varied between 33 and 770 xg per 100 mL, and free or unconjugated equol concentration was between 2 and 10 xg per 100 mL. Lundh (1995) has estimated that of the total equol concentration about 5% in cows and 1% in sheep exist as free. The plasma concentrations measured for conjugated formononetin, daidzein, genistein, or biochanin A were 1-55 jig per 100 mL. Concentrations for unconjugated forms were usually very small, less than 1 jig per 100 mL. 

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