Isoflavones absorption

Rice-Evans, C.A. (2004). Flavonoids and isoflavones absorption, metabolism and bioaclivity. Free Radical Biology and Medicine, 36, 827-828. 

TSUNODA N, POMEROY s, NESTED p (2002) Absorption in hiunans of isoflavones from soy and red clover is similar. JNutr 132, 2199-2201. 

The mucosa of the GIT represents an interface between the external and internal environments. The expansive surface area is necessary for the efficient hydrolysis of foodstuffs and the absorption of energy and nutrients. The mucosa also influences the systemic availability of non-nutrient compounds in the diet, both beneficial and detrimental. Digestion and absorption of glucosinolates are critical determinants of health benefits (see Chapter 4) Similarly, the bioavailability and health benefits of phytoestrogens, such as genistein (see Chapters 5 and 10) are at least partly dependent on the carrier-mediated processes of absorption associated with the GIT (Oitate et al, 2001). Moreover, the metabolic activities of the mucosa can influence the systemic concentrations and forms of dietary phytochemicals, as exemplified by research with soy isoflavones (Andlauer et al., 2000). 

Setchell, K.D., Brown, N.M., Zimmer-Nechemias, L., et al. (2002a). Evidence for lack of absorption of soy isoflavone glycosides in humans, supporting the crucial role of intestinal metabolism for bioavailability. Am. J. Clin. Nutr., 2, 447-53. 

LC UV is valuable for the identification of isoflavones since their spectra differ in absorption properties from most of the other flavonoids. They have a C2-C3 double bond, with the B-ring at C3, which prevents conjugation of the phenyl group with the pyrone carbonyl group. This reduces the contribution of the B-ring to the UV spectrum and results in a peak of very low intensity in the 300 to 330 nm range (band I). 

Few studies have been carried out in infants fed on soya formula. Absorption of isoflavones by the infant was demonstrated from the appearance of daidzein and genistein in the urine of 4-month-old infants fed soy formulas. Equol was not detected in the urine [94]. A later study by Setchell et al [95] did not confirm these results because equol was not detectable or present only in traces in the serum of 4-month-old infants fed soya infant formulas. Isoflavone concentration in human breast milk increased after the consumption of a soya-rich diet, but their contribution seems trivial in comparison to that from soy infant formulas [93]. 

The flavanones have received less attention in comparison to flavonols and isoflavones, although their intake from the diet can be high and they exhibit promising biological activity. Little information is available about the absorption or the kinetic behavior of the flavanones naringenin, hesperetin and their glycosylated forms naringin, hesperidin, and narirutin. 

Cui, S., Zhao, C., Chen, D., He, Z. (2005). Self-microemulsilying drug delivery systems (SMEDDS) for improving in vitro dissolution and oral absorption of Pueraria lobata isoflavone. Drug Development and Industrial Pharmacy, 31, 349-356. 

The differences in the spectral characteristics of individual isoflavones are small but very important in their identification (Har-borne, 1967). Isoflavones can be readily distinguished by their UV spectra, which typically exhibit an intense Band II (240 to 280 nm) absorption with only a shoulder or low-intensity peak representing Band I (300 to 330 nm). Band I absorption involves the B ring (cin-namoyl system Figure 11.6.1), and Band II absorption involves the A ring (benzoyl sys-... 

The basis for understanding the health benefits of isoflavones requires detailed knowledge on the absorption, distribution, metabolism, elimination, and bioavailability of these phytoestrogens that demands robust, precise, accurate, and affordable analyses from biological and other matrices. 

King R. 2002. Digestion, absorption, and metabolism of isoflavones. In Gilani G, Ed. Phytoestrogens and Health. Illinois AOCS Press, PP. 209-234. 

Setchell KD. 2000. Absorption and metabolism of soy isoflavones-from food to dietary supplements and adults to infants. J Nutr 130 654S-655S. 

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