Isoflavones compounds

Dietary isoflavones contain at least one hydroxyl group in their structure, which makes it difficult for their analysis by GC/MS without derivatization. Electron impact GC/MS has been used for the analysis of isoflavones. However, prior to analysis, TMS ether derivatives were necessary to increase the volatility and thermal stability of the isoflavones.2 Additionally, a cleanup procedure is usually employed to remove coextracted compounds. Wang et al.113 separated five isoflavone compounds in Puerariae radix within 6 minutes using HPCE in a 20-mM borax-NaOH (pH 10.1) buffer. 

Red clover contains isoflavones, compounds that are structurally similar to the human hormone estradiol and capable of binding to estrogen receptors (Umland et al. 2000). Some studies have indicated that red clover isoflavones have a greater affinity for the estrogen receptor P (found primarily in bone, brain, heart, and vascular system) than estrogen receptor a (found primarily in uterus, breast, ovaries, and adrenal glands) (Beck et al. 2005 Dornstauder et al. 2001). 

Soy is rich in isoflavones, compounds that are structurally and functionally similar to estrogen. Several animal experiments suggest that intake of these isoflavones may provide protection against CHD, but human data on efficacy and safety are still awaited. Naturally occurring isoflavones, isolated with soy protein, reduced the plasma concentrations of total and LDL cholesterol without affecting the concentrations of triglycerides or HDL cholesterol in hypercholesterolemic individuals. 

In the chemical shift range for alkenes and aromatic and heteroaromatic compounds enol ether fragments (furan, pyrone, isoflavone, 195-200 Hz) ... 

Many stilbenelike thiophene compounds have been prepared for a study of estrogenic activity, especially by Buu-Hoi et al. Thiophene derivatives of nonhydroxylated stilbene types showed no significant activitywhereas weak estrogenic activity was found in 5-acetyl-, 5-propionyl-, and 5-benzoyl-2-(-stilbenyl)thiophene. 1-Bromo-l,2-diphenyl-2-(5-bromo-2-thienyl)ethylene (258) was found to inhibit body growth and to produce extensive testicular atropy in male rats. A thiophene analog of estrogenic isoflavones (259)... 

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). 

An inverse correlation between thyroid cancer risk and phytoestrogens was recently proposed as a result of a multi-ethnic population-based case control study conducted in the San Francisco Bay Area (Hom-Ross et al., 2002). In this study, dietary habits and phytoestrogen consumption were assessed by a food-frequency questionnaire and by a nutrient database. The outcome of the study was that soy-based foods and alfalfa sprouts were associated with a reduction of thyroid cancer risk, whereas a Western diet did not influence cancer risk. No difference was observed between American and Asian women or between pre- and postmenopausal women. Furthermore, among the few compounds examined, the isoflavones genistein and daidzein and the lignan secoisolariciresinol were the phytoestrogens most frequently associated with risk reduction (Horn-Ross et al., 2002). 

Data on safety have been obtained from in vitro as well as in vivo animal and human studies (see also Section 10.4). About 50 years ago, Australian farmers observed an infertility syndrome in sheep associated with the consumption of clover species (Bennets et al., 1946). The clover compounds shown to cause the infertility (genistein, daidzein, equol, biochanin A, formononetin) were members of the isoflavone family (Bradbury and White, 1951 Shutt and Braden, 1968), raising the question of whether soy might cause infertility in humans (see also Section 10.4.9). A variety of reports further supported adverse effects of isoflavones on animal reproductive systems (Santell et al., 1997 Flynn et al., 2000a,b). 

To obtain an updated set of data on the phytoestrogens content in foods and diets, we suggest checking the following websites http //www.venus-ca.org/database.htm (phytoestrogen database of the EU-funded project VENUS) http //www.nal.usda.gov/fhic/foodcomp/Data/isoflav/isoflav.html (USDA-Iowa State University database on the isoflavones content of foods) and http //www.ilf.bbsrc.ac.uk/phytochemicals/Links.htm (Institute of Food Research Database on the levels of bioactive compounds in plant foods). 

Now that an haustorial inducing factor has been characterized in a host plant that could be grown in the laboratory, the levels of the compounds actually exuded could be analyzed. John Steffens and Rody Spivey focused on developing methods that would allow for suitable quantitation. Efforts were made to quantitate not only the terpenoid components, but also the flavanoid, genistein (4, 5,7-trihydroxyiso-flavone), which was found to be a major isoflavone of Lespedeza. Genistein was analyzed to gain an estimate of levels of phenylpro-... 

AOPP has been used in many studies to examine the role of PAL in the synthesis of secondary aromatic compounds. The results summarized in Table I indicate that levels of AOPP that have little or no effect on growth can strongly affect production of secondary aromatic products. Other studies have shown rapid cessation of isoflavone synthesis in Cicer ariethinum by 0.3 mM AOPP (61). 

Food and plant phenolics are commonly detected using DAD detectors (Tan and others 2008). Photodiode array detection allows collection of the entire UV spectrum during the elution of a chromatographic peak, which makes it possible to identify a phenolic compound by its spectra. Simple phenols, phenolic acids, flavanones, benzophenones, isoflavones, and flavan-3-ols have maximum absorbance at 280 nm, hydroxycinnamic acids at 320 nm, flavonols, flavones, and dihydroflavonols at 365 nm, and anthocyanins at 520 nm (Ibern-G6mez and others 2002 Merken Hand Beecher 2000). Hydrolyzable tannins show a characteristic shoulder at 300 nm, suitable for identifying them (Arapitsas and others 2007). For stilbenes, maximum absorbance of trans-forms are at 306 nm and at 285 nm for cA-forms (Lamuela-Raventos and others 1995). 

New detection methods of phenolic compounds are being developed. Based on the principle of the enzyme-linked immunosorbent assay (ELISA), a method has been developed to quantify phenolic compounds such as isoflavones (Vergne and others 2007). 

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