Isoflavone, chemical structure

Figure 11.6.2 (above and at right) Common name, chemical name, and chemical structure of soy isoflavones. 

Flavonoids are divided into many classes and subclasses, each with a slightly different chemical structure and function. Classes of flavonoids include flavanols, flavanones, catechins, anthocyanins, and isoflavones. 

Figure 4.1 Chemical structures of the principal classes of polyphenols. The examples shown are of polyphenols with hydroxyl groups in the 7- and 4"-positions. Anthocyanins may also be found in oligomeric forms. The coumestane is coumestrol, The isoflavone (daidzein) differs from the flavonoid h the substitution of the phenolic group. For the flavonoid it is in the 2-position, whereas it is in the 3-position in the isoflavone.

Figure 4.3 Chemical structures of Isoflavone glycosides. In soy foods, Isoflavones form 7-0-P-glucosIde conjugates. A Is the simple glucoside commonly found In soy milk, B Is the 6"-0-malonyl-7-0-p-glucoslde from the soybean, and C Is the 6"-0-acetyl-7-O-p-glucoside, a product of toasting of soy flour. D is the 7-0-P-glucuronide that is the principal conjugate in the blood.

Chemical structures of flavonoids. These flavonoids consisted of three groups flavone (apigenin and lutolin), flavonols (flavonol, kaempferol, quercetin, myricetin, tangeretin, and nobiletin) and isoflavones (daizein, genistein, biochanin A, and equol). 

Once the benefits of a key component in food are documented, the challenge is to increase its concentration, and presumably its benefits, while maintaining safety. For example, isoflavones in soy are phytoestrogens with a chemical structure similar to estrogen. Isoflavones may reduce cholesterol, but what is the risk of increasing the intake of a compound that may modulate estrogens Knowledge of the toxicity of functional food components is crucial to improve their benefit-risk ratio. The efforts... 

Fig. (3). Chemical structures of major isoflavones, metabolic derivatives, coumestrol and estradiol.

Figure 2 Chemical structures of selected plant polyphenols. Structures include a flavonol (quercetin), isoflavone (daidzein), cinnamic acid (chlorogenic acid), flavan-3-ol (catechin), a lignan microbial metabolite (enterodiol), and a stilbene (resveratrol).

Figure 1 Chemical structures of two major isoflavones and an estrogen. The structures of genistein (4H-henzopyran-4-one-5, 7-dihydroxy-3-(4-hydroxyphenyl) or 4, 5,7-trihy-droxyisoflavone), daidzein (4H-henzopyran-4-one-7-hydroxy-3-(4-hydroxyphenyl) or 4, 7-dihydroxyisoflavone), and estradiol are shown. The purification schemes of the isoflavones and their physical properties are reported in Ref. 98.

FIGURE 8.5 Chemical structures of naturally occurring isoflavone and coumestan phytoestrogens and endogenous estradiol. 

Figure 8.1 A diagram t)T ihc chemical structures of the isoflavone aglycones found in soybean as well as conjugates of daidzein. Similar conjugates arc fornicd of genistein and glycitein.

The most important members of the flavonoid family include anthocyanidins (e.g., cyanidin, delphinidin, malvidin), flavonols (e.g., quercetin, kaempferol), flavones (e.g., luteolin, apigenin), flavanones (e.g., myricetin, naringin, hesperetin, naringenin), flavan-3-ols (e.g., catechin, epicatechin, gallocatechin) and, although sometimes classified separately, the isoflavones (e.g., genistein, daidzein). For chemical structures see Figure 1. All these phytochemical are frequently referred to as bioflavonoids due to well established effects in human health maintenance. 

Isoflavones are flavonoids commonly called as phytoestrogens and one of the most extensively investigated polyphenols. These are present in soybeans, soybean products, and other pulses, widely consumed in Asian and Southeast Asian coim-tries. Isoflavones have attracted attention mainly due to their role in the ameliora-ti(Mi of postmenopausal symptoms such as hot flushes and osteoporosis [52,58,59]. The other beneficial and important biological properties have been established which are related to effects on cardiovascular diseases, cognitive functions, and breast and prostate cancers. These conclusions were based on wide-ranging studies and parameters which showed positive effects, for example, reduction of hot flushes, the excretion of Ixme resorption markers, increase in bone mineral density, the lower LDL and total cholesterol, reduction in colon cancer, and modulation of immune function [60, 61]. Chemical structures of some important molecules of these phytochemical classes are represented in Fig. 82.3. 

Fig. 82.3 Chemical structures of some important molecules (a) glucosinolates, (b) caffeine, (c) beta carotene, (d) beta sitosterol, (e) isoflavones, and (f) resveratrol...

Isoflavones have a chemical structure similar to that of mammalian estrogens and are referred as phytoestrogens [36]. Isoflavones are quite weak, possessing 1/1000 to 1/10,000 the estrogenic activity of 17-G-p-estradiol. How-... 

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