**8. References**

122 Recent Trends for Enhancing the Diversity and Quality of Soybean Products

Besides their antioxidant properties, catechins have been described to display pro-oxidant activity having the potential to oxidize the quinones or semiquinones resulting in redox cycling and reactive oxygen species production as well as in thiol, DNA and protein

Our previous study shows that the oxidation products of catechins are formed within the cellular matrix but also in the extracellular medium (Chedea et al., 2010). We have demonstrated by UV-Vis spectroscopy, that the quinones are involved in the modulation of lipoxygenase activity in the presence of catechins within the cells (Chedea et al., 2010). This conclusion is in agreement with that of Sadik et al. (2003) and Banerjee (2006). An irreversible covalent modification of soybean LOX by flavonoids has been suggested by Sadik et al. (2003) whereby during the formation of fatty acid peroxyl radical in the LOX pathway, the flavonoids are co-oxidized to a semi-quinone or quinone, which in turn may bind to sulfhydryl or amino groups of the enzyme

The knowledge presented in this study addressed the lipoxygenase pathway inhibition by antioxidant polyphenols at two levels: human diet and human health or to a larger extent human disease prevention and treatment. Review articles (Jachak, 2006; Schneider & Bucara, 2005; Schneider & Bucarb, 2005) summarize natural products with inhibitory properties toward LOX (Skrzypczak-Jankun et al., 2007). Natural remedies almost never consist of a single ingredient and usually are a mixture of many in proper proportions, with a synergistic effect of their simultaneous action being absolutely necessary for beneficial medicinal results. Thus, one should proceed with caution, since the action of a selected single compound may not be the same (Skrzypczak-Jankun et al., 2007). The X-ray studies of soybean complexes with quercetin, curcumin, EGCG, EGC indicated conversion of these inhibitors into their metabolites (Skrzypczak-Jankun et al., 2007), which is not surprising considering the co-oxidative activity of LOXs (Kulkarni, 2001). As already presented a question arises concerning the lipoxygenase inhibion: "What is really inhibiting LOX, a given chemical or its LOX metabolite?" (Skrzypczak-Jankun et al., 2007). The results presented so far indicate a complex mode of inhibition involving the inhibitor itself but also

The lipoxygenase researcher faces the next antinomy: despite the difference in the number of amino acids between plant and mammalian LOXs, these proteins are amazingly similar in topology with high similarities in the active site of these enzymes. It is believed that all LOXs follow the same catalytic mechanism; however, it is probably the vicinity of the iron site that determines the regio and stereospecificity of the particular enzyme (Skrzypczak-Jankun et al., 2003). In this contradictorily state of facts soybean lipoxygenases stands as a

V.S. Chedea is a Japan Society for the Promotion of Science (JSPS) postdoctoral fellow. The authors wish to thank Dr. Ewa Skrzypczak-Jankun for the enlightening discussions during this manuscript writing and Ms. Nana Henmi for helping with the structures drawing.

alkylation (Galati & O'Brien, 2004; van der Woude et al., 2006).

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its reaction product with lipoxygenase.

**7. Aknowledgements** 

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**7** 

*Serbia* 

**Soybean Phytoestrogens – Friends or Foes?** 

Proper and balanced nutrition is very important in prevention and treatment of chronic diseases. Many individuals modify their diet and/or take different nutraceuticals expecting to attain optimum health, extend their lifespan and prevent diseases such as cardiovascular,

Based on "Japanese phenomenon" (Adlercreutz, 1998), numerous advertisements suggest that soy-based diet, and its phytoestrogens (PE) in particular, provide protection against many chronic diseases and contribute to the long lifespan often observed in Asia. That is why soy and other phytoestrogen - rich plants became increasingly popular in the U.S. and western countries in the past 30 years. Furthermore, in these countries, PEs are often consumed in its purified form, as nutritional supplements, "designed" for special medical purposes. These supplements are freely available in pharmacies, health food shops, grocery shops and are usually consumed without medical control. There is a lack of awareness that uncontrolled consumption of natural PEs may be potentially harmful to human health. Even more concerning is that some people consume supplements in excess of suggested daily

The soybean (*Glycine max*), compared to other legumes, is richer in protein levels and quality, based on its digestibility and concentration of essential amino acids (Rand et al., 2003). It is also good source of fiber, certain vitamins and minerals, such as folate and potassium (Rochfort and Panozzo, 2007). It has very high antioxidant content, similar to fruits famous for their antioxidant activity (Galleano et al., 2010). Also, despite their high carbohydrate content, the glycemic load of soybeans is relatively low due to their low glycemic index. In addition, soy-food has high levels of iron in the form of ferritin (Lönnerdal et al., 2006). The concentration of calcium in soymilk is much lower than in cow milk, however, its absorption from soy milk is similar to that from cow milk (Reinwald and

Besides the favorable nutritional attributes, soybean contains a number of biologically active components (saponins and lunasin, phytic acids, phytosterols, trypsin inhibitors, and peptides) including isoflavones genistein (G), daidzein (D) and glycitein (Gy). As soybean phytoestrogens, isoflavones are considered the most important in prevention and treatment of hormone-dependent cancers, cardiovascular diseases, osteoporosis, menopausal symptoms and other age-related diseases. In addition, some studies suggest that soy and its

Modern world is a controversy with ever-increasing obesity on one side, and a high percent of starving people around the globe, on the other side. Having that in mind, combined with

**1. Introduction** 

dosage (Wuttke et al., 2007).

isoflavones affect body weight homeostasis.

Weaver, 2010).

cancer, osteoporosis, obesity, or diabetes type II.

Branka Šošić-Jurjević, Branko Filipović and Milka Sekulić *University of Belgrade, Institute for Biological Research "Siniša Stanković",* 

