2 Phytochemicals in Soy and Their Health Effects *

Consumption of soy foods has been associated, at least in part, with lower incidences of a number of chronic diseases indicated by epidemiological studies (1-4). Soy-based foods have been consumed in Asian countries such as China, Japan and Korea for many centuries. The lower rates of several chronic diseases in Asia, including cardiovascular diseases and certain types of cancer, have been partly attributed to consumption of large quantities of soy foods (5, 6).


Introduction
Consumption of soy foods has been associated, at least in part, with lower incidences of a number of chronic diseases indicated by epidemiological studies (1)(2)(3)(4).Soy-based foods have been consumed in Asian countries such as China, Japan and Korea for many centuries.The lower rates of several chronic diseases in Asia, including cardiovascular diseases and certain types of cancer, have been partly attributed to consumption of large quantities of soy foods (5,6).
Soy-based food was first introduced on a large scale to the general U.S. population as a source of high quality protein.A significant increase in soy food consumption during the last decade of the 20 th century occurred because of the health benefits soy food might offer independent of their nutrient content (7).In the last few decades, extensive efforts have been made towards identifying bioactive components in soy foods that are responsible for the health benefits.Among them, isoflavones and soy proteins are the two major groups of components that have received the most attention (8)(9)(10)(11).Isoflavones belong to a broad group of plant-derived compounds that have structural and functional similarities to estrogens, which has led to the term phytoestrogens (12,13).Indeed, more than half of the soy-related papers are related to isoflavones (7).The analysis, bioavailability and the health effects of isoflavones have been extensively studied and frequently reviewed (12,(14)(15)(16)(17)(18)(19)(20)(21).Consumption of isoflavones has been suggested to have multiple beneficial effects i n a n u m b e r o f c h r o n i c d i s e a s es and medical conditions (4,22,23).However, accumulating evidence has also suggested that isoflavones only reflected certain aspects of the health effects associated with soy consumption.Other components in soy, such as soyasaponins, phytic acid or plant sterols, display a wide range of bioactivities, including anti-cancer, anti-oxidative, anti-viral, cardiovascular protective effects, and hepatoprotective actions (24).contents of major phytochemicals from high to low in soybean are: phytic acid (1.0-2.2%)(25), sterols (0.23-0.46%) (26), saponins (0.17-6.16%) (27), isoflavones (0.1-0.3%) (23), and lignans (0.02%) (28).Secondly, the potential health effects of the major phytochemicals are outlined.For many years, the studies of health effects of soybean phytochemicals primarily focused on isoflavones.However, other phytochemicals in soy, such as soyasaponins, phytosterols, lignans, phytic acid, and oligosaccharides, have also been found to exert biological activities.These may contribute to overall health effects observed with soy consumption.

Health effects of isoflavones
Health effects of isoflavones were initially thought to be related to their estrogenic activity (23).The molecular structures of isoflavones, especially genistein (2), are similar to that of 17estradiol (Figure 2).Isoflavones can bind to both and isoforms of esterogen receptor (ER), but their binding affinity to ER is about 20 times higher than that to ER (11).However, compared to physiological estrogen such as 17 -estradiol, isoflavones have approximately 100 times weaker affinities (32).Estrogen-like effects have been proposed as one of the major mechanism of action of isoflavone related to their health effects (8).A second mechanism of action of isoflavones, particularly of genistein, was discovered that genistein is a protein tyrosine kinase (PTK) inhibitor (8).Since then, isoflavones have been shown to affect a diverse array of intracellular signaling pathways (7).For instance, genistein and other isoflavones were found to interact with the peroxisome proliferator activated receptors, PPAR / .These nuclear receptors are activated by fatty acids (PPAR ) and prostaglandins (PPAR ) and serve as transcription factors (32).As polyphenols, isoflavones also have antioxidant activities, which were proposed as another important mechanism of action of isoflavones.However, isoflavones are not strong antioxidant may not be able to scavenge oxidants directly.They therefore are considered as antioxidants because of their effects on gene expression of enzymes that enhance antioxidant defenses (32).In addition to what has been discussed above, several other mechanism have been proposed for the activities of isoflavones, including stimulation/inhibition of enzyme activities involved in steroid synthesis and metabolism, targeting thyroid peroxidase, and inhibiting cancer metastasis (32).Consumption of isoflavones has been suggested to have multiple beneficial effects in a number of chronic diseases and medical conditions, including certain types of cancer (33)(34)(35), heart disease (36)(37)(38), bone functions (39)(40)(41)(42) and most recently, prevention of obesity (43,44).Many excellent reviews regarding the different aspects of health effects of soy isoflavone can be found in the literatures, thus, only a brief outline of the health effects of isoflavones is provided in this chapter.

Isoflavones and prevention of cancer
The incidences of breast and prostate cancers are much higher in the United States and European countries compared to Asian countries such as Japan and China.One of the major differences in diet between these populations is that the Japanese and the Chinese consume a traditional diet high in soy products (35).Epidemiological evidence together with preclinical data from animal and in vitro studies strongly supported a correlation between soy isoflavone consumption and protection towards breast and prostate cancers (45)(46)(47).However, clinical studies assessing soy consumption and risk of breast cancer have yielded inconsistent results.In a most recent meta-analysis of prospective studies suggested that soy isoflavones intake is associated with a significantly reduced risk of breast cancer incidence in Asian populations, but not in Western populations.Further studies are warranted to confirm the finding of an inverse association of soy consumption with risk of breast cancer recurrence (48).
Except for breast and prostate cancer, isoflavones also showed inhibitory effects on other hormone-related (e.g.endometrial, ovarian cancer) or hormone-independent cancers (e.g.leukemia and lung cancer) (49).

Isoflavones and prevention of cardiovascular diseases
A number of cardioprotective benefits have been attributed to dietary isoflavones including reduction in LDL cholesterol, inhibition of pro-inflammatory cytokines, cell adhesion proteins and inducible nitric oxide production, potential reduction in the susceptibility of the LDL particle to oxidation, inhibition of platelet aggregation and an improvement in vascular reactivity (50).There are not randomized trials investigating the action of isoflavones on the incidence of clinical events.A few recent, well-designed studies have suggested an association of the ingestion of isoflavones with a reduction in the atherosclerotic burden, as indicated by the measurement of the intima-media thickness in carotid vessels (51).

Isoflavones and bone health
Observational studies have suggested that populations in Asia with a high dietary soy intake have a lower incidence of osteoporosis-related fractures when compared to Western populations.Isoflavones were suggested to prevent bone loss associated with menopause.Though extensive research using animal models has provided convincing data to indicate a significant improvement in bone mass or other end points following feeding with soyabean, results from intervention studies are still controversial (52).Additional research is needed to determine if isoflavones are an effective alternative to hormone replacement therapy for the prevention and treatment of osteoporosis (42).

Isoflavones and prevention of obesity
The prevalence of obesity and related diseases has increased rapidly in the Western world.Obesity is a disorder of energy balance and is associated with hyper-insulinemia, insulin resistance, and abnormalities in lipid metabolism, and it is one of the most important risk factors in the development of Type II diabetes, cardiovascular disease, atherosclerosis, and certain cancers (44).In recent years, evidence is emerging that soy isoflavones play a beneficial role in obesity and diabetes.Nutritional intervention studies in animals and humans indicate that consumption of soy isoflaovne or soy protein containing isoflavones reduces body weight and fat mass by lowering plasma cholesterol and triglycerides as well as by other mechanisms (43,44,53).Though the published results suggest a beneficial effect of soy isoflavone on obesity in human, these results also suggest that the effect may be dependent on whether the isoflavones are consumed in combination with soy protein (44).

Chemical characteristics of soyasaponins and soyasapogenols
Saponins are sterol or triterpene glycosides that occur in a wide variety of plants.Soy-based foods are primary dietary sources of saponins (54).Chemical studies of saponins in soy track back to the 1930's (55,56).From the 1980's to 1990's, a number of papers, especially those published by Japanese researchers, significantly enriched our knowledge about chemical structure and diversity of this type of compounds in soy (57)(58)(59)(60)(61)(62)(63)(64)(65).
Saponins in soy are often referred to soyasaponins.They differ from each other by the types of aglycones and the position where the sugar chain is attached.Generally, saponins are classified into four major groups, on the basis of their aglycone structures: group A, B, E and DDMP.Group A saponins have a hydroxyl group at the C-21 position, and group B saponins have a hydrogen atom at the same position.Group E saponins differ from group A and B by having a carbonyl group at C-22.Group B saponins may contain a DDMP (2,3dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one) moiety at C-22 position, which are denoted as DDMP saponins (66) (Figure 3) .DDMP soyasaponins and the acetylated soyasaponins of group A are sometimes considered as the genuine forms of groups A and B in soybeans.Group E soyasaponins are also considered to be phyto-oxidation products of group B soyasaponins (62,67,68).All four groups of soysaponins are glycosides of oleanan triterpene aglycones known as soyasapongenols.The oleanan aglycone contains one or more hydroxyl groups, and carboxylic groups and double bonds may also be present.The sugar moieties are generally attached at the C-3 position and sometimes at the C-22 postion of the aglycones.Group A soysaponins have two sugar chains, separately attached to C-3 and C-22 positions of soyasapogenol A, except for A3 (33), which has only one sugar chain at C-3 (Table 1).C-3 sugar chain consists of two or three sugar residues, starting with a glucoronyl residue (glcUA) (67).C-22 side chain consists of two sugar residues, starting with an anarabinosyl, and ending with a xylosyl or glycosyl residue (58,63,65,69) (Figure 3).Group B soysaponins have one sugar chain attached to the C-3 position of soyasapogenol B, with three exceptional compounds that have two sugar chains at C-3 and C-22 positions (41-43) (57, 59, 69-71) (Figure 3).Most recently, a new soyasaponin Bh (40) was identified to bear an unique five-membered ring containing a hemiacetal functionality (Figure 3) (72).Group E soysaponins contain only one sugar chain at the C-3 position.They are considered to be formed by photo-oxidation at C-22 of group B (63, 69) (Figure 3).DDMP soyasaponins are categorized under B type soyasaponins by some researchers (27).Their structures were characterized as having DDMP group conjugated to group B at C-22 (67,68,73,74) (Figure 3).Similar to B type soyasaponins, DDMP soyasaponins only contain one sugar chain attached to C-3 postion.There are about 36 soysaponins identified in soybean.Their structures and the related references are listed (Tables 1-4).57) are considered by some researchers not to be genuine aglycones of soyasaponins, but as the acid hydrolysis products of soyasapogenol B (55) (76).
Fig. 4. The chemical structures of soyasapogenols A-E (hydrolysis products of soysaponins).

Health effects of soyasaponins and soyasapogenols
Plant saponins as a whole have been reported to have a wide range of biological activities, which were summarized with a long list in a recent review (77).Soyasaponins and soyasapogenols have been reported to display diverse health effects (78), including anticancer, cardiovascular protective effects, anti-virus, hepatoprotective actions and antioxidant activities (24,27,79,80).Their health effects largely depend on their chemical structures (81).Since this class of soy compounds are so poorly absorbed, their bioactivity maybe caused by indirect actions within the GI tract.

Anti-carcinogenic activities
Epidemiological studies have linked soy consumption to lower incidences of various types of cancer (82).As a group of major phytochemicals in soy, soyasaponins may be partially responsible (27).The evidence for soyasaponins having anti-carcinogenic effects in animal models is limited.Nevertheless, soyasaponins and soyasapogenols have been shown to have the anti-carcinogenic effects in a number of carcinoma cell lines.Before summarizing the data, we must keep in mind that since soy saponins are poorly absorbed, in vitro studies of these compounds in cell lines may not be able to provide much meaningful indication regarding their in vivo bioactivities.
The proposed mechanisms of anticarcinogenic properties of soyasaponins and soyasapogenols include direct cytotoxicity, induction of apoptosis, anti-estrogenic activity, inhibition of tumor cell metastasis, anti-mutagenic activity effect, bile acid binding action and normalization of carcinogen-induced cell proliferation (Table 5) (89).From these studies done in different cancer cell lines, we've learned that there are at least three major factors that may affect the observed effects of soyasaponins and soyasapogenols.The first factor is the testing materials.Some researchers used crude extracts while others used purified saponins.It is possible that components of the crude extract interact synergistically, thus inducing effects not observed with pure saponins.Therefore, investigations with purified saponins are indispensable for matching a result to the molecular action of a specific saponin (90).The second factor is the type of cell lines.It is clearly shown that different cancer cell lines respond differently to soy saponins.For instance, soyasaponin I (35) had no effect on HT-29 colon cell growth (81), but it can decrease the migratory ability of B16F10 melanoma cells (91).The third factor is the dose.In another study, soyasaponin III (37) showed significant growth suppression at the highest concentration tested (50 ppm), and no significant effects from concentrations 6 to 25 ppm.

Cardiovascular protective effects
Soyasaponins showed cardiovascular protective effects through several different mechanisms.
The hypocholesterolemic effects of soy saponins have long been recognized (92)(93)(94)(95).Two mechanisms by which saponins can affect cholesterol metabolism were suggested (96): 1) some saponins with particularly defined structural characteristics form insoluble complexes with cholesterol.When this complex-forming process occurs in the gut, it inhibits intestinal absorption of both endogenous and exogenous cholesterol.2) Saponins can interfere with the entero-hepatic circulation of bile acids by forming mixed micelles.The re-absorption of bile acids from the terminal ileum is effectively blocked (92).
In animal models, soyasaponins were found to significantly reduce serum total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), triglycerides (TG) concentrations, and to increase high-density lipoprotein-cholesterol (HDL-C) levels in rats (97).24  The anti-thrombogenic action of soyasaponins was evaluated in a model of disseminated intravascular coagulation (DIC) induced by infusion of endotoxin or thrombin in rats.Total soyasaponins prevented the decrease of blood platelets and fibrinogen, and the increase of fibrin degradation products during DIC induced by infusion of endotoxin or thrombin in rats.In vitro experiments, total soyasaponins, soyasaponins I (35), II (36), A 1 (27), and A 2 (28) inhibited the conversion of fibrinogen to fibrin (100).
Total soyasaponins decreased elevated blood sugar and LPO levels, and reversed the decreased levels of SOD in streptozocin-induced diabetic rats (101).In an -glucosidase inhibitory assay, groups B, E and DDMP soyasaponins were shown to have potent inhibitory activities with IC 50 values of 10-40 mol/L (102).

Anti-viral activities
Soyasapogenols A (54), B ( 55), E (58), and soyasaponin I (35), a major constituent of group B saponins, completely inhibited HIV-induced cytopathic effects 6 days after infection at concentration greater than 0.25 mg/mL, but had no direct effect on HIV reverse transcriptase activity.Soyasaponin I ( 35) also inhibited HIV-induced cell fusion in the MOLT-4 cell system (103).
Total soyasaponins showed significant inhibitory effect on the replication of HSV-1 and CoxB3.A soyasaponin cream was used in the treatment of patients suffering from herpes labialis.The treatment was found to be highly effective with a cure rate of 88.8% for the disease (104).Soyasaponin II (36) is more potent than soyasaponin I (35) as shown by a reduction of simplex virus type 1 (HSV-1) production.Soyasaponin II (36) was also found to inhibit the replication of human cytomegalovirus and influenza virus.This action was not due to inhibition of virus penetration and protein synthesis, but may involve a virucidal effect (105).In a structure-activity relationship study, the activity of soyasapogenol A (54) was less than 1/20 of that of soyasapogenol B (55), and the hydroxylation at C-21 seemed to reduce anti-HSV-1 activity (106).

Hepatoprotective actions
The group B soyasaponins I (35), II (36), III (37), and IV (38) all exhibit hepato-protective actions towards immunologically induced liver injury in primary cultured rat hepatocytes.The action of soyasaponin II (36) is almost comparable with that of soyasaponin I (35), whereas soyasaponins III (37) and IV (38) are more effective than soyasaponins I (35) and II (36).This suggests that the disaccharide group shows greater action than the trisaccharide group.Furthermore, the soyasaponins having a hexosyl unit shows a slightly greater action than that of the pentosyl unit in each disaccharide group or trisaccharide group.Structureactivity relationships suggest that the sugar moiety linked at C-3 may play an important role in hepato-protective actions of soyasaponins (107).
Also in in vivo experiments, total soyasaponins inhibit the elevation of liver transaminases when administered orally to rats with peroxidized corn oil.The liver injury caused by peroxidized salad oil is inhibited by the addition of soyasaponin A 1 (27) during peroxidation (108).

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Phytochemicals in Soy and Their Health Effects 55

Antioxidant activities
One mg of DDMP saponin/mL scavenges superoxide at a degree equivalent to 17.1 units of superoxide dismutase/mL by the ESR spin trapping method.The scavenging superoxide activity of DDMP soyasaponins is caused by the DDMP moiety attached to the triterpene aglycon since soyasaponin I (35), which is derived from soyasaponin βg (50).Lack of this group didn't show the scavenging activity (109).

Chemical characteristics of triterpenes and sterols
Triterpenes and sterols are found in soybean oil unsaponifiable matter.They are both present in minor quantities.
Three triterpenes have been identified in soy.They are 24-methylenecycloartenol (59) (98), cycloartenol (60) ( 98) and bacchara-12,21-dien-3-ol (61) (Figure 5) (110), respectively.Compounds 59 and 60 belong to the type of lanostane triterpene.In addition to having the basic structural characters of lanostane, they bear an extra tri-atomic ring in their structures that are formed by cyclization between methyl at C-18 and methine at C-9. Lanostane triterpenes in soy were believed to be the original materials for the biosynthesis of soy sterols.Bacchara-12,21-dien-3-ol ( 61) is a natural occurring of baccharane-type triterpene which has all six-membered tetracyclic skeleton, and its side chain is at position C-17.This type of triterpene is extremely rare in nature and no more than 20 compounds of this type have been separated and identified.

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Phytochemicals -Bioactivities and Impact on Health 56 Fig. 5.The chemical structures of triterpenes in soy.

Health effects of phytosterols
Phytosterols (not restricted to soy-based sources) that have long been known to reduce intestinal cholesterol absorption, lead to decreased blood LDL-cholesterol levels and lower cardiovascular disease risk.However, other biological activities for phytosterols have also been reported, including anti-cancer and immune modulatory effects.

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Phytochemicals in Soy and Their Health Effects 57 Fig. 6.The chemical structures of sterols in soy.

Phytosterols and cholesterol absorption
In the 1950's, phytosterols from soybeans were found to lower serum cholesterol level (116).
Since then, the cholesterol-lowering effects of phytosterols have been extensively demonstrated in both humans and animals (117)(118)(119)(120).A meta-analysis of 41 clinical trials showed that intake of 2 g/d of stanols or sterols reduced low-density lipoprotein (LDL) by 10%, with little additional reduction at higher doses (121).The U.S. National Cholesterol Education Program has recommended adding 2.0 g/day of phytosterols to the diet of adults to reduce LDL cholesterol and coronary heart disease risk (122).
Because phytosterols are not systemically absorbed, they are thought to act primarily in the intestinal lumen.As cholesterol analogs phytosterols compete for cholesterol in absorptive micelles resulting in reduced solubility of cholesterol (118).However, recent evidence suggests that the mechanism of action of phytosterols may be more complicated than originally thought (119,123).As summarized in a recent review (123), since phytosterols/phytostanols do not need to be present in the intestinal lumen simultaneously with cholesterol to inhibit its absorption (120), other studies have suggested that phytosterols/phytostanols may exert an unknown molecular action inside enterocytes and hepatocytes.In line with this, injected phytosterols/phytostanols reduced plasma cholesterol levels in hamsters (124).To gain insight into the phytosterol/phytostanol affects on circulating cholesterol concentration via mechanisms independent of the luminal incorporation of cholesterol into mixed micelles, the effects of these plant compounds on intestinal LXR-mediated targets involved in sterol absorption have been evaluated.Conclusive studies using ABCA1 and ABCG5/G8-deficient mice demonstrated that the phytosterol-mediated inhibition of intestinal cholesterol absorption is independent of these ATP-binding cassette (ABC) transporters.Other reports have raised questions as to whether phytosterols/phytostanols regulate cholesterol metabolism in intestinal and hepatic cells through independent-LXR pathways.A number of studies have proposed a phytosterol/phytostanol action on cholesterol esterification and lipoprotein assembly (ACAT, apoB), cholesterol internalisation (NPC1L1, ANXA2), cholesterol synthesis (HMG-CoA reductase, C-24-reductase) and removal of apoB100-containing lipoproteins (LDLr).However, the impact of phytosterol/phytostanol intake on these physiological processes in vivo remains unclear (123).
In one study specifically using soybean-derived phytosterols (125), it was found that consumption of phytosterol-supplemented ground beef lowered plasma TC and LDLcholesterol concentrations and TC:HDL cholesterol from baseline by 9.3%, 14.6%, and 9.1%, respectively.

Anti-cancer effects of phytosterols
In addition to their cholesterol-lowering actions, mounting evidence suggests that phytosterols possess anti-cancer effects against a number of different types of cancers (126)(127)(128)(129)(130)(131)(132).Phytosterols seem to act through multiple mechanisms of action, including inhibition of carcinogen production, cancer-cell growth, angiogenesis, invasion and metastasis, and through the promotion of apoptosis of cancerous cells.Phytosterol consumption may also increase the activity of antioxidant enzymes and thereby reduce oxidative stress.In addition to altering cell-membrane structure and function, phytosterols probably promote apoptosis by lowering blood cholesterol levels (127).

Physterols and immune function
Several reports in the literature suggest that phytosterols may have some immunological activity as highlighted in animal models of inflammation or even in in vitro and in vivo models of cancer (colorectal and breast cancer).Their direct immune modulatory activity on human lymphocytes has been proven, and the mechanism of action in cancer cells has been elucidated (133,134).

Anticancer activity
Estrogenic enterolignans, END or ENL are the major metabolites of lignans in the mammalian gut.Because estrogens were linked to some cancers, especially breast cancer, enterolignans could affect some cancer risk.To our knowledge, the estrogenic or antiestrogenic effects of enterolignans in humans are not very clear (142).For example, while weak estrogenic activity of ENL was demonstrated the anti-estrogenic activity of ENL was disclosed through depression of estrogen-stimulated rat uterine RNA synthesis (143).
The lignan ENL was found to have a bi-phasic effect on DNA synthesis in human breast cancer MCF-7 cells, showing induction at 10-50 M and inhibition at higher concentrations, with an IC 50 of 82.0 M (144).END and ENL are weak and moderate inhibitors of aromatase enzyme activity in a pre-adipose cell culture system (143).In human colon tumor cell (Figure 8), is a naturally occurring polyphosphorylated carbohydrate.It is widely distributed in the plant kingdom.Phytate serves as a storage form of phosphorous and minerals and contains ~75% of total phosphorous of the kernels (25).It is the major source of phosphorus in soy (79).Phytate is considered as a strong chelator of important minerals such as calcium, magnesium, iron, and zinc, and can contribute to mineral deficiencies in people.However, recent studies demonstrate that this "antinutrient" effect of IP6 is only manifested when large quantities of IP6 are consumed in combination with an oligoelements-poor diet (146).
Fig. 8.The chemical structures of phytic acid in soy.

Anti-cancer activities
Phytic acid (83) plays an important role in signal transduction, cell proliferation and differentiation (147).Recently phytic acid (83) has received much attention for its role in cancer prevention and control of experimental tumor growth, progression, and metastasis (148).A great majority of the studies were done in animals and showed that phytic acid had anti-neoplastic properties in breast, colon, liver, leukemia, prostate, sarcomas, and skin cancer (149,150).The results and proposed mechanism of anti-carcinogenic activities of IP6 in various cell lines are summarized in Table 6 (151)(152)(153)(154).
In animal studies, phytic acid can increase blood NK cell activity in DMH-induced colon tumors in rats, suppress rhabdomyosarcoma cell growth in a xeno-grafted nude mouse model (155), inhibit tumor growth and metastasis in rats (156), prolong survival of tumorbearing mice, and reduce the numbers of pulmonary metastases (157).Phytic acid can also inhibit DMBA-induced mouse skin tumor development and this inhibitory effect is likely, by modulating proliferation, differentiation, or apoptosis (158).

Other health effects
For a long time IP6 has been recognized as a natural antioxidant.In addition, IP6 possesses other significant benefits for human health, such as the ability to enhance the immune  6.The anti-carcinogenic activities of IP system, prevent pathological calcification and kidney stone formation, lower elevated serum cholesterol, and to reduce pathological platelet activity (148).IP6 inhibited the replication of HIV-1 in a T cell line and in a freshly isolated strain in peripheral blood mononuclear cells, possibly acting on HIV-1 early replicative stage (149)

Constituents formed during processing
Food processing may dramatically change the compositions and relative contents of the constituents in soy products and artificial compounds may also occur (159).The processing of foods can improve nutrition, quality, and safety; though processing could also lead to the formation of anti-nutritional and toxic compounds.These multi-faceted consequences of food processing result from molecular interactions among nutrients and with other food ingredients, both natural and added (160).Some components isolated from soy products such as soy sauce and fermented products do not occur naturally in the soybean.And the types of these compounds vary among different soy products based upon processing methods.These compounds may be formed by 1) soybean processing or fermentation; 2) compounds from other ingredients of soy products; 3) compounds from reactions of components in soybean and/or other ingredients during processing.Even though these compounds are not found naturally in soybean, they do exist widely in various soy products and may contribute to important beneficial or detrimental biological effects associated with soy consumption.Unfortunately, the key role of these compounds is largely ignored.
In Japan, soybeans molasses and soy fermented with Bacillus subtilis (natto) are very popular daily foodstuffs (161).Six isoflavones which differ from that isolated from soy were generated by this process.Another group of well-known compounds formed during food processing in soy is The Maillard reaction products (163,164).The Maillard reaction is the heat-induced reaction of amino groups of amino acids, peptides, and proteins with carbonyl groups of reducing sugars such as glucose, that results in the concurrent formation of so-called Maillard browning products and acrylamide (165).In the past, extensive work has been done on Maillard reaction products in food products including several excellent reviews (160,(164)(165)(166)(167). Five Maillard reaction products, fructose-lysine (92), fructose-alanine (93), fructosevaline (94), fructose-leucine (95) and fructose-isoleucine (96) (Figure 11) were isolated from soy sauce and miso (168,169).

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Phytochemicals -Bioactivities and Impact on Health 66 Processing may also significantly elevate or reduce certain naturally occurring soybean components.For instance, a remarkable increase in folate content was found after fermentation, 5.2-fold and 1.7-fold higher than that of the boiled soybeans and soybean seeds, respectively (175).Thus, we must be aware that the composition of soybean products may differ substantially from the native soybean.

Conclusion
The soy bean has been used as a human food source of high quality protein and other nutrients for hundreds of years and is currently a major source of protein in commercial food products for the beef, pork and chicken industry.This chapter summarizes our current knowledge about chemical structures and health effects of the major phytochemicals in soy.Clearly, the observed health effects from soy or soy-based foods (other than those attributed to nutrients like protein) are not solely from the actions of certain individual or types of compounds, but rather are due to the mixed effects of different compounds.Additive, synergistic, and/or antagonistic effects of different soy components combine to provide a final effect of soy foods and these effects may also be altered by phytochemicals from other non-soy foods in the meal.In order to fully understand the mechanism of health effects of soy, it is important to identify the genuine bioactive compounds in soy.

Phytochemicals -Bioactivities and Impact on Health 64 Fig. 10 .
Fig. 10.The chemical structures of new isoflavones generated during food processing in soy products.

Fig. 11 .
Fig. 11.The chemical structures of other components generated during food processing in soy products.

Table 1 .
The structures and molecular formulas of group A soyasaponins

Table 2 .
The structures and molecular formulas of group B soyasaponins

Table 3 .
The structures and molecular formulas of group E soyasaponins

Table 4 .
The structures and molecular formulas of group DDMP soyasaponins www.intechopen.comPhytochemicals-Bioactivities and Impact on Health

Table 5 .
The anti-carcinogenic activities of soyasaponins and soyasapogenols