Isoflavone Levels in Soy Foods Consumed by Multiethnic Populations in Singapore and Hawaii

Isoflavone Levels in Soy Foods Consumed by MultiethnicPopulations in Singapore and Hawaii

Adrian A. Franke,*,† Jean H. Hankin,† Mimi C. Yu,‡ Gertraud Maskarinec,†Siew-Hong Low,§ and Laurie J. Custer†

Cancer Research Center of Hawaii, 1236 Lauhala Street, Honolulu, Hawaii 96813, University of SouthernCalifornia/Norris Comprehensive Cancer Center, 1441 Eastlake Avenue, Los Angeles, California 90033, andDepartment of Community, Occupational and Family Medicine, University of Singapore, Singapore 119074

Concentrations and glucosidic conjugation patterns of isoflavones were determined in soy foodsconsumed by multiethnic populations in Singapore and Hawaii. Six raw and 11 cooked food groupstraditionally consumed in Singapore and 8 food groups consumed in Hawaii were analyzed byreversed-phase high-pressure liquid chromatography with diode array detection. Mean totalisoflavone levels varied between 35 and 7500 ppm, with the lowest values found in soy milk andburgers and the highest levels observed in soybean and its seeds and in supplements. Total isoflavonelevels and conjugation patterns varied as a function of soybean variety, storage conditions, andfood processing. A large contribution to the differences in total isoflavone content between foodgroups was due to the water content in foods and to leaching of polar analytes into the water phaseduring boiling. Soy protein drinks and traditional soy foods were found to possess very similarisoflavone amounts considering usual serving sizes.

Keywords: Isoflavones; genistein; daidzein; glycitein; isoflavone conjugates; soy foods; supplements;high-pressure liquid chromatography; diode array detection

INTRODUCTION

Soy consumption has been implicated in the preven-tion of cancer and other chronic conditions due to thelow disease risk of Asian populations with high soyintake (Adlercreutz and Mazur, 1997; Lee et al., 1991;Barnes et al., 1994b). This hypothesis is supported bythe observation that Asians experience an increase inincidence of these chronic conditions after migrating tothe West, suggesting a causal role of environmentalfactors (Nomura et al., 1978; Ziegler et al., 1993). Thestrongest protective effect of soy intake was reportedfor breast, prostate, and colon cancer (Messina et al.,1994; Adlercreutz, 1995; Kurzer and Xu, 1997) andpotentially also endometrial cancer (Goodman et al.,1997). Recent case-control studies observed lower en-dogenous estrogen levels in Japanese women with highsoy intake (Nagata et al., 1997) and a 15% reduction inbreast cancer risk with every serving of tofu consumed(Wu et al., 1996). The prominent phytochemicals thatare believed to contribute to the biological effectsobserved after soy consumption include isoflavones(Barnes et al., 1994b) and also phytate, saponins,sterols, and protease inhibitors (Messina et al., 1994).The cancer protective effects of isoflavones may be basedon their antioxidant (Wei et al., 1995), antiestrogenic(Mousavi and Adlercreutz, 1993; Adlercreutz et al.,1993; Makela et al., 1995; Cassidy et al., 1994), anti-mutagenic and antiproliferative (Hirano et al., 1994;

Peterson and Barnes, 1993), transformation-inhibiting(Franke et al., 1998a), differentiation-inducing (Con-stantinou and Huberman, 1995), angiogenesis-inhibit-ing (Fotsis et al., 1995), and apoptosis-inducing (Kyleet al., 1997) effects. The anticarcinogenic activity ofisoflavones is supported by the prevention of mammary,prostate, and leukemic cancers in various animal models(Barnes et al., 1990; Lamartiniere et al., 1995; Murrillet al., 1996; Pollard and Luckert, 1997; Zhang et al.,1997; Uckun et al., 1995). Humans are exposed toisoflavones mainly through soybeans, including blacksoybeans (Franke et al., 1995) and its food products(Franke et al., 1994, 1998b; Adlercreutz and Mazur,1997).

Gas and liquid chromatographic techniques withphotodiode array, electrochemical, fluorometric, andmass spectrometric detection have been applied previ-ously to determine isoflavone levels in soybeans and itsproducts (Franke and Custer, 1994; Barnes et al., 1994a;Coward et al., 1993; Adlercreutz and Mazur, 1997;Pettersson and Kiessling, 1984). Daidzein, genistein,and glycitein are the major isoflavones found in thesefoods, occurring predominantly as glucosides and ma-lonyl glucosides and to a minor extent as acetyl gluco-sides and “free” aglycons (Franke et al., 1998b; Kudouet al., 1991; Wang and Murphy, 1994a; Barnes et al.,1994a). In soybean seeds, total isoflavone levels averageat 2000 ppm relative to dry weigt, but these concentra-tions vary depending on a variety of factors such asenvironmental, genetic, harvesting, and processingconditions (Wang and Murphy, 1994b; Tsukamoto et al.,1995; Barnes et al., 1994a; Coward et al., 1993). Morerecently, isoflavone levels in soy-based infant formulawere added to the growing list of isoflavone-containing

* Author to whom correspondence should be addressed[telephone (808) 586-3008; fax (808) 586-2973/-2970; [email protected]].

† Cancer Research Center of Hawaii.‡ University of Southern California.§ University of Singapore.

977J. Agric. Food Chem. 1999, 47, 977−986

10.1021/jf9808832 CCC: $18.00 © 1999 American Chemical SocietyPublished on Web 02/03/1999

foods (Franke et al., 1998c; Setchell et al., 1987, 1997;Murphy et al., 1997).

Here we report concentrations of isoflavones, includ-ing data on conjugated and unconjugated analytes(Figure 1), in little investigated foods commonly con-sumed by Asians and Americans in Singapore andHawaii. These results will support future epidemiologicstudies exploring the role of soy consumption in diseaseprevention.

MATERIALS AND METHODS

Apparatus. HPLC analyses were carried out on a systemGold chromatograph with an autosampler model 507, a dualchannel diode array detector model 168 (all units from Beck-man, Fullerton, CA), and a Coulochem II-5200 electrochemicaldetector (ESA, Bedford, MA) using a 5011 coulometric cell.Absorbance readings were obtained from a DU-62 spectropho-tometer (Beckman). Evaporation was performed with a SavantAS 160 Speed-Vac (Farmingdale, NY) at room temperature.

Chemicals. Methanol, acetic acid, 96% ethanol, dimethylsulfoxide (DMSO), ethyl acetate, and all solvents used forHPLC and absorbance readings were of analytical grade orHPLC grade from Fisher Scientific (Fair Lawn, NJ). Butylatedhydroxytoluene (BHT), sodium acetate, and genistein werepurchased from Sigma Chemical Co. (St. Louis, MO). Daidzeinand genistein were obtained from ICN (Costa Mesa, CA),flavone was from Aldrich (Milwaukee, WI), and coumestrol wasfrom Serva (New York, NY).

Food Items. Soy foods from Singapore and Hawaii wereobtained from open markets or from local stores: Garcinia-max diet shake, Rainbow Light Nutritional Systems, SantaCruz, CA; Light and Fit Energy Shake, Earthrise Co., Peta-luma, CA; Slim and Trim diet shake, Nature’s Way ProductsInc., Springville, UT; soy protein, Down to Earth, Honolulu,HI; Spiru-tein cappuccino high-protein meal, Nature’s Plus,Melville, NY; soy flour, Arrowhead Mills, Hereford, TX; soyflour, Miller Co., St. Louis, MO; genistein food supplement,Source Naturals, Inc., Scotts Valley, CA; Soy Super Complex,Rainbow Light Nutritional Systems, Santa Cruz, CA; vegetar-ian enzyme complex, Futurebiotics, Brattleboro, VT; fat-freeSoya Kaas jalapeno Monterey Jack style, American NaturalSnacks, St. Augustine, FL; natto prepared cultured soybean,Aloha Tofu Factory, Inc., Honolulu, HI; Veggy Singles, Swissalternative, Soyco Foods, Orlando, FL; Nu Tofu mozzarellacheese alternative and Nu Tofu Cheddar cheese alternative,Cemac Foods Corp., Philadelphia, PA; Veggy Singles, Ameri-can alternative, Soy Power Co., Inc., Los Angeles, CA; WhiteWave dairyless vanilla, White Wave, Boulder, CO; Nancy’s soyyogurt, Springfield Creamer, Eugene, OR; Garden Veggie,

Wholesome and Hearty Foods, Inc., Portland, OR; NaturalTouch vegan burger, Worthington Foods, Inc., Worthington,OH; Boca Burger, Boca Burger Co., Ft. Lauderdale, FL; Soysingles, American alternative, Soymage, Orlando, FL; SuperGreen Pro-96, Nature’s Life, Golden Grove, CA; TakeCareplain, Protein Technologies International, St. Louis, MO; soychocolate milk, Trader Joe, South Pasadena, CA; white soymilk, Pacific Foods of Oregon, Inc., Tualatin, OR; soybeanseeds, Health Foods, San Diego, CA; roasted soybean seeds,Health Foods, Little Rock, AR.

Fresh items were frozen or cooked immediately afterpurchase followed by freeze-drying prior to extraction andanalysis. Items of the same food group were collected on thesame day from different sources/markets. Cooking was per-formed exclusively by boiling. All items from Singapore wereboiled for 5 min except for soybeans (10 min). Boiling time foritems from Hawaii was 3 min for soy sprouts, 5 min for taupok (fried pressed tofu), 7 min for soybeans, 10 min for foojook (soybean curd sticks), and 60 min for dry soybean seeds.

Soy Protein Drink Test. Eight soy protein drinks weretested in 33 volunteers regarding aroma, texture, color, flavor,acceptance, and willingness to consume again as criteria. Ascore scaled from 1 (worst) to 5 (best) was given to eachcriterion of all eight items after being consumed by thevolunteers. An item was considered qualified for use inintervention studies when the mean score of each criterionexceeded a value of 3.1.

Extraction of Isoflavones from Soy Foods. Soy foodswere freeze-dried and homogenized as described previously(Franke et al., 1998b), and 0.5 g of dry powder was extractedwith 80% aqueous methanol (v/v) containing 20 ppm flavoneas internal standard by sonication (10 min) and stirring (2 h)at room temperature, yielding isoflavone conjugates andoriginally present aglycons. After centrifugation, a clear aliquotwas diluted 1:1 with 0.2 M acetate buffer (pH 4) and 20 µLwas injected into the HPLC system. In a parallel experiment20 µL of a 1:1 mixture of 80% aqueous methanol (v/v)containing 20 ppm flavone and 0.2 M acetate buffer (pH 4)was injected into the HPLC system in the same batch forinternal standard recovery calculation purposes.

Standard Solutions, Calibration Curves, and Calcula-tion of Food Levels. As detailed previously (Franke et al.,1994), we determined stock solution concentration of authenticstandards with absorbance readings at the wavelength withmaximum absorption (λmax) using molar extinction coefficients(ε) (Ollis, 1962). Glycitein values (λmax ) 256 nm, ε ) 22387)were used as previously determined (Kelly et al., 1993). Dueto the lack of availability of authentic standards for certainconjugated analytes, λmax and ε values of the respectiveaglycons were applied (Coward et al., 1993). We and othersmade this assumption because 7-O-substituents do not change

Figure 1. Soy isoflavone structures and codes assigned.

978 J. Agric. Food Chem., Vol. 47, No. 3, 1999 Franke et al.

the flavonoid chromophores significantly (Markham and Mab-ry, 1975; Markham et al., 1990) and because isoflavoneresponse factors do not change with variable retention timeswhen diode array detection is applied (Franke et al., 1998b).In addition, the identity of analytes was confirmed by usingan external standard consisting of an extract from authentictoasted soy obtained from Dr. Stephen Barnes (University ofAlabam), which has been analyzed by LC/MS (Barnes et al.,1994a).

Chromatographic Conditions. All HPLC analyses werecarried out as reported previously (Franke et al., 1998b;Franke and Custer, 1994) on a NovaPak C18 (150 × 3.9 mmi.d.; 4 µm) reversed-phase column (Waters, Milford, MA)coupled to an Adsorbosphere C18 (7.5 × 4.6 mm i.d.; 5 µm)direct-connect guard column (Alltech, Deerfield, IL). Elutionwas performed at a flow rate of 0.8 mL/min with the followinglinear gradient: A ) acetic acid/water (10:90 v/v), B )methanol/acetonitrile/dichloromethane (10:5:1 v/v/v); B in A(v/v), 5% for 5 min, from 5 to 45% in 20 min, from 45 to 70%in 6 min, and from 70 to 5% in 3 min with equilibration for 15min before subsequent injection. Analytes were monitored bydiode array detection at 260 and 280 nm and coulometricallyat +500 mV during the entire HPLC run simultaneously.Observed peaks were scanned between 190 and 400 nm foridentification purposes.

RESULTS AND DISCUSSION

Individual and total isoflavone levels and isoflavoneconjugation and aglycon patterns in soy foods weredetermined for items typically consumed by Chinesepeople in Singapore (Table 1, 6 food groups), by Asianpeople in Hawaii (Table 2, 11 food groups), and byWestern populations in Hawaii (Tables 3 and 4, 8 foodgroups). The results presented summarize and detailthe dietary data used for recent epidemiologic studieson soy intake and urinary isoflavone excretion (Maskari-nec et al., 1998; Seow et al., 1998). Each soy food grouptested consisted of three to eight items, which werecollected from different markets on the same day toaccount for variability within the same food type. Theisoflavone concentrations were obtained by previouslydeveloped HPLC methods using diode array detection(Franke and Custer, 1994; Franke et al., 1998b) and arepresented in aglycon units to account for differences inmolecular weight of the various analytes. Most raw orunprocessed items such as raw foo jook (soybean curdsticks), raw tau kwa (pressed tofu), raw tau pok (friedpressed tofu), and raw soybeans are rarely consumedunprocessed, but data on these items (Franke et al.,1998b) were included here to explore differences due toprocessing (boiling). Treatment of soy extracts withacids or enzymes including glucuronidase/sulfatasemixtures (Franke and Custer, 1994; Setchell et al., 1987)leads to less complex chromatograms by hydrolyzing theconjugates into aglycons. However, conjugated andunconjugated isoflavones have different pharmacoki-netic properties and biopotencies (Barnes et al., 1994b).Isoflavones are absorbed very quickly, with peaks inplasma levels reached 1 h and again 6-8 h after intake(Franke et al., 1997, 1998b), and are eliminated within1-2 days, predominantly as glucuronide and sulfateconjugates through the kidney (Xu et al., 1994; Frankeet al., 1994, 1998b; Franke and Custer, 1994; Setchell,1985). Fermented items containing mainly aglyconswere suggested to have higher isoflavone bioavailabilitycompared to nonfermented soy items that containmainly glucosides (Hutchins et al., 1995). We thereforedecided to analyze conjugated and unconjugated isofla-vones as occurring in soy foods by extraction withaqueous methanol (Barnes et al., 1994a).

Mean total isoflavone levels in the food groupsinvestigated varied between 35 and 7500 ppm, withlowest values found in soy milk and burgers and highestlevels found in soybean and its seeds and, of course, insupplements. Most foods we investigated varied between100 and 800 ppm of total isoflavones, with low levelsobserved in items processed by mixing with nonsoycomponents (cheeses) and with high levels observed in“dry” items (soy protein drink powders). A large contri-bution to the variability in isoflavone content was foundto be due to moisture. This occurred because most foodswere found to have very similar isoflavone levels aftercorrecting for water content, which is also apparent fromthe difference observed for raw (dry) and cooked (wet)foods, especially, in foo jook and soybeans (Table 1).Differences between raw and cooked foods that couldnot be explained by moisture were partly due to leachingof the polar isoflavone conjugates into the boiling waterduring processing. We determined isoflavone levels inthe water used for boiling of some representative boileditems and found isoflavone amounts equaling almostexactly the difference between cooked and raw itemsafter adjustment of moisture (data not shown). This wastrue not only for total isoflavones but, in particular, forthe polar conjugates. Boiling for up to 1 h did notconsiderably change the conjugation or aglycon pattern.The temperature applied was probably too low and theperiod of boiling too short to lead to a sufficienthydrolysis and decarboxylation of the conjugates ordegradation of the aglycons observed with dry heat suchas roasting, toasting, or frying in oil (Coward et al.,1993; Barnes et al., 1994a; Franke et al., 1994). Withinthe soy milk group, the item with higher fat contentshowed significantly higher isoflavone levels, indicatingthat defatting removes isoflavones.

Similar to recent reports about isoflavones in varioussoy foods (Franke et al., 1994, 1998b; Kudou et al., 1991;Barnes et al., 1994a; Wang and Murphy, 1994a), wefound typically a total isoflavone ratio of 45:45:10 fordaidzein/genistein/glycitein, which did not change sub-stantially between food groups or with processing.Supplements presented an exception; they had highlyvariable ratios of isoflavones. In contrast to total isofla-vones, conjugation patterns in all soy foods were highlyvariable between and even within food groups. Glucosylmalonates are the predominant conjugate in the soy-bean seed (Kudou et al., 1991). We found the highestratio of this conjugate (65-72%) in unprocessed soybeanand its seeds, particularly when stored frozen, and insoy flours (Tables 1-3). Boiling soybeans for 1 h resultedin an 8% decrease in glucosyl malonates and a concomi-tant increase in 6% and each 1% of glucosides, acetyl-glucosides, and aglycons, respectively, whereas tau pok(fried and pressed tofu) showed the highest ratio ofacetyl glucosides (24%). This can be explained by theheat applied during the processing of these itemsleading to conditions that cause hydrolysis in hot waterand to decarboxylation by frying in oil, respectively(Barnes et al., 1994a).

Exclusively aglycons were detected in fermented tofu(Table 1), but miso, which is produced by incubationwith Aspergillus soja, showed only incomplete hydrolysisof the isoflavone conjugates with a yield of ∼50%aglycons (Table 2). An even lower aglycon yield wasobserved for natto, which is fermented with Bacillusnatto (Table 2). This is consistent with previous analysesof fermented products known to contain predominantly

Isoflavones in Soy Foods from Singapore and Hawaii J. Agric. Food Chem., Vol. 47, No. 3, 1999 979

Tab

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763

30

217

214

139

1714

129

741

452

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(nc

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48-

556-

1039

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33-

108

3-9

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107-

177

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425

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592-

36-

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222

332

270

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112

1329

218

2913

160

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467

5561

649

20

216

213

124

1511

925

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442

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(n)

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6-8

38-

7340

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3-8

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310

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103-

150

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287

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Tab

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Mea

nIs

ofla

von

eL

evel

san

dP

atte

rns

inT

rad

itio

nal

Asi

anS

oyF

ood

sfr

omH

awai

ia

mg/

kg%

b

DG

LY

GD

-Mal

GL

Y-

Mal

G-M

alD

-Ac

GL

Y-

Ac

G-A

cD

EG

LY

EG

Eto

tal

DE

tota

lG

LY

Eto

tal

GE

tota

lis

ofla

von

esgl

uco

s-id

esm

alon

ylgl

uco

side

sac

etyl

glu

cosi

des

agly

-co

ns

firm

tofu

6214

6577

1365

20

229

323

169

3115

535

537

411

21ra

nge

(nc

)3)

20-

106

6-24

19-

101

24-

121

4-24

20-

970-

30-

11-

326

-3

1-4

15-

2773

-25

614

-54

67-

217

154-

497

30-

4431

-46

9-39

inte

rite

mS

Dd

439

4249

1040

10

23

27

9220

7817

97

90

16so

ftto

fu51

1453

6713

602

02

183

1413

730

129

297

4044

115

ran

ge(n

)3)

28-

737-

2225

-72

23-

100

5-21

18-

771-

20-

11-

310

-23

1-4

6-20

73-

185

16-

4761

-16

415

1-37

738

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31-

531-

24-

28in

teri

tem

SD

237

2539

836

00

17

28

5816

5912

72

120

12ra

wta

ukw

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2711

586

2080

51

558

950

238

5725

054

542

342

22ra

nge

(n)

3)75

-10

514

-39

110-

124

69-

113

18-

2365

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85-

61-

24-

654

-65

6-13

39-

6220

3-25

939

-77

230-

276

523-

574

39-

4330

-42

18-

25in

teri

tem

SD

1513

824

324

00

06

311

3019

2426

37

04

cook

edta

upo

k33

549

111

1514

223

465

5110

314

138

254

3511

1539

ran

ge(n

)3)

19-

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623

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7-13

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11-

3118

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3-8

22-

8152

-13

418

-65

-19

512

5-34

730

-36

10-

1414

-16

34-

45in

teri

tem

SD

132

223

06

50

1126

230

445

6711

64

20

6co

oked

foo

jook

468

698

18

30

444

625

101

1610

522

355

73

34ra

nge

(n)

3)18

-82

8-14

62-

109

3-17

0-4

3-15

1-4

0-1

3-6

24-

833-

1212

-40

48-

186

6-31

66-

170

120-

386

47-

674-

93-

426

-35

inte

rite

mS

D32

637

82

62

02

335

1474

1356

143

103

08

cook

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ybea

ns

233

3325

314

824

135

171

1820

320

418

6142

590

457

344

5ra

nge

(n)

3)20

7-25

827

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207-

321

128-

1651

23-

2699

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615

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2415

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15-

2539

6-43

856

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364-

536

827-

1037

53-

6229

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3-5

4-5

inte

rite

mS

D25

560

182

345

05

50

521

496

116

45

00

cook

edgr

een

soyb

ean

seed

sf16

1320

5730

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12

22

176

4671

193

2470

23

ran

ge(n

)3)

9-27

11-

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26-

3531

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1-3

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31-

31-

31-

254

-10

342

-51

42-

9114

7-23

621

-31

64-

732-

32-

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teri

tem

SD

101

1114

415

00

00

00

255

2644

55

00

cook

edso

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rou

ts11

119

385

460

10

00

050

867

125

2472

21

ran

ge(n

)2)

8-14

12-

2730

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4-6

35-

580-

139

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47-

8693

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622

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71-

741-

2in

teri

tem

SD

40

1112

116

00

00

00

162

2845

32

00

soy

mil

k21

624

298

220

00

70

558

1552

125

4641

211

ran

ge(n

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815

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5-9

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153

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73

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00

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02

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2733

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mis

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236

112

114

04

6012

6498

1611

523

030

123

55ra

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(n)

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18-

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1015

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2925

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435

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14-

3651

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090

-41

823

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8-24

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47-

65in

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tem

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101

289

18

50

553

1552

6917

8416

99

102

9n

atto

(n)

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216

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027

288

1916

323

4955

319

849

012

4173

44

19

mea

nin

tra-

assa

yC

Vg

(%)

37

38

127

320

42

53

36

32

32

75

aL

evel

sin

food

sas

con

sum

edan

dex

pres

sed

inag

lyco

nu

nit

sde

term

ined

bydu

plic

ate

anal

ysis

(giv

ein

bold

face

type

);co

okin

gti

me

was

boil

ing

for

3m

info

rso

ysp

rou

ts,5

min

for

tau

pok,

7m

info

rso

ybea

ns,

10m

info

rfo

ojo

ok,

and

60m

info

rdr

yso

ybea

nse

eds.

Abb

revi

atio

ns

are

list

edin

Fig

ure

1.b

Rou

ndi

ng

may

lead

toa

tota

lof

mor

eor

less

than

100%

.c

n)

nu

mbe

rof

diff

eren

tfo

odso

urc

es;0

)be

low

dete

ctio

nli

mit

(see

Tab

le1)

.dIn

teri

tem

SD

)st

anda

rdde

viat

ion

betw

een

diff

eren

tfo

odit

ems.

eT

aukw

a)

pres

sed

tofu

;tau

pok

)fr

ied

tau

kwa;

foo

jook

)sk

imm

eddr

ysu

pern

atan

tob

tain

edby

boil

ing

soyb

ean

mea

l(s

oybe

ancu

rdst

icks

).fF

roze

nra

wm

ater

ial.

gM

ean

intr

a-as

say

coef

fici

ent

ofva

rita

ion

for

dupl

icat

ean

alys

isof

all

29it

ems.


Tab

le3.

Isof

lavo

ne

Lev

els

and

Pat

tern

sin

Wes

tern

Soy

Foo

ds

from

Haw

aiia

mg/

kg%

b

DG

LY

GD

-Mal

GL

Y-

Mal

G-M

alD

-Ac

GL

Y-

Ac

G-A

cD

EG

LY

EG

Eto

tal

DE

tota

lG

LY

Eto

tal

GE

tota

lis

ofla

v-on

esgl

uco

s-id

es

mal

onyl

glu

cos-

ides

acet

ylgl

uco

s-id

esag

ly-

con

s

soy

prot

ein

drin

ksG

arci

nia

-max

diet

shak

e,ch

ocol

ate

7122

101

7232

104

152

2011

511

170

6023

646

542

458

6

Lig

ht

and

Fit

ener

gysh

ake

207

3236

710

040

177

234

2643

3046

373

106

617

1097

5529

511

Sli

man

dT

rim

diet

shak

e30

647

3619

5914

225

619

1187

4714

227

730

4115

13

Dow

n-t

o-E

arth

114

2317

716

784

324

5016

6240

1933

371

143

596

1110

2852

128

Spi

ru-t

ein

,ca

ppu

ccin

o51

1074

6279

111

224

308

3011

143

123

226

492

2851

1110

Spi

ru-t

ein

,ch

ocol

ate

pean

ut

butt

er60

1172

5863

102

264

389

3313

154

112

224

490

2946

1411

Su

per

Gre

enP

ro-9

677

3316

418

974

300

n.d

.12

5133

232

299

121

547

967

2858

77

Tak

eCar

e,pl

ain

213

6134

136

077

399

456

7023

534

641

149

845

1634

3851

74

mea

n(n

c)

8)10

325

168

131

5919

728

640

2218

2428

010

842

981

635

4710

9in

teri

tem

SD

d14

643

251

295

3325

623

533

163

2041

750

500

921

1110

31

soy

mil

kch

ocol

ate

235

281

02

00

00

00

245

3160

945

00

Pac

ific

52

40

00

00

00

00

52

411

972

01

mea

n(n

)2)

143

160

01

00

00

00

153

1735

953

01

inte

rite

mS

D5

14

00

00

00

00

05

14

112

10

0so

ych

eese

sja

lape

no

Mon

tere

yJa

ck,f

atfr

ee23

335

4311

399

112

26

178

2188

188

3350

125

Veg

gyS

ingl

es,

Sw

iss

alte

rnat

ive

125

123

031

04

03

71

1817

4479

3643

615

Veg

gyS

ingl

es.

Am

eric

anal

tern

ativ

e4

85

60

140

35

76

017

1724

5830

3412

24

Nu

Tof

um

ozza

rell

a10

1312

92

00

03

36

321

2119

6158

175

20N

uT

ofu

Ch

edda

r10

1411

80

10

01

25

020

1913

5266

182

14so

yG

ourm

etM

ozza

rell

ast

yle

00

32

00

00

00

30

33

39

4227

030

Soy

Sin

gles

2917

6632

2553

2311

2214

08

9853

150

301

3737

188

mea

n(n

)7)

139

2115

520

53

64

52

3721

4910

743

328

16in

teri

tem

SD

2312

7335

4457

4315

2915

011

9837

161

286

1214

144

soy

yogu

rts

Wh

ite

Wav

eda

iryl

ess

van

illa

115

4514

612

441

131

523

418

517

309

9429

870

144

428

6

Nan

cy’s

soy

yogu

rt88

2211

257

1554

102

876

467

230

4324

051

343

244

29m

ean

(n)

2)10

134

129

9028

9231

36

474

4227

069

269

607

4333

617

inte

rite

mC

V(%

)19

4719

5267

5994

4039

8713

8421

5315

220

3853

94ve

geta

rian

burg

ers

Gar

den

Veg

gie

00

02

110

00

00

50

216

017

073

027

Nat

ura

lTou

chve

gan

burg

er4

40

32

317

48

33

027

1212

5116

1556

12

Boc

aB

urg

er8

1412

50

610

012

02

023

1730

7049

1633

3m

ean

(n)

3)4

64

34

39

27

13

017

1514

4622

3530

14in

teri

tem

SD

817

203

05

91

110

00

183

3240

5715

312

soy

flou

rsA

rrow

hea

d45

521

335

790

732

672

777

2648

5628

2214

9659

311

5532

4332

605

3D

own

toE

arth

204

103

239

488

194

621

126

912

36

715

306

876

1897

2969

11

mea

n(n

)2)

330

158

298

697

260

674

4416

2934

1514

1106

449

1015

2570

3065

32

inte

rite

mS

D11

051

6720

770

6912

59

113

535

713

817

070

32

61

0


isoflavone aglycons through bacterial hydrolysis of theconjugates (Wang and Murphy, 1994a; Coward et al.,1993; Franke et al., 1998b). Variable conjugate ratioswere found in other food groups, which may be due todifferential handling, processing, storage, and exposureto bacterial enzymes. Our observations are consistentwith earlier findings on factors that influence theisoflavone conjugation pattern: the predominating glu-cosyl malonates in soy plants (Kudou et al., 1991) willbe converted easily as a result of heat, water, andexposure to bacterial enzymes that form acetyl gluco-sides by decarboxylation of the malonyl moiety, gluco-sides by hydrolysis of the acyl group, and aglycons byhydrolysis of the sugar moiety, respectively (Barnes etal., 1994a; Wang and Murphy, 1994a; Franke andCuster, 1994).

There was no consistent pattern when mean isofla-vone amounts were compared between the same foodsgroups from Singapore and Hawaii. Our data indicatedthat mean isoflavone levels of raw tau kwa (pressedtofu) and cooked tau pok (fried pressed tofu) weresmaller by a factor of ∼2 in Singapore items versusHawaii items, and the opposite was true for cooked foojook (soybean curd sticks) and fermented items, whereasother foods did not show any significant difference. Adetailed analysis was very difficult in this respect dueto the large variability within the food groups of eachgeographical area, and no conclusions could thereforebe drawn regarding patterns of isoflavone contents asa function of geographical area. Isoflavone levels willdepend ultimately on the individual processing andhandling of the food item. The small intra-assay vari-ability underscored the validity of the analytical pro-cedure applied and could not explain the large differencewe observed between or within food groups.

Soy protein drinks and soy supplements have becomeincreasingly popular in North America in recent yearsand are a major source of isoflavone exposure inCaucasian populations. Although serving sizes werevery similar, the composition of soy protein drinksvaried in protein, carbohydrate, energy, and total isofla-vone amount by factors of 4, 7, 2, and 5, respectively(Table 4). Three of 8 items analyzed contained fat inamounts of 1-3 g per serving, which may be of impor-tance due to the presence of vitamin E in the lipophiliccompartment. We found R-, γ-, and δ-tocopherol levelsin fat-containing soy drinks ranging from 1 to 7 µg/gapplying HPLC techniques developed for plasma mi-cronutrient analysis (Franke et al., 1993). Tocopherolpatterns in these items were observed to be typical forthose in soy oils (Cooney et al., 1997), indicating thatthe lipids found in these drinks stem from the soyprotein preparation rather than from additives. Mostnonfat items were found to contain R-tocopherol acetate(60-985 µg/g) as an additive.

For compliance-related purposes, in future interven-tion trials soy protein drinks were tested regardingvarious criteria including acceptability, flavor, andwillingness to consume again using a score scale from1 (worst) to 5 (best) among 33 volunteers. We foundlarge differences between the acceptance of these drinks(mean score ) 1.4-3.5), with two items (Slim and Trim,TakeCare) being favored unanimously, whereas theother drinks did not qualify for use in interventionstudies. According to our findings, one serving of soyprotein drink results in total soy isoflavone exposuresimilar to a typical 4 oz serving size (Messina et al.,

soyb

ean

seed

sra

w41

319

768

267

6728

849

436

220

4575

075

1317

2142

565

363

roas

ted

347

4139

835

855

377

2538

972

057

830

7489

918

0344

544

7m

ean

(n)

2)38

030

583

318

6133

237

413

470

5179

075

1108

1973

505

405

inte

rite

mS

D43

2217

97

08

7111

3254

09

600

240

219

80

64

soy

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t20

6123

5161

020

6910

9232

223

2812

7352

324

863

4667

0547

7915

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3927

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enz-

yme

com

plex

2650

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9611

341

249

3524

383

mea

n(n

)3)

1096

1460

346

962

508

173

1411

926

346

149

4233

3617

2936

898

7451

3822

373

inte

rite

mS

D25

4210

2024

1539

3210

51

088

9535

219

26

50

mea

nin

tra-

assa

yC

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(%)

717

99

133

923

2011

3017

413

55

35

26

aL

evel

sin

food

sas

con

sum

edan

dex

pres

sed

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lyco

nu

nit

sde

term

ined

bydu

plic

ate

anal

ysis

(giv

enin

bold

face

type

);co

okin

gti

me

was

boil

ing

3m

info

rso

ysp

rou

ts,5

min

for

tau

pok,

7m

info

rso

ybea

ns,

10m

info

rfo

ojo

ok,a

nd

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info

rdr

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nse

eds.

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ayle

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tal

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ore

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ffer

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tect

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dard

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1994) of traditional soy foods. Although total energyintake should be considered, this demonstrates theusefulness of soy drinks compared to traditional soyfoods to be used in intervention trials.

In conclusion, the results presented summarize theisoflavone content and conjugation pattern of foodscommonly consumed in Singapore and Hawaii. Our dataare in very good agreement with recent reports onisoflavone content and conjugation patterns in soy foodsconsumed elsewhere (Coward et al., 1993; Barnes et al.,1994a; Wang and Murphy, 1994a; Franke et al., 1995).The original conjugation pattern of soy foods withpredominating malonates (Kudou et al., 1991) changedas a function of treatment by heat and bacterialfermentation. Acetyl glucosides were formed in soyitems when fried in oil. Boiling soybeans resulted in adecrease in glucosyl malonates and a concurrent in-crease in glucosides, with minor losses observed in totalisoflavone content, probably by leaching of the polaranalytes into the water. Fermented items containedpredominantly aglycons. Although isoflavone levels insoy foods depend on environmental, genetic, harvesting,and processing conditions, it is important to note thatisoflavone levels reported from the same food groups butfrom different laboratories may vary due to differentanalytical techniques applied. It has to be emphasizedthat instrument calibration, accurate determination ofstock solution concentration by absorbance readings,and quality assurance using internal and externalstandards are urgently required for the production ofreliable data (Song et al., 1998). A highly significantcorrelation between urinary isoflavone excretion and soyconsumption was discovered in different ethnic groups,suggesting that urinary isoflavone measurements canserve as an excellent biomarker for soy intake (Seow etal., 1998; Maskarinec et al., 1998). Urinary isoflavoneexcretion was shown to be higher in populations withlow breast cancer risk (Adlercreutz et al., 1991) andhigher in controls relative to breast cancer cases inmultiethnic (Ingram et al., 1997) and Asian (Zheng etal., 1998) populations, supporting the hypothesis of acancer protective effect of soy and/or isoflavone expo-sure. Large variability of isoflavone content between andalso within certain food groups needs to be consideredwhen food composition databases are used in futureepidemiologic studies evaluating the effects of isoflavoneconsumption.

ACKNOWLEDGMENT

We appreciate the supply of TakeCare protein drinksby Protein Technologies International, St. Louis, MO.We are very grateful to Dr. Stephen Barnes (Universityof Alabama at Birmingham) for the supply of authentictoasted soy, to Betty Bhagavan and Jeanne Yeh (CancerResearch Center of Hawaii) for assistance in providingfood specimens and in food processing, and to Lisa Meng(Cancer Research Center of Hawaii) for the preparationand data processing of the protein drink test. Weacknowledge the skillful performance of the HPLC assayby Yuichiro Tanaka.

LITERATURE CITED

Adlercreutz, H. Phytoestrogens: Epidemiology and a possiblerole in cancer protection. Environ. Health Perspect. 1995,103, 103-112.

Adlercreutz, H.; Mazur, W. Phyto-estrogens and Westerndiseases. Ann. Med. 1997, 29, 95-120.

Adlercreutz, H.; Honjo, H.; Higashi, A.; Fotsis, T.; Hamalainen,E.; Hasegawa, T.; Okada, H. Urinary excretion of lignansand isoflavonoid phytoestrogens in Japanese men andwomen consuming a traditional Japanese diet. Am. J. Clin.Nutr. 1991, 54, 1093-1100.

Adlercreutz, H.; Bannwart, C.; Wahala, K.; Makela, T.;Brunow, G.; Hase, T.; Arosemena, P. J.; Kellis, J.; Vickery,L. E. Inhibition of human aromatase by mammalian lignansand isoflavonoid phytoestrogens. J. Steroid Biochem. Mol.Biol. 1993, 44, 147-153.

Barnes, S.; Grubbs, C.; Setchell, K. D. R.; Carlson, J. Soybeansinhibit mammary tumors in models of breast cancer. InMutagens and Carcinogens in the Diet; Pariza, W., Aesch-bacher, U., Felton, J. S., Sato, S., Eds.; Wiley-Liss: NewYork, 1990; pp 239-254.

Barnes, S.; Kirk, M.; Coward, L. Isoflavones and their conju-gates in soy foods: extraction conditions and analysis byHPLC-mass spectrometry. J. Agric. Food Chem. 1994a, 42,2466-2474.

Barnes, S.; Peterson, T. G.; Grubbs, C.; Setchell, K. D. R.Potential role of dietary isoflavones in the prevention ofcancer. In Diet and Cancer: Markers, Prevention andTreatment; Jacobs, M., Ed.; Plenum Press: New York,1994b; pp 135-147.

Cassidy, A.; Bingham, S.; Setchell, K. D. R. Biological effectof a diet of soy protein rich in isoflavones on the menstrualcycle of premenopausal women. Am. J. Clin. Nutr. 1994,60, 333-340.

Constantinou, A.; Huberman, E. Genistein as an inducer oftumor cell differentiation: possible mechanisms of action.Proc. Soc. Exp. Biol. Med. 1995, 208, 109-115.

Table 4. Composition of Protein Drinksa and Soy Supplementsb

total isoflavones

servingsize (g) fat (g)

protein(g)

carbo-hydrate (g)

energy(cal) mg

mg/g ofprotein mg/kcal

soy potein drink (powder)Garcinia-max diet shake, chocolate 27 0 6 18 100 12.6 2.1 125.6Light and Fit energy shake 28 0 14 8 90 30.7 2.2 341.2Slim and Trim diet shake 28 3 15 30 207 9.1 0.6 44.1Down-to-Earth 28 1 24 0 110 31.1 1.3 282.4Spiru-tein, cappuccino 32 0 14 11 100 15.7 1.1 157.4Spiru-tein, chocolate peanut butter 31 0 14 11 99 15.2 1.1 153.4Super Green Pro-96 28 0 23 0 100 27.1 1.2 270.7TakeCare, plain 29 1 20 4 100 47.4 2.4 473.9

soy supplements (pills)genistein food supplement 16973.3Soy Super Complex 9972.0vegetarian enzyme complex 204.5

a Amount per serving. b Amount per pill.


Cooney, R. V.; Mordan, L. J.; Franke, A. Multiple mechanismsof cancer prevention by phytochemicals: Interactions be-tween cellular proliferation and endogenous mutagens. InFood Factors for Cancer Prevention; Ohigashi, H., Osawa,T., Terao, J., Watanabe, S., Yoshikawa, T., Eds.; Springer:Tokyo, 1997; pp 26-29.

Coward, L.; Barnes, N. C.; Setchell, K. D. R.; Barnes, S. Theantitumor isoflavones, genistein and daidzein, in soybeanfoods of American and Asian diets. J. Agric. Food Chem.1993, 41, 1961-1967.

Fotsis, T.; Pepper, M.; Adlercreutz, H.; Hase, T.; Montesano,R.; Schweigerer, L. Genistein, a dietary ingested isofla-vonoid, inhibits cell proliferation and in vitro angiogenesis.J. Nutr. 1995, 125 (Suppl.), 790S-797S.

Franke, A. A.; Custer, L. J. High-performance liquid chroma-tography assay of isoflavonoids and coumestrol from humanurine. J. Chromatogr. B 1994, 662, 47-60.

Franke, A. A.; Custer, L. J.; Cooney, R. V. Quantitation ofLipid-Phase Micronutrients in Plasma by HPLC withSynthetic Carotenoids as Internal Standards. J. Chro-matogr. B 1993, 614, 43-57.

Franke, A. A.; Custer, L. J.; Cerna, C. M.; Narala, K. K.Quantitation of phytoestrogens in legumes by HPLC. J.Agric. Food Chem. 1994, 42, 1905-1913.

Franke, A. A.; Custer, L. J.; Cerna, C. M.; Narala, K. RapidHPLC analysis of dietary phytoestrogens from legumes andfrom human urine. Proc. Soc. Exp. Biol. Med. 1995, 208,18-26.

Franke, A. A.; Custer, L. J.; Tanaka, Y.; Maskarinec, G.Isoflavonoids in soy drinks and availability in human bodyfluids. Proc. Am. Assoc. Cancer Res. 1997, 38, 112.

Franke, A. A.; Custer, L. J.; Cooney, R. V.; Mordan, L. J.;Tanaka, Y. Inhibition of Neoplastic Transformation AndBioavailability of Dietary Phenolic Agents. In Flavonoidsin the Living System; Manthey, J. A., Buslig, B., Eds.;Plenum Press: New York, 1998a; pp 237-248.

Franke, A. A.; Custer, L. J.; Wang, W.; Shi, S. J. HPLCanalysis of isoflavonoids and other phenolic agents fromfoods and from human fluids. Proc. Soc. Exp. Biol. Med.1998b, 217, 263-273.

Franke, A. A.; Custer, L. J.; Tanaka, Y. Isoflavones in humanbreast milk and other biological fluids. Am. J. Clin. Nutr.1998c, 68, 1466S-1473S.

Goodman, M. T.; Wilkens, L. R.; Hankin, J. H.; Lyu, L.-C.;Wu, A.; Kolonel, L. N. Association fo Soy and Fiber Con-sumption with the Risk of Endometrial Cancer. Am. J.Epidemiol. 1997, 146, 294-306.

Hirano, T.; Gotoh, M.; Oka, K. Natural flavonoids and lignansare potent cytostatic agents against human leukemic HL-60 cells. Life Sci. 1994, 55, 1061-1069.

Hutchins, A. M.; Slavin, J. L.; Lampe, J. W. Urinary isofla-vonoid phytoestrogen and lignan excretion after consump-tion of fermented and unfermented soy products. J. Am.Diet. Assoc. 1995, 95, 545-551.

Ingram, D.; Sanders, K.; Kolybaba, M.; Lopez, D. Case-controlstudy of phyto-oestrogens and breast cancer. Lancet 1997,350, 990-997.

Kelly, G. E.; Nelson, C.; Waring, M. A.; Joannou, G. E.; Reeder,A. Y. Metabolites of dietary (soya) isoflavones in humanurine. Clin. Chim. Acta 1993, 223, 9-22.

Kudou, S.; Fluery, Y.; Welti, D.; Magnolato, D.; Uchida, T.;Kitamura, K.; Okubo, M. Malonyl isoflavone glycosides insoybean seeds (Glycine max Merrill). Agric. Biol. Chem.1991, 55, 2227-2233.

Kurzer, M. S.; Xu, X. Dietary phytoestrogens. Annu. Rev. Nutr.1997, 17, 353-381.

Kyle, E.; Neckers, L.; Takimoto, C.; Curt, G.; Bergan, R.Genistein-induced apoptosis of prostate cancer cells ispreceded by a specific decrease in focal adhesion kinaseactivity. Mol. Pharmacol. 1997, 51, 193-200.

Lamartiniere, C. A.; Moore, J.; Holland, M.; Barnes, S.Neonatal genistein chemoprevents mammary cancer. Proc.Soc. Exp. Biol. Med. 1995, 208, 120-123.

Lee, H. P.; Gourley, L.; Duffey, S. W.; Esteve, J.; Lee, J.; Day,N. E. Dietary effects on breast-cancer risk in Singapore.Lancet 1991, 337, 1197-1200.

Makela, S. I.; Pylkkanen, L. H.; Santti, R. S. S.; Adlercreutz,H. Dietary soybean may be antiestrogenic in male mice. J.Nutr. 1995, 125, 437-445.

Markham, K. R.; Mabry, T. J. Ultraviolet-visible and protonmagnetic resonance spectroscopy of flavonoids. In TheFlavonoids; Harborne, J. B., Mabry, T. J., Mabry, H., Eds.;Academic Press: New York, 1975; pp 45-77.

Markham, K. R.; Franke, A. A.; Molloy, B. P. J.; Webby, R.Flavonoid profiles of New Zealand Libocedrus and relatedspecies. Phytochemistry 1990, 29, 501-507.

Maskarinec, G.; Singh, S.; Meng, L.; Franke, A. A. Dietary soyintake and urinary isoflavone excretion among women froma multi-ethnic. Cancer Epidemiol. Biomarkers Prev. 1998,7, 613-619.

Messina, M.; Persky, V.; Setchell, K. D. R.; Barnes, S. Soyintake and cancer risk: A review of in vitro and in vivo data.Nutr. Cancer 1994, 21, 113-131.

Mousavi, Y.; Adlercreutz, H. Genistein is an effective stimula-tor of sex hormone-binding globulin production in hepato-carcinoma human liver cancer cells and suppresses prolif-eration of these cells in culture. Steroids 1993, 58, 301-304.

Murphy, P. A.; Song, T.; Buseman, G.; Barua, K. Isoflavonesin soy-based infant formulas. J. Agric. Food Chem. 1997,45, 4635-4638.

Murrill, W. B.; Brown, N. M.; Zhang, J.-X.; Manzolillo, P. A.;Barnes, S.; Lamartiniere, C. A. Prepubertal genisteinexposure suppresses mammary cancer and enhances glanddifferentiation in rats. Carcinogenesis 1996, 17, 1451-1457.

Nagata, C.; Kabuto, M.; Kurisu, Y.; Shimizu, H. Decreasedserum estradiol concentration associated with high dietaryintake of soy products in premenopausal Japanese women.Nutr. Cancer 1997, 29, 228-233.

Nomura, A. M. Y.; Hendersen, B. E.; Lee, J. Breast cancer anddiet among Japanese in Hawaii. Am. J. Clin. Nutr. 1978,31, 2020-2025.

Ollis, W. D. The isoflavonoids. In The Chemistry of FlavonoidCompounds; Geissman, T. A., Ed.; MacMillan: New York,1962; pp 353-405.

Peterson, T. G.; Barnes, S. Isoflavones inhibit the growth ofhuman prostate cancer cell lines without inhibiting epider-mal growth factor receptor autophosphorylation. Prostate1993, 22, 335-345.

Pettersson, H.; Kiessling, K.-H. Liquid chromatographic de-termination of the plant estrogen coumestrol and isoflavonesin animal feed. J. Assoc. Off. Anal. Chem. 1984, 67, 503-506.

Pollard, M.; Luckert, P. H. Influence of isoflavones in soyprotein isolates on development of induced prostate-relatedcancers in L-W rats. Nutr. Cancer 1997, 28, 41-45.

Seow, A.; Shi, C.-Y.; Franke, A. A.; Hankin, J.; Lee, H.-P.; Yu,M. C. Isoflavonoid levels in spot urine are associated withfrequency of dietary soy intake in a population-based sampleof middle-aged and older Chinese in Singapore. CancerEpidemiol. Biomarkers Prev. 1998, 7, 135-140.

Setchell, K. D. R. Naturally occurring non-steroidal estrogensof dietary origin. In Estrogens in the Environment;McLauchlan, J. A., Ed.; Elsevier: New York, 1985; pp 69-83.

Setchell, K. D. R.; Welch, M. B.; Lim, C. K. HPLC analysis ofphytoestrogens in soy protein preparations with ultraviolet,electrochemical and thermospray mass spectrometric detec-tion. J. Chromatogr. 1987, 386, 315-323.

Setchell, K. D. R.; Zimmer-Nechemias, L.; Cai, J.; Heubi, J.E. Exposure of infants to phyto-oestrogen from soy-basedinfant formula. Lancet 1997, 350, 23-27.

Song, T. T.; Barua, K. K.; Buseman, G.; Murphy, P. A. Soyisoflavone analysis: quality control and new internal stan-dard. Am J. Clin. Nutr. 1998, 68, 1474S-1479S.

Tsukamoto, C.; Shimada, S.; Igita, K.; Kudou, S.; Kokubun,M.; Okubo, K.; Kitamura, K. Factors affecting isoflavonecontent in soybean seeds: changes in isoflavones, saponins,


and composition of fatty acids at different temperaturesduring seed development. J. Agric. Food Chem. 1995, 43,1184-1192.

Uckun, F. M.; Evans, E.; Forsyth, C. J.; Waddick, K. G.; T.-Ahlgren, L.; Chelstrom, L. M.; Burkhardt, A.; Bolen, J.;Myers, D. E. Biotherapy of B-cell precursor leukemia bytargeting genistein to CD19-associated tyrosine kinases.Science 1995, 267, 886-891.

Wang, H.; Murphy, P. A. Isoflavone content in commercialsoybean foods. J. Agric. Food Chem. 1994a, 42, 1666-1673.

Wang, H.; Murphy, P. A. Isoflavone composition of Americanand Japanese soybeans in Iowa: Effects of variety, cropyear, and location. J. Agric. Food Chem. 1994b, 42, 1674-1677.

Wei, H.; Bowen, R.; Cai, Q.; Barnes, S.; Wang, Y. Antioxidantand antipromotional effects of the soybean isoflavonegenistein. Proc. Soc. Exp. Biol. Med. 1995, 208, 124-130.

Wu, A. H.; Ziegler, R. G.; Horn-Ross, P. L.; Nomura, A. M. Y.;West, D. W.; Kolonel, L. N.; Rosenthal, J. F.; Hoover, R. N.;Pike, M. C. Tofu and risk of breast cancer in Asian-Americans. Cancer Epidemiol. Biomarkers Prev. 1996, 5,901.

Xu, X.; Wang, H.-J.; Murphy, P. A.; Cook, L.; Hendrich, S.

Daidzein is a more bioavailable soymilk isoflavone than isgenistein in adult women. J. Nutr. 1994, 124, 825-832.

Zhang, J.-X.; Hallmans, G.; Landstrom, M.; Bergh, A.; Damber,J.-E.; Aman, P.; Adlercreutz, H. Soy and rye diets inhibitthe development of Dunning R3327 prostatic adenocarci-noma in rats. Cancer Lett. 1997, 114, 313-314.

Zheng, W.; Dai, Q.; Custer, L. J.; Shu, X. O.; Wen, W. Q.; Jin,F.; Franke, A. A. Urinary excretion of isoflavones and therisk of breast cancer. Cancer Epidemiol. Biomarkers Prev.1998, 8.

Ziegler, R. G.; Hoover, R. N.; Pike, M. C.; Hildesheim, A. M.;West, D. W.; Wu-Williams, A. H.; Kolonel, L. N.; Horn-Ross,P. L.; Rosenthal, J. F.; Hyer, M. B. Migration patterns andbreast cancer risk in Asian-American women. J. Natl.Cancer Inst. 1993, 85, 1819-1827.

Received for review August 10, 1998. Revised manuscriptreceived November 30, 1998. Accepted December 4, 1998. Thisstudy was partly supported by NIH Grant K12 CA 01708 andR35 CA 53890.

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Isoflavone Levels in Soy Foods Consumed by Multiethnic Populations in Singapore and Hawaii