Bioavailability Of Isoflavones Research Articles

Review of the Factors Affecting Bioavailability of Soy Isoflavones in Humans

Soy isoflavones have anticarcinogenic, antioxidant, and antiatherosclerotic activities. They also interact with the estrogen receptor, which makes them weak or moderate phytoestrogens. Because of their bioactivity, isoflavone bioavailability has been extensively studied in humans. This review summarizes data from intervention studies in humans, focusing on the factors that affect bioavailability. Summarizing data from 16 studies shows that the maximum concentration in plasma normalized to a constant dose of genistin is ∼1.6 times that of genistein, and daidzin is ∼1.8-fold higher than daidzein, whereas the half-life is not significantly different for aglycone and glucoside. There is a wide variation in the reported percentage urinary excretion that is not dependent on dose. Bioavailability is increased by a rapid gut transit time and by low fecal digestion rates and is decreased by a fiber-rich diet. There is no difference in bioavailability between pre- and postmenopausal women. The daily ingestion of soymilk for 1 wk does not affect bioavailability, but daily ingestion for a month increases excretion of equol in women. The factors or habitual diet characteristics that influence equol production are not clear, but equol production is limited with an immature flora. There is no consensus on which source of isoflavones results in the highest isoflavone bioavailability, and published studies present different results, although bioavailability is affected by whether the dose is given as food or drink. In conclusion, it is important to consider the factors affecting bioavailability of isoflavones when designing intervention studies.

The enhancement of isoflavones water solubility by complexation with modified cyclodextrins: A spectroscopic investigation with implications in the pharmaceutical analysis

The improvement of isoflavones bioavailability by complexation with chemically modified cyclodextrins (CyDs) has been exploited to analyse the drug/macrocycle binding affinity by a conventional method with new useful measures. Genistein (Gen) and daidzein (Daidz) were investigated in aqueous medium and in presence an amount of (2-hydroxypropyl)-β-cyclodextrin (HP-β-CyD) at different host/guest molar ratios. The solubility in pure water, ∼3 × 10 −6 M for Gen and ∼10 × 10 −6 M for Daidz, was obtained by distributing the of guest molecule between water and the organic solvent. The stoichiometric ratios and stability constants describing the extent of formation of the complexes have been determined by phase-solubility UV–vis measurements and confirmed by circular dichroism data. These results have implications in the determination of the carrier's capacity for the complexation of the drug in water solution.

Quantitative determination of acetyl glucoside isoflavones and their metabolites in human urine using combined liquid chromatography–mass spectrometry

To investigate whether the bioavailability of isoflavones could be an alternative to fermented soy foods, the conjugated forms of soy nutritional supplement (containing 98% acetyl glucoside isoflavones) were consumed by eight human volunteers (three were Asian people and five were British). Their daily urine samples were collected before and after a 5-week consumption of supplementation period. Conjugated isoflavones of genistein, daidzein and glycitein were hydrolyzed by enzyme, extracted with methyl tert-butyl ether and analysed using liquid chromatography coupled with electrospray tandem mass spectrometry. Daidzein, genistein, glycitein, dihydrogenistein, dihydrodaidzein and O-desmethylangolensin were identified and quantified simultaneously with high recoveries. The levels of free isoflavones and total isoflavones were compared, and isoflavone glucuronides were identified much higher than the corresponding sulfates or aglycone isoflavones. This method provided the measurement of isoflavones with high sensitivity and specificity and simplified the sample pre-treatment procedure. The limitation of detections of dihydrodaidzein, 3′-hydroxydaidzein, glycitein, daidzein, genistein, dihydrogenistein and O-desmethylangolensin were 37, 23.5, 12.2, 15.4, 14.8, 2.20 and 0.31 pmol, respectively. Only 0.5 ml of urine sample was needed.

Modulation of soy isoflavones bioavailability and subsequent effects on bone health in ovariectomized rats: the case for equol

Soy products are of particular interest because of their potential health benefits in a range of hormonal conditions, such as osteoporosis, due to their high content in phytoestrogens. Because equol, the main metabolite from soy isoflavones, is thought to be powerful, the present study was designated to evaluate the bone-sparing effects of equol by either providing the molecule through the diet or by eliciting its endogenous production by modulating intestinal microflora by short-chain fructooligosaccharides (sc-FOS) or live microbial (Lactobacillus casei) together with daidzein, its precursor. A comparison with daidzein and genistein was also performed. Rats (3 months old) were ovariectomised (OVX) or sham-operated (SH). Ovariectomised rats were randomly assigned to six experimental diets for 3 months: a control diet (OVX), the control diet supplemented with either genistein (G), or daidzein (D), or equol (E) at the level of 10 microg/g body weight/d. The remaining OVX rats were given daidzein at the dose of 10 mug/g body weight/d, simultaneously with short-chain FOS (Actilight, Beghin-Meiji) (D+FOS) or Lactobacillus casei (Actimel, Danone) (D+L). The SH rats were given the same control diet as OVX. Genistein, daidzein or equol exhibited a bone sparing effect. Indeed, total femoral bone mineral density (BMD) was significantly enhanced (compared to that of OVX rats), as was the metaphyseal compartment. Bone strength was improved by E consumption, but not by genistein or daidzein given alone. As far as the FOS diet is concerned, the addition of prebiotics significantly raised efficiency of the daidzein protective effect on both femoral BMD and mechanical properties. The effects of lactobacillus were similar, except that the increase in metaphyseal-BMD was not significant. In conclusion, long-term equol consumption, like genistein and daidzein, in the ovariectomized rat, provides bone sparing effects. Adding indigestible sugars, such as FOS or live microbial as L. casei, in the diet significantly improves daidzein protective effects on the skeleton.

Dihydrogenistein-Producing Bacterium TM-40 Isolated from Human Feces

Recently there has been great interest in the biological effects of isoflavones. Intestinal flora play an important role in the metabolism and bioavailability of isoflavones. To estimate the effects of dietary isoflavones on physiological function, it is also important to estimate the role of intestinal flora on the metabolism and absorption of isoflavones. However, to date there have been few reports of intestinal bacteria that metabolize genistein into dihydrogenistein. Formerly, we isolated the dihydrodaidzein-producing intestinal bacterium TM-40 from a healthy boy's feces. The strain TM-40 produce dihydrodaidzein from daidzein and daidzin. The 16S rRNA partial sequence of strain TM-40 showed a 93% similarity to that of Coprobacillus catenaformis (Accession no: AB030218). This strain seems to be a new species and was found to metabolize genistein into dihydrogenistein. We demonstrate that the dihydrogenistein-producing intestinal bacterium was harbored in a healthy boy's feces. This is the first report of a dihydrogenistein-producing intestinal bacterium being harbored in a healthy boy's feces.

Isolation of an isoflavone-metabolizing, Clostridium-like bacterium, strain TM-40, from human faeces

Recently, the biological effects of isoflavones have attracted much attention. Intestinal microbiota plays an important role in the metabolism and bioavailability of isoflavones. However, few reports have discussed intestinal bacteria that metabolize daidzein into dihydrodaidzein. In this study, we isolated the dihydrodaidzein-producing intestinal bacterium TM-40 from a healthy boy's faeces. The bacteria from faecal samples were incubated with daidzein. Among all tested bacteria, one strain (strain TM-40) produced dihydrodaidzein both from daidzein and daidzin. However, in our experimental conditions, strain TM-40 did not produce equol from daidzein. The 16S rRNA partial sequence of strain TM-40 ( AB249652) exhibited a 93% similarity to that of Coprobacillus catenaformis ( AB030218). This strain seems to be a new species.

Bioavailability and urinary excretion of isoflavones in humans: Effects of soy-based supplements formulation and equol production

Soy isoflavones (IF) are of particular interest for their possible estrogenic effects on the symptoms of menopause. The bioavailability of IF is clearly a factor influencing their biological activity. The first aim of this study was to elucidate the impact of the matrix process and especially the formulation of soy-based capsules on IF bioavailability. Twelve healthy volunteers were recruited for a randomized, double-blind, two-way crossover trial and received a single dose of the two soy-based formulations, one containing a pure soy standardized extract of IF, and the other containing soy flour in addition to the standardized extract of IF. Using a new and validated ELISA method, we measured the plasma and urinary concentrations of genistein, daidzein and its metabolite equol. Based on European Medicine Evaluation Agency recommendations, the main pharmacokinetic parameters allowed us to demonstrate the bioequivalence of the two formulations, indicating that the presence or absence of soy flour did not alter either the absorption or the elimination of daidzein and genistein. As bioequivalence was demonstrated, we pooled data collected during the two study-periods to address another original issue: Did the ability to produce equol affect the bioavailability of daidzein? We demonstrated that daidzein excretion was significantly lower in equol producers compared with equol non producers over the entire elimination period of the soy IF. This difference disappeared when equol excretion was added to daidzein excretion in equol producers. Our results indicated that the production of equol could partly explain the difference in daidzein bioavailability after IF ingestion.

Bioavailability of Isoflavones after Ingestion of Soy Beverages in Healthy Adults

AbstractIt is unknown whether the bioavailability of isoflavones is affected by the concomitant ingestion of glucosides or aglycones. This study was designed to investigate the effects of soymilk-based beverages containing different types of isoflavones on their absorption, excretion, and metabolism. Twelve healthy volunteers consumed 3 kinds of soymilk: untreated soymilk, β-glucosidase–treated soymilk, and fermented soymilk. Blood samples were collected after 0, 1, 2, 3, 4, 5, 6, 7, 8, and 24 h. Urine samples were collected from 0 to 48 h. Concentrations of isoflavones and daidzein metabolites in serum and urine were measured by liquid chromatography-mass spectrometry. After the ingestion of soymilk, the total concentration of isoflavones in serum rose slowly and reached a maximum of 0.94 ± 0.39 μmol/L at 6.0 ± 1.2 h. However, β-glucosidase–treated soymilk and fermented soymilk increased the serum isoflavone concentration significantly more quickly with maximum concentrations at 1.0 h of 1.75 ± 0.33 μmol/L and 2.05 ± 0.32 μmol/L, respectively. The urinary excretion of isoflavones after ingesting of these aglycone-enriched preparations was significantly greater than after consumption of untreated soymilk up to 8 h after injection, but not thereafter. The total and individual concentrations of isoflavones in serum and urine did not differ when subjects consumed the 2 aglycone-enriched soymilks. However, in equol producers (n = 5), the ingestion of ESM tended to increase urinary excretion of equol compared with the consumption of FSM (P = 0.08). These results demonstrated that the isoflavone aglycones of soymilk were absorbed faster and in greater amounts than their glucosides in healthy adults and that the metabolism of isoflavones might be affected by the type of soymilk consumed.

Isoflavones in breastfed infants after mothers consume soy1–3

The bioavailability of isoflavones in children after soy exposure is uncertain. We aimed to compare isoflavone patterns in infants exposed to isoflavone-containing breast milk (BF), in tofu-fed (TF) infants, and in mothers consuming a soy beverage. Eighteen nursing mothers who were not feeding soy foods to their infants consumed one daily serving of a soy protein beverage for 2-4 d and collected their own milk and urine and infant urine. Plasma was collected from infants if venous blood draws were ordered by pediatricians. Blood and urine were collected from additional children after they consumed tofu. Isoflavones were measured by liquid chromatography-mass spectrometry. In 7 subjects, isoflavone values increased significantly from baseline after mothers ate soy: in maternal urine (x +/- SEM) from 18.4 +/- 13.0 to 135.1 +/- 26.0 nmol/mg creatinine, in breast milk from 5.1 +/- 2.2 to 70.7 +/- 19.2 nmol/L, and in infant urine from 29.8 +/- 11.6 to 111.6 +/- 18.9 nmol/mg creatinine. The mean isoflavone concentration in plasma obtained from 11 BF infants was 19.7 +/- 13.2 nmol/L. TF infants had much higher mean isoflavone values (urine, 229 +/- 129 nmol/mg creatinine; plasma, 1049 +/- 403 nmol/L). Statistically significant correlations were observed between the types of fluids investigated within mothers, between mothers and infants, and within infants. Urinary isoflavone excretion per hour adjusted for dose per body weight was 81% lower for BF infants and 24% higher for TF infants than for their mothers after eating soy. More isoflavones appear in children than in adults after adjustment for isoflavone intake. Systemic isoflavone exposure in infants can be determined by urinary analysis.

The effects of fructo-oligosaccharides in combination with soy protein on bone in osteopenic ovariectomized rats

The intestinal microflora is important in rendering soy isoflavones bioavailable by facilitating their conversion to equol. Hence, substances that can modulate the intestinal microflora could affect the bioavailability of isoflavones. In this study, we examined the effects of fructo-oligosaccharides (FOS), a prebiotic, on enhancing the effects of soy isoflavones on bone in ovariectomized osteopenic female rats. Sixty-three 9-month-old female Sprague-Dawley rats were either sham-operated (Sham; one group) or ovariectomized (Ovx; four groups) and were fed a control diet for 3 months to induce bone loss. After bone loss was confirmed via dual-energy x-ray absorptiometry, rats were placed on dietary treatment for 4 months. The Sham and one Ovx group received a control diet, and the remaining Ovx groups received either a soy protein-based diet (Soy), a FOS-supplemented diet (FOS), or a soy protein-based and FOS-supplemented diet (Soy+FOS). Before the termination of the study, whole-body bone mineral density (BMD) and bone mineral content (BMC) were assessed under anesthesia. Immediately after euthanasia, bone specimens were collected for the assessments of BMD, BMC, and biomechanical and microarchitectural properties. Whole-body BMD values were significantly higher in FOS and Soy+FOS groups compared with Ovx controls. The tibial BMC increased by 10%, 6%, and 4% in Soy, FOS, and Soy+FOS groups, respectively, compared to the Ovx control group. FOS and FOS+Soy treatments had the most pronounced effects in enhancing lumbar BMC and BMD. The FOS+Soy combination effectively improved tibial microarchitectural properties by enhancing trabecular number and lowering trabecular separation compared with Ovx controls. The effects of dietary treatments on lumbar microarchitectural properties were minimal and biomechanical properties of the femur were not affected by any of the dietary treatments. Our findings suggest that, although incorporation of either soy or FOS in the diet of Ovx rats can improve BMD of the whole body, tibiae, and lumbar vertebrae, their combination had no any additive effects. However, in terms of microarchitecture, the combination of soy and FOS had a greater effect in reversing the loss of certain microarchitectural parameters such as tibial trabecular number, separation, and thickness.

Guest Editorial: Assessing Risks and Benefits of Genistein and Soy

Guest Editorial: Assessing Risks and Benefits of Genistein and Soy

INFLUENCE OF HEAT TREATMENT AND GRAIN GERMINATION ON THE ISOFLAVONE PROFILE OF SOY MILK

Soy foods have attracted much attention for their possible effects on human health because of their phytochemical content, mainly isoflavones. Twelve forms of isoflavones have been identified in soybeans and soy products. Technological processes like heat treatment or fermentation can change the isoflavone profile of soy products. In this study, the effects of heat treatment and grain germination on isoflavone profile of soy milk prepared from BRS 213 soybean variety were evaluated. Isoflavone forms were separated and quantified by reversed-phase high-performance liquid chromatography. Heat treatment by autoclaving for 5 min did not affect the total isoflavone content, but led to a 90% decrease in malonyl forms, whereas β-glycosides increased by 70%. Autoclaving for 15 min led to a 20% loss of total isoflavones. Germination for 3 days did not change the total isoflavone content, but changed the distribution profile (15% increase of malonyl forms and 30% decrease of β-glycosides). Germination for 7 days increased the bioavailability of aglycone isoflavones in soy milk by seven times.

Cooperative effects of isoflavones and exercise on bone and lipid metabolism in postmenopausal Japanese women: a randomized placebo-controlled trial

Cooperative effects of isoflavones and exercise on bone and lipid metabolism have been exhibited in estrogen-deficient animals; however, results from clinical trials have not been published. In this study, we determined the effects of isoflavone intake and walking and their interaction on bone and lipid metabolism in postmenopausal women over 24 weeks. The bioavailability and metabolism of isoflavones (daidzein in particular) were also examined to clarify the mechanism of their bone-protective effects in humans. One hundred twenty-eight subjects were randomly assigned to 4 groups: placebo; placebo combined with walking (3 times per week); isoflavone intake (75 mg of isoflavones conjugates per day); and isoflavone combined with walking. The subjects were classified by equol status (producers or nonproducers) as identified using production of equol from daidzein in fecal culture. Bone mineral density (BMD), body composition, and serum concentrations of isoflavones were assessed. Serum high-density lipoprotein cholesterol concentration significantly increased (6.1%, P = .03), and fat mass in the whole body significantly decreased (−4.3%, P = .0003) from the baseline in the combined intervention group. There were no significant differences in BMD between baseline and postintervention in any of the treatment groups. However, the percent changes in BMD in equol producers were −0.53% and +0.13% in the sub–whole body and total hip, respectively. This was significantly different compared with −1.35 and −1.77 for the sub–whole body and total hip, respectively, in nonproducers in the isoflavone group ( P = .049 and .040, respectively). The mean serum equol concentration was significantly higher in equol producers than in nonproducers in the isoflavone groups, but not in the placebo group. The combination of isoflavones and exercise exhibited favorable effects on serum lipid and body composition of postmenopausal women. The findings of this study suggest that the preventive effects of isoflavones on bone loss depend on the individual's intestinal flora for equol production.

Isoflavone bioavailability after soy intake during childhood and effects by oral antibiotic treatment

Isoflavone bioavailability after soy intake during childhood and effects by oral antibiotic treatment

Profiling urinary isoflavone metabolites after the consumption of either fermented or unfermented soy products in humans

Soy isoflavones are reported to have many health benefits including anticarcinogenic and estrogenic activity. The primary soy isoflavones are geneistein and daidzein and their respective beta-glycosides genistin and daidzin. In soybeans and unfermented soy foods the isoflavones are present primarily as beta-glucosides, in fermented soy products (e.g. tempeh, miso, soy paste) the isoflavones are present as aglycones. To date there is controversy whether soy isoflavones in the aglycone form are more bioavailable than isoflavone glycosides. To date, few studies address the bioavailability of soy isoflavones from unfermented and fermented soy foods. The following study describes LC/MS/MS methodology for comparing the kinetics of the urinary excretion of soy isoflavones and their metabolites in humans after the consumption of fermented soy paste or unfermented soy flour. Mass spectra indicate that the majority of isoflavone metabolites (genistein, daidzein, O-desmethylangolensin, equol, dihydrogenistein, dihydrodaidzein) are present as glucuronide coujugates. Additional conjugates identified include sulfate conjugates (e.g. sulfoglucuronides of isoflavones). LC/MS spectra demonstrate difference in the kinetics profiles for the excretion of isoflavone metabolites and demonstrate the strength of this approach for these types of studies. This work is supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD). (KRF-2005-214-F00053)

Urinary Isoflavone Excretion and Soy Consumption in Three Generations of Japanese Women in Hawaii

Isoflavone (IFL) bioavailability and metabolism may differ depending on lifetime exposure to soy foods. 43 Japanese women in Hawaii ages 18–78 years belonging to families of two to three generations collected an overnight baseline urine sample followed by a second overnight urine sample after consumption of a serving of soymilk. A participant was considered first generation (1G) if she was over age 60, second generation (2G) if she was age 30–59, and third generation (3G) if she was under age 30. IFL intakes during the last year were estimated using a 12-item soy food-frequency and a lifetime soy consumption questionnaire, and published nutritional databases. Urinary isoflavone excretion (UIE) of daidzein, genistein, and equol was determined by LC/MS. Most popular soy foods were, miso soup and green soybeans. The mean self-reported intake of dietary soy isoflavones for all participants was 11.5 mg/day (±12.8). The highest mean IFL intake was observed by 2G, followed by 1G and lastly by 3G. UIE at baseline was highest for 1G followed by 2G and lastly by 3G. After intervention 3G had the highest mean UIE, followed by 1G, and lastly 2G. 1G excreted the greatest amount of equol, while the other generations showed trace amounts. This suggests that 1G is exposed habitually to greatest amounts of IFL and metabolizes them differently from the other generations.

Isoflavone excretion phenotypes influence plasma cholesterol in golden Syrian hamsters

We hypothesized that hamsters sorted into high and low isoflavone excreter phenotypic categories would show significant differences in plasma cholesterol status, the high isoflavone excreters having lower cholesterol. One-year-old hamsters were fed either 1.18 mmol of total isoflavones per kilogram diet (5 males and 5 females) or 1.77 mmol of total isoflavones per kilogram diet (5 males and 4 females) for 10 days. Urine and feces were collected for 24 hours in metabolic cages, and blood collected at euthanasia after 16 hours of fast. According to a cluster analysis, hamsters were sorted into 2 distinct urinary isoflavone phenotypes: high and low excreters with mean total isoflavone excretion of 44% ± 5% vs 14% ± 7%; daidzein excretion of 30% ± 7% vs 8% ± 3%; glycitein excretion of 84% ± 6% vs 28% ± 13%; and genistein excretion of 35% ± 7% vs 8% ± 4% of the ingested dose. Urinary excretion of all isoflavones was strongly correlated (0.93 < r < 0.98; P < .001). Fasting plasma total cholesterol was significantly lower in high vs low excreters (eg, based upon total isoflavones, 6.1 ± 1.9 vs 8.3 ± 1.5 mmol/L, respectively), regardless of sex. Although females had significantly better bioavailability than males for total isoflavones (33% ± 18% vs 17% ± 9%), daidzein (24% ± 14% vs 11% ± 6%) and genistein (27% ± 15% vs 10% ± 6%), cholesterol concentrations were not significantly different by sex, probably because of the lesser difference in bioavailability between sexes than between urinary isoflavone excretion clusters. These data support our hypothesis. Golden Syrian hamsters may be good models to study the link between bioavailability and cholesterol-lowering effects of isoflavones because they sort into isoflavone bioavailability clusters similar to that noted previously in humans.

Factors Affecting the Bioavailability of Soy Isoflavones in Humans after Ingestion of Physiologically Relevant Levels from Different Soy Foods

The precise role that isoflavones play in the health-related effects of soy foods, and their potential for adverse effects are controversial. This may be due in part to a lack of basic knowledge regarding their bioavailability and metabolism, particularly as it relates to the soy source. To date, there is little information concerning possible differences in the bioavailability of isoflavones derived from natural soy foods consumed at physiologically relevant intakes and whether age- or gender-related differences influence that bioavailability. In the current study of healthy adults [premenopausal (n = 21) and postmenopausal (n = 17) women and a group of men (n = 21)], we examined the effect of age, gender, and the food matrix on the bioavailability of isoflavones for both the aglycon and glucoside forms that are naturally present in 3 different soy foods, soy milk, textured vegetable protein, and tempeh. The study was designed as a random crossover trial so that all individuals received each of the 3 foods. The dose of isoflavones administered to each individual as a single bolus dose was 0.44 mg/kg body weight. Pharmacokinetic parameters were normalized to mg of each isoflavone ingested per kilogram body weight to account for differences in daidzein and genistein content between the diets. Serum isoflavone concentrations in all individuals and groups increased rapidly after the ingestion of each soy food; as expected, genistein concentrations exceeded daidzein concentrations in serum. In this small study, gender differences in peak concentrations of daidzein were observed, with higher levels attained in women. Consumption of tempeh (mainly isoflavone aglycon) resulted in higher serum peak levels of both daidzein (P < 0.001) and genistein (P < 0.01) and the associated area under the curve (P < 0.001 and P < 0.03, respectively) compared with textured vegetable protein (predominantly isoflavone glucosides). However, soy milk was absorbed faster and peak levels of isoflavones were attained earlier than with the other soy foods. Only 30% of the subjects were equol producers and no differences in equol production with age or gender were observed.

Effects of Intestinal Flora on the Metabolism and Absorption of Isoflavones

Soybean and soy foods are rich sources of isoflavones. Much attention has focused on isoflavonoids because of their beneficial effects on human health. Isoflavones belong to the group of phytoestrogens. Phytoestrogens are estrogenic compounds found in plants. Intestinal flora plays an important role in the absorption and metabolism of isoflavones. Some dietary components and chemical composition of isoflavones are also known to affect the absorption of isoflavones. Human metabolism and excretion of isoflavones following the consumption of soy products show considerable variation. The bioavailability of soybean isoflavones to women is dependent on gut microflora. Equol is a metabolite ofdaidzein produced by intestinal flora. Equol has many biological activities related to human health, and its production might be affected by compositions of diets and intestinal flora. To achieve higher production ofequol from daidzein in the gut, control of the metabolic activity of intestinal flora might be of importance.

High-performance liquid chromatography–tandem mass spectrometry for identification of isoflavones and description of the biotransformation of kudzu root

High-performance liquid chromatography-tandem mass spectrometry has been used to identify isoflavone aglycones and glycosides in kudzu root. Fourteen isoflavones were detected. Among these, six were identified by comparison with authentic standards. Tentative identifications of the other isoflavones are based on UV spectra, mass spectra of protonated and deprotonated molecules, and MS-MS data. Several are reported for the first time in kudzu root. The bioactivity and bioavailability of isoflavone aglycones are usually greater than those of their glycosides. To improve the bioavailability of kudzu root isoflavones, crude beta-glycosidases prepared from microbes were used to hydrolyze the isoflavone glycosides. Several MS modes are combined not only to identify the isoflavones in kudzu root, but also to describe the biotransformation of kudzu root isoflavone glycosides. It is also proved that crude beta-glycosidases have high selectivity toward the O-glycosides of isoflavones.