Oxidative metabolism of the soy isoflavones daidzein and genistein in humans in vitro and in vivo.

The soy isoflavones daidzein and genistein are found in high concentrations in human plasma and urine after soy consumption. However, in vitro and in vivo data regarding the oxidative metabolism of isoflavones in humans are scarce. Therefore, we have studied the oxidative metabolites of these compounds formed in human liver microsomes and excreted in urine of male and female humans ingesting soy products for 2 days. Human liver microsomes transformed the soy isoflavone daidzein to three monohydroxylated and three dihydroxylated metabolites according to GC/MS analysis. On the basis of a previous study with rat liver microsomes and with the help of reference substances, these metabolites were identified as 6,7,4'-trihydroxyisoflavone, 7,3',4'-trihydroxyisoflavone, 7,8,4'-trihydroxyisoflavone, 7,8,3',4'-tetrahydroxyisoflavone, 6,7,8,4'-tetrahydroxyisoflavone, and 6,7,3',4'-tetrahydroxyisoflavone. Significant amounts of the same metabolites except 6,7,8,4'-tetrahydroxyisoflavone were also found in urine of female and male volunteers after soy intake. Genistein was metabolized by human liver microsomes to six hydroxylation products. The main metabolites were the three aromatic monohydroxylated products 5,6,7,4'-tetrahydroxyisoflavone, 5,7,8,4'-tetrahydroxyisoflavone and 5,7,3',4'-tetrahydroxyisoflavone. The aliphatic monohydroxylated metabolite 2,5,7,4'-tetrahydroxyisoflavone and two aromatic dihydroxylated metabolites, 5,7,8,3',4'-pentahydroxyisoflavone and 5,6,7,3',4'-pentahydroxyisoflavone, were formed in trace amounts. The same hydroxylated genistein metabolites except the aliphatic hydroxylated one could also be detected in human urine samples. Methylated forms of the catechol metabolites, which were generated by incubations with catechol-O-methyltransferase in vitro could be detected only in trace amounts in the urine samples. This implies that this reaction does not play a major role in the biotransformation of the hydroxylated daidzein and genistein metabolites in vivo. Most of these oxidative metabolites are described as human in vivo metabolites for the first time. Their biological significance remains to be established.     

Oxidative metabolism of the mammalian lignans enterolactone and enterodiol by rat, pig, and human liver microsomes.

Hepatic microsomes from aroclor-treated male Wistar rats biotransform enterolactone to 12 metabolites, six of which carry an additional hydroxy group at the aromatic and six at the aliphatic moiety according to HPLC/MS and GC/MS analysis. The aromatic hydroxylation products were identified with the help of synthesized reference compounds as enterolactone monohydroxylated in the para position and in both ortho positions of the original phenolic hydroxy group of either aromatic ring. The synthesis of the reference compounds and their spectroscopic characterization is described. Enterodiol is metabolized by hepatic microsomes from aroclor-treated male rats to three aromatic and four aliphatic monohydroxylated metabolites. Aromatic hydroxylation occurs in the para position and the two ortho positions of the original phenolic hydroxy group. Most of the metabolites of enterolactone and enterodiol were also formed with microsomes from uninduced rat, pig, and human liver, suggesting that oxidative metabolism is a common feature in the disposition of these lignans in the mammalian organism.     

Tissue distribution of lignans in rats in response to diet, dose-response, and competition with isoflavones

This paper investigates the occurrence and distribution of the lignan metabolites enterodiol (END) and enterolactone (ENL) and the isoflavone daidzein (DAID) in rat tissues by use of liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MSn) following a variety of dietary regimes. Furthermore, we examined the dose-response and distribution of END and ENL in liver, testes, prostate, and lung, and we investigated the effects of competition between lignans and isoflavones on metabolite distribution. In liver, testes, prostate, and lung tissue, dose-related increases in END concentration were observed. In the testes, coadministration of 60 mg/kg secoisolariciresinol diglycoside (SDG) with 60 mg/kg isoflavones produced alterations in the resulting metabolite profile, causing increased END concentration and decreased DAID concentration. Results indicate lignan accumulation in tissues occurs, and coadministration of lignans with isoflavones affects the metabolite profile, with effects dependent on tissue type.     

Studies on the metabolism of the plant lignans secoisolariciresinol and matairesinol

The plant lignans secoisolariciresinol and matairesinol occur in numerous foods such as oil seeds, whole grains, vegetables, and fruits. We have studied the hitherto unknown oxidative metabolism of secoisolariciresinol and matairesinol in hepatic microsomes from untreated and Aroclor 1254-induced Wistar rats and from humans. Five oxidative metabolites of secoisolariciresinol and 10 oxidative metabolites of matairesinol were detected in rat liver microsomes, and their chemical structures were elucidated. The pathways in the metabolism of both secoisolariciresinol and matairesinol included aliphatic and aromatic hydroxylation, whereas oxidative demethylation was only observed for matairesinol. Human hepatic microsomes were able to metabolize secoisolariciresinol whereas matairesinol was only poorly metabolized. This study clearly shows that secoisolariciresinol and matairesinol are substrates of cytochrome P450-mediated metabolism. However, from preliminary experiments with rats dosed orally with secoisolariciresinol and matairesinol, it appears that the intestinal absorption and subsequent oxidative metabolism of these plant lignans occur only to a very small extent due to the highly efficient conversion of secoisolariciresinol and matairesinol to the mammalian lignans enterodiol and enterolactone by the gut microflora.     

Metabolism of furametpyr. 2. (14)C excretion, (14)C concentrations in tissues, and amounts of metabolites in rats

14C-Labeled furametpyr [N-(1,3-dihydro-1,1, 3-trimethylisobenzofuran-4-yl)-5-chloro-1, 3-dimethylpyrazole-4-carboxamide, Limber] was dosed to male and female rats at 1 (low dose) and 200 or 300 mg/kg (high dose). Elimination of furametpyr was rapid, and the dosed (14)C was substantially excreted within 7 days (45.5-53.3% in feces, 44.1-53. 8% in urine, and 0.01% in expired air). However, (14)C excretion rate showed sex- and dose-related differences, more rapid in males at low dose. (14)C concentrations in tissues decreased rapidly to generally low levels at 7 days (<0.004 ppm with the low dose and <1. 1 ppm with the high dose). Forty metabolites were detected, and 13 metabolites and 4 glucuronides were identified. A small amount of unchanged furametpyr was detected in feces (0.1-0.5% of the dose). The major metabolites in tissues were N-demethylated metabolites. In a bile study, 52.5-54.2% of the dosed (14)C was rapidly excreted into bile within 2 days. The absorption ratio was estimated to be >93.7% for the low dose (1 mg/kg). Major metabolites in bile were glucuronic acid conjugates of furametpyr hydroxides. On the basis of the results, furametpyr is substantially absorbed from the gastrointestinal tract after oral administration, rapidly distributed to tissues, extensively metabolized, and excreted into urine and bile or feces.     

Disposition and metabolic profiling of bisphenol F in pregnant and nonpregnant rats

The distribution of bisphenol F (4,4'-dihydroxydiphenyl-methane, BPF) was studied in female Sprague-Dawley rats. Pregnant and nonpregnant animals were gavaged with a single dose of 7 or 100 mg/kg [3H]BPF and were kept for 96 h in metabolic cages. The excretion of BPF residues occurred mainly in urine (43-54% of the administered dose), which was found to contain at least six different metabolites, and to a lesser extent in feces (15-20% of the administered dose). Sulfatase treatment and subsequent high-performance liquid chromatography analyses suggest that the major urinary metabolite (more than 50% of the radioactivity present in urine) is a sulfate conjugate of BPF. At 96 h, BPF residues were detectable in all tissues examined with the largest amounts in the liver (0.5% of the dose). In pregnant rats dosed at day 17 of gestation, BPF residues were detected in the uterus, placenta, amniotic fluid, and fetuses (0.9-1.3% of the administered dose). Large amounts of radioactivity (8-10% of the dose) were still located in the digestive tract lumen at the end of the study. After administration of a single oral dose of [3H]BPF, 46% of the distributed radioactivity was excreted in bile over a 6 h period. In rats, BPF and/or its metabolites very likely undergo enterohepatic cycling, which could be responsible for the relatively high amounts of residues still excreted 4 days after BPF administration. This bisphenol is efficiently absorbed and distributed to the reproductive tract in female rats, and its residues pass the placental barrier at a late stage of gestation in rats.     

Tissue distribution and cytochrome p450 inhibition of sesaminol and its tetrahydrofuranoid metabolites

Sesame lignans such as sesamin, sesaminol, and sesamolin are major constituents of sesame oil, and all have a methylenedioxyphenyl group and multiple functions in vivo. It was previously reported that sesaminol, a tetrahydrofurofuran type lignin, was metabolized to mammalian lignans. The present study examined the tissue distribution of sesaminol in Sprague-Dawley (SD) rats. Changes in the concentration of sesaminol and its metabolites (sesaminol glucuronide/sulfate, hydroxymethylsesaminol-tetrahydrofuran, enterolactone, and enterodiol) were determined in tissues within a 24 h period after tube feeding (po 220 mg/kg) to SD rats. The concentrations of enterodiol and enterolactone were significantly higher than those of sesaminol and its tetrahydrofuranoid metabolites in the organs (liver, heart, brain, and kidney). This study demonstrates that sesaminol has potent inhibition of cytochrome P450 (CYPs), compared to tetrahydrofuranoid metabolites. The IC(50) values of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 for sesaminol were determined as 3.57, 3.93, 0.69, 1.33, and 0.86 μM, respectively. In addition, hydroxymethylsesaminol-tetrahydrofuran and enterodiol were weak inhibitors of CYP2C9 and CYP1A2, respectively.     

Absorption, tissue distribution, excretion, and metabolism of clothianidin in rats

Absorption, distribution, excretion, and metabolism of clothianidin [(E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2-nitroguanidine] were investigated after a single oral administration of [nitroimino-(14)C]- or [thiazolyl-2-(14)C]clothianidin to male and female rats at a dose of 5 mg/kg of body weight (bw) (low dose) or 250 mg/kg of bw (high dose). The maximum concentration of carbon-14 in blood occurred 2 h after administration of the low oral dose for both labeled clothianidins, and then the concentration of carbon-14 in blood decreased with a half-life of 2.9-4.0 h. The orally administered carbon-14 was rapidly and extensively distributed to all tissues and organs within 2 h after administration, especially to the kidney and liver, but was rapidly and almost completely eliminated from all tissues and organs with no evidence of accumulation. The orally administered carbon-14 was almost completely excreted into urine and feces within 2 days after administration, and approximately 90% of the administered dose was excreted via urine. The major compound in excreta was clothianidin, accounting for >60% of the administered dose. The major metabolic reactions of clothianidin in rats were oxidative demethylation to form N-(2-chlorothiazol-5-ylmethyl)-N'-nitroguanidine and the cleavage of the carbon-nitrogen bond between the thiazolylmethyl moiety and the nitroguanidine moiety. The part of the molecule containing the nitroguanidine moiety was transformed mainly to N-methyl-N'-nitroguanidine, whereas the thiazol moiety was further metabolized to 2-(methylthio)thiazole-5-carboxylic acid. With the exception of the transiently delayed excretion of carbon-14 at the high-dose level, the rates of biokinetics, excretion, distribution, and metabolism of clothianidin were not markedly influenced by dose level and sex.     

Inhibition of reactive nitrogen species effects in vitro and in vivo by isoflavones and soy-based food extracts

Recent studies have shown that soy isoflavone inhibits inducible nitric oxide (NO) synthase activities and is reported to have peroxynitrite scavenging ability. Consequently, we investigated whether isoflavones (daidzein and genistein) and extracts from soy-based products (miso, soymilk, tofu, soy sprout, black soybean, soybean, and yuba) would inhibit the reactive nitrogen species (RNS) effect in vitro and in vivo. In the in vitro experiments [including the protection of cellular DNA from peroxynitrite or sodium nitroprusside damage, an inhibitory effect on nitric oxide production from lipopolysaccharide (LPS)-induced RAW 264.7 cells, and nitric oxide scavenging ability], extracts from soy-based foods showed a potent antioxidant activity and an inhibiting effect on RNS activity. These effects were correlated with total isoflavone content. In the in vivo experiments, rats were given isoflavones (4.0 mg/kg bw) or soy-based product extracts (1.0 g/kg bw) orally for 1 week and were injected with vehicle H(2)O (1 mL/kg bw) or LPS (10 mg/kg bw) on the day 7. Twelve hours after treatment, the rats were killed, and blood serum was collected for analysis. The intraperitoneal administration of LPS resulted in an increase in serum nitrite, nitrate, and nitrotyrosine concentrations. These are stable metabolite end products of nitric oxide, to 4-, 16-, and 5-fold levels, (4, 10 microM and 58 +/- 14 pmol/mL), of the placebo control, respectively. Results showed that oral administration of isoflavones and extracts from soy-based products significantly decreased serum nitrite, nitrate, and nitrotyrosine levels in LPS-induced rats. This study demonstrates that soy isoflavone supplementation may inhibit RNS-induced oxidation both in vitro and in vivo.     

Metabolism of the lignan macromolecule into enterolignans in the gastrointestinal lumen as determined in the simulator of the human intestinal microbial ecosystem

Estrogenic plant compounds from the human diet such as the lignan secoisolariciresinol diglucoside (SDG, 1) can exert biological activity in the human body upon ingestion and bioactivation to enterodiol (END, 5) and enterolactone (ENL, 6). Bioavailability of lignans is influenced by the food matrix and gut microbial action, of which the latter is subject to a large interindividual variation. In this study, the fate of the lignan precursor SDG, present in the lignan macromolecule of flax seed ( Linum usitatissimum), was determined during an artificial stomach and small intestinal digestion and during metabolism by two different enterolignan phenotypes in a TWINSHIME environment (TWIN Simulator of the Human Intestinal Microbial Ecosystem). The lignan macromolecule acted as a delivery system of SDG in the large intestine. SDG was only hydrolyzed into secoisolariciresinol (SECO, 2) through microbial action in the ascending colon, after which it was bioactivated into enterolignans from the transverse colon onward. Single demethylation was a first step in the bioactivation, followed by dehydroxylation. Enterolignan phenotypes remained stable throughout the experimental period. The establishment of END and ENL production equilibria reflected the subdominance of ENL-producing bacteria in the gastrointestinal tract.     

Urinary and biliary metabolic patterns of chlorothalonil in germ-free and conventional rats.

The metabolic fate of chlorothalonil, a broad spectrum fungicide that is known to be metabolized via glutathione conjugation, was examined through the analysis of urine and bile metabolites. The role of digestive microflora in the metabolism of chlorothalonil was assessed by comparing the metabolic patterns in germ-free and conventional rats. Low urinary and biliary excretion of radioactivity was observed in both conventional and germ-free rats. However, the urinary excretion of radioactivity was higher in conventional than in germ-free rats. Radio-HPLC analysis of urine and bile showed a complex metabolic profile in both conventional and germ-free rats. Methylthio metabolites of chlorothalonil were determined in ethyl acetate extracts of urine and bile of conventional and germ-free rats. These metabolites were excreted in a higher amount in the urine of conventional rats than in the urine of germ-free rats. This study shows the complexity of chlorothalonil metabolism and the role of the digestive microflora in chlorothalonil metabolism.     

Oxidative in vitro metabolism of the soy phytoestrogens daidzein and genistein

The oxidative metabolism of the major soy isoflavones daidzein and genistein was investigated using liver microsomes from Aroclor-treated male Wistar rats. Both daidzein and genistein were extensively metabolized and are therefore excellent substrates for cytochrome P450 enzymes. The identity of the metabolites was elucidated using high-performance liquid chromatography (HPLC) with diode array detection, gas chromatography-mass spectrometry (GC/MS), and HPLC/atmospheric pressure ionization electrospray mass spectrometry (API-ES MS) as well as reference substances. Daidzein was converted to nine metabolites, comprising four monohydroxylated, four dihydroxylated, and one trihydroxylated metabolite. Genistein was metabolized to four monohydroxylated and two dihydroxylated products. With both isoflavones the additional hydroxy groups are exclusively introduced into the ortho positions of existing phenolic hydroxy groups. The major metabolites of daidzein were identified as 6,7,4'-trihydroxyisoflavone, 6,7,3',4'-tetrahydroxyisoflavone, 7,8, 4'-trihydroxyisoflavone, and 5,6,7,4'-tetrahydroxyisoflavone. The main microsomal metabolites of genistein were 5,6,7, 4'-tetrahydroxyisoflavone and 5,7,8,4'-tetrahydroxyisoflavone. Furthermore, the GC/MS and HPLC/API-ES MS analysis support the conclusion that one monohydroxylated metabolite of daidzein and genistein is hydroxylated at the aliphatic position C-2 of the C-ring. The UV-vis, GC/MS, and HPLC/MS data of all detected metabolites as well as the derived chemical structure of the metabolites are presented. Most metabolites are reported in this paper for the first time. On the basis of these findings it is suggested that hydroxylation reactions may also play an important role in the in vivo metabolism of the soy isoflavones daidzein and genistein.     

Urinary and plasma levels of resveratrol and quercetin in humans, mice, and rats after ingestion of pure compounds and grape juice

The present study investigates the bioavailability of resveratrol and quercetin in humans, mice, and rats after oral ingestion of grape juice preparations or pure aglycones. Oral administration of resveratrol and quercetin to humans yielded detectable levels of resveratrol, quercetin, and their derivatives in the plasma and urine. Urinary levels of resveratrol, quercetin, and their metabolites were observed in human subjects receiving 600 and 1200 mL of grape juice, whereas quercetin metabolites were identified in urine samples even after receiving 200 mL of grape juice. The cumulative amounts of resveratrol and quercetin excreted in the urine of mice receiving concentrated grape juice for 4 days were 2.3 and 0.7% of the ingested doses, respectively. After i.g. administration of resveratrol to rats (2 mg/kg), up to 1.2 microM resveratrol was observed in the plasma. The study demonstrates that the glycoside forms of resveratrol and quercetin in grape juice are absorbed to a lesser extent than the aglycones.     

Bound ferulic acid from bran is more bioavailable than the free compound in rat

Ferulic acid (FA) is reported as a good antioxidant absorbed by human or rat but only few data deal with the influence of the food matrix on its bioavailability and with its potential protection against cardiovascular diseases and cancer. Wheat bran is used as a source of ferulic acid, the compound being mainly bound to arabinoxylans of the plant cell walls. Pharmacokinetic profiles of FA and its metabolites are established in rats. Free and conjugated FA quickly appear in plasma, reach a plateau 1 h after intake and remain approximately constant at 1 microM up to 24 h. 2.3% of FA are eliminated in urine. Compared with results obtained after intake of free FA, the presence of FA-arabinoxylans bonds in the food matrix increases the occurrence time of FA in the organism and decreases the level of urinary excretion in 24 h. Nevertheless, sulfated FA is still the main plasmatic form. The antioxidant activity of plasmas of rats fed with a standard diet (containing no FA), pure ferulic acid (5.15 mg FA/kg bw) or bran (4.04 mg FA/kg bw) are measured in an ex vivo test using AAPH as free radical inducer. Plasmas of rats fed with bran show a better antioxidant activity than the control group and the pure FA supplemented group, increasing the resistance of erythrocytes to hemolysis by factors of 2 and 1.5, respectively. These results show the good bioavailability of FA from bran and its potential efficiency to protect organism against pathology involving radical steps of development.     

Identification of metabolites of (-)-epicatechin gallate and their metabolic fate in the rat

After intravenous administration of (-)-epicatechin gallate to Wistar male rats, its biliary metabolites were examined. Deconjugated forms of (-)-epicatechin gallate metabolites were prepared by beta-glucuronidase/sulfatase treatment and purified by HPLC. Five compounds were subjected to FAB-MS and NMR analyses. These metabolites were shown to be (-)-epicatechin gallate, 3'-O-methyl-(-)-epicatechin gallate, 4'-O-methyl-(-)-epicatechin gallate, 4' '-O-methyl-(-)-epicatechin gallate, and 3',4' '-di-O-methyl-(-)-epicatechin gallate. After oral administration, five major metabolites excreted in rat urine were purified in their deconjugated forms and their chemical structures identified. They were degradation products from (-)-epicatechin gallate, pyrogallol, 5-(3,4-dihydroxyphenyl)-gamma-valerolactone, 4-hydroxy-5-(3,4-dihydroxyphenyl)valeric acid, 3-(3-hydroxyphenyl)propionic acid, and m-coumaric acid. Time course analysis of the identified (-)-epicatechin gallate metabolites showed that (-)-epicatechin gallate and its conjugate appeared in the plasma with their highest levels 0.5 h after oral administration; their levels rapidly decreased, and then they disappeared by 6 h. The degradation products, mainly in their conjugated forms, emerged at 6 h, peaked at 24 h, and disappeared by 48 h. In urine samples, (-)-epicatechin gallate and its methylated metabolites were hardly detected and the degradation products began to be excreted in the 6-24 h period, peaked in the 24-48 h period, and then began to disappear. The most abundant metabolite in both the plasma and the urine was found to be the conjugated form of pyrogallol. On the basis of these results, a possible metabolic route of (-)-epicatechin gallate orally administered to the rat is proposed.     

Intestinal distribution and excretion of sesaminol and its tetrahydrofuranoid metabolites in rats

Sesame seeds (Sesamum indicum L.) are unique because of potent and various physiological activities imparted by their bioactive lignans. This investigation studied the intestinal distribution and excretion of sesaminol in Sprague-Dawley (SD) rats. To investigate the distribution of sesaminol (per oral 220 mg/kg), the changes in concentration of sesaminol and its metabolites were determined in the intestines and plasma within the 24 h period after tube feeding of sesaminol to SD rats. Results show that the epimerization of sesaminol appeared to be catalyzed by acid in the simulated gastric fluids. The major sesaminol epimer was characterized as 2-episesaminol using 2D-NMR. These findings indicate that sesame sesaminol and its epimer are poorly absorbed prior to reaching the rectum and that substantial amounts pass from the small to the large intestine, where they are metabolized by the colonic microflora to tetrahydrofuranoid metabolites. Sesaminol in plasma was largely present as phase II conjugates, and the seven metabolites were detected as the 2-episesaminol, sesaminol-6-catechol, methylated sesaminol-catechol, R,R-hydroxymethylsesaminol-tetrahydrofuran, S,R-hydroxymethylsesaminol-tetrahydrofuran, enterolactone, and enterodiol. Excretions of sesaminol in urine and feces within the 24 h period were equivalent to 0.02 and 9.33% of the amount ingested, respectively.     

In vitro metabolism of plant lignans: new precursors of mammalian lignans enterolactone and enterodiol.

The metabolism of the plant lignans matairesinol, secoisolariciresinol, pinoresinol, syringaresinol, arctigenin, 7-hydroxymatairesinol, isolariciresinol, and lariciresinol by human fecal microflora was investigated to study their properties as mammalian lignan precursors. The quantitative analyses of lignan precursors and the mammalian lignans enterolactone and enterodiol were performed by HPLC with coulometric electrode array detector. The metabolic products, including mammalian lignans, were characterized as trimethylsilyl derivatives by gas chromatography-mass spectrometry. Matairesinol, secoisolariciresinol, lariciresinol, and pinoresinol were converted to mammalian lignans only. Several metabolites were isolated and tentatively identified as for syringaresinol and arctigenin in addition to the mammalian lignans. Metabolites of 7-hydroxymatairesinol were characterized as enterolactone and 7-hydroxyenterolactone by comparison with authentic reference compounds. A metabolic scheme describing the conversion of the most abundant new mammalian lignan precursors, pinoresinol and lariciresinol, is presented.     

Metabolism of [(1)(4)C]prometryn in rats.

[(1)(4)C]Prometryn, 2, 4-bis(isopropylamino)-6-(methylthio)-s-triazine, was orally administered to male and female rats at approximately 0.5 and 500 mg/kg; daily urine and feces were collected. After 3 or 7 days rats were sacrificed, and blood and selected tissues were isolated. The urine and feces extracts were characterized for metabolite similarity as well as for metabolite identification. Over 30 metabolites were observed, and of these, 28 were identified mostly by mass spectrometry and/or cochromatography with available reference standards. The metabolism of prometryn was shown to occur by N-demethylation, S-oxidation, S-S dimerization, OH substitution for NH(2) and SCH(3), and conjugation with glutathione or glucuronic acid. Rat liver microsomal incubations of prometryn were conducted and compared to the in vivo metabolism. Both in vivo and in vitro phase I metabolisms of prometryn were similar, with S-oxidation and N-dealkylation predominating. The involvement of cytochrome P-450 and flavin-containing monooxidase in the in vitro metabolism of prometryn was investigated.     

Identification and antioxidant activity of flavonoid metabolites in plasma and urine of eriocitrin-treated rats

Eriocitrin, a flavonoid glycoside present in lemon fruit, is metabolized in vivo to a series of eriodictyol, methylated eriodictyol, 3,4-dihydroxyhydrocinnamic acid, and their conjugates. Plasma antioxidant activity increased following oral administration of aqueous eriocitrin solutions to rats. Eriocitrin metabolites were found in plasma and renal excreted urine through HPLC and LC-MS analyses. Eriocitrin was not detected in plasma and urine, but eriodictyol, homoeriodictyol, and hesperetin in their conjugated forms were detected in plasma of 4.0 h following administration of eriocitrin. In urine for 24 h, both nonconjugates and conjugates of these metabolites were detected. 3,4-Dihydroxyhydrocinnamic acid, which is metabolized from eriodictyol by intestinal bacteria, was detected in slight amounts with each form in 4.0-h plasma and 24-h urine. Eriocitrin was suggested to be metabolized by intestinal bacteria, and then eriodictyol and 3,4-dihydroxyhydrocinnamic of its metabolite were absorbed. Following administration of eriocitrin, plasma exhibited an elevated resistance effect to lipid peroxidation. Eriocitrin metabolites functioning as antioxidant agents are discussed.     

Absorption and excretion of luteolin and apigenin in rats after oral administration of Chrysanthemum morifolium extract

Chrysanthemum morifolium extract (CME) has the protective effect on cardiovascular diseases. Luteolin and apigenin are two major bioactive components in vivo when CME is orally administrated to experimental animal. The present paper shows the study of the absorption and excretion of luteolin and apigenin in rats after a single oral dose of CME (200 mg/kg). The levels of luteolin and apigenin in plasma, urine, feces, and bile were measured by HPLC after deconjugation with hydrochloric acid or beta-glucuronidase/sulfatase. The results showed that the plasma concentrations of luteolin and apigenin reached the highest peak level at 1.1 and 3.9 h after dosing, respectively. The area under the concentration-time curves (AUC) for luteolin and apigenin were 23.03 and 237.6 microg h mL-1, respectively. The total recovery of the dose was 37.9% (6.6% in urine; 31.3% in feces) for luteolin and 45.2% (16.6% in urine; 28.6% in feces) for apigenin. The cumulative luteolin and apigenin excreted in the bile was 2.05% and 6.34% of the dose, respectively. All of the results suggest apigenin may be absorbed more efficiently than luteolin in CME in rats, and both luteolin and apigenin have a slow elimination phase, with a quick absorption, so a possible accumulation of the two flavonoids in the body can be hypothesized.