Metabolism and disposition of resveratrol in rats: extent of absorption, glucuronidation, and enterohepatic recirculation evidenced by a linked-rat model

Resveratrol bioavailability and toxicity in humans

Numerous data are now available on the beneficial properties of the polyphenolic compound resveratrol including its anti-inflammatory and antitumor effects. However, few studies have been performed with resveratrol in humans, and the results of these studies appear fragmentary and sometimes contradictory due to variations in conditions of administration, protocols and methods of assessment. This review article presents the results of recent studies investigating the pharmacokinetics, bioavailability, and toxicity of resveratrol in humans. Resveratrol is well absorbed, rapidly metabolized, mainly into sulfo and glucuronides conjugates which are eliminated in urine. Resveratrol seems to be well tolerated and no marked toxicity was reported. These data are important in the context of human efficacy studies, and they provide further support for the use of resveratrol as a pharmacological drug in human medicine.

Resveratrol enhances p53 acetylation and apoptosis in prostate cancer by inhibiting MTA1/NuRD complex

Dietary compounds and epigenetic influences are well recognized factors in cancer progression. Resveratrol (Res), a dietary compound from grapes, has anticancer properties; however, its epigenetic effects are understudied. Metastasis-associated protein 1 (MTA1) is a part of the nucleosome remodeling deacetylation (NuRD) corepressor complex that mediates posttranslational modifications of histones and nonhistone proteins resulting in transcriptional repression. MTA1 overexpression in prostate cancer (PCa) correlates with tumor aggressiveness and metastasis. In this study, we have identified a novel MTA1-mediated mechanism, by which Res restores p53-signaling pathways in PCa cells. We show, for the first time, that Res causes down-regulation of MTA1 protein, leading to destabilization of MTA1/NuRD thus allowing acetylation/activation of p53. We demonstrated that MTA1 decrease by Res was concomitant with accumulation of Ac-p53. MTA1 knockdown further sensitized PCa cells to Res-dependent p53 acetylation and recruitment to the p21 and Bax promoters. Furthermore, MTA1 silencing maximized the levels of Res-induced apoptosis and pro-apoptotic Bax accumulation. HDAC inhibitor SAHA, like MTA1 silencing, increased Res-dependent p53 acetylation and showed cooperative effect on apoptosis. Our results indicate a novel epigenetic mechanism that contributes to Res anticancer activities: the inhibition of MTA1/NuRD complexes due to MTA1 decrease, which suppresses its deacetylation function and allows p53 acetylation and subsequent activation of pro-apoptotic genes. Our study identifies MTA1 as a new molecular target of Res that may have important clinical applications for PCa chemoprevention and therapy, and points to the combination of Res with HDAC inhibitors as an innovative therapeutic strategy for the treatment of PCa.

Determination of Z-3,5,4'-trimethoxystilbene in rat plasma by a simple HPLC method: application in a pre-clinical pharmacokinetic study

A simple HPLC method had been developed and validated to quantify Z-3,5,4'-trimethoxystilbene (Z-TMS), a phyto-stilbene with potent anti-cancer activities in rat plasma. Chromatographic separation was achieved on a reversed phase-HPLC column, which was protected by a guard column through a 13.5-min gradient delivery of a mixture of acetonitrile and water at a flow rate of 1.5 ml/min at 50 degrees C. The UV absorbance at 300 nm was recorded. Z-TMS and E-stilbene (internal standard) eluted at 8.8 and 9.3 min, respectively. The calibration curve was linear within the range of 33-2500 ng/ml (R(2)>0.9995) and 10 ng/ml was the lower limit of detection. The intra- and inter-day precisions were good and the relative standard deviation was all lower than 10%. The analytical recovery of Z-TMS in plasma ranged from 94.6+/-9.1% to 97.0+/-2.1%. This HPLC method was successfully applied to assess the pharmacokinetic profile of Z-TMS in Sprague-Dawley rats using hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) as a dosing vehicle. Although Z-TMS displayed negligible oral bioavailability, it had a fairly long terminal elimination half-life, abundant plasma drug exposure and limited clearance following intravenous administration. As Z-TMS had favorable intravenous pharmacokinetic profile, further investigation on its potential as a cancer chemotherapeutic agent is warranted.

Resveratrol-loaded calcium-pectinate beads: effects of formulation parameters on drug release and bead characteristics

Resveratrol has potential therapeutic efficacy on several lower gastro-intestinal (GI) diseases such as colitis and colorectal cancer. But resveratrol is quickly absorbed and metabolized at the upper GI tract, which renders it unsuitable for this purpose. This study aimed at devising a delayed release formulation of resveratrol as calcium-pectinate (Ca-pectinate) beads and investigated the impact of various formulation parameters on bead characteristics. Ca-pectinate beads were prepared by varying six formulation parameters (cross-linking pH, cross-linker concentration, cross-linking time, drying condition, pectin concentration, and resveratrol concentration). Their effects were investigated on calcium entrapment, moisture content and weight loss during drying, particle shape and size, resveratrol entrapment and loading efficiency, swelling-erosion, and resveratrol retention pattern of formulated beads. Preparative conditions were optimized from these studies and optimized beads were further subjected to morphological examination, drug-polymer interaction, and enzymatic degradation study. Almost all prepared beads were spherical with approximately 1 mm diameter. Swelling-erosion and drug retention pattern were changed with formulation variables. Release data of almost all beads showed linearity of the plots for the cumulative percent resveratrol released versus square root of time often after an initial lag period. Observations from the present study revealed that optimized Ca-pectinate beads can encapsulate a very high amount of resveratrol (>97.5%) and can be used for delayed release and site-specific delivery to the lower GI tract. Depending on the formulation parameters, release of resveratrol after 10 h incubation in the intestinal media was 80-100%.

trans-Resveratrol as a neuroprotectant

Epidemiological evidence indicates that nutritionally-derived polyphenols such as resveratrol (RES) have neuroprotective properties. Administration of RES to culture media protects a wide variety of neuronal cell types from stress-induced death. Dietary supplementation of RES can ameliorate neuronal damage and death resulting from both acute and chronic stresses in rodents. The specific molecular mechanisms by which RES acts at the cellular level remain incompletely understood. However, many experimental data indicate that RES reduces or prevents the occurrence of oxidative damage. Here we discuss possible mechanisms by which RES might exert protection against oxidative damage and cell death. Evidence suggesting that RES’s chemical antioxidant potential is not sufficient explanation for its effects is discussed. Putative biological activities, including interactions with estrogen receptors and sirtuins are critically discussed. We provide a synthesis of how RES’s phytoestrogenic properties might mediate the neuronal stress resistance underlying its observed neuroprotective properties.

Glucuronidation of trans-resveratrol by human liver and intestinal microsomes and UGT isoforms

Resveratrol (trans-resveratrol, trans-3,5,4′-trihydroxystilbene) is a naturally occurring stilbene analogue found in high concentrations in red wine. There is considerable research interest to determine the therapeutic potential of resveratrol, as it has been shown to have tumour inhibitory and antioxidant properties. This study was performed to investigate the glucuronidation of resveratrol and possible drug interactions via glucuronidation. Two glucuronide conjugates, resveratrol 3-O-glucuronide and resveratrol 4′-O-glucuronide, were formed by human liver and intestinal microsomes. UGT1A1 and UGT1A9 were predominantly responsible for the formation of the 3-O-glucuronide (Km = 149 μm) and 4′-O-glucuronide (Km = 365 μm), respectively. The glucuronide conjugates were formed at higher levels (up to 10-fold) by intestinal rather than liver microsomes. Resveratrol was co-incubated with substrates of UGT1A1 (bilirubin and 7-ethyl-10-hydroxycamptothecin (SN-38)) and UGT1A9 (7-hydroxytrifluoromethyl coumarin (7-HFC)). No major changes were noted in bilirubin glucuronidation in the presence of resveratrol. Resveratrol significantly inhibited the glucuronidation of SN-38 (Ki = 6.2 ± 2.1 μm) and 7-HFC (Ki = 0.6 ± 0.2 μm). Hence, resveratrol has the potential to inhibit the glucuronidation of concomitantly administered therapeutic drugs or dietary components that are substrates of UGT1A1 and UGT1A9.

The effect of resveratrol in tracheal tissue of rats exposed to cigarette smoke

OBJECTIVE

The aim of this study was to evaluate the effect of resveratrol on the tracheal tissue of rats exposed to cigarette smoke.

MATERIALS AND METHODS

40 adult Wistar albino rats were divided into four groups for an experiment of 6 weeks. Animals in group 1 were controls (n = 10). Rats in group 2 were exposed to cigarette smoke only, and rats in group 3 received daily intraperitoneal injections of resveratrol (10 mg/kg/d). Animals in group 4 were exposed to both cigarette smoke and intraperitoneal injections of resveratrol. Rats of all groups were sacrificed using cervical dislocation. The tracheas were removed and embedded in paraffin blocks. Sections of 4-5 mum thickness were prepared from the blocks. These sections were stained with hematoxylin and eosin, periodic acid-Schiff, and Alcian blue and viewed with a Leica DFC 280 light microscope.

RESULTS

Tracheal sections showed that, in group 2 (cigarette smoke group), there was desquamation of epithelial cells into the tracheal lumen, loss of cilia in the epithelial layer, an increase of goblet cells, activation of serous glands at the submucosa, and cell infiltration. In group 4 (cigarette smoke + resveratrol group), all these findings also existed but only a few sections were affected. It was observed that cigarette smoking caused morphological changes such as epithelial degeneration in the upper airway. These morphological changes were correlated with the amount of toxic substances in the cigarette smoke.

CONCLUSION

We found that resveratrol had a preventive role in the histopathological changes caused by cigarette smoking in the rat trachea.

The Benefits of Calorie Restriction and Calorie Restriction Mimetics as Related to the Eye

The effects of calorie restriction without malnutrition seem to possess many beneficial effects in numerous disease states. Recently, studies related to calorie restriction mimetics that biochemically mimic the effects of calorie restriction are also becoming increasingly popular. Both calorie restriction and calorie restriction mimetics trigger an adaptive response reminiscent of mild-stress or low-dose toxic response, which is frequently referred to as hormesis in the toxicology literature. Although some benefits of calorie restriction and calorie restriction mimetics have been studied, the role of hormesis-related pathways in the eye has not been given a special attention. This review will present the current literature on calorie restriction and calorie restriction mimetics as related to most prominent eye diseases and provide insights on the therapeutic role of hormesis in eye diseases.

Resveratrol: its biologic targets and functional activity

The polyphenolic phytoalexin resveratrol (RSV) and its analogues have received tremendous attention over the past couple of decades because of a number of reports highlighting their benefits in vitro and in vivo in a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. These studies have underscored the high degree of diversity in terms of the signaling networks and cellular effector mechanisms that are affected by RSV. The activity of RSV has been linked to cell-surface receptors, membrane signaling pathways, intracellular signal-transduction machinery, nuclear receptors, gene transcription, and metabolic pathways. The promise shown by RSV has prompted heightened interest in studies aimed at translating these observations to clinical settings. In this review, we present a comprehensive account of the basic chemistry of RSV, its bioavailability, and its multiple intracellular target proteins and signaling pathways.

A simple and sensitive HPLC-UV method for the quantification of piceatannol analog trans-3,5,3',4'-tetramethoxystilbene in rat plasma and its application for a pre-clinical pharmacokinetic study

A simple and sensitive HPLC-UV method was developed and validated for the quantification of piceatannol analog trans-3,5,3',4'-tetramethoxystilbene (M-PIC) in rat plasma. Following protein precipitation with three volumes of acetonitrile, the analytes were separated on a RP-HPLC column, which was protected by a guard column through gradient delivery of a mixture of acetonitrile-water at 40 degrees C. The UV absorbance at 325nm was recorded to quantify M-PIC. The retention time of M-PIC and trans-3,5-dimethoxystilbene (internal standard) was 7.4 and 8.4min, respectively. The calibration curves were linear (R(2)>0.9989) with a lower limit of quantification of 15ng/ml. The intra- and inter-day precisions, in terms of RSD, were all lower than 7.5%. The average analytical recovery ranged from 97.0 to 104.3% while the average absolute recovery ranged from 101.8 to 105.0%. This reliable HPLC method was subsequently applied to assess the pharmacokinetic profile of M-PIC in Sprague-Dawley rats using 2-hydroxypropyl-beta-cyclodextrin as a dosing vehicle. The terminal elimination half-life (t(1/2lambdaz)) and clearance (Cl) of M-PIC were 313+/-20min and 33.1+/-3.9ml/min/kg, respectively; and its absolute oral bioavailability was as high as 50.7+/-15.0%. M-PIC appeared to have a favorable pharmacokinetic profile and further pharmacological investigation on this phyto-stilbene was warranted.

Interaction between phenolics and gut microbiota: role in human health

Dietary phenolic compounds are often transformed before absorption. This transformation modulates their biological activity. Different studies have been carried out to understand gut microbiota transformations of particular polyphenol types and identify the responsible microorganisms. Although there are potentially thousands of different phenolic compounds in the diet, they are typically transformed to a much smaller number of metabolites. The aim of this review was to discuss the current information about the microbial degradation metabolites obtained from different phenolics and their formation pathways, identifying their differences and similarities. The modulation of gut microbial population by phenolics was also reviewed in order to understand the two-way phenolic-microbiota interaction. Clostridium and Eubacterium genera, which are phylogenetically associated, are other common elements involved in the metabolism of many phenolics. The health benefits from phenolic consumption should be attributed to their bioactive metabolites and also to the modulation of the intestinal bacterial population.

Resveratrol alters proliferative responses and apoptosis in human activated B lymphocytes in vitro

We hypothesized that the phytochemicals resveratrol, quercetin, and kaempferol would modulate B lymphocyte proliferation, Ig synthesis, and apoptosis after activation. Peripheral blood mononuclear cells (PBMC) were isolated from 12 healthy adult human volunteers and incubated with pokeweed mitogen plus 0, 2, 5, and 10 mumol/L resveratrol, quercetin, or kaempferol. After 6 d, CD19+ B cells were analyzed for proliferation, B cell lymphoma-2 (Bcl-2) expression, and activation of caspase-3 using flow cytometry. After 8 d, cell supernatants were collected and IgM and IgG were measured by ELISA. Resveratrol at a concentration of 5 mumol/L increased the percentage of CD19+ cells compared with mitogen only-stimulated cells (P < 0.01), and a trend for increased proliferation was observed for cells treated with 0, 2, and 5 mumol/L resveratrol (P-trend = 0.01). However, 10 mumol/L resveratrol inhibited proliferation of B lymphocytes (P < 0.01). Expression of Bcl-2 and caspase-3 activation increased in B cells treated with 10 mumol/L resveratrol compared with mitogen alone (P < 0.01), and trends for dose-responsive increases in Bcl-2 expression and caspase-3 activation were observed (P-trend < 0.0001). Differences in IgM and IgG production were not observed for PBMC treated with resveratrol. Kaempferol at 10 mumol/L slightly inhibited proliferative responses (P < 0.05) but did not affect B cell function or apoptosis. Quercetin did not alter B cell proliferation, function, or apoptosis. These data show that human B lymphocyte proliferation and apoptosis are modified by physiological concentrations of resveratrol and suggest that exposure of human B cells to resveratrol may increase survival by upregulating Bcl-2.

Sirtuin activators

BACKGROUND

Sirtuin 1-7 (SIRT1-7) are deacetylases that are dependent on NAD(+) for their activity. SIRT1 down-regulates p53 activity, increasing lifespan, cell survival, and neuroprotection; it also deacetylates peroxisome proliferator-activated receptor-gamma and its coactivator 1alpha, promoting fat mobilization, increasing mitochondrial size and number, and positively regulating insulin secretion. Sirtuins link nutrient availability and energy metabolism. Calorie restriction, which increases lifespan and is beneficial in age-related disorders, activates sirtuin. Major efforts are thus focused to developing sirtuin activators.

OBJECTIVE

After discussing the potential involvement of sirtuins in pathophysiological processes, this review looks at new, synthetic sirtuin activators.

CONCLUSIONS

To date, resveratrol is the most potent natural compound able to activate SIRT1, mimicking the positive effect of calorie restriction. Resveratrol might help in the treatment or prevention of obesity and in preventing the aging-related decline in heart function and neuronal loss. As resveratrol has low bioavailability and interacts with multiple molecular targets, the development of new molecules with better bioavailability and targeting sirtuin at lower concentrations is a promising field of the medicinal chemistry. New SIRT1 activators that are up to 1000 times more effective than resveratrol have recently been identified. These improve the response to insulin and increase the number and activity of mitochondria in obese mice. Human trials with a formulation of resveratrol with improved bioavailability and with a synthetic SIRT1 activator are in progress.

Effect of resveratrol and zinc on intracellular zinc status in normal human prostate epithelial cells

To evaluate the influence of resveratrol on cellular zinc status, normal human prostate epithelial (NHPrE) cells were treated with resveratrol (0, 0.5, 1, 2.5, 5, and 10 microM) and zinc [0, 4, 16, and 32 microM, representing zinc-deficient (ZD), zinc-normal (ZN), zinc-adequate (ZA), and zinc-supplemented (ZS) conditions, respectively]. A progressive reduction in cell growth was observed in cells treated with increasing amounts of resveratrol (2.5-10 microM). Resveratrol at 5 and 10 microM resulted in a dramatic increase in cellular total zinc concentration, especially in ZS cells. Flow cytometry indicated that 10 microM resveratrol induced arrest of the cell cycle at the G(2)/M phase in association with the observed cell growth inhibition. Data from an in vitro experiment using zinquin as an indicator of intracellular free Zn(II) status demonstrated complex interactions between resveratrol and Zn(II). Fluorescence spectrofluorometry and fluorescence microscopic analyses revealed that intracellular free labile zinc was progressively elevated from nearly twofold in ZS cells with no resveratrol to multifold in ZA and ZS cells with 10 microM resveratrol compared with the corresponding ZN cells. Furthermore, increases in cellular zinc status were associated with elevated levels of reactive oxygen species and senescence, as evidenced by morphological and histochemical changes in cells treated with 2.5 or 10 microM resveratrol, especially in ZA and ZS cells. Taken together, the interaction between resveratrol and zinc in NHPrE cells increases total cellular zinc and intracellular free labile zinc status and, subsequently, reactive oxygen species production and senescence.

Dose-dependent absorption and metabolism of trans-polydatin in rats

There is considerable evidence that stilbenes provide health benefits. trans-Polydatin is one of the major stilbenoid compounds in red wine. The purpose of this study is to investigate the dose-dependent absorption and metabolism of trans-polydatin in rats. trans-Polydatin was administered to rats by gavage at three different doses (50, 100, and 300 mg x kg(-1)). Blood samples were then collected at different time points. In situ perfusion of rat small intestine and liver was used to investigate the first-pass metabolism of trans-polydatin. trans-Polydatin and its metabolites were detected by LC-MS/MS. trans-Polydatin and its metabolites resveratrol, glucuronidated resveratrol, and glucuronidated trans-polydatin were detected in plasma within 10 min following oral administration of trans-polydatin; in situ perfusion of the rat small intestine and liver with trans-polydatin yielded the same result. The AUC(0-infinity) of trans-polydatin and its metabolites increased in a dose dependent manner following oral administration of trans-polydatin. This indicates that in the rats, trans-polydatin is absorbed in a dose-dependent manner and undergoes extensive first-pass deglycosylation and glucuronidation. Orally administered trans-polydatin, therefore, is metabolized primarily to resveratrol in the small intestine and liver, where it is further metabolized to the glucuronidated resveratrol.

Safety studies conducted on high-purity trans-resveratrol in experimental animals

trans-Resveratrol is a naturally occurring polyphenolic compound found in a variety of foods, but predominantly in grapes. Safety studies were conducted on high-purity trans-resveratrol (Resvida), including skin and eye irritation, dermal sensitization, subchronic and reproductive toxicity, genotoxicity, and absorption, metabolism and excretion. Resvida was non-irritating to skin and eyes and non-sensitizing. It was non-mutagenic in a bacterial reverse mutation assay in Salmonella typhimurium and Escherichia coli, but exhibited clastogenic activity in a chromosomal aberration test in human lymphocytes. However, in an in vivo bone marrow micronucleus test in rats, Resvida was non-genotoxic. In a 28-day study, Resvida caused no adverse effects in rats at 50, 150 and 500 mg/kg bw/day. Similarly, in a 90-day study, Resvida did not cause any adverse effects in rats at up to 700 mg/kg bw/day; the highest dose tested. Resvida did not induce any adverse reproductive effects in an embryo-fetal toxicity study in rats at a dose of 750 mg/kg bw/day. Also, in vitro and in vivo absorption, metabolism, and excretion studies in Caco-2 cells, rat primary hepatocytes and male and female rats (in vivo) show that Resvida is readily absorbed, metabolized and excreted. These studies provide evidence that Resvida is well tolerated and non-toxic.

Wine, Resveratrol and Health: A Review

Several studies have cited the Mediterranean diet as an example of healthy eating. In fact, the Mediterranean diet has become the reference diet for the prevention of cardiovascular disease. Red wine seems to be an essential component of the diet, since moderate consumption of wine is associated with lower risk and mortality from cardiovascular disease. Evidence is also accumulating that wine helps prevent the development of certain cancers. Of all the many components of wine, resveratrol, which is a natural component specifically present in wine, has been identified as being mainly responsible for these health-promoting properties. Many valuable properties such as cardioprotective and anticarcinogenic activity have been attributed to resveratrol; however, its bioavailability is quite low. The bioactivity of metabolites derived from resveratrol, and the accumulation of resveratrol in vital organs are still under study, but there are high expectations of positive results. Other stilbene compounds are also considered in this review, despite being present in undetectable or very small quantities in wine. The present paper reviews all aspects of the health properties of wine, bioactive compounds found in wine, and their concentrations, bioavailability and possible synergistic effects.

Trans-resveratrol alone and hydroxystilbenes of rhubarb (Rheum rhaponticum L.) root reduce liver damage induced by chronic ethanol administration: a comparative study in mice

The hepatoprotective effects and pharmacokinetics of trans-resveratrol and hydroxystilbenes of the garden rhubarb (Rheum rhaponticum L., R. rhaponticum) root ethanol extract were studied. Ethanol was administered to male BALB/c mice for 35 days in an inhalation chamber. During this time vehicle, trans-resveratrol (20 mg/kg per day) or R. rhaponticum extract was intraperitoneally (i.p.) administered and mice were sacrificed for the collection of liver and blood. In an additional experiment, the level of parent compounds and metabolites was estimated in the blood after acute i.p. administration of trans-resveratrol or R. rhaponticum extract. The levels of hydroxystilbenes, their metabolites and fatty acid oxy-metabolites (oxylipins) were studied by LC-tandem DAD-MS/MS. Ethanol induced hepatotoxicity, as evidenced by histological changes and accumulation of oxylipins in the blood. Both trans-resveratrol and R. rhaponticum extract reduced the extent of these changes. The pharmacokinetics of trans-resveratrol was characterized by a rapid removal from the blood and metabolism to sulfates and glucuronides. After the administration of R. rhaponticum extract, in addition to trans-resveratrol glucoside and its metabolites, several other hydroxystilbenes were found. Inhibition of oxidation of polyunsaturated fatty acids is proposed as a basis of the hepatoprotective effect of both trans-resveratrol and R. rhaponticum extract.

Quantification of trans-resveratrol and its metabolites in rat plasma and tissues by HPLC

trans-Resveratrol, a polyphenol from grapes, is being recognized as a bioactive agent with potential beneficial effects on health. However, little is known about its distribution in the organism mainly because of the lack of accurate and precise detection methods. Consequently the aim of the present study was to develop a methodology of extraction and quantification of trans-resveratrol and its metabolites in plasma, brain, testis, liver, lungs and kidney by HPLC. To this end, the time of homogenization and liquid extraction were adapted to the different tissues. The methods were validated using homogenized tissues spiked with pure trans-resveratrol. The precision (% R.S.D.) ranged from 3.7% in testis to 13.2% in lungs. Recoveries were 98.5+/-3.2% (liver), 100.1+/-1.8% (kidney), 96.5+/-7.6% (lungs), 99.0+/-0.7% (brain) and 103+/-2.7% (testicle). The limits of detection ranged from 5.5 nM in testis to 11.2 nM in kidney. After validation, the methods were applied to the assessment of the bioavailability and distribution of trans-resveratrol in rats after the intravenous administration of 15 mg/kg. At 90 min, trans-resveratrol and its glucuronide and sulfate conjugates were widely distributed in all the tissues studied. The highest concentrations (nmol/g tissue) were found in kidney (resveratrol: 1.45+/-0.35; glucuronide: 2.91+/-0.19; sulfate: not detected), and the lowest in brain (resveratrol: 0.17+/-0.04; glucuronide: not detected; sulfate: 0.04+/-0.01). In conclusion, accurate and reproducible methods have been described to identify target tissues of resveratrol as a first step to understand its mechanisms of action in vivo.

Piceatannol, a derivative of resveratrol, moderately slows I(Na) inactivation and exerts antiarrhythmic action in ischaemia-reperfused rat hearts

BACKGROUND AND PURPOSE

Piceatannol is more potent than resveratrol in free radical scavenging in association with antiarrhythmic and cardioprotective activities in ischaemic-reperfused rat hearts. The present study aimed to investigate the antiarrhythmic efficacy and the underlying ionic mechanisms of piceatannol in rat hearts.

EXPERIMENTAL APPROACH

Action potentials and membrane currents were recorded by the whole-cell patch clamp techniques. Fluo-3 fluorimetry was used to measure cellular Ca2+ transients. Antiarrhythmic activity was examined from isolated Langendorff-perfused rat hearts.

KEY RESULTS

In rat ventricular cells, piceatannol (3-30 micromol.L(-1)) prolonged the action potential durations (APDs) and decreased the maximal rate of upstroke (V(max)) without altering Ca2+ transients. Piceatannol decreased peak I(Na) and slowed I(Na) inactivation, rather than induced a persistent non-inactivating current, which could be reverted by lidocaine. Resveratrol (100 micromol.L(-1)) decreased peak I(Na) without slowing I(Na) inactivation. The inhibition of peak I(Na) or V(max) was associated with a negative shift of the voltage-dependent steady-state I(Na) inactivation curve without altering the activation threshold. At the concentrations more than 30 micromol.L(-1), piceatannol could inhibit I(Ca,L), I(to), I(Kr), Ca2+ transients and Na+-Ca2+ exchange except I(K1). Piceatannol (1-10 micromol.L(-1)) exerted antiarrhythmic activity in isolated rat hearts subjected to ischaemia-reperfusion injury.

CONCLUSIONS AND IMPLICATIONS

The additional hydroxyl group on resveratrol makes piceatannol possessing more potent in I(Na) inhibition and uniquely slowing I(Na) inactivation, which may contribute to its antiarrhythmic actions at low concentrations less than 10 micromol.L(-1).

Sulfation of resveratrol in human liver: Evidence of a major role for the sulfotransferases SULT1A1 and SULT1E1

Sulfation of resveratrol, a polyphenolic compound present in grapes and wine with anticancer and cardioprotective activities, was studied in human liver cytosol. In the presence of 3'-phosphoadenosine-5'-phosphosulfate, three metabolites (M1-3) whose structures were identified by mass spectrometry and NMR as trans-resveratrol-3-O-sulfate, trans-resveratrol-4'-O-sulfate, and trans-resveratrol-3-O-4'-O-disulfate, respectively. The kinetics of M1 formation in human liver cytosol exhibited an pattern of substrate inhibition with a K(i) of 21.3 +/- 8.73 microM and a V(max)/K(m) of 1.63 +/- 0.41 microLmin(-1)mg(-1) protein. Formation of M2 and M3 showed sigmoidal kinetics with about 56-fold higher V(max)/K(m) values for M3 than for M2 (2.23 +/- 0.14 and 0.04 +/- 0.01 microLmin(-1)mg(-1)). Incubation in the presence of human recombinant sulfotransferases (SULTs) demonstrated that M1 is almost exclusively catalysed by SULT1A1 and only to a minor extent by SULT 1A2, 1A3 and 1E1, whereas M2 is selectively formed by SULT1A2. M3 is mainly catalysed by SULT1A2 and 1A3. In conclusion, the results elucidate the enzymatic pathways of resveratrol in human liver, which must be considered in humans following oral uptake of dietary resveratrol.

trans-Resveratrol, an extract of red wine, inhibits human eosinophil activation and degranulation

BACKGROUND AND PURPOSE

trans-Resveratrol, a non-flavonoid polyphenol found abundantly in red wine possesses antiproliferative and anti-inflammatory activity in various inflammatory disease conditions. However, the effect of trans-resveratrol on eosinophil activation in relation to allergy has not been investigated.

EXPERIMENTAL APPROACH

Human eosinophils were isolated and purified from whole blood and incubated for 16 h with trans-resveratrol. Eosinophil chemotaxis, activation and degranulation, and apoptosis were investigated. The effect of trans-resveratrol on the inhibition of p38 and ERK1/2 activation was examined.

KEY RESULTS

Treatment of human eosinophils with trans-resveratrol at concentrations <100 microM for 16 h did not induce eosinophil apoptosis. Similar results were seen after 24 h and 48 h incubations. trans-Resveratrol (<100 microM) significantly inhibited eosinophil peroxidase release after activation with IL-5 (IC(50)=2.9+/-0.9 microM) or C5a (IC(50)=3.9+/-0.5 microM) after 5 min priming with cytochalasin B (CB). Similarly, the production of leukotriene C4 after stimulation with calcium ionophore, and eosinophil chemotaxis in response to eotaxin, as well as CD11b upregulation and CD62 L shedding was also significantly reduced by trans-resveratrol, at concentrations above 5 microM. All the activators induced p38 and ERK1/2 phosphorylation maximal at 2 min of activation. trans-Resveratrol potently inhibited p38 and ERK1/2 activation after calcium ionophore and CB and C5a activation.

CONCLUSIONS AND IMPLICATIONS

trans-Resveratrol is effective at inhibiting human eosinophil activation and degranulation at concentrations <100 microM, while not inducing apoptosis. This potent anti-inflammatory activity of trans-resveratrol and possibly its metabolites on eosinophils may be worth investigating for the treatment of eosinophil-related allergic diseases.

Sirt1 is involved in energy metabolism: the role of chronic ethanol feeding and resveratrol

Sirt1, a deacetylase involved in regulating energy metabolism in response to calorie restriction, is up regulated after chronic ethanol feeding using the intragastric feeding model of alcohol liver disease. PGC1 alpha is also up regulated in response to ethanol. These changes are consistent with activation of the Sirt1/PGC1 alpha pathway of metabolism and aging, involved in alcohol liver disease including steatosis, necrosis and fibrosis of the liver. To test this hypothesis, male rats fed ethanol intragastrically for 1 month were compared with rats fed ethanol plus resveratrol or naringin. Liver histology showed macrovesicular steatosis caused by ethanol and this change was unchanged by resveratrol or naringin treatment. Necrosis occurred with ethanol alone but was accentuated by resveratrol treatment, as was fibrosis. The expression of Sirt1 and PGC1 alpha was increased by ethanol but not when naringin or resveratrol was fed with ethanol. Sirt3 was also up regulated by ethanol but not when resveratrol was fed with ethanol. These results support the concept that ethanol induces the Sirt1/PGC1 alpha pathway of gene regulation and both naringin and resveratrol prevent the activation of this pathway by ethanol. However, resveratrol did not reduce the liver pathology caused by chronic ethanol feeding.

Resveratrol: a natural compound with pharmacological potential in neurodegenerative diseases

Resveratrol is a phytoalexin structurally related to stilbenes, which is synthesized in considerable amounts in the skin of grapes, raspberries, mulberries, pistachios and peanuts, and by at least 72 medicinal and edible plant species in response to stress conditions. It was isolated in 1940 and did not maintain much interest for around five decades until its role in treatment of cardiovascular diseases was suggested. To date, resveratrol has been identified as an agent that may be useful to treat cancer, pain, inflammation, tissue injury, and other diseases. However, currently the attention is being focused in analyzing its properties against neurodegenerative diseases and as antiaging compound. It has been reported that resveratrol shows effects in in vitro models of epilepsy, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and nerve injury. However, evidences in vivo as well as in human beings are still lacking. Thus, further investigations on the pharmacological effects of resveratrol in vivo are necessary before any conclusions on its effects on neurodegenerative diseases can be obtained.

Resveratrol protects primary rat hepatocytes against necrosis induced by reactive oxygen species

Reactive oxygen species can be important mediators of damage to cell molecules and structures. Besides the endogen antioxidant defences, the antioxidant intake in the diet has an important role in the protection against the development of diseases produced by oxidative damage. Resveratrol is a naturally occurring compound present in many plants some of which are part of the human diet. This molecule has been thoroughly investigated because of its antioxidant and anticarcinogenic properties among others. We investigated whether resveratrol could provide protective antioxidant action in primary rat hepatocyte cultures. Primary rat hepatocytes cultures were exposed to 300 microM tert-butyl hydroperoxide; 25, 50 or 75 microM resveratrol or to 300 microM tert-butyl hydroperoxide plus 25, 50 or 75 microM resveratrol for different time periods. Necrosis was evaluated by lactate dehydrogenase liberation to the medium. Apoptosis was evaluated by caspase 3 activity measurement. Changes in cellular morphology after the different treatments were recorded using bright field microscopy. Inhibition of the reactive oxygen species by resveratrol was studied by confocal microscopy and spectrofluorimetrically. Resveratrol inhibited necrosis induced by tert-butyl hydroperoxide. No apoptosis was observed in any treatment. It also was effective in eliminating reactive oxygen species. At 75 microM, the highest concentration tested, resveratrol became slightly cytotoxic. Our results show that resveratrol protects primary rat hepatocytes in culture from oxidative stress induced cell death. These results suggest that resveratrol could enhance the antioxidant status of hepatic cells.

Differential effects of resveratrol on androgen-responsive LNCaP human prostate cancer cells in vitro and in vivo

Resveratrol is a phytochemical that has been under consideration for use as a prostate cancer chemopreventive agent. However, the efficacy, as well as the mechanisms of action of resveratrol on prostate cancer prevention, remains largely unknown. This study seeks to address these questions and examine the cancer preventive effects of resveratrol using complementary human LNCaP prostate cancer cell culture and xenograft models. In cultured LNCaP cells, we found that resveratrol inhibited cell growth. The growth inhibitory effects of resveratrol appeared to be through modulation of both androgen- and estrogen-mediated events. Global gene expression analysis using microarrays identified androgen-responsive genes as a group of genes universally affected by resveratrol in LNCaP cells in vitro. The effect of resveratrol on expression of these genes appeared to be through inhibition of both androgen- and estrogen-mediated transcription. In a xenograft model, resveratrol delayed LNCaP tumor growth and inhibited expression of a marker for steroid hormone responses. However, exposure to resveratrol also led to increased angiogenesis and inhibition of apoptosis in the xenograft. In summary, resveratrol may act through modulation of steroid hormone-dependent pathways to inhibit prostate cancer cell growth in both culture and xenografts, but exposure in vivo may be of concern.

Preclinical factors affecting the pharmacokinetic behaviour of tanshinone IIA, an investigational new drug isolated from Salvia miltiorrhiza for the treatment of ischaemic heart diseases

Tanshinone IIA (TSIIA) is a major active triterpenoid isolated from Salvia miltiorrhiza. The purposes of this study were to investigate various preclinical factors that determined the pharmacokinetics of TSIIA. After oral dosing at 6.7, 20, and 60 mg kg(-1), TSIIA was detected mainly as glucuronidated conjugate (TSIIAG) with only small amounts of the unchanged in the plasma. TSIIA was predominantly excreted into the bile and faeces as TSIIAG, and urine to a minor extent. The C(max) and AUC(0-)(t) of TSIIAG after i.p. administration were significantly lower than those after intragastric administration. The plasma concentration-time profiles of TSIIA following oral dosing of TSIIA showed multiple peaks. The C(max) and AUC(0-)(t) of TSIIA and its glucuronides in rats with intact bile duct were significantly lower than those of rats with bile duct cannulation. Studies from the linked-rat model and intraduodenal injection of bile containing TSIIA and its metabolites indicate that TSIIA glucuronides underwent hydrolysis and the aglycone was reabsorbed from the gut and excreted into the bile as conjugates. TSIIA had a wide tissue distribution, with a very high accumulation in the lung, but very limited penetration into the brain and testes. TSIIA was metabolized by rat CYP2C, 3A and 2D, as ticlopidine, ketoconazole and quinidine all inhibited TSIIA metabolism in rat liver microsomes. Taken collectively, these findings indicate that multiple factors play important roles in determining the pharmacokinetics of TSIIA.

Metabolism and Disposition of Resveratrol in the Isolated Perfused Rat Liver: Role of Mrp2 in the Biliary Excretion of Glucuronides

In this study, the hepatic metabolism and transport system for resveratrol was examined in isolated perfused livers from Wistar and Mrp2-deficient TR(-) rats. Based on extensive metabolism to six glucuronides and sulfates (M1-M6), the hepatic extraction ratio and clearance of resveratrol was very high in Wistar and TR(-) rats (E: 0.998 vs. 0.999; Cl: 34.9 mL/min vs. 36.0 mL/min). However, biliary excretion and efflux of conjugates differs greatly in TR(-) rats. While cumulative biliary excretion of the glucuronides M1, M2, M3, and M5 dropped dramatically to 0-6%, their efflux into perfusate increased by 3.6-, 1.8-, 2.5-, and 1.5-fold. In contrast, biliary secretion of the sulfates M4 and M6 was partially maintained in the Mrp2-deficient rats (61% and 39%) with a concomitant decline of their efflux into perfusate by 33.2% and 78.1%. This indicates that Mrp2 exclusively mediates the biliary excretion of resveratrol glucuronides but only partly that of sulfates. Cumulative secretion of unconjugated resveratrol into bile of TR(-) rats was only reduced by 40%, and into perfusate by 19%, suggesting only a minor role of Mrp2 in resveratrol elimination. In summary, resveratrol was dose-dependently metabolized to several conjugates whereby the canalicular transporter Mrp2 selectively mediated the biliary excretion of glucuronides.

Postischemic treatment by trans-resveratrol in rat liver ischemia-reperfusion: a possible strategy in liver surgery

Liver ischemia-reperfusion (I/R) injury occurs in many clinical conditions, including liver surgery and transplantation. Oxygen free radicals generated during I/R reduce endogenous antioxidant systems and contribute to hepatic injury. trans-Resveratrol (trans-3,5,4'-trihydroxystilbene) is reported to have antioxidant properties. We investigated the effect of trans-resveratrol on liver injury induced by I/R. After 1 hour of ischemia, administered 5 minutes before 3 hours of reperfusion, trans-resveratrol was hepatoprotective at a low dose (0.02 mg/kg). It significantly decreased aminotransferase levels by about 40% and improved sinusoidal dilatation. trans-Resveratrol preserved antioxidant defense by preventing total and reduced glutathione depletion caused by I/R. At 0.2 mg/kg, trans-resveratrol significantly increased glutathione reductase, Cu/Zn-superoxide dismutase, and catalase activities. However, at a high dose (20 mg/kg), trans-resveratrol became prooxidant with an aggravation of liver injury evaluated by aminotransferase release and histological analysis and associated with a depletion of total and reduced glutathione levels and a decrease of antioxidant enzyme activities. In conclusion, a prereperfusion treatment by trans-resveratrol only at low doses decreases liver injury induced by I/R by protecting against antioxidant defense failure. This administration protocol could reduce liver damage during surgery or transplantation.

Resveratrol stimulates nitric oxide production by increasing estrogen receptor alpha-Src-caveolin-1 interaction and phosphorylation in human umbilical vein endothelial cells

Epidemiological studies correlate moderate red wine consumption to reduced incidence of cardiovascular disease. Resveratrol is a polyphenolic compound in red wine that has cardioprotective effects in rodents. Although endothelial cell (EC) studies indicate that micromolar resveratrol has diverse biological activities, these concentrations are not physiologically relevant because human oral ingestion provides only brief exposure to nanomolar plasma levels. Previously, we reported that nanomolar resveratrol activated ERK1/2 signaling in bovine aortic ECs (BAECs). The goal of this study was to determine the mechanisms by which nanomolar resveratrol rapidly activates endothelial nitric oxide synthase (eNOS) in human umbilical vein ECs (HUVECs). We report for the first time that resveratrol increased interaction between estrogen receptor alpha (ER alpha), caveolin-1 (Cav-1) and c-Src, and increased phosphorylation of Cav-1, c-Src, and eNOS. Pretreatment with the lipid raft disruptor beta-methyl cyclodextrin or G alpha inhibitor pertussis toxin blocked resveratrol- and E(2)-induced eNOS activation and NO production. Depletion of endogenous ER alpha, not ERbeta, by siRNA attenuated resveratrol- and E(2)-induced ERK1/2, Src, and eNOS phosphorylation. Our data demonstrate that nanomolar resveratrol induces ER alpha-Cav-1-c-SRC interaction, resulting in NO production through a G alpha-protein-coupled mechanism. This study provides important new insights into mechanisms for the beneficial effects of resveratrol in ECs.

Pharmacometrics of pterostilbene: preclinical pharmacokinetics and metabolism, anticancer, antiinflammatory, antioxidant and analgesic activity

The present study evaluated the preclinical pharmacokinetics and pharmacodynamics of trans-pterostilbene, a constituent of some plants. Right jugular vein cannulated male Sprague-Dawley rats were dosed i.v. with 20 mg/kg of pterostilbene and samples were analysed by the reverse phase HPLC method. Serum AUC, serum t(1/2), urine t(1/2), Cl(total) and Vd(beta) were 17.5 +/- 6.6 microg/h/mL, 1.73 +/- 0.78 h, 17.3 +/- 5.6 h, 0.960 +/- 0.025 L/h/kg and 2.41 +/- 1.13 L/kg (mean +/- SEM), respectively. A pterostilbene glucuronidated metabolite was detected in both serum and urine. The in vitro metabolism in rat liver microsomes furthermore suggests phase II metabolism of pterostilbene. Pterostilbene demonstrated concentration-dependent anticancer activity in five cancer cell lines (1-100 microg/mL). An in vitro colitis model showed concentration-dependent suppression of PGE(2) production in the media of HT-29 cells. Antiinflammatory activity was examined by inducing inflammation in canine chondrocytes followed by treatment with pterostilbene (1-100 microg/mL). The results showed decreased levels of MMP-3, sGAG and TNF-alpha compared with control levels. Pterostilbene exhibited concentration-dependent antioxidant capacity measured by the ABTS method. Pterostilbene increased the latency period to response in both tail-flick and hot-plate analgesic tests.

Metabolism of resveratrol in breast cancer cell lines: impact of sulfotransferase 1A1 expression on cell growth inhibition

Resveratrol is a polyphenolic compound present in grapes and wine with anticancer activities that undergoes pronounced metabolism in humans. In order to determine whether metabolism of resveratrol also occurs in tumor cells and whether biotransformation has any impact on cytotoxicity, metabolism experiments were conducted with hormone-dependent ZR-75-1 and hormone-independent MB-MDA-231 human breast cancer cells. Along with resveratrol, it was possible to identify one metabolite, namely, resveratrol-3-O-sulfate in both cell lines. Its concentration in the cytoplasm and culture medium was 5.4- to 9-fold higher in ZR-75-1 cells than in MDA-MB-231 cells, concomitant with a 3.1-fold higher IC(50) value in the ZR-75-1 cell line (74 microM compared to 38 microM). By using RT-PCR, expression of sulfotransferase (SULT)1A1 mRNA, but not of other SULTs investigated, showed a close correlation with resveratrol 3-O-sulfate formation which was particularly high in ZR-75-1 and very low in MDA-MD-231 cells. In conclusion, we demonstrate that SULT1A1-based biotransformation reduces the anticancer activity of resveratrol in breast cancer cells, which must be considered in humans following oral uptake of dietary resveratrol as a chemopreventive agent.

Phase I dose escalation pharmacokinetic study in healthy volunteers of resveratrol, a potential cancer chemopreventive agent

The red grape constituent resveratrol possesses cancer chemopreventive properties in rodents. The hypothesis was tested that, in healthy humans, p.o. administration of resveratrol is safe and results in measurable plasma levels of resveratrol. A phase I study of oral resveratrol (single doses of 0.5, 1, 2.5, or 5 g) was conducted in 10 healthy volunteers per dose level. Resveratrol and its metabolites were identified in plasma and urine by high-performance liquid chromatography-tandem mass spectrometry and quantitated by high-performance liquid chromatography-UV. Consumption of resveratrol did not cause serious adverse events. Resveratrol and six metabolites were recovered from plasma and urine. Peak plasma levels of resveratrol at the highest dose were 539 +/- 384 ng/mL (2.4 micromol/L, mean +/- SD; n = 10), which occurred 1.5 h post-dose. Peak levels of two monoglucuronides and resveratrol-3-sulfate were 3- to 8-fold higher. The area under the plasma concentration curve (AUC) values for resveratrol-3-sulfate and resveratrol monoglucuronides were up to 23 times greater than those of resveratrol. Urinary excretion of resveratrol and its metabolites was rapid, with 77% of all urinary agent-derived species excreted within 4 h after the lowest dose. Cancer chemopreventive effects of resveratrol in cells in vitro require levels of at least 5 micromol/L. The results presented here intimate that consumption of high-dose resveratrol might be insufficient to elicit systemic levels commensurate with cancer chemopreventive efficacy. However, the high systemic levels of resveratrol conjugate metabolites suggest that their cancer chemopreventive properties warrant investigation.

Predicting the physiological relevance of in vitro cancer preventive activities of phytochemicals

There is growing interest in the ability of phytochemicals to prevent chronic diseases, such as cancer and heart disease. However, some of these agents have poor bioavailability and many of the in-depth studies into their mechanisms of action have been carried out in vitro using doses which are unachievable in humans. In order to optimize the design of chemopreventive treatment, it is important to determine which of the many reported mechanisms of action are clinically relevant. In this review we consider the physiologically achievable doses for a few of the best studied agents (indole-3-carbinol, diindolylmethane, curcumin, epigallocatechin-3-gallate and resveratrol) and summarize the data derived from studies using these low concentrations in cell culture. We then cite examples of in vitro effects which have been observed in vivo. Finally, the ability of agent combinations to act synergistically or antagonistically is considered. We conclude that each of the compounds shows an encouraging range of activities in vitro at concentrations which are likely to be physiologically relevant. There are also many examples of in vivo studies which validate in vitro observations. An important consideration is that combinations of agents can result in significant activity at concentrations where any single agent is inactive. Thus, for each of the compounds reviewed here, in vitro studies have provided useful insights into their mechanisms of action in humans. However, data are lacking on the full range of activities at low doses in vitro and the benefits or otherwise of combinations in vivo.

Resveratrol and its analogs: defense against cancer, coronary disease and neurodegenerative maladies or just a fad?

Resveratrol (3,5,4'-trihydroxy-trans-stilbene; RV), a dietary constituent found in grapes and wine, exerts a wide variety of pharmacological activities. Because the grape skins are not fermented in the production process of white wines, only red wines contain considerable amounts of this compound. RV is metabolized into sulfated and glucuronidated forms within approximately 15min of entering the bloodstream, and moderate consumption of red wine results in serum levels of RV that barely reach the micromolar concentrations. In contrast, its metabolites, which may be the active principle, circulate in serum for up to 9h. RV has been identified as an effective candidate for cancer chemoprevention due its ability to block each step in the carcinogenesis process by inhibiting several molecular targets such as kinases, cyclooxygenases, ribonucleotide reductase, and DNA polymerases. In addition, RV protects the cardiovascular system by a large number of mechanisms, including defense against ischemic-reperfusion injury, promotion of vasorelaxation, protection and maintenance of intact endothelium, anti-atherosclerotic properties, inhibition of low-density lipoprotein oxidation, and suppression of platelet aggregation, thereby strongly supporting its role in the prevention of coronary disease. Promising data within the use of RV have also been obtained regarding progressive neurodegenerative maladies such as Alzheimer's, Huntington's, and Parkinson's diseases. Because neurotoxicity is often related to mitochondrial dysfunction and may be ameliorated through the inclusion of metabolic modifiers and/or antioxidants, RV may provide an alternative (and early) intervention approach that could prevent further damage. RV induces a multitude of effects that depend on the cell type (e.g., NF-kappaB modulation in cancer cells vs. neural cells), cellular condition (normal, stressed, or malignant), and concentration (proliferative vs. growth arrest), and it can have opposing activities. RV affects whole pathways and sets of intracellular events rather than a single enzyme and, therefore, may be an effective therapy to restore homoestasis. Nonetheless, the question of whether RV or its metabolites can accumulate to bioactive levels in target organs remains to be addressed.

Simultaneous determination of trans-resveratrol-3-O-glucoside and its two metabolites in rat plasma using liquid chromatography with ultraviolet detection

A sensitive and selective high-performance liquid chromatographic method was developed for simultaneous determination of trans-resveratrol-3-O-glucoside (TRG) and its metabolites, trans-resveratrol-3-O-glucuronide (TRN) and trans-resveratrol (TR) in rat plasma. The plasma proteins were precipitated with acetonitrile and supernatant was evaporated to dryness. The analytes and internal standard baicalin were chromatographed on a C(18) column. The mobile phase consisted of 25% acetonitrile and 75% H(2)O adjusted with formic acid to pH 3.5. The flow-rate was 1.0 ml/min and ultraviolet detection was set at 320 nm. Standard curves were linear over the concentration range of 0.04-40 microg/ml for TRG and TRN, and 0.04-10 microg/ml for TR, respectively. The precision, expressed as the intra-day R.S.D. and inter-day R.S.D., was below 9.3% for TRG, TRN and TR. The accuracy, expressed as the relative error (RE) was within +/-7.4% for all analytes. The mean recoveries of TRG, TRN, TR and I.S. were 93.6%, 93.1%, 91.0% and 87.9%, respectively. This method was successfully applied to a pharmacokinetic study of TRG after an oral dose of 150 mg/kg to Wistar rats.

Pharmacokinetics of selected stilbenes: rhapontigenin, piceatannol and pinosylvin in rats

The pharmacokinetics of piceatannol, pinosylvin and rhapontigenin were characterized in male Sprague-Dawley rats after single intravenous doses of 10 mg kg(-1) of each stilbene. Serial blood samples were collected via a catheter inserted into the right jugular vein and plasma samples were analysed for the selected stilbenes concentrations using reverse phase HPLC methods. After an acute intravenous dose of piceatannol, plasma AUC, urine t(1/2), CL and V(d) were 8.48+/-2.48 micro g h mL(-1), 19.88+/-5.66 h, 2.13+/-0.92 Lh(-1) kg(-1) and 10.76+/-2.88 L kg(-1)(mean+/-s.e.m.), respectively. The acute intravenous dose of pinosylvin yielded the plasma AUC, urine t(1/2), CL and V(d) values of 5.23+/-1.20 micro g h mL(-1), 13.13+/-2.05 h, 1.84+/-0.44 Lh(-1) kg(-1) and 2.29+/-0.56 L kg(-1)(mean+/-s.e.m.), respectively. Rhapontigenin intravenous dosing yielded the plasma AUC, urine t(1/2), CL and V(d) values of 8.39+/-0.10 micro g h mL(-1), 25.31+/-1.46 h, 1.18+/-0.035 Lh(-1) kg(-1) and 11.05+/-0.17 L kg(-1)(mean+/-s.e.m.), respectively. Each stilbene was extensively glucuronidated. These stilbenes were predominantly eliminated via non-urinary routes. All three stilbenes were highly distributed into tissues and were highly extracted by the liver. The detectable plasma half-lives of these xenobiotics appear to be relatively short. However, utilizing urinary concentration-time data, much longer elimination half-lives were evident. The estimates of oral bioavailability characterize these stilbenes as poorly bioavailable compounds.

Pharmacokinetics of eugenol and its effects on thermal hypersensitivity in rats

Neuropathic pain is a type of chronic pain following central or peripheral nervous system lesions that cause allodynia (pain initiated by a non-painful stimulus) and hyperalgesia (increased pain sensation following a painful stimulus). The first objective of the study was to evaluate the pharmacokinetics of eugenol, the principle chemical constituent of clove oil, following a gavage administration (40 mg/kg) in male Sprague-Dawley rats. The second objective was to evaluate the effect of repeated oral administrations of eugenol on hyperalgesia and allodynia using an experimental model of neuropathic pain in rats. Thermal and mechanical sensitivity (Hargreave's test and von Frey filaments) were determined in sciatic nerve cuff-implanted rats. Sensitivities were assessed following repeated oral administrations of 40 mg/kg of eugenol or saline for 5 days (n=6 per group). Pharmacokinetic parameters were calculated using noncompartmental methods. Serial blood samples were collected over 24 h. Concentrations of eugenol in blood and plasma peaked rapidly following oral administration. Mean T(1/2) values of eugenol in plasma and blood were long (14.0 and 18.3 h, respectively), suggesting a potential accumulation of the drug following repeated administrations. Reaction time to thermal stimuli appeared to increase constantly following repeated administrations of eugenol. On the last day of treatment, eugenol treatments resulted in a statistically significant prolongation of the reaction time to thermal stimuli in rats compared to the saline group (Mean+/-S.E.M.: 11.4+/-1.23 vs. 6.1+/-0.53 s, P<0.01). These results support the hypothesis that eugenol may alleviate neuropathic pain and that the cumulative effect of the drug may be in part responsible for this effect following repeated daily administrations.

Distribution of [H]trans-resveratrol in rat tissues following oral administration

Resveratrol has been widely investigated for its potential health properties, although little is known about its metabolism in vivo. Here we investigated the distribution of metabolic products of [3H]trans-resveratrol, following gastric administration. At 2 h, plasma concentrations reached 1.7 % of the administered dose, whilst liver and kidney concentrations achieved 1.0 and 0.6 %, respectively. Concentrations detected at 18 h were lower, being only 0.5 % in plasma and a total of 0.35 % in tissues. Furthermore, whilst kidney and liver concentrations fell to 10 and 25 %, respectively, of concentrations at 2 h, the brain retained 43 % of that measured at 2 h. Resveratrol-glucuronide was identified as the major metabolite, reaching 7 microm in plasma at 2 h. However, at 18 h the main form identified in liver, heart, lung and brain was native resveratrol aglycone, indicating that it is the main form retained in the tissues. No phenolic degradation products were detected in urine or tissues, indicating that, unlike flavonoids, resveratrol does not appear to serve as a substrate for colonic microflora. The present study provides additional information about the nature of resveratrol metabolites and which forms might be responsible for its in vivo biological effects.