Breast Cancer Resistance Protein (ABCG2) Determines Distribution of Genistein Phase II Metabolites: Reevaluation of the Roles of ABCG2 in the Disposition of Genistein

ABSTRACT: It was recently proposed that the improved oral bioavailability of genistein aglycone and conjugates in Bcrp1(؊/؊) mice is mainly due to increased intestinal absorption of aglycone and subsequent elevated exposure to conjugation enzymes. Here we tested this proposed mechanism and found that intestinal absorption of genistein aglycone did not increase in Bcrp1(؊/؊) mice compared with wild-type mice using an in situ mouse intestinal perfusion model and that inhibition of breast cancer resistance protein (BCRP) in Caco-2 cells also did not significantly increase permeability or intracellular concentration of aglycone. Separately, we showed that 5-to 10-fold increases in exposures of conjugates and somewhat lower fold increases (<2-fold) in exposures of aglycone were apparent after both oral and intraperitoneal administration in Bcrp1(؊/؊) mice. In contrast, the intestinal and biliary excretion of genistein conjugates significantly decreased in Bcrp1(؊/؊) mice without corresponding changes in aglycone excretion. Likewise, inhibition of BCRP functions in Caco-2 cells altered polarized excretion of genistein conjugates by increasing their basolateral excretion. We further found that genistein glucuronides could be hydrolyzed back to genistein, whereas sulfates were stable in blood. Because genistein glucuronidation rates were 110% (liver) and 50% (colon) higher and genistein sulfation rates were 40% (liver) and 42% (colon) lower in Bcrp1(؊/؊) mice, the changes in genistein exposures are not mainly due to changes in enzyme activities. In conclusion, improved bioavailability of genistein and increased plasma area under the curve of its conjugates in Bcrp1(؊/؊) mice is due to altered distribution of genistein conjugates to the systemic circulation

Factors Influencing Oral Bioavailability of Thai Mango Seed Kernel Extract and Its Key Phenolic Principles

Mango seed kernel extract (MSKE) and its key components (gallic acid, GA; methyl gallate, MG; and pentagalloyl glucopyranose, PGG) have generated interest because of their pharmacological activities. To develop the potential use of the key components in MSKE as natural therapeutic agents, their pharmacokinetic data are necessary. Therefore, this study was performed to evaluate the factors affecting their oral bioavailability as pure compounds and as components in MSKE. The in vitro chemical stability, biological stability, and absorption were evaluated in Hanks’ Balanced Salt Solution, Caco-2 cell and rat fecal lysates, and the Caco-2 cell model, respectively. The in vivo oral pharmacokinetic behavior was elucidated in Sprague-Dawley rats. The key components were unstable under alkaline conditions and in Caco-2 cell lysates or rat fecal lysates. The absorptive permeability coefficient followed the order MG > GA > PGG. The in vivo results exhibited similar pharmacokinetic trends to the in vitro studies. Additionally, the co-components in MSKE may affect the pharmacokinetic behaviors of the key components in MSKE. In conclusion, chemical degradation under alkaline conditions, biological degradation by intestinal cell and colonic microflora enzymes, and low absorptive permeability could be important factors underlying the oral bioavailability of these polyphenols

Determination of Pharmacokinetics of Chrysin and Its Conjugates in Wild-Type FVB and Bcrp1 Knockout Mice Using a Validated LC-MS/MS Method

Chrysin, a flavone found in many plants, is also available as a dietary supplement because of its reported anticancer activities. However, its bioavailability is very poor due to extensive phase II metabolism. The purpose of this study was to develop an UPLC-MS/MS method to simultaneously quantify chrysin and its phase II metabolites, and to determine its pharmacokinetics in FVB wild-type and Bcrp knockout (Bcrp1 −/−) mice. In addition, the role of BCRP in chrysin phase II disposition was further investigated in Caco-2 cells. The results showed that our sensitive and reproducible UPLC-MS/MS method was successfully applied to the pharmacokinetic study of chrysin in wild-type and Bcrp1 (−/−) FVB mice after oral administration (20 mg/kg). Although there was no significant change in systemic exposure of chrysin and its metabolites, it was found that the <i>T</i>_max for chrysin glucuronide was significantly shorter (<i>p</i> < 0.01) in Bcrp1-deficient mice. Furthermore, it was shown that inhibition of BCRP by Ko143 significantly reduced the efflux of chrysin sulfate in Caco-2 cells. In conclusion, BCRP had significant but less than expected impact on pharmacokinetics of chrysin and its conjugates, which were determined using a newly developed and validated LC-MS/MS method

Hepatoenteric recycling is a new disposition mechanism for orally administered phenolic drugs and phytochemicals in rats

Many orally administered phenolic drugs undergo enterohepatic recycling (EHR), presumably mediated by the hepatic phase II enzymes. However, the disposition of extrahepatically generated phase II metabolites is unclear. This paper aims to determine the new roles of liver and intestine in the disposition of oral phenolics. Sixteen representative phenolics were tested using direct portal vein infusion and/or intestinal perfusion. The results showed that certain glucuronides were efficiently recycled by liver. OATP1B1/1B3/2B1 were the responsible uptake transporters. Hepatic uptake is the rate-limiting step in hepatic recycling. Our findings showed that the disposition of many oral phenolics is mediated by intestinal glucuronidation and hepatic recycling. A new disposition mechanism ‘Hepatoenteric Recycling (HER)”, where intestine is the metabolic organ and liver is the recycling organ, was revealed. Further investigations focusing on HER should help interpret how intestinal aliments or co-administered drugs that alter gut enzymes (e.g. UGTs) expression/activities will impact the disposition of phenolics

Pharmacokinetic and Metabolic Profiling of Key Active Components of Dietary Supplement Magnolia officinalis Extract for Prevention against Oral Carcinoma

Among the three key active components (KACs) of Magnolia officinalis bark extract (ME), 4-O-methylhonokiol and honokiol showed higher antiproliferation activities than magnolol in the oral squamous cancer cell lines (Cal-27, SCC-9, and SCC-4). Oral bioavailabilities of ME-KACs were poor (\u3c0.2%) in C57BL/6 mice primarily due to their extensive first-pass phase II metabolism and poor solubilities. High plasma concentration of glucuronides upon oral administration and faster rate of glucuronidation by intestinal microsomes indicated intestine as one of the major metabolic organs for ME-KACs. Despite the increase in bioavailabilities of ME-KACs (∼8-10-fold) and decrease in AUC0-24 of glucuronides (∼10-fold) upon ME solubility enhancement, systemic exposure of ME-KACs failed to improve meaningfully. In conclusion, we propose a quality-controlled and chemically defined ME mixture, containing an optimized ratio of three KACs, delivered locally in the oral cavity as the most promising strategy for ME use as an oral cancer chemopreventive dietary supplement

Design and Synthesis of a Novel NIR Celecoxib-Based Fluorescent Probe for Cyclooxygenase-2 Targeted Bioimaging in Tumor Cells

Cyclooxygenase-2 (COX-2) imaging agents are potent tools for early cancer diagnosis. Almost all of the COX2 imaging agents using celecoxib as backbone were chemically modified in the position of N-atom in the sulfonamide group. Herein, a novel COX-2 probe (CCY-5) with high targeting ability and a near-infrared wavelength (achieved by attaching a CY-5 dye on the pyrazole ring of celecoxib using a migration strategy) was evaluated for its ability to probe COX-2 in human cancer cells. CCY-5 is expected to have high binding affinity for COX-2 based on molecular docking and enzyme inhibition assay. Meanwhile, CCY-5 caused stronger fluorescence imaging of COX-2 overexpressing cancer cells (Hela and SCC-9 cells) than that of normal cell lines (RAW 264.7 cells). Lipopolysaccharide (LPS) treated RAW264.7 cells revealed an enhanced fluorescence as LPS was known to induce COX-2 in these cells. In inhibitory studies, a markedly reduced fluorescence intensity was observed in cancer cells, when they were co-treated with a COX-2 inhibitor celecoxib. Therefore, CCY-5 may be a selective bioimaging agent for cancer cells overexpressing COX-2 and could be useful as a good monitoring candidate for effective diagnosis and therapy in cancer treatment

Development and validation of ultra-high-performance liquid chromatography–mass spectrometry method for the determination of raloxifene and its phase II metabolites in plasma: Application to pharmacokinetic studies in rats

The aim of this study is to establish a reliable liquid chromatography–mass spectrometry method to simultaneously quantitate raloxifene, and its major metabolites, raloxifene-6-glucuronide, raloxifene-4′-glucuronide, and raloxifene-6-sulfate in rat plasma samples for pharmacokinetic studies. The separation of the analytes was achieved on a Waters BEH C18 column. Water (0.1% formic acid) and acetonitrile were used as the mobile phases for elution. A one-step protein precipitation using a mixture solvent was applied for plasma sample preparation. The method was validated following the FDA guidance. The results showed that the linear range were 1.95–1000 nM for raloxifene-6-glucuronide, and raloxifene-4′-glucuronide, 0.195–100 nM for raloxifene-6-sulfate, and 0.195–200 nM for raloxifene, respectively. The lower limit of quantification was 1.95, 1.95, 0.195, and 0.195 nM for raloxifene-6-glucuronide, raloxifene-4′-glucuronide, raloxifene-6-sulfate, and raloxifene, respectively. Only 20 µl of plasma sample was required since the method is sensitive. The intra- and interday variance is \u3c15% and the accuracy is within 85–115%. The variance of matrix effect and recovery were \u3c15%. The method was successfully applied in a pharmacokinetic study in rats with oral administration of raloxifene

Development and validation of ultra-high-performance liquid chromatography–mass spectrometry method for the determination of raloxifene and its phase II metabolites in plasma: Application to pharmacokinetic studies in rats

The aim of this study is to establish a reliable liquid chromatography–mass spectrometry method to simultaneously quantitate raloxifene, and its major metabolites, raloxifene-6-glucuronide, raloxifene-4′-glucuronide, and raloxifene-6-sulfate in rat plasma samples for pharmacokinetic studies. The separation of the analytes was achieved on a Waters BEH C18 column. Water (0.1% formic acid) and acetonitrile were used as the mobile phases for elution. A one-step protein precipitation using a mixture solvent was applied for plasma sample preparation. The method was validated following the FDA guidance. The results showed that the linear range were 1.95–1000 nM for raloxifene-6-glucuronide, and raloxifene-4′-glucuronide, 0.195–100 nM for raloxifene-6-sulfate, and 0.195–200 nM for raloxifene, respectively. The lower limit of quantification was 1.95, 1.95, 0.195, and 0.195 nM for raloxifene-6-glucuronide, raloxifene-4′-glucuronide, raloxifene-6-sulfate, and raloxifene, respectively. Only 20 µl of plasma sample was required since the method is sensitive. The intra- and interday variance is \u3c15% and the accuracy is within 85–115%. The variance of matrix effect and recovery were \u3c15%. The method was successfully applied in a pharmacokinetic study in rats with oral administration of raloxifene

Transport–Glucuronidation Classification System and PBPK Modeling: New Approach To Predict the Impact of Transporters on Disposition of Glucuronides

Glucuronide metabolites require the action of efflux transporters to exit cells due to their hydrophilic properties. In this study, we proposed a transport–glucuronidation classification system and developed a PBPK model to predict the impact of BCRP on systemic exposure of glucuronides. The clearance by UGTs in S9 fractions and the efflux clearance of glucuronides by BCRP in human UGT1A9-overexpressing HeLa cells were incorporated in the classification system and PBPK model. Based on simulations for glucuronide AUC for theoretical compounds in the classification system, it was indicated that BCRP was more important for compounds with greater efflux clearance of their glucuronides by BCRP regardless of differences in clearance by UGTs. Pharmacokinetic studies were performed in WT and Bcrp1 (−/−) mice for 8 compounds to verify our predictions. Among eight compounds, the glucuronide AUC of daidzein and genistein increased significantly in Bcrp1 (−/−) mice, while only slight increases in systemic exposure were observed for other glucuronides. The results from pharmacokinetic studies were in agreement with the predictions except for resveratrol, which was effluxed predominantly by transporters other than BCRP. Therefore, for glucuronides that were predominantly mediated by BCRP, this study provided a useful approach in predicting the impact of BCRP on its disposition and the potential DDIs involving BCRP