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Oroxylin A, obtained from the root of Scutellaria baicalensis Georgi, is a flavonoid with antitumor and other pharmacological activities. Our previous studies showed for the first time that it is mainly metabolized to oroxylin A sodium sulfonate by sulfotransferase enzymes in beagle dogs. In this study, rapid, universal, selective, and robust ultra-high-performance liquid chromatography-tandem mass spectrometry methods were established and fully validated to quantitatively detect oroxylin A, oroxylin A 7-O-glucuronide, and oroxylin A sodium sulfonate in beagle dog plasma. The quantitative analysis for oroxylin A sodium sulfonate was reported for the first time. Plasma samples were processed with acetonitrile, a universal protein precipitant. Gradient elution was performed to resolve carryover effects and to achieve separation efficiency and sufficient chromatographic retention. The linear relationships of oroxylin A, oroxylin A 7-O-glucuronide, and oroxylin A sodium sulfonate in plasma were in the range of 2.0-500.0, 5.0-500.0, and 1.881-940.5 ng/mL, respectively. The assay method was successfully applied to pharmacokinetic study. This is the first paper that reveals the pharmacokinetic profile of oroxylin A, oroxylin A 7-O-glucuronide, and oroxylin A sodium sulfonate after single-dose intravenous and oral administration of Oroxylin A in beagle dogs., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Oroxylin A is a flavonoid monomer extracted from Scutellaria baicalensis Georgi with neuroprotective, anti-tumor activity and many other biological functions. However, the interaction between Oroxylin A and the drug transporters has not been clearly reported. The purpose of this study is to investigate the interaction between Oroxylin A and the solute carrier transporters (OATP1B1, OATP1B3, OAT1, OAT3, OCT2, MATE1, and MATE2K), and ATP-binding cassette transporters (BCRP, MDR1). The HEK293 cell lines (HEK293-OATP1B1, HEK293-OATP1B3, HEK293-OAT1, HEK293-OAT3, HEK293-OCT2, HEK293-MATE1, and HEK293-MATE2K) that stably expressing previous listed human-derived transporters were employed to evaluate the solute carrier transporters. Vesicles expressing human BCRP and MDR1 transporters was employed to research ATP-binding cassette transporters. Our work suggested that Oroxylin A was a substrate of OATP1B1, OATP1B3, but not a substrate of the other transporters in the concentration range of our study. Oroxylin A shows concentration-dependent inhibition of OATP1B1, OAT1, OAT3 and BCRP transportation with the half-inhibitory concentration (IC50) of 7.03, 0.961, 0.112 μM, and 0.477 μM, respectively. No inhibitory effects on the transport activities of other transporters were observed for Oroxylin A. Drug transporters profile of Oroxylin A was first confirmed by our work, which provides important information for its pharmacokinetics, pharmacodynamics, and drug-drug interactions studies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Oroxylin A (OA), as a natural flavonoid extracted from the root of Scutellaria baicalensis Georgi, is a candidate drug with multiple pharmacological activities. However, pharmacokinetic studies of OA have rarely been reported up to now. The present study aim to conduct a systemic evaluation on the pharmacokinetics, tissue distribution and excretion of OA in rats, with quantification of both OA and its two metabolites, Oroxylin A 7-O-glucuronide (OG) and Oroxylin A sodium sulfonate (OS) by the sensitive and rapid UPLC-MS/MS methods. The results show that OA was rapidly eliminated in vivo after a single-dose (2 mg/kg) i.v. administration of OA. The relative bioavailability of OA in all three i.g. administration groups (40, 120, and 360 mg/kg) were <2%. The AUC 0-t values of OA, OG, and OS in rats show an apparent dose-proportionality. OA, OG, and OS all underwent a rapid and widespread tissue distribution after i.g. administration (120 mg/kg) of OA. Except for stomach and intestine, the major distribution tissues of OA and its two metabolites in rats were liver, kidney, respectively. And OA was more widely distributed in tissue than its metabolites. After i.g. administration (120 mg/kg) of OA, it was mainly excreted from the feces, and OG mainly excreted from bile and urine, while OS almost free of excretion. This work present a comprehensive pharmacokinetics information for further investigation of OA and its two metabolites., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Human cytochrome P450 1B1 (CYP1B1)-mediated formation of 4-hydroxyestradiol (4-OHE2) from 17β-estradiol plays an important role in the progression of human breast cancer, while the biotransformation of 17β-estradiol to 2-hydroxyestradiol mediated by cytochrome P450 1A1 (CYP1A1) is considered as a less harmful pathway. In this study, inhibitory effects of flavonoids baicalein and oroxylin A, a metabolite of baicalein in human body, on CYP1A1 and 1B1 activities were investigated in vitro. The inhibition intensities of baicalein and oroxylin A towards CYP1B1 were greater than towards CYP1A1 with a mixed mechanism. In addition, oroxylin A showed a stronger inhibitory effect than baicalein towards the CYP1B1-mediated 17β-estradiol 4-hydroxylation, with the IC 50 values of 0.0146 and 2.27 μM, respectively. Docking studies elucidated that oroxylin A had a stronger binding affinity than baicalein for CYP1B1. In MCF-7 cells, compared with baicalein-treated groups, oroxylin A with lower doses decreased and increased the formation of 4-OHE2 and 2-hydroxyestradiol, respectively, with a preferential induction of mRNA of CYP1A1 over CYP1B1. In conclusion, this study demonstrated that oroxylin A showed a stronger inhibitory effect than baicalein on CYP1B1-mediated 4-OHE2 formation in MCF-7 cells, providing crucial implications for their possibly preventive/therapeutic potential against breast cancer via inhibition of CYP1B1, particularly of oroxylin A., (© 2019 John Wiley & Sons, Ltd.)

GL-V9, a derivative of wogonin, has potent anti-cancer activity. The absorption and metabolism of this compound have not been investigated systematically. This study aims to illustrate the pharmacokinetic characters of GL-V9 by exploring its metabolic status under different administration routes. To further clarify the absorption mechanism of GL-V9, an in situ single-pass perfusion model and a Caco-2 cell monolayer model were used. Meanwhile, a microsomal incubation system was used to evaluate the enzyme kinetic parameters. In vivo, the obtained gastrointestinal availability (F a × F g ) was 21.28 ± 5.38%. The unmetabolized fraction in the gut wall (F gut wall ) was 98.59 ± 9.74%, while the hepatic bioavailability (F h ) was 29.11 ± 5.22%. These results indicated that poor absorption and extensive metabolism may contribute greatly to the low bioavailability of GL-V9. The effective permeability (P eff ) in the duodenum and jejunum was 1.34 ± 0.50 × 10 -4 and 0.90 ± 0.27 × 10 -4  cm/s, respectively. The high permeability of GL-V9 indicated that other unknown factors (such as metabolism) may account for its systemic exposure problem. Studies in rat liver microsomal (RLMs) confirmed this hypothesis, and the Cl int, CYP450s and UGT of GL-V9 was 0.20 ml/min/mg protein. In conclusion, these results suggest that GL-V9 possesses higher permeability than wogonin and the metabolism of GL-V9 is related to its disposition in rat intestine and liver., (© 2019 John Wiley & Sons, Ltd.)

Targeting therapy of anti-cancer drugs has been gaining increasing attention. Cell pharmacokinetics have been used for in vitro disposition evaluation, as well as drug-drug interaction for anti-cancer drugs, revealing their fate after entering tumor. Flavonoid compound oroxylin A (OA) possesses strong anti-cancer effects especially on the liver and breast cancer. However, despite the low bioavailability, the disposition of OA and its active metabolite in the target cancer cells remained unclear. In current study, a highly sensitive and selective solid phase extraction (SPE)-UPLC-MS/MS method was developed and validated to simultaneously quantify the concentrations of OA and its major active metabolite oroxylin A 7-O-d-glucuronide (OG) in HepG2 cell lysate and multiple subcellular organelle fractions. The proposed method appeared to be suitable for the analysis with desirable linearity(R 2  > 0.99). The relative standard deviations (RSDs) of intra- and inter-assay precision and accuracy were less than 9.9% and -7.7%, 8.4% and 11% for OA and OG in cell lysate respectively. The intra- precision and accuracy was less than 9.5% and -11.3%, 9.4% and 12.3% for OA and OG in subcellular organelles respectively. The range of absolute recovery of this method in the cell lysate was from 73.1% ± 1.4% to 87.9% ± 6.7%. The RSDs of matrix effects of the quality control (QC) samples were below 15%. The uptake and distribution experiments demonstrated a time-dependent transport characteristic in HepG2 cell lines. Furthermore, both OA and OG were mainly distributed into nuclei after taken up by the tumor cells. In addition, OG was also distributed into mitochondria, which indicates another potential target of OG. The present study, for the first time, reports the in vitro cell pharmacokinetics profiles of OA and OG in tumor cell lines in vitro., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Flavanoids are important phytochemistry compositions in foods and traditional Chinese medicines (TCM) and are mainly oxidized by CYP1A family in vivo. Some methoxyflavones could also be metabolized through demethylation. Usually, flavanoids own one or more phenolic hydroxyl group in their molecular structures, which facilitate conjugation with glucuronic acid and sulphuric acid, forming metabolites with good water-solubility to excrete. Natural flavanoids mainly exist in glycoside, and after oral ,they would be easily metabolized to aglycone by hydratase in gut microflora and then absorbed into blood. Besides, many flavanoids have strong inhibitory actions on Cytochrome P450 enzymes, which are significant mechanisms in cancer precaution and tumor inhibition. In this paper, we reviewed lots of articles and summarized metabolism characteristics of flavanoids and metabolism interaction with Cytochrome P450 enzymes.

Oroxylin A, the main component of Scutellaria baicalensis Georigi has been widely studied due to its well-known pharmacological effects. According to previous studies, Oroxylin A with low bioavailability was converted into glucuronidation and sulphonated metabolites, which had high exposure in plasma and generated certain activities. It is necessary to study the metabolites and metabolic pathways of Oroxylin A. This study aimed to explore the metabolites of Oroxylin A in liver microsomes, primary hepatocyte incubation samples of five different species (human, monkey, dog, mouse, rat), and in bile, urine and faeces of rats. It would provide a systematic description of metabolic pathway of Oroxylin A. Also, a method of high-performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry detector (HPLC-Q-TOF-MS/MS) for identification of each metabolite in various biological matrices was developed. This experiment illustrated that phase II metabolites were the main form of Oroxylin A in vitro and in excretion of rats, accompanied with a small amount of phase I metabolites. Furthermore, there were obvious species differences among the metabolism in vitro, especially in phase II. Monkeys and rats may be more suitable for preclinical research than dogs and mice as non-rodent or rodent species. [ABSTRACT FROM AUTHOR]