Metabolites identification and species comparison of Oroxylin A, an anti-cancer flavonoid, in vitro and in vivo by HPLC-Q-TOF-MS/MS.

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.

Interactions between Oroxylin A with the solute carrier transporters and ATP-binding cassette transporters: Drug transporters profile for this flavonoid.

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.

Permeability and transport mechanism of trihexyphenidyl hydrochloride in Caco-2 cell monolayer model with a validated UPLC-MS/MS method.

A rapid and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was applied to investigate the permeability characteristics and transport mechanism of trihexyphenidyl hydrochloride (TH) in D-hanks with the Caco-2 cells model. Analytes were separated using an Zorbax Extend-Agilent C18 (1.8 µm, 4.6 × 30 mm) column following a simple methanol precipitation treatment. The mobile phase consisted of methanol and water containing 0.1% formic acid, and the total gradient program time was 1.5 min. Method validation results showed TH was linear in 2-500 ng/mL (r2 > 0.99), and the lower limit of quantification (LLOQ) was 2 µg/mL. The intra-run and inter-run precision (coefficient of variation, CV) was within 2.80%, and the accuracy (relative error, RE) was within ±11.10%. Stability of TH was evaluated in different storage conditions, including short-term I-III, long-term I-III, 2 and 4 h in the artificial gastrointestinal tract, respectively. There was no obvious interference between TH and internal standards (IS). With the established Caco-2 monolayer permeability model, Papp(AB) of TH was calculated as 46.29 ±â€¯8.31 × 10-6 cm/s, and the efflux ratio (ER) value was calculated as 0.22, indicating a high permeability character of TH. The transmembrane transport of TH followed the concentration-dependent, temperature-independent, and energy-free manner. Collectively, these characteristics indicate that TH is a highly permeable drug and the transport mechanism is mainly via passive diffusion.