Study On The Absorption And Metabolism Of Baicalin In Animals

Baicalin (baicalein 7-O-β-glucopyranuronoside, BG) is a bioactive flavonoid isolated from the root of Scutellaria baicalensis George, a medicinal herb that has been used since ancient times to treat inflammation, fever and allergic diseases. Baicalin was readily hydrolyzed by β-glucuronidase to free aglycone baicalein, which has similar pharmacology effects to baicalin. In previous studies on the metabolism, baicalin underwent two main metabolic pathways including glucuronidation and methylation. Due in part to difficulties in establishing a sensitive and specific assay for baicalin and its metabolites, the absorption data of baicalin differed with each other. Most studies suggested that the absorption of baicalin was poor because of its low hydrophilicity, which was always encountered in study of other flavonoids, and baicalin has been found absorbed from the gastrointestinal tract as its aglycone after the hydrolysis of intestinal bacteria. In recent years, baicalin has attracted increasing interest due to its various beneficial biological activities to human health, which made it necessary to further study the metabolism, disposition and pharmacokinetics of baicalin to elucidate its biological effects. It is important for rational evaluation of animal data as well as extrapolation to humans, and for guiding clinical use.The thesis aimed to investigate the fate of baicalin in vivo by applying liquid chromatography-mass spectrometry technique (LC/MS~n) with the aid of HPLC/UV and GC/MS, to establish the rational animal model for the study, to evaluate the contribution of enterohepatic recirculation to absorption, and to reveal the absorption mechanism of baicalin. It would offer some references and inspirations for drug design and dosage form modification.1. Baicalin metabolism in lab animalsThe metabolic profiles of BG and its aglycone in rats, dogs, golden hamsters, Guinea pigs, rabbit and human were investigated. The metabolites were identified and the species differences were interpreted among animals and humans. Totally 8 metabolites were measured in the tested animals, and were identified as baicalin (M1), baicalein 6-O-β-glucopyranuronoside glucuronide (M2), baicalein 6-O-glucoside-7-O-β-glucopyranuronoside (M3), baicalein 6,7-di-O-β-glucopyranuronoside (M4),...