title: [Study on absorption kinetics of betulic acid in rat's intestines].
abstract: OBJECTIVE
  To establish a HPLC-DAD method for determining concentrations of betulic acid and phenol red in intestinal circulation liquid, and probe into the absorption kinetic characteristics of betulic acid at different intestine segments in rats and the effect of different drug concentrations on absorption.
  
  
  METHODS
  The rat intestinal absorption model was established to detect the impact of absorption site, drug concentration and pH value on drug absorption.
  
  
  RESULTS
  Within the range from 75-125 mg x L(-1), the absorption rate and the quality concentration of betulic acid had a linear relation, with Ka value keeping unchanged. The absorption rate for each intestinal segment showed no remarkable difference, with Ka values in duodenum, jejunum, ileum and colon being (0.151 +/- 0.0049), (0.159 +/- 0.0056), (0.156 +/- 6.0083), (0.149 +/- 0.0041) h(-1), respectively.
  
  
  CONCLUSIONS
  Betulic acid is proved to be well absorbed in intestines marked by no specific absorption site in the intestine. The absorption mechanism of the drug conforms to passive transport mechanism and first-order kinetics. The bioavailability of betulic acid preparation can be increased by enhancing the dissolution rate and the solubility.
authors.affiliation: Department of Pharmaceutical Analysis, School of Pharmacy, Hebei Medical University, Shijiazhuang 050017, China. xunuonuo19791103@163.com
authors.forename: Huijun
authors.initials: H
authors.lastname: Xu
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Ren
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Du
authors.forename: Lantong
authors.initials: L
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Ge
authors.forename: Huijie
authors.initials: H
authors.lastname: Wang
mesh_terms: D000818:Animals; D019380:Anti-HIV Agents / Q000493:pharmacokinetics; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D053978:Pentacyclic Triterpenes; D051381:Rats; D017207:Rats, Sprague-Dawley; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014315:Triterpenes / Q000493:pharmacokinetics*; D000094062:Betulinic Acid
chemical_list: D019380:Anti-HIV Agents; D000972:Antineoplastic Agents, Phytogenic; D053978:Pentacyclic Triterpenes; D014315:Triterpenes; D000094062:Betulinic Acid