Study On Oral Absorption Mechanism Of Indirubin

Indirubin is the active component of Indigo Naturalis, and it is considered as a good anticancer drug due to its low toxicity. However, because of its special physico-chemical property, indirubin has some natural disadvantages, such as poor absorption and high administration dose. Accordingly, it is very important to develop eligible dosage forms to solve the problem of absorption. And the purpose of this study is to provide novel ideas and approaches for modernize the theoretical basis of dosage forms designed by utilizing the latest measures and models based on the principles of biopharmaceutics and pharmacokinetics.Results of in situ gastric perfusion suggested that there is no significant difference among the absorption fractions (per hour) with low, middle and high dose of indirubin. The result idicated absorption of indirubin in stomach is a first-order process with the passive diffusion mechanism.Results of in situ gut perfusion suggested that dissolution and permeation are two factors limited its absorption, and absorptive rate constants (K_a) of indirubin were 0.086, 0, 0.077, 0.046 h^-1 at duodenum, jejunal, ileum and colon, respectively. The absorption of indirubin is a first-order process with the passive diffusion mechanism. Whether ligating bile duct or not might influence the lnX-t curves, although no significant difference was investigated on permeability coefficients of indirubin.Results of in vivo experiment and ansa intestinalis model clearly indicated that The absorption mechanisms of indirubin across the intestinal epithelium are rather complex, which involve carrier-mediated transport, passive transcellular diffusion, enterohepatic circulation, intestinal excretion and intestinal metabolism. The absolute bioavailability of indirubin is rather low, but phospholipid and bile salt can enhance absorption and oral bioavailability of indirubin for improving lipophilicity or hydrophilicity.Due to those absorption properties mentioned above, indirubin solid dispersion and indirubin-phospholipid complex were prepared and were used to carry out ansa intestinalis experiments. The positive results suggested that absorption property of indirubin might be improved by pharmaceutical means.Correlations between different models were evaluated by statistical test. There exists a certain qualitative correlation between absorption fractions of the two models, but hardly exists correlation between absorption rates. The deference between the two models probably depends on several factors, such as model factor, dosages factor and physiological factor. In summary, in situ or in vitro models can be effective optional ways to investigate absorption mechanisms and anticipate absorption pattern. Therefore, utilizing two or more methods to synthetically evaluate the absorption result could obtain more reliable conclusions.The difficulties of this study were as follows: (1) It is difficult to develop both in situ and in vivo models applying to such drugs with low solubility and poor stability as indirubin; (2) Both amount and influence of solubilizer are hard to investigate; (3) Detection sensitivity is hard to achieve after oral absorption, and there existed big interindividual variation; (4) The pretreatment method of blood sample is not so simple to establish; (5) The physiological disposition of indirubin is complicated.The novelties of this study were as follows: (1) It is the first time that in situ perfusion model of indirubin on rat was established after the solubilizer was used to increase its solubility; (2) RP-HPLC determination of indirubin in Rat blood samples provided in this research had never been reported before; (3) Oral absorption, intestine excrete, enterohepatic cycle and absorption promoter of indirubin were researched systematically; (4) Multi-models were used to develop feasible preparations of naturally occurring drugs, and there is no similar report in literature on this study conception at present.The thesis developed rationale and practice to improve oral bioavailability of indirubin, as well as provided a feasible mode to evaluate TCM absorption. The accomplishment of the project is a great achieve of biopharmaceutics and pharmacokinetics, and it also provides a novel idea for developing modern preparations of TCM with high effect, high quality and high standard, as well.