Self-micelle formation and the incorporation of lipid in the formulation affect the intestinal absorption of Panax notoginseng

The purpose of this research is to evaluate the effect of self-micelle formation and incorporation of lipid in the formulation on absorption of ginsenosides Rgl and Rbl from intestinal tract in rats. Ginsenosides Rgl and Rbl were extracted from Panax notoginseng saponins (PNS). The critical micellar concentration (CIVIC) of PNS in deionzied water was determined to be 0.339 mg/ml. At normal physiological ionic strengths, PNS was salted out from the solution above the CIVIC. The particle size of the micelle grows as PNS concentration increases. By in situ injection to a closed loop of the ratjejunum, AUCO-6 h obtained after administration of low concentration solution (12 mg/ml) was 3.61 times for ginsenoside Rgi and 3.84-folds for ginsenoside Rbl compared with high concentration solution (120 mg/ml). The release rate of ginsenosides in aqueous medium was too slow to complete in 24 h, especially for Rbl. The data suggested that the self-micelle formation tendency-in ginsenosides might prevent them from permeation or absorption through the cell membrane of gastrointestinal (GI) tract. To inhibit the formation of micelles, lipid was incorporated in the PNS formulation. The intracluodenal bioavailability in rats showed that the bioavailability was enhanced remarkably relative to the aqueous solution. AUCO-_ of ginsenoside Rgl and Rbl in the lipidbased formulation were 207.52 53.95 and 1961.72 686.60 I.Lg ml-1 h, compared with 7.87 2.85 and 148.58 36.73 I.Lg ml-1 h, respectively from its aqueous solution. These findings suggested a new strategy to increase the absorption of amphiphilic saponins. (c) 2008 Published by Elsevier B.V.