The present study aimed to investigate the intestinal kinetic absorptive characteristics of geniposide as well as the absorptive behavior influenced by the co-administration of notoginsenoside R1 using an in vitro everted rat gut sac model.
The results showed good linear correlation between the geniposide absorption in sac contents and the incubation time from 0 to 120 min. The concentration dependence showed a non-linear correlation between the geniposide absorption and the concentrations 0.356-1.424 mg/mL, the absorption was saturated about 1.424 mg/mL. Notoginsenoside R1 at 0.1 and 0.2 mg/mL concentrations was able significantly to enhance the absorption of geniposide (1.424 mg/mL) by 1.7- and 1.4-fold. Moreover, verapamil, a well-known P-glycoprotein inhibitor, was able significantly to elevate the absorption of geniposide 2.4-fold. Notoginsenoside R1 influenced geniposide's absorption in a way similar to that of a P-glycoprotein inhibitor.
In conclusion, notoginsenoside R1 significantly enhances the intestinal absorption of geniposide. As for the mechanism underlying the improvement of geniposide's bioavailability, it is proposed that notoginsenoside R1 was able to decrease the efflux transport of geniposide by P-glycoproteins.