Comparison between the characteristics of absorption and pharmacokinetic behavior of ginsenoside Rg₁ and ginsenoside Rb₁ of panax notoginseng saponins

To compare the characteristics of absorption and pharmacokinetic behavior of ginsenoside Rg₁ (Rg₁) with ginsenoside Rb₁ (Rb₁) of panax notoginseng saponins(PNS), bile excretion of both Rg₁ and Rb₁ were studied after iv and ig of PNS solution. Plasma protein binding ratios were studied using equilibrium dialysis method, and referred to pharmacokinetic parameters. It shows that (61.48±18.30)% dose of Rg₁ and (3.94±1.49)% dose of Rb₁ were separately excreted into bile 10 hours after iv administration (PNS 50 mg·mL^-1), and (0.91±0.51)% dose of Rg₁ and (0.055±0.02)% dose of Rb₁ were excreted into bile 12 hours after ig administration (PNS 1 500 mg·mL^-1). Plasma protein binding degrees of Rg₁ and Rb₁ were 6.56%-12.74% and 80.11%-89.69%, respectively. Stomach, intestinal and hepatic throughput efficiency (F_S, F_I and F_H) for Rg₁ were 49.85%, 13.05%, 50.56%, respectively, and 25.82%, 4.18%, 65.77% for Rb₁. Therefore, poor intestinal absorption is a primary reason for the low bioavailability of both Rg₁ and Rb₁. Rg₁ possesses relatively high bile excretion and low plasma protein binding rate, in contrast, Rb₁ possesses low bile excretion and high plasma protein binding rate. Membrane permeability and elimination rate of Rb₁ were lower than that of Rg₁, meanwhile, longer MRT and bigger AUC could be found for Rb₁.