Enhancing effect of natural borneol on the absorption of geniposide in rat via intranasal administration.

Both geniposide (Ge) and natural borneol (NB) are bioactive substances derived from traditional Chinese herbs. The effect of NB on the pharmacokinetics of Ge in rat via intranasal administration was investigated. The concentrations of Ge in plasma were determined by reversed-phase high-performance liquid chromatography (HPLC) after intranasal administration of Ge (4 mg/kg) alone and combined with different doses (0.08, 0.8, and 8 mg/kg) of NB. The intravenous administration was given as a reference (4 mg/kg of Ge and 8 mg/kg of NB). Compared with the intravenous administration, the absolute bioavailability of Ge was 76.14% through intranasal administration combined with NB. Compared with the intranasal administration of Ge alone, Ge could be absorbed rapidly in the nasal cavity combined with NB; the peak time of Ge in the plasma became shorter (3-5 min vs. 40 min); the peak concentration became higher (1.32-4.25 μg/ml vs. 0.67 μg/ml); and, the relative bioavailability of Ge combined with NB was 90.3%-237.8%. The enhancing effect was attenuated as the dose of NB decreased. The results indicated that NB can accelerate the absorption of Ge dose-dependently in the nasal cavity.