The blood-brain barrier permeability of 20（S） and 20（R）-protopanaxatriol epimers and dammar-20（22）E,24-diene- 313,6α,12β-triol were investigated using the MDCK-pHaMDR cell monolayer model. The bidirectional permeability tests were carried out, and the apparent permeability coefficients （Papp） were calculated. The two protopanaxatriol epimers showed good permeability with Papp values of-10^-5 cm/s, whereas dammar-20（22）E,24-diene-3β,6α, 12β-triol showed poor permeability with Papp of 〈1 × 10^-7 cm/s. The three compounds showed differences in intracellular accumulations due to their different structures. Inhibition of P-gp with verapamil showed that the transport mechanisms in MDCK-pHaMDR cell monolayer for compounds 1 and 2 epimers were not only simple passive diffusion but also involving an effiux way mediated by P-gp. These findings provided new basis for the further study of compounds 1 and 2 acting on the brain.
