Stereoselective Property of 20(S)-Protopanaxadiol Ocotillol Type Epimers Affects Its Absorption and Also the Inhibition of P-Glycoprotein

Abstract

Stereoselectivity has been proved to be tightly related to drug action including pharmacodynamics and pharmacokinetics. (20S,24R)-epoxy-dammarane-3,12,25-triol (24R-epimer) and (20S,24S)-epoxy-dammarane-3,12,25-triol (24S-epimer), a pair of 20(S)-protopanaxadiol (PPD) ocotillol type epimers, were the main metabolites of PPD. Previous studies have shown that 24R-epimer and 24S-epimer had stereoselectivity in pharmacological action and pharmacokinetics. In the present study, the aim was to further study the pharmacokinetic characteristics of both epimers, investigate their absorption mechanism and analyze the selectivity effects of ocotillol type side chain and C24 stereo-configuration on P-glycoprotein (P-gp) in vivo and in vitro. Results showed that the absolute bioavailability of 24R-epimer was about 14-fold higher than that of 24S-epimer, and a linear kinetic characteristic was acquired in doses of 5–20 mg/kg for both epimers after oral administration. Furthermore, the apparent permeability coefficients of 24R-epimer were 5–7 folds higher than that of 24S-epimer having lower efflux ratios in Caco-2 cell models. Moreover, both 24R-epimer and 24S-epimer had similar inhibitory effects on P-gp by increasing cellular retention of rhodamine 123 in Caco-2 cells and decreasing efflux of digoxin across Caco-2 cell monolayers. In situ in vivo experiments showed that the inhibition of 24R-epimer on P-gp was stronger than that of 24S-epimer by single-pass intestinal perfusion of rhodamine 123 in rats. Western blot analyses demonstrated that both epimers had no action on P-gp expression in Caco-2 cells. In conclusion, with respect to the stereoselectivity, C24 S-configuration of the ocotillol type epimers processed a poor transmembrane permeability and could be distinguished by P-gp. Sharing a dammarane skeleton, both 24R-epimer and 24S-epimer were potent inhibitors of P-gp. This study provides a new case of stereoselective pharmacokinetics of chiral compounds which contributes to know the chiral characteristics of P-gp and structure-action relationship of PPD type and ocotillol type ginsenosides as a P-gp inhibitor.

A Novel Model of P‐Glycoprotein Inhibitor Screening Using Human Small Intestinal Organoids

“…The transport experiments were divided into control group (Rh123 alone) and treated groups (Rh123 together with verapamil or mitotane). The concentration of Rh123 was 5 lM [26]. The concentration of P-gp inhibitors was 20 lM as in our previous study [24].…”

Molecular Insight into Stereoselective ADME Characteristics of C20-24 Epimeric Epoxides of Protopanaxadiol by Docking Analysis

“…This result provided an additional evidence for similar P-gp inhibition potency of PQD epimers from the viewpoint of similar hydrophobic interaction with the P-gp molecule. The previously reported studies based on Western blot analyses demonstrated such a structure-activity relationship, i.e., that PDQ epimers and 20S-Rh2 shared the same dammarane skeleton as the pharmacophore responsible for P-gp inhibiting activity, while the ocotillol side chain and C-24 stereoconfiguration of PDQ epimers had no effect on the expression of P-gp in Caco-2 cells [38]. The findings from in silico molecular docking analysis were highly consistent with those from in vitro cell-based assays and brought a further insight into molecular mechanism of P-gp inhibiting activity of gesenosides.…”

“…The research work of Zhang et al revealed the differential regulations of P-gp by ginsenoside Rh2 epimers in vivo, which provided new evidence of the chiral characteristics of this protein and was helpful to elucidate the stereoselective P-gp regulation mechanism of ginsenoside epimers from a pharmacokinetic view [17]. Interestingly, it was further reported that both 24S-and 24R-PDQ, which share the same dammarane skeleton, could be distinguished by P-gp and had similar inhibitory effects on P-gp by decreasing efflux of digoxin across Caco-2 cell monolayers [38]. P-gp thus was selected as a target protein in our present study for ligand-protein interaction analysis to investigate possible molecular mechanism responsible for such inhibitory effect of PDQ epimers on this stereoselective biomacromolecule P-gp, and the X-ray crystal structure with an ID of 5KOY in PDB was selected for molecular docking.…”

“…Biomolecules 2020, 10, x 9 of 12 distinguished by P-gp and had similar inhibitory effects on P-gp by decreasing efflux of digoxin across Caco-2 cell monolayers [38]. P-gp thus was selected as a target protein in our present study for ligand-protein interaction analysis to investigate possible molecular mechanism responsible for such inhibitory effect of PDQ epimers on this stereoselective biomacromolecule P-gp, and the X-ray crystal structure with an ID of 5KOY in PDB was selected for molecular docking.…”

Discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins

“…24( S )-Ocotillol type epimer processed poor transmembrane permeability and can be distinguished by P-gp [81].…”