**5. Conclusions**

The present study evaluated the e ffects of *R. acetosa* extract on 2 active transporters, P-gp and OATP1A2 and the resulting e ffects on fexofenadine absorption through in vitro and in vivo studies. The findings sugges<sup>t</sup> that emodin can enhance fexofenadine absorption via an inhibitory e ffect on *P*-gp. In addition, *R. acetosa* extract could decrease the absorption of fexofenadine via intervention in the aqueous solubility and the drug transporters.

**Funding:** This research was funded by the National Research Foundation of Korea (NRF) gran<sup>t</sup> funded by the Korean governmen<sup>t</sup> (MSIP; Ministry of Science & ICT), Grant Number 2017R1C1B5017343.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Author Contributions:** Conceptualization, H.J.C.; methodology, H.J.C.; validation, J.K. and N.U.R.; formal analysis, J.K.; investigation, J.H.A., J.K. and H.-J.K.; resources, M.-J.A. and H.J.C.; data curation, J.H.A., J.K. and H.J.C.; writing—original draft preparation, J.K. and N.U.R.; writing—review and editing, H.J.C.; visualization, J.K.; supervision, H.J.C. and M.-J.A.; project administration, H.J.C.; funding acquisition, H.J.C. All authors have read and agreed to the published version of the manuscript.
