The inhibitory effects of the bioactive components isolated from Scutellaria baicalensis on the cellular uptake mediated by the essential solute carrier transporters.

Solute carrier transporters (SLCs), in particular the organic anion transporters (OATs), OAT polypeptides (OATPs), and organic cation transporters (OCTs/OCTNs), are the important membrane proteins responsible for the cellular influx of various drugs. Baicalein (BA), baicalin (BG), and wogonin (WG) are the three major bioactive components of Scutellaria baicalensis. In this study, we evaluated the inhibitory effects of BA, BG, and WG on the cellular uptake of specific substrates mediated by the essential SLCs in human embryonic kidney-293 cells. Our data demonstrated that BA and WG significantly inhibit the OAT1-, OAT3-, and OATP1B3-mediated uptake; BG effectively reduces the influx of substrates of OAT3, OAT4, OATP1B3, and OATP2B1; WG is a potent inhibitor of OCT3. Our further kinetic analysis derived the IC50 values of these compounds with pronounced inhibitory effects on SLCs, particularly the inhibitions of WG on OAT1 and OCT3 and that of BA and WG on OAT3. Our study comprehensively evaluated the inhibitory effects of three bioactive components of Scutellaria baicalensis on the uptake of specific substrates mediated by the essential SLC transporters, which suggested that precautions will be needed when coadministrating drugs with Scutellaria baicalensis so as to prevent the unfavorable drug-drug/herb interactions in human.