Ginger and Its Purified Major Components Inhibit Clinically Relevant Uptake and Efflux Transporters In Vitro

Background/Objectives: Ginger (Zingiber officinale Roscoe) is a flowering plant widely used as a spice and natural medicine for millennia. Ginger demonstrates multiple protective effects, regulates cholesterol, and may reduce the risk of cancer and colitis. However, little attention has been paid to its potential to cause herb–drug interactions (HDIs). The aim of this study was to investigate the interaction of ginger extract and its major components 6-gingerol and 6-shogaol with clinically relevant uptake and efflux transporters in vitro. Methods: Transporter-overexpressing cell lines of 25 uptake transporters and inside-out membrane vesicles containing 8 efflux transporters were employed to measure potential interactions. Results: Zingiber officinale extract at 150 µg/mL interacted with 17 of 33 transporters examined. These were further investigated for interactions with the purified active components. Seven and 16 transporters interacted with pure 6-gingerol (100 µM) and 6-shogaol (100 µM), respectively. To evaluate the risk of in vivo inhibition, IC50 values were determined for the affected transporters. Based on standard risk assessment calculations, we confirmed previously reported inhibitory effects of ginger components on MDR1 (67.64 µM) and BCRP (9.931 µM), and revealed novel potential interactions with renal OAT3 (0.956 µM) and URAT1 (5.887 µM), hepatic OCT1 (4.287 µM) and BSEP (25.45 µM), and the ubiquitously expressed ENT1 (11.62 µM) (6-shogaol IC50 values are shown in parentheses). Strong and isoform-selective inhibition of OAT3 by 6-shogaol is particularly intriguing. Additionally, via cell viability experiments on a set of human cervical, breast, and oropharyngeal cancer cell lines, we demonstrated the antiproliferative effect of 6-shogaol in vitro. Conclusions: Prolonged consumption of high-dose ginger supplements may pose a risk of transporter-mediated HDIs when consumed concomitantly with conventional medications. Our study encourages follow-up of the suspected effects in vivo.