PROJECT SUMMARY
Herb-drug interactions (HDI) have been a significant public health concern for over a quarter century.1 Such
concerns are bolstered by the fact that nearly 70% of the U.S. population takes some form of dietary supplement,
and almost 30% of all prescription drug users take botanical dietary supplements (BDS) concomitantly. Currently
tens of thousands of BDS are on the U.S. market, many containing phytochemicals rarely encountered in the
normal diet. Because these unique phytochemicals utilize the same absorption, distribution, metabolism and
excretion pathways as conventional medications, the chance for pharmacokinetic-mediated HDI (PK-HDI) is
high. PK-HDI are those in which single or multiple phytochemicals modulate various human drug metabolizing
enzymes and/or transporters (DMET) that, in turn, affect the biotransformation and disposition of concurrently
administered medications.2 To date, only a few botanicals appear to pose risks for clinically relevant PK-HDI. Of
these, St. John’s wort (SJW) is the most problematic as it renders many medications ineffective by inducing their
metabolism and reducing their oral bioavailability. SJW’s tremendous HDI potential is due to hyperforin, a unique
phytochemical that potently activates a key protein nuclear receptor (NR) known as the human pregnane
xenobiotic receptor (hPXR). Like all NRs, hPXR upregulates the expression and activity of various DMET.
Preliminary data from the University of Mississippi’s National Center for Natural Products Research (NCNPR)
indicates that other botanicals also harbor phytochemicals capable of activating hPXR along with other important
NRs like the aromatic hydrocarbon receptor (AhR) and constitutive androstane receptor (CAR). Thus, there is a
critical need for systematic screening of popular BDS to determine their PK-HDI risk via NR activation. Equally
important is the need for properly characterized botanical extracts in which to screen. Since 1995, the NCNPR
has amassed one of the world’s largest botanical extract repositories. In this grant submission, we propose a 4-
phased approach to screen 30 of the top-selling BDS for their ability to activate NRs (i.e., hPXR, AhR, CAR)
using well-characterized ethanolic extracts from the NCNPR repository. (1) Initial high throughput NR screenings
will utilize standard in vitro techniques employing transfected cell lines. (2) Extracts capable of activating NRs
will be assessed for their ability to upregulate both gene expression and protein function for specific DMET (e.g.,
CYP1A2, CYP2C9, CYP2C19, CYP3A4, ABCB1) using standard human hepatoma and intestinal cell assays.
(3) Culpable phytochemicals within candidate extracts will be isolated and identified. (4) Finally, in lieu of primary
human hepatocyte cultures, extracts/phytochemicals exhibiting positive results from the first two screening
phases will be evaluated for their PK-HDI risk using the novel Emulate™ human “Liver-on-Chip” technology. For
extracts exhibiting positive results in all screening stages, a data “dossier” will be provided to the Center of
Excellence for Natural Product Interaction Research for confirmatory analyses and possible future clinical PK-
HDI studies.
