Application of cryopreserved human intestinal mucosa and cryopreserved human enterocytes in the evaluation of herb-drug interactions: Evaluation of CYP3A inhibitory potential of grapefruit juice and commercial formulations of twenty nine herbal supplements

Commercial formulations of 29 commonly used herbal supplements (HS) and grapefruit juice were evaluated for drug interaction potential via quantification of their CYP3A inhibitory potential in two in vitro experimental models of human small intestine, cryopreserved human intestinal mucosa (CHIM) and cryopreserved human enterocytes (CHE). Two CYP3A substrates were used - in the studies with CHIM, CYP3A activity was quantified via LC/MS-MS quantification of midazolam 1'-hydroxylation while in CHE, luciferin IPA metabolism to luciferin was quantified by luminescence. Upon treatment of CHIM with the estimated lumen concentration of the HS upon each oral administration (manufacturers' recommended dosage dissolved in 200 mL of culture medium), >80% CYP3A inhibition was observed for green tea extract, St. John's wort, valerian root, horehound and grapefruit juice. Less than 50% inhibition was observed for fenugreek, aloe vera, guarana, soy isoflavone, maca, echinacea, spirulina, evening primrose, milk thistle, cranberry, red yeast rice, rhodiola, ginkgo biloba, turmeric, curcumin, white kidney bean,, garlic, cinnamon, saw palmetto berries, panax ginseng, black elderberry, wheat grass juice, flaxseed oil, black cohosh, and ginger root. The results were confirmed in a a dose-response study with HS obtained from three suppliers for the four inhibitory HS (green tea extract, horehound, St. John's wort, valerian root), and three representative non-inhibitory HS (black cohosh, black elderberry, echinacea). Similar results were obtained with the inhibitory HS in CHE. The results illustrate that CHIM and CHE represent physiologically relevant in vitro experimental models for the evaluation of drug interaction potential of herbal supplements. Significance Statement In vitro evaluation of 29 popular herbal supplements in cryopreserved human intestinal mucosa identified green tea extract, horehound, St. John's wort, valerian root to have CYP3A inhibitory potential similar to that for grapefruit juice, suggesting their potential to have clinically-significant pharmacokinetic interaction with orally administered drugs that are CYP3A substrates. The results suggest that CHIM can be used for in vitro evaluation of drug interactions involving enteric drug metabolism.

Keywords: drug-drug interactions; gastrointestinal cytochrome P450; natural products.