Potential Interactions of Herbal Extracts of St. John´s Wort with Metabolites of Diazepam in an Organotypical Sandwich Culture of Primary Porcine Hepatocytes

Extracts of St. John’s Wort (Hypericum perforatum) are known to cause interactions with certain conventional drugs. Herein, we focus on two clinically relevant concepts. First, St. John´s Wort has been used by people of all ages as an herbal treatment for depression without medical prescription. Second, diazepam-like substances called endogenous benzodiazepines are found in cases of acute liver failure without previous exposure to diazepam. Currently diazepam has over 500 brands name and well marketed throughout the world and became one most frequently prescribed medication in different form (oral, injectable, inhalation and rectal forms) for four decades. Based on this concept, we investigated diazepam biotransformation by incubation of a widely accepted in vitro organotypical culture model with Hypericum methanolic extract, powdered drug, infusion, oil, and with the pure Hypericum compounds hyperforin and hypericin. The amounts of the preparations and compounds were chosen according to the recommended daily medication doses. We measured the activities of ethoxyresorufin-O-deethylase (EROD), ethoxy coumarin O-deethylase (ECOD) and the potential induction of diazepam metabolites (desmethyldiazepam, temazepam and oxazepam) during biotransformation. None of the preparations or substances induced EROD or ECOD. However, different preparations did induce the formation of desmethyldiazepam and temazepam. The strongest activity was caused by the extract, followed by the powdered drug and hyperforin. All preparations and compounds increased the formation of the diazepam metabolite oxazepam, but only the extract, the drug powder and the pure compounds had marked effects. Therefore, we report here the potential interference of St. John´s Wort with all three metabolites of diazepam in an organotypical sandwich model that can be utilized to study potential interaction of metabolites of many drugs with herbal ingredients in preclinical stage of drug discovery process.