The discovery that various drugs (e.g., phenobarbital) stimulate their own metabolism through a mechanism coined as enzymatic induction opened up a fascinating road that eventually led to the accurate biochemical characterization of the pregnane X receptor. After numerous studies, researchers have concluded that this receptor is activated by different endogenous steroids and a number of foreign lipophile ligands. Once activated, it induces the synthesis of oxygenases and conjugating enzymes. The activating ligands identified to date include many synthetic drugs, along with a number of natural products. The present review summarizes the data relating to the origin, chemistry, and pharmacological activity of the newest natural products that have been found to interact with the pregnane X receptor.
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