Traditional preparations and methanolic extracts of plants from Papua New Guinea exhibit similar cytochrome P450 inhibition

Human immunodeficiency virus (HIV) and tuberculosis (TB) infections constitute a large portion of the disease burden in Papua New Guinea (PNG). Treatment of HIV and TB require long-term administration of antiretroviral and anti-TB drugs, respectively. In addition to Western medicine, traditional medicine (TM) is widely practiced in PNG. There is increasing concern that traditional medicines may antagonize antiretroviral and anti-tuberculin drug efficacy. Plant-drug, or drug-drug, interactions can occur at the level of metabolism through two major mechanisms: enzyme induction or enzyme inhibition. Our previous study of commonly-used medicinal plants from PNG extracted in methanol found almost one third of TM extracts induced cytochrome P450 (CYP) subtype expression of CYP1A2 or CYP3A4, or both. In addition, almost two thirds inhibited CYP1A2, CYP3A4, or CYP2D6, or combinations thereof. In PNG, the most common route by which traditional medicines are consumed is ingestion of expressed juice, succus. We investigated CYP inhibition of independently recollected medicinal plants (n = 17) and compared CYP inhibition by succus to the previous methanolic study through pair-wise comparisons of like genus and species. Results for the recollected succus samples were not significantly different from results obtained with methanolic extracts (p < 0.05). Therefore, data obtained previously with methanolic extracts likely represents biological activities found in more traditional medicinal preparations. In addition, these results confirm previous in vitro data that indicate use of traditional medicines concomitantly with ART or anti-TB drugs could dramatically alter their efficacy.