The inhibition of CYP1A2, CYP2C9, and CYP2D6 by pterostilbene in human liver microsomes

This study used human liver microsomes to assess pterostilbene's effect on the metabolic activity of cytochrome P450 (CYP) 1A2, CYP2C9, and CYP2D6. The metabolism of their substrates (phenacetin, tolbutamide, and dextromethorphan) was assayed by quantifying their relevant metabolites by HPLC. The IC50 value was used to express the strength of inhibition, and the value of a volume per dose index (VDI) was used to indicate the metabolic ability of the enzyme. In this study, pterostilbene inhibited CYP1A2, CYP2C9, and CYP2D6's metabolic activities in vitro. CYP2C9's activity was most significantly inhibited by pterostilbene; its IC50 value was 0.12±0.04 μM. The IC50 value of CYP1A2 and CYP2D6 was 56.3±10.4 μM and 62.33±11.4 μM, respectively. The finding that suggests that pterostilbene has the potential to interact with CYP2C9 substrates in vivo. These results warrant clinical studies to assess the in vivo significance of these interactions.