1. Scutellarin is a flavonoid glycoside widely used in the treatment of cardio-cerebrovascular diseases in China. In this study, we investigated the effect of scutellarin on cytochrome P450 3A4 (CYP3A4) and CYP3A5 expression. Furthermore, we studied the expression of hsa-miR-27a, hsa-miR-27b, hsa-miR-148a, hsa-miR-298 and hsa-miR-451a in humans to determine whether scutellarin regulated CYP3A4 and CYP3A5 expression by altering levels of those micro-ribonucleic acids (miRNAs).

2. In vitro CYP3A4 and CYP3A5 expression was measured in Chang liver cells via quantitative real-time polymerase chain reaction (qPCR) and western blot. In vivo CYP3A4 and CYP3A5 expression was evaluated through the metabolism of their substrate midazolam (MID), and detected via ultra-performance liquid chromatography-mass spectrometry. The relative miRNA levels in the plasma of study participants were investigated via qPCR.

3. Results showed that scutellarin significantly inhibited the CYP3A4 and CYP3A5 expression both in vitro and in vivo. However, the levels of hsa-miR-27a, hsa-miR-27b, hsa-miR-148a, hsa-miR-298 and hsa-miR-451a in scutellarin group did not show significant changes when compared with those of the placebo group (p > 0.05), suggesting that the expression of these miRNAs is not relevant to the scutellarin-induced down-regulation of CYP3A4 and CYP3A5.