The intestinal uptake of paclitaxel is hampered by trans-membrane efflux transporters such
as P-glycoprotein (P-gp), and paclitaxel is mainly metabolized by cytochrome P450 3A4
(CYP3A4) presented in the liver. Our previous results demonstrated that flavonoids extracted
from Taxus yunnanensis could improve the oral absorption of paclitaxel. The current study
was purposed to investigate the effects of the flavonoid extracts on P-gp and CYP3A4 in vitro.
The expression and activity of P-gp were detected by western blotting and intracellular
rhodamine 123 accumulation assay in Caco-2 cells treated with the flavonoids extract. The
expression of CYP3A4 was investigated by western blotting in mouse primary hepatocytes
and the activity of CYP3A4 was detected by LC-MS/MS method using rat liver microsomes.
Our results showed that the flavonoid extracts from T. yunnanensis could inhibit P-gp activity
and concurrently decrease the expression and activity of CYP3A4. In conclusion, activity of
P-gp and CYP3A4 could be inhibited by flavonoids extracted from T. yunnanensis which might
be potential candidates for development of oral formulation of paclitaxel