Luteoin is one of the main flavones and the crucial effective component of peanut hull extract (PHE). The present paper aims to elucidate the absorption mechanism of luteolin and clarify whether its absorption occurs primarily at a specific site of the intestine by an in situ single-pass intestinal perfusion (SPIP) model. Moreover, the paper investigates the difference in absorption of luteolin when it is administered in PHE form and as pure luteolin by the SPIP model and in vivo pharmacokinetics studies. Results showed that the effective permeability ( P eff) and absorption rate constant ( k a) of pure luteolin(5.0 microg/mL) in duodenum and jejunum were not significantly different, but markedly higher than that in the colon and ileum. The P eff and k a of luteolin in jejunum were concentration-independent, and the ATP inhibitor (DNP) did not influence P eff and k a of pure luteolin. However, the P eff and k a of luteolin in PHE were significantly greater than that of pure luteolin. The pharmacokinetics study showed that following oral administration of a single dose of pure luteolin (14.3 mg/kg) or PHE (= 14.3 mg/kg of luteolin) in rats, the peak concentration of luteolin in plasma ( C max) and the area under the concentration curve (AUC) for pure luteolin were 1.97 +/- 0.15 microg/mL and 10.7 +/- 2.2 microg/mL.h, respectively. These parameters were significantly lower than those of the PHE group ( P < 0.05), C max = 8.34 +/- 0.98 microg/mL and AUC = 20.3 +/- 1.3 microg/mL.h, respectively. It can be concluded that luteolin is absorbed passively in the intestine of rats and that its absorption is more efficient in the jejunum and duodenum than in the colon and ileum. The bioavailability of luteolin in PHE form is significantly greater than that of pure luteolin.