Luteolin is a flavonoid present in plants in the form of aglycone or glucosides. 
In this study, luteolin glucosides (i.e., luteolin-7- O-β-d-glucoside, 
luteolin-7- O-[2-(β-d-apiosyl)-β-d-glucoside], and luteolin-7- 
O-[2-(β-d-apiosyl)-6-malonyl-β-d-glucoside]) prepared from green pepper leaves 
as well as luteolin aglycone were orally administered to rats. Regardless of the 
administered luteolin form, luteolin glucuronides were mainly detected from 
plasma and organs. Subsequently, luteolin aglycone, the most absorbed form of 
luteolin in rats, was orally administered to humans. As a result, luteolin-3'- 
O-sulfate was mainly identified from plasma, suggesting that not only luteolin 
form but also animal species affect the absorption and metabolism of luteolin. 
When LPS-treated RAW264.7 cells were treated with luteolin glucuronides and 
luteolin sulfate (the characteristic metabolites identified from rats and 
humans, respectively), the different luteolin conjugates were metabolized in 
different ways, suggesting that such difference in metabolism results in their 
difference in anti-inflammatory effects.