Luteolin and luteolin-7-O-glucoside were isolated from the ethanolic extract of Dendranthema morifolium Ramat Tzvel. The structures of these analytes were identified by nuclear magnetic resonance ((1)H and (13)C NMR) and mass spectrometry. Ethanolic and water extracts contained luteolin-7-O-glucoside at 4.19 and 6.56%, respectively. However, the level of luteolin was only 0.19% in the ethanolic extract, and luteolin was not detected in the water extract. To examine the pharmacokinetics and bioavailability of luteolin and luteolin-7-O-glucoside in rats, parallel studies of luteolin (10 mg/kg, iv; and 100 mg/kg, po) and luteolin-7-O-glucoside (10 mg/kg, iv; and 1 g/kg, po) were conducted. The analytes were detected by high-performance liquid chromatography coupled with a photodiode array detector. A phenyl-hexyl (150 × 4.6 mm iv; 5.0 μm) column was used to separate the analytes from the biological samples. The pharmacokinetic data demonstrate that the areas under the concentration curves (AUCs) of luteolin were 261 ± 33 and 611 ± 89 (min μg/mL) after luteolin administration (10 mg/kg, iv; and 100 mg/kg, po, respectively). The oral bioavailability of luteolin was 26 ± 6%. The AUCs of luteolin-7-O-glucoside were 229 ± 15 and 2109 ± 350 (min μg/mL) after administration of luteolin-7-O-glucoside (10 mg/kg, iv; and 1 g/kg, po, respectively). The oral bioavailability of luteolin-7-O-glucoside was approximately 10 ± 2%. In the group that received luteolin-7-O-glucoside orally, a biotransformed luteolin product was detected, but this product was not detected in the group that received luteolin-7-O-glucoside intravenously. The biotransformation ratio of luteolin to luteolin-7-O-glucoside (the AUC ratio of metabolite/parent compound) was approximately 48.78 ± 0.12%. These results demonstrate that luteolin-7-O-glucoside is primarily hydrolyzed to luteolin in the gastrointestinal tract and then absorbed into the systemic circulation.
Keywords: bioavailability; flavonoid; herbal medicine; pharmacokinetics; traditional Chinese medicine.