Studies On The Metobolites Of Four Kinds Of Flavonoids In Blood

Flavonoids is a kind of important secondary metabolites in plants and has varied activities such as anti-inflammatory, anti-free radical, anti-aging, antiviral, anti-cancer, anti-angiocardiopathy, et al.(1) In this paper, flavonoids in licorice residue was investigated, and 6 compounds (1～6) were isolated from the 95% ethanol extract of licorice residue by chromatographic methods. On the basis of spectroscopic analysis (¹H-NMR, ¹³C-NMR, EI-MS), they were identified as licochalcone A (1), licochalcone B (2), echinatin (3), licoflavone (4), 7, 4'-dihydroxyflavone (5), and 5, 7, 4'-trihydroxy-8-isopenenylflavone (6).(2) An HPLC-UV method was developed for the determination of licochalcone A in licorice residue and in licorice. The analysis was carried on the column of BISCHOFF C₁₈ (2.0 mm×150 mm, 5μm), with the mobile phase consisted of methanol- tetrahydrofuran-1% acetic acid (46: 10: 44). The flow rate was 0.3 ml/min with the detect wavelength at 377 nm, and the column temperature in 30℃. The method displayed excellent linearity in the ranges 1～32μg/ml with the regression coefficient at 0.9997. The average recovery of licochalcone A was 95.7% (RSD=3.0%). With this method, the content of licochalcone A had been compared between licorice residue and licorice from different regions.(3) On the basis of the chemical study, the metabolites of licochalcone A in rat serum were investigated. With the estabolished methods of HPLC-DAD and LC-MS, 2 metabolites together with the parent drug were verified as licochalcone A 4-O-glucuronide, licochalcone A 4'-O-glucuronide, and licochalcone A.(4) 6-hydroxykaempferol 3-O-glucoside (7) was isolated and accumulated from Carthamus tinctorius L. And the metabolites of 6-hydroxykaempferol 3-O-glucoside in rat serum were investigated. Serum sample after oral administration of 6-hydroxykaempferol 3-O-glucoside was analyzed by HPLC-DAD and LC-MS/MS, and 7 metabolites were detected and identified as 6-hydroxykaempferol 6, 4'-di-O-glucuronide, 6-hydroxykaempferol 3,6-di-O-glucuronide, 6-hydroxykaempferol 3-O-glucuronide, 6-hydroxykaempferol 4'-O-glucuronide, 6-hydroxykaempferol 6-O-glucuronide, 6-hydroxy-7-methoxykaempferol 3-O-glucuronide, and 6-hydroxy-3-methoxykaempferol 7-O-glucuronide.(5) The HPLC-DAD and LC-MS/MS methods for determination of scutellarein and its metabolites in rat plasma were established. 4 metabolites together with the parent drug were detected and identified as scutellarin, scutellarein 6-O-glucuronide, 6-methoxyscutellarin, scutellarein 4'-O-glucuronide (or scutellarein 5-O-glucuronide), and scutellarein.(6) Metabolites of baicalein after oral administration were investigated in rats and in humans, respectively. With the estabolished methods of HPLC-DAD and LC-MS/MS, 5 metabolites and together with the parent drug were detected from the rat serum and identified as baicalein 6, 7-di-O-glucuronide, baicalein 7-O-glucuronide (baicalin), 6-methoxybaicalein 7-O-glucuronide, baicalein 6-O-glucuronide, baicalein 7-O-glucuronyl methyl ester, and baicalein. 5 metabolites and the parent drug were detected in the plasma of humans, and were identified as baicalein 6, 7-di-O-glucuronide, baicalein 7-O-glucuronide (baicalin), 6-methoxybaicalein 7-O-glucuronide, baicalein 6-O-glucuronide, 7-methoxybaicalein 6-O-glucuronide, and baicalein. The major metabolite of baicalein both in rats and in human beings is baicalin, while the metabolites in human beings are not all the same as those in rats.