Comparative pharmacokinetics and bioavailability studies of quercetin, kaempferol and isorhamnetin after oral administration of Ginkgo biloba extracts, Ginkgo biloba extract phospholipid complexes and Ginkgo biloba extract solid dispersions in rats

The aim of this study was to improve the oral bioavailability of Ginkgo biloba extract (GBE) through preparing G. biloba extract phospholipid complexes (GBP) and G. biloba extract solid dispersions (GBS). Firstly we prepared the GBP and GBS and studied their physicochemical properties by differential scanning calorimetry (DSC), powder X-ray diffraction (XRD) and dissolution. Then we studied the pharmacokinetic characteristics and bioavailability in rats. The results showed that the bioavailability of quercetin, kaempferol and isorhamnetin in rats was increased remarkably after oral administration of GBP and GBS comparing with GBE. The bioavailabilities of GBP increased more than that of GBS.     

In vitro metabolism in Sprague-Dawley rat liver microsomes of forsythoside A in different compositions of Shuang-Huang-Lian

Shuang–Huang–Lian (SHL), a traditional Chinese formula containing Lonicerae japonicae flos (LJF), Scutellariae radix (SR) and Forsythiae fructus (FF), is commonly used to treat acute upper respiratory tract infection, acute bronchitis and light pneumonia. Forsythoside A is one of the main active ingredients in Forsythiae fructus, a key herb in SHL. In the present study, effects of different compositions in SHL on the in vitro metabolism in Sprague–Dawley rat liver microsomes of forsythoside A were investigated. The observations from Sprague–Dawley rat liver microsomes in the presence of β-NADPH or UDPGA that forsythoside A may be the substrates of CYP3A4, CYP2C9, CYP1A2, UGT1A6, UGT1A3, UGT1A1 and UGT1A9; Chlorogenic acid may be the substrates of CYP3A4, CYP2C9, CYP1A2, CYP2C19, UGT1A6, UGT1A3 and UGT1A1; Baicalin may be the substrates of CYP3A4, CYP2C19, CYP1A2, UGT1A9, UGT1A1 and UGT1A3; Baicalein may be the substrates of CYP3A4, CYP2E1 and UGT1A6. It was also found that the residue of forsythoside A in SHL, FF + LJF and FF + SR was greatly increased compared with that in FF in Sprague–Dawley rat liver microsomes in the presence of β-NADPH or UDPGA, which indicated that the metabolism of forsythoside A in SHL may be influenced by chlorogenic acid in LJF acting on the CYP3A4, CYP2C9, CYP1A2, UGT1A6, UGT1A3 and UGT1A1; baicalin in SR acting on the CYP3A4, CYP1A2, UGT1A9, UGT1A1 and UGT1A3; baicalein acting on the CYP3A4 and UGT1A6 respectively.     

Intestinal absorption of forsythoside A in different compositions of Shuang-Huang-Lian

Shuang-Huang-Lian (SHL), a traditional Chinese formula containing Lonicerae japonicae flos (LJF), Scutellariae radix (SR) and Forsythiae fructus (FF), is commonly used to treat acute upper respiratory tract infection, acute bronchitis and light pneumonia. Forsythoside A is one of the main active ingredients in Forsythiae fructus, a key herb in SHL. In the present study, effects of different compositions in SHL on the intestinal absorption of forsythoside A were investigated. The observations from in situ intestinal circulation model showed that A/%(h^− 1) of forsythoside A in FF + LSF, FF + SR and SHL were all reduced greatly compared with that in FF. However, in pharmacokinetics study, C_max and AUC_0 → 1440 of forsythoside A all increased and T_1/2 prolonged in SHL, FF + LJF and FF + SR compared with FF. The results indicated that the different compositions of SHL decreased absorption but increased bioavailability of forsythoside A, which may be related to its metabolism inhibited in intestine or liver.