Ionization constants of ginkgolide B in aqueous solution.

The thermodynamic ionization constants (pK(a)(1), pK(a)(2), and pK(a)(3)) of ginkgolide B (9H-1,7a-(epoxymethano)-1H,6aH-cyclopenta[c]furo[2,3-b]furo-[3',2':3,4]cyclopenta[1,2-d]furan-5,9,12-(4H)-trione, 3-tert-butylhexahydro-4,7b,11-trihydroxy-8-methyl-) in aqueous solution have been settled by pH-metric and NMR studies. The three macroscopic pK(a) values as well as the water solubility and the water/n-octanol partition coefficient have been extracted from pH-metric data by means of a nonlinear regression methodology. NMR spectroscopy provided confirmation of the values of the macroscopic constants, information about the effective ionization pathways, and an estimation of the proportions of the various forms under physiologically relevant conditions.

[Pharmacokinetic properties of Bilobalide and Ginkgolides A and B in healthy subjects after intravenous and oral administration of Ginkgo biloba extract (EGb 761)].

The pharmacokinetics of Ginkgolide A, Ginkgolide B and Bilobalide, which are compounds extracted from the dried leaves of the Ginkgo biloba tree, were investigated in 12 young healthy volunteers (six men and six women; mean +/- SD age = 25 +/- 5 years) after single-dose administration of Ginkgo biloba extract. Subjects were given, on three occasions, Ginkgo biloba extract as a solution either orally (in fasting conditions and after a standard meal) or intravenously; corresponding to single doses of Ginkgolide A, Ginkgolide B and Bilobalide ranging from 0.90 mg to 3.

Cicletanine binding to human plasma proteins and erythrocytes, a particular HSA-drug interaction.

The binding of cicletanine to human serum, isolated proteins and red blood cells was studied in vitro by equilibrium dialysis. Our results show this drug is highly bound to serum (97.3%) at therapeutic levels.