Two aminooligosaccharides. isovalertatins D03 (1) and D23 (2). were isolated from the culture filtrate of Streptomyces luteogriseus. Their structures were reinvestigated and revised by spectroscopic evidences including ESI multistage mass spectrometry and 2-dimensional NMR techniques.
A simple, rapid and sensitive method for the determination of protopanaxadiol in rat plasma with ginsenoside Rh2 as internal standard was developed and validated. The analyte and internal standard were extracted from plasma with ether-dichloromethane（3：2, volume ratio） and then were analyzed by reversed-phase HPLC on a short Zorbax Extend C18 column（50 mm×2.1 mm, 3.5 μm i. d.） eluted with a mobile phase consisting of acetonitrile/methanol 0.10 mmol/L ammonium acetate（45：45：10, volume ratio） at 0.4 mL/min. Detection was performed on an Applied Biosystems Sciex API 4000 mass spectrometer set at unit resolution in the multiple reaction monitoring mode. Electrospray ionization was used for ion production. The assay method shows linear over a range of 5-2000 ng/mL and intra- and inter-day precisions over this range were 〈10.0% with accuracy ranged from 86.3% to 114.1%. The limit of detection was 500 pg/mL in the plasma. The method was successfully applied to a preclinical pharmacokinetic study of protopanaxadiol（17.5 mg/kg） administered as a single oral dose.
