Purification of astilbin and isoastilbin in the extract of smilax glabra rhizome by high-speed counter-current chromatography

Purification of astilbin from the rhizome extract of Smilax glabra was conducted using a high-speed counter-current chromatograph equipped with a 700 mL column. In a single operation, 1.5 g of crude sample was separated to yield 105 mg of component astilbin and 48 mg of isoastilbin while the upper phase of the two-phase solvent system composed of n-hexane-n-butanol-water (1:1:2, v/v/v) was used for stationary phase. The chemical structures of the two flavonoid glycosides were confirmed by electrospray ionization ion trap multiple mass spectrometry and nuclear magnetic resonance experiments.     

Direct liquid chromatographic analysis of resveratrol derivatives and flavanonols in wines with absorbance and fluorescence detection

Wine contains a large number of polyphenols including stilbenes, flavanols and anthocyanins. Of these, stilbenes have been reported to have potential chemopreventive activities. We describe the simultaneous determination of six resveratrol derivatives in wines by liquid chromatography (LC) with fluorescence detection. The levels of pallidol, the symmetrical dimer of resveratrol, are reported for the first time. Quantifications were carried out at optimal wavelengths for each compound during separation. A total of 19 red and 30 white commercial wines from South-Western France were analysed, and the highest stilbene concentrations were found in red wines. In addition, the levels of catechins and two flavanonols recently isolated in red wine are reported.     

Cationic zirconocene- or hafnocene-based Lewis acids in organic synthesis: glycoside-flavonoid analogy

Cationic metallocene species, generated from Cp₂MCl₂ and AgClO₄ (M=Zr, Hf), were used for the glycosylation of catechin derivative 2, enabling a concise synthesis of a glycosyl flavonoid, astilbin (1). Further study revealed the efficiency of this Lewis acidic species for S_N1-type activation of the C(4) position of catechin derivative 11, enabling selective substitution with various nucleophiles.     

Rapid Quantification of Astilbin in Rat Plasma by Liquid Chromatography-tandem Mass Spectrometry and Its Application to Pharmacokinetic Study

Astilbin is a potential immunosuppressive agent with minor cytotoxicity. Its oral bioavailability is supposed to be rather low and therefore a sensitive analytical method is required for its pharmacokinetic study after oral administration. A simple, sensitive and rapid liquid chromatography-tandem mass spectrometry（LC-MS/MS） method was developed and validated for the determination of astilbin in rat plasma. Plasma samples were subjected to liquid-liquid extraction with ethyl acetate and separated by reversed phase high performance liquid chromatography（HPLC） with methanol-0.01%（volume fraction） formic acid（50：50, volume ratio） as mobile phase. Quantitive determination was achieved on negative LC-MS/MS by a multiple reaction moitoring method with transitions m/z 449.1→150.9（quantifier） and m/z 449.1→284.9（qualifier） for astilbin and m/z 128.9→42.0 for internal standard（IS）. A lower limit of quantification（LLOQ） of ng/mL was achieved within a short cycle time of 3.4 min. The method was successfully applied to a pharmacokinetic study involving oral and intravenous administrations of 6 mg/kg astilbin to six rats.