A rapid determination of drug candidate tyrosol galactoside in rat plasma by HPLC and its application to the pharmacokinetics study.

A simple and sensitive HPLC method has been developed and validated for the determination of tyrosol galactoside (TG) in rat plasma. After one-step protein precipitation with methanol, plasma samples were separated on an Ultimate AQ-C18 column (150 mm×4.6 mm, 5 µm) using acetonitrile-water (7:93, v/v) as mobile phase at a flow rate of 1.2 mL/min. The ultraviolet detection wavelength was set at 275 nm. The lower limit of quantification was 1.140 µg/mL. The calibration curve was linear over a concentration range of 1.140-228.0 µg/mL. The assay accuracy and precision were within the range of 99.6-103.0 and 2.17-6.23%, respectively. The developed method was successfully applied to the pharmacokinetics study of TG in rats after intravenous and oral administration. The bioavailability of TG in rats is 27.9%.

Water-soluble cholesteryl-containing phosphorothioate monogalactosides: synthesis, properties, and use in lowering blood cholesterol by directing plasma lipoproteins to the liver.

The synthesis of several monogalactoside-terminated phosphorothiolated cholesteryl derivatives is described. Monogalactosyl derivatives are coupled by phosphorothiolation to cholesterol by using ethylene glycol units as hydrophilic spacer moieties. The resulting compounds are easily soluble in water. Upon addition of such solutions to human serum (to 2 mM final concentration) the compounds are readily incorporated into lipoproteins. Isolated low-density lipoprotein (LDL) and high-density lipoprotein (HDL), preloaded with the compounds, are rapidly cleared from the circulation by the liver. The hepatic association is blocked by N-acetylgalactosamine, which indicates that galactose-specific recognition sites are responsible for the increased liver uptake. The plasma clearance and hepatic uptake of LDL loaded with the compounds is substantially higher (about 2-fold) than clearance and uptake of HDL containing the compounds. The selectivity of the effects of monogalactoside-terminated phosphorothiolated cholesteryl derivatives on the in vivo behavior of LDL as compared to that of HDL indicates that these compounds might be used to lower specifically LDL levels in patients with a high LDL-cholesterol level.

Interaction of hemin with erythrocyte membranes: alterations in the physical state of the major sialoglycoprotein.

Hemin has been shown to disrupt erythrocyte membrane skeletal protein-protein interactions, initially those involving band 4.1 (Shaklai et. al. (1986) Biochem. Int. 13, 467-477). We have used electron spin resonance (ESR) spin labels specific for cell-surface carbohydrates, skeletal membrane proteins, or bilayer lipids to find: (1) simultaneous reaction of the protein-specific spin label, MAL-6, which binds to skeletal protein SH residues, and 10 microM hemin suggested that hemin decreased skeletal protein-protein interactions; (2) 10 microM hemin markedly decreased (greater than 60%, P less than 0.001) the rotational motion of spin-labeled erythrocyte membrane cell-surface sialic acid residues, 70% of which are located on the major transmembrane sialoglycoprotein, glycophorin A; and (3) 10 microM hemin caused a small, but significant (P less than 0.02), decrease in the motion of a lipid bilayer specific spin label (5-NS) in the erythrocyte membrane. Since glycophorin A is reportedly linked to the erythrocyte membrane skeletal protein network by band 4.1, it is conceivable that hemin-induced disruption of skeletal protein interactions, particularly those of band 4.1, could subsequently lead to the alterations in the motion of cell-surface sialic acid presented in this report.