In vivo metabolism of Talosin A, new isoflavonol glycoside from Kitasatospora kifunensis, in rats

The isoflavonol glycoside Talosin A, genistein (GT)-7-alpha-L-6-deoxy talopyranose (GT-Tal), was first isolated from the culture broth of Kitasatospora kifunensis MJM341. The aim of the present study was to evaluate the oral absorption and metabolism of the newly isolated isoflavonol glycoside, GT-Tal compared to genistin (GT-7-O-beta-D-glucopyranoside; GT-Glu). Free GT-Glu and GT-Tal could not be detected prior to enzymatic hydrolysis of the corresponding conjugates in rat plasma. Following oral administration of GT-Tal (15 min), GT-Tal was rapidly absorbed through the gastrointestinal tract and metabolized into GT-Tal conjugates with a mean Cmax of 2.74 microg/mL. GT-Tal was further metabolized to its aglycone, free GT and conjugated GT. After oral administration, GT-Glu was absorbed after being convereted to its aglycone and then further metabolized into its conjugate metabolites (free GT with a mean Cmax of 0.24 mg/mL at 1.25 h; conjugated GT with a mean Cmax of 1.31 mg/mL at 2.00 h). Significant differences in absorption and metabolism of GT-Tal and GT-Glu were observed. GT-Tal was metabolized into its corresponding conjugates or underwent deglycosylation to form GT, whereas GT-Glu was metabolized into its aglycone, GT.

Simultaneous Determination of Various Macrolides by Liquid Chromatography/Mass Spectrometry

Macrolides are frequently used in veterinary medicine as therapeutic and preventive agents for various diseases. It is difficult to determine macrolides simultaneously with conventional methods due to their similar structures. A simultaneous analysis for erythromycin, roxithromycin, tiamulin and tylosin with LC/MS has been developed. Separation was performed on C18 reversed phase column. Mobile phase was gradiently flowed with 10 mM ammonium acetate and methanol. The mass spectrometer was run in the positive mode and selective ion monitoring mode. The molecular ions were [M+H]+ form at m/z 837.5 for erythromycin, at m/z 859.5 for roxithromycin, at m/z 494.2 for tiamulin and at m/z 916.7 for tylosin. Limits of detection were in the range from 0.001 to 0.01 microgram/g lower than their MRLs.