Occurrence of orally administered mulberry 1-deoxynojirimycin in rat plasma

1-deoxynojirimycin (DNJ), a potent glucosidase inhibitor, is a characteristic constituent of the mulberry leaf. Dietary mulberry DNJ may be beneficial for the suppression of abnormally high blood glucose levels, thereby preventing diabetes mellitus. Although there is considerable interest in the effects of mulberry DNJ, the intestinal absorption and pharmacokinetic profile of orally administered mulberry DNJ have never been characterized. In this study, we developed a method for determining the level of plasma DNJ by hydrophilic interaction chromatography coupled to a mass spectrometric detector (HILIC-MS) to investigate the absorption and metabolism of orally administered mulberry DNJ in rats. DNJ was separated from plasma extract on a TSK gel Amide-80 column, a representative column for HILIC. At postcolumn, DNJ was concurrently detected and identified by MS. The plasma DNJ concentration in fasted rats was below the detection limit [<1 microg (6 nmol)/mL]; however, the concentration reached a maximum [15 microg (92 nmol)/mL] 30 min after the administration of mulberry DNJ (110 mg/kg of body weight), and the DNJ concentration decreased rapidly thereafter. When the rats received different amounts of mulberry DNJ (1.1, 11, and 110 mg/kg of body weight), dose-dependent incorporation of DNJ into the plasma was confirmed. We did not detect any DNJ metabolites in the plasma. These findings indicate that orally administered mulberry DNJ is absorbed as an intact form from the alimentary tract and then is quickly excreted from the body. The developed HILIC-MS method could be applied in determining levels of DNJ in urine and tissues, and therefore, the method would be a powerful tool for studying the metabolic fate of mulberry DNJ as well as its bioavailability.