Abstract:

A method of pre-column derivatization with FMOC-Cl followed by RP-HPLC with UV detection was established for the determination of 1-deoxynojirimycin (DNJ) content in different varieties and sites of mulberry leaves. DNJ was extracted from mulberry leaves using 0.05 mol/L HCl and derivatized using FMOC-Cl in borate buffer solution (pH 8.50) prior to RP-HPLC detection. The chromatographic separation was achieved on a Waters X-Terra column using a mobile phase consisting of a mixture of acetonitrile and 0.1% aqueous acetic acid (55:45, V/V). There was a high positive correlation between the peak area and concentration of DNJ-FMOC with a correlation coefficient of 0.9852. The DNJ content was varied in different varieties of mulberry leaves. Among 15 varieties of mulberry, Qingyang Qing mulberry leaves contained the highest DNJ (0.1486%), while Pi mulberry leaves the lowest (0.04291%). Also, mulberry leaves in different sites contained different DNJ contents. It decreased from the top to bottom gradually, indicating DNJ content is reduced with the maturation of mulberry leaves.

Key words: mulberry leaves, 1-deoxynojirimycin (DNJ), RP-HPLC, derivatization