Inhibitory Compounds of .ALPHA.-Glucosidase Activity from Arctium lappa L.

Methanol extract from Arctium lappa L. showed an inhibitory activity of α-glucosidase. The methanol extract was re-extracted with ethyl acetate and water. The ethyl acetate extract showed inhibitory activity. The inhibitory compound was isolated from the ethyl acetate extract and identified as sitosterol-β -D-glucopyranoside (1) by EI-MS, FAB-MS, IR, 1H and 13C NMR spectroscopy. Compound 1 inhibited 97.3% of α-glucosidase activity at a concentration of 200.0 μ mol/mL, and the ID50 (50% inhibition dose) value was 30 μ mol/mL. In addition, the inhibitory compounds from the ethyl acetate extract were also identified as methyl palmitate (2), methyl linoleate (3) and methyl linoleneate (4) by GC-MS analysis. Compound 2-4 inhibited 73.4%, 66.5% and 68.5% of α-glucosidase activity at a concentration of 200 μ mol/mL, and the ID50 values were 52.8, 47.5 and 46.7 μ mol/mL. To research the structure-activity relationship, methyl steareate (5), methyl oleate (6), palmitic acid (7), linoleic acid (8), linolenic acid (9), stearic acid (10) and oleic acid (11) were also assayed.