β-Secretase inhibition by -methylisoflavones from .

The methanol extract of suspension cultures were subjected to column chromatography to identify potential inhibitors of β-secretase, which is a major factor in Alzheimer's disease development. Two new -methylisoflavones boeravinone T () and U () were isolated with three knowns boeravinone B (), J () and X (). The half-maximal inhibitory concentration (IC) values of compounds - were 18.29, 8.57, 7.87, 12.02 and 5.30 μM, respectively. The most potent , non-competitively inhibited β-secretase [inhibition constant (K) = 3.79 μM]. Compounds - did not inhibit other proteases such as chymotrypsin, trypsin and elastase at concentrations up to 1 mM, indicating that they were relatively specific inhibitors of β-secretase. A free hydroxyl group at C-3 position of the -methylisoflavone skeleton appeared to be responsible for the stronger inhibitory activity against β-secretase.