α-Amylase Inhibitory Triterpene from Abrus precatorius Leaves

In the screening experiments for porcine pancreatic a-amylase inhibitors in 18 plants obtained from Indonesia, a potent inhibitory activity was detected in the extract of leaves of Abrus precatorius. The enzyme assay-guided fractionation of the extract led to the isolation of a triterpene ketone, lupenone (1), as a potent alpha-amylase inhibitor, together with 24-methylenecycloartenone (2) and luteolin (3). The mode of inhibition of compound 1 against porcine pancreatic alpha-amylase was a mixed inhibition. This is the first report that describes the potent alpha-amylase inhibitory activity of the low-polar triterpene ketone similar to compound 1. A comparison of the activities of the isolate and related compounds indicated the importance of C-3 ketone and the lupane skeleton in the alpha-amylase inhibitory activity.