α-Glucosidase inhibitor from Buthus martensi Karsch.

A bioassay-guided fractionation of an ethanol extract of Buthus martensi Karsch led to the isolation of a potent α-glucosidase inhibitor (compound S). The structure was elucidated as a novel β-carboline glucoalkaloid, harmanyl β-d-glucopyranoside, on the basis of spectral data, including (1)H NMR, (13)C NMR, (1)H-(1)H COSY, NOESY, and HMBC. Compound S showed potent inhibitory activity against α-glucosidase, with an IC(50) value of 24 μM. A Lineweaver-Burk plot indicated that its inhibition of α-glucosidase was uncompetitive, with a Ki value of 16.1 μM.