Kurarinone, a flavanone from Sophora flavescens roots, is a potent activator of the large-conductance calcium-activated potassium channel (BKCa channel). Kurarinone exhibits strong preference to potentiate the homomeric BKCa channel composed only of the α subunits. Kurarinone reduces acetylcholine induced contraction of rat urinary bladder strips and decreased the voiding frequency in a rat OAB model. Kurarinone exhibits cytotoxic and antiinflamatory activity. Kurarinone sensitizes TRAIL-induced tumor cell apoptosis via suppression of NF-KB-dependent cFLIP expression.