Silybin B and silybin A are potent inhibitors of both raloxifene 4'- and 6-glucuronidation in all enzyme systems; they show strong effects on cell growth inhibition and apoptosis induction in human chronic myeloid leukemia K562 cells. Silybin B exhibits 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity.