Steroid lactone that displays anti-inflammatory, antitumor and antiangiogenic activity. Inhibits endothelial cells (HUVEC) sprouting in vitro (IC50 = 12 nM) and in vivo. Prevents NF-κB activation by inhibiting activation of IKKβ. Also inhibits chymotrypsin-like activity of the 20S proteasome. Purity 98%. MW (observed): 470.6