A diterpene tanshinone with diverse biological activities; inhibits RHL-2H3 mast cell degranulation (IC50 = 14.3 μM); prevents HuR binding to RNA in a cell-free assay (Ki = 3.74 nM); inhibits the production of TNF mRNA and protein in MCF-7 cells; reduces the viability of MCF-7, MDA-MB-231, and SK-BR-3 breast cancer cells (IC50s = 0.84, 0.92, and 1.2 μM, respectively); reduces collagen-induced aggregation of washed rabbit platelets (IC50 = 8.7 μM); reduces HL-60 leukemia tumor growth in a mouse xenograft model by 68% at 25 mg/kg; increases latency to step-through in a passive avoidance test in mice with scopolamine-induced learning and memory impairment at 2-4 mg/kg, p.o.