15,16-Dihydrotanshinone I

15,16-Dihydrotanshinone I (DHTS) is a diterpene tanshinone that has been found in the roots of S. miltiorrhiza with diverse biological activities.{39842} DHTS inhibits RHL-2H3 mast cell degranulation with an IC50 value of 14.3 ?M and reduces the tyrosine phosphorylation of phospholipase Cy2 (PLCy2) and ERK.{39843} It prevents HuR binding to RNA in a cell-free assay (Ki = 3.74 nM) and inhibits the production of TNF mRNA and protein in MCF-7 cells.{39842} DHTS reduces the viability of MCF-7, MDA-MB-231, and SK-BR-3 breast cancer cells with IC50 values of 0.84, 0.92, and 1.2 ?M, respectively. It also reduces collagen-induced aggregation of washed rabbit platelets (IC50 = 8.7 ?M).{39844} In vivo, DHTS (25 mg/kg per day) reduces tumor growth in an HL-60 leukemia mouse xenograft model by 68% relative to control without decreasing body weight.{39845} In mice with scopolamine-induced learning and memory impairment, DHTS (2-4 mg/kg, p.o.) increases latency to step-through in a passive avoidance test by approximately 3- to 4-fold, and it inhibits acetylcholinesterase in brain homogenate (IC50 = 25 ?M).{39846}