Isolated from sponge Axinella carteri. A potent inhibitor of mitogen-activated protein kinase kinase-1 (MEK-1) (IC₅₀ = 6nM). Blocks the in vivo phosphorylation of the microtubule-binding protein tau at sites that are hyperphosphorylated by glycogen synthase kinase-β (GSK-3β) and CDK5/p35 in Alzheimer’s disease. Inhibitor of DNA damage checkpoint at G2 phase (IC₅₀ = 6 µM), cyclin-dependent kinases CDK1/cyclin B (IC₅₀ = 22 nM), CDK2/cyclin A (IC₅₀= 70 nM), CDK2/cyclin E (IC₅₀= 40 nM), CDK4/cyclin D1 (IC₅₀ = 600 nM), CDK5/p25 (IC₅₀ = 28 nM), GSK-3β (IC₅₀ = 10 nM), and casein kinase 1 (CK1) (IC₅₀ = 35 nM).