Strophanthidin

Strophanthidin is a cardenolide that has been found in A. schimperi and has diverse biological activities.^1,2,3,4 It is an inhibitor of N-acetyltransferase (IC₅₀ = ~1.2 µM).¹ Strophanthidin (1 µM) reduces maximal Na⁺/K⁺-ATPase pump activity and cell attachment and increases cell death in MDCK-C7 cells.² It decreases the levels of steroid receptor coactivator 3 (SRC-3) in MCF-7 breast cancer cells when used at a concentration of 500 nM.³ Strophanthidin (50 µM) increases calcium efflux and sarcoplasmic reticulum calcium levels in a voltage-clamp assay using isolated and perfused guinea pig hearts.⁴

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1. González-García, C., Ceña, V., and Klein, D.C. Characterization of the α+-like Na⁺,K⁺-ATPase which mediates ouabain inhibition of adrenergic induction of N-acetyltransferase (EC 2.3.1.87) activity: Studies with isolated pinealocytes. Mol. Pharmacol. 32(6), 792-797 (1987).

2. Akimova, O.A., Bagrov, A.Y., Lopina, O.D., et al. Cardiotonic steroids differentially affect intracellular Na⁺ and [Na⁺]i/[K⁺]i-independent signaling in C7-MDCK cells. The Journal of Biological Chemisty 280(1), 832-839 (2005).

3. Wang, Y., Lonard, D.M., Yu, Y., et al. Bufalin is a potent small-molecule inhibitor of the steroid receptor coactivators SRC-3 and SRC-1. Cancer Res. 74(5), 1506-1517 (2014).

4. Bennett, D.L., O'Neill, S.C., and Eisner, D.A. Strophanthidin-induced gain of Ca²⁺ occurs during diastole and not systole in guinea-pig ventricular myocytes. Pflugers Arch. 437(5), 731-736 (1999).