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. Author manuscript; available in PMC: 2009 Jan 1.
Published in final edited form as: Steroids. 2007 Sep 2;73(1):27–40. doi: 10.1016/j.steroids.2007.08.012

Figure 1.

Figure 1

Structures of Δ4-pregnane-3,20-dione (progesterone) and the cardiotonic steroid ouabain. Compounds with an unsaturated five-membered lactone ring are cardenolides and those with an unsaturated six-membered lactone ring are bufadienolides. In the formulae, bonds or atoms or groups above the plane of the ring system are depicted as solid wedges; those below the plane are depicted as open, dashed wedges.