Inhibiting effect of cytotoxic bromine-containing compounds from sponges (Aplysinidae) on Na-K-ATPase activity

—The bromine-containing compounds from sponges of the Aplysinidae family inhibit, in vitro, the Na⁺-K⁺-ATPase activity of the rat brain microsomal fraction. The extent of inhibition is dependent on concentration and chemical structure of the compounds. The substances containing the dienone fragment, such as 3,5-dibromo-1-hydroxy-4-oxo-2,5-cyclohexadien-1-acetamide (IV), 3,5-dibromo-1-acetoxy-4-oxo-2,5-cyclohexadien-1-acetonitrile (V) and 3,5-dibromo-1-hydroxy-4-oxo-2,5-cyclohexadien-1-ethylacetate (VI), are powerful inhibitors of Na⁺-K⁺-ATPase.