The interaction of several biogenic amines and Compound A (2-(4-acetoxyphenyl)-2-chloro- N-methyl-ethylammonium chloride), an analogue of the active substance in a HPLC fraction isolated from the shrub, Salsola tuberculatiformis Botsch., with cytochrome P450c11 was investigated. Noradrenaline, octopamine and Compound A inhibited the type I DOC induced difference spectrum of P450c11 and elicited a type II difference spectrum when added alone. The Ks-values for noradrenaline, octopamine, and Compound A were 0.8 mM, 0.16 mM and 0.36 mM, respectively. Dopamine, adrenaline and synephrine did not interact with, or inhibit, P450c11. Further investigation of Compound A indicated that it is a mixed inhibitor of sheep P450c11 with a stronger competitive (Kic = 106-110 µM) than uncompetitive (Kiu = 667-737 µM) element.
