Abstract
Plumbagin, an active principle from Plumbaginaceous plants, produced a triphasic inotropic
response (first positive, second negative, and third positive phases) in guinea-pig
papillary muscle. The inotropic potency of plumbagin at the first positive phase was
pD2 6.40, and the methylation of 5-hydroxy group of plumbagin reduced the potency. The
triphasic pattern of inotropism of plumbagin was unaffected by reserpine or propranolol
treatments. Plumbagin did not produce the positive inotropic effects under anoxic
conditions or in the presence of mitochondrial oxidative phosphorylation inhibitors
such as 2,4-dinitrophenol and dicumarol.
Key words
Plumbaginaceae - plumbagin - cardiac muscle - inotropic activity
