Digitalis contains 0.2 to 0.45% mixture of both primary and secondary cardiac glycosides (cardenolides).

Purpurea glycosides A and B and glucogitaloxin are primary glycosides.

Digitalis also contains several other glycosides such as odoroside H, gitaloxin,verodoxin, and glucoverodoxin.

The primary glycosides are less absorbed and iess stable than secondary glycosides such as digitoxin, gitoxin and gitaloxin.

The products of hydrolysis of purpurea glycoside A and purpurea glycoside B are the chief active constituents of the drug.