The active constituents in both senna leaf and pod are dianthrone glycosides, principally sennoside A and B. They are di-O-glucosides of rhein dianthrone (Sennidin A and B) and liberate upon hydrolysis two molecules of glucose and the aglycones sennidin A and B. Minor constituents include sennosides C and D, which are glycosides of heterodianthrones involving rhein and aloe-emodin, palmidin etc. Two naphthalane glycosides have also been isolated from senna.

Senna leaf suitable for medicinal use contains NLT 2.5% dianthrone glycosides, calculated in terms of sennoside B. Sennoside content of Indian senna is 1.2% to 2.5%, while that of Alexandrian senna is 2.5% to 4.5%. Apart from its use in several herbal teas, senna preparations in the form of powdered leaf, powdered pods or extracts are typically standardized to a given sennoside content. Senna glycosides in the form of stabler calcium sennosides are also available.

The chief constituent of Ispaghula is the mucilage contained in the epidermal cells. Two fractions, one soluble in cold water and the other in hot water, have been separated from it.