Senna contains many chemicals called sennosides. It works by interacting with the bacteria in the digestive tract, resulting in intestinal contractions. These contractions are caused by the anthraquinone that is contained in senna. These dimeric glycosides anthraquinone derivatives are known as Senna glycosides or sennosides. They are named after their abundant occurrence in these plants of the genus Senna.

The main forms of these glycosides are often referred to by: A, B, C & D. Sennosides irritate the lining of the bowel, which causes a laxative effect. Senna is an FDA-approved nonprescription laxative. Senna Extract has diuretic properties which makes it good for flushing excess water and other fluids in the body. Like Epsom salt uses for slimming, it will help you lose excess water weight and make you lose weight fast.

The glycoside compound works as laxative by smoothening the muscles as digested food moves through the intestines. This helps to enhance the stool volume and move it out of the colon. The process is caused by the chain of fatty acids that promote digestion, fermentation and successfully converting the glycosides into a purgative agent.

It is used to treat constipation and also to clear the bowel before diagnostic test such as colonoscopy. It is also used for irritable bowel syndrome (IBS), hemorrhoids, and weight loss. It was considered a "cleansing" herb because of its cathartic effect.

In addition, the leaves were sometimes made into a paste, and applied to various skin diseases; acne and ringworm were both treated in this way.