Economic part in Senna is

The economic part of Senna is both leaf and pods.
Senna is an herb. The leaves and the fruit of the plant are used to make medicine. When cultivated as a medicinal herb, the plants are cut down semi-annually, dried in the sun, stripped, and packed in palm-leaf bags.
Senna contains many chemicals called sennosides. Sennosides irritate the lining of the bowel, which causes a laxative effect.