A 25 year old colonscopy showed pigmentary deposits and microscopy showed pigment laden macrophages. The women in on laxatives for past one year. Which of the following is the cause of it ?

Ref. KDT. Page. 677. Senna is obtained from leaves and pod of certain Cassia sp., while Cascara sagrada is the powdered bark of the buck-thorn tree. These and a number of other plant purgatives contain anthraquinone glycosides, also called emodins. Senna is most popularly used. MOA – They not active as such. Unabsorbed in the small intestine, they are passed to the colon where bacteria liberate the active anthrol form, which either acts locally or is absorbed into circulation—excreted in bile to act on small intestine. The purgative action and uses of anthraquinones are quite similar to diphenylmethanes. Taken at bed time The active principle acts on the myenteric plexus to increase peristalsis and decrease segmentation. They also promote secretion and inhibit salt and water absorption in the colon. ADR: Skin rashes, fixed drug eruption are seen occasionally, Regular use for 4–12 months causes colonic atony and mucosal pigmentation (melanosis).