Anthraquinones

These are glycosides which are yellow, and were often used in the past to produce dyes. They act to stimulate muscular contractions of the large intestine and so have a laxative effect.

Herbs such as dock, cascara, senna and aloes contain anthraquinones, which taken alone can cause griping in the bowel. For this reason they are best combined with carminative (flatulence-treating) herbs such as ginger or fennel which prevent this from happening.

Such laxative herbs are best used for short term treatment of constipation while the underlying causes are dealt with, for longer use can reduce normal bowel reflexes and cause habituation.