Anthraquinone
Anthraquinones are a class of compounds which are derivatives of anthracene and quinones. They are compounds such as aloe emodin and chrysophanol, and are found in aloe vera, buckthorn, and other plants. Anthraquinones, when ingested, remain in the intestine and cause peristalsis by irritating the intestinal wall. They are primarily used as laxatives.
References
Leung, Albert Y. 1980. Encyclopedia of Common Natural Ingredient used in Food, Drugs and Cosmetics. John Wiley and Sons, N Y. 409 pp.
Weiner, Michael and A. Janet Weiner. 1980. Weiner's Herbal The Guide to Herb Medicine. Stein and Day, New York. 224 pp.