Anthraquinones

Sources: Yellow Dock, Cascara Sagrada, Senna, Aloe, etc. Stimulant laxatives, irritant in excess

The anthraquinones (named after anthracene, a three-ring hydrocarbon from coal tar) contain three fused rings, with the quinone in the middle. They are distinctively reddish-orange compounds, and frequently occur in the form of water-soluble glycosides. These familiar molecules have the undisputed physiological effect of stimulating peristalsis in the bowels. Anthraquinones are found in classic 'laxative' herbs such as Senna (the sennosides -anthraquinone dimers), Cascara (the cascarosides), Aloe (e.g. aloe-emodin) and the milder Yellow Dock (emodin, chrysophanol and rhein). The anthraquinone-containing laxative herbs should be used on a reasonably limited basis, as these compounds can be irritants to sensitive persons and can cause (perhaps superficial) damage to the mucosal lining of the colon. Quinones as isolated compounds have been associated with the development of cancer, because they are reactive and can bind to the DNA. This is not known to happen with he commonly-used herbs, although avoiding overdoses of such plants makes cautious sense. (-Ganora)

Primary Qualities in Phytotherapy and Traditional Medicines: a Statistical Study,  Ramezany et.al; Journal of Drug Delivery & Therapeutics; 2013, 3(3), 1-6 -  identified anthraquinones as "wettest" in terms of primary qualities, along with iridoids.

Anthraquinones can cause discoloration of the urine interfering with urinalysis