Anthraquinones and their medical uses by Ray Sahelian, M.D.

Four anthraquinones, physcion, emodin, citreorosein and anthraglycoside B, and two stilbenes, resveratrol, and piceid, are found in the root of Polygonum cuspidatum. Anthraquinone glycosides are poorly absorbed from the gastrointestinal tract but are cleaved by gut bacteria to produce aglycones (such as emodin) that are more readily absorbed and are responsible for the purgative properties of these preparations.

Anthraquinones are moderate to strong inhibitors of tyrosinase. Physcion exhibit has potent tyrosinase inhibition and is comparable to kojic acid. Anthraquinones permeate skin. Physcion can permeate skin more potently than emodin. As naturally occurring tyrosinase inhibitors, anthraquinones from Polygonum cuspidatum may be useful as skin-whitening agents to inhibit tyrosinase for dermal use.