Hydroxy-methyl-anthraquinones and their methyl ethers occur widely, either in the free state or as glucosides, in the leaves, bark and roots of various plants, forming natural drugs and coloring matters. Six natural trihydroxy-methyl-anthraquinones have been reported in the literature, the most important being emodin, found in Cascara sagrada, Franzgula, rhubarb and other plants. The probable structures which have been suggested for a few of these ...
