1,3-Dihydroxyanthraquinone, also called purpuroxanthin or xanthopurpurin, is an organic compound with formula that occurs in the plant Rubia cordifolia (Indian madder).[1] It is one of ten dihydroxyanthraquinone isomers. Its molecular structure can be viewed as being derived from anthraquinone by replacement of two hydrogen atoms (H) by hydroxyl groups (-OH).
Xanthopurpurin occurs in small amounts (as a glycoside) in the root of the common madder plant, Rubia tinctorum, together with alizarin, purpurin and other anthraquinone derivatives.[2]
Xanthopurpurin is insoluble in hexane but soluble in chloroform. It can be obtained from solutions in the latter as reddish crystals that melt at 270–273 °C.[1]
Like many dihydroxy- and trihydroxyanthraquinones, it has a purgative action, although only 1/6 as effective as 1,2,7-trihidroxyanthraquinone (anthrapurpurin).[3]