Chrysophanic acid

from The Collaborative International Dictionary of English v.0.48

Rumicin \Ru"mi*cin\, n. (Chem.)
   A yellow crystalline substance found in the root of yellow
   dock ({Rumex crispus}) and identical with {chrysophanic
   acid}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Chrysophanic \Chrys`o*phan"ic\, a.
   Pertaining to, or derived from, or resembling, chrysophane.
   [1913 Webster]

   {Chrysophanic acid} (Chem.), a yellow crystalline substance
      extracted from rhubarb, yellow dock, sienna, chrysarobin,
      etc., and shown to be a derivative of an anthracene. It is
      used in the treatment of skin diseases; -- called also
      {rhein}, {rheic acid}, {rhubarbarin}, etc.
      [1913 Webster]