The Collaborative International Dictionary of English v.0.48:

Rutin \Ru"tin\ (r[udd]"t[i^]n), n. (Chem.)
   A glucoside resembling, but distinct from, quercitrin. Rutin
   is found in the leaves of the rue (Ruta graveolens) and
   other plants, and obtained as a bitter yellow crystalline
   substance which yields quercitin on decomposition.
   [1913 Webster]