The Collaborative International Dictionary of English v.0.48:

Quercitrin \Quer"cit*rin\, n. [Cf. F. quercitrin. See
   Quercitron.] (Chem.)
   A glucoside extracted from the bark of the oak (Quercus) as
   a bitter citron-yellow crystalline substance, used as a
   pigment and called quercitron.
   [1913 Webster]