The Collaborative International Dictionary of English v.0.48:

Parillin \Pa*ril"lin\, n. [Shortened fr. sarsaparillin.] (Chem.)
   A glucoside resembling saponin, found in the root of
   sarsaparilla, smilax, etc., and extracted as a bitter white
   crystalline substance; -- called also smilacin,
   sarsaparilla saponin, and sarsaparillin.
   [1913 Webster]