The Collaborative International Dictionary of English v.0.48:

Lilacin \Lil"a*cin\ (l[i^]l"[.a]*s[i^]n), n. (Chem.)
   See Syringin.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Syringin \Sy*rin"gin\, n. (Chem.)
   A glucoside found in the bark of the lilac (Syringa) and
   extracted as a white crystalline substance; -- formerly
   called also lilacin.
   [1913 Webster]