The Collaborative International Dictionary of English v.0.48:

Helleborin \Hel*leb"o*rin\ (? or ?), n. (Chem.)
   A poisonous glucoside found in several species of hellebore,
   and extracted as a white crystalline substance with a sharp
   tingling taste. It possesses the essential virtues of the
   plant; -- called also elleborin.
   [1913 Webster]