The Collaborative International Dictionary of English v.0.48:

Lupulin \Lu"pu*lin\, n. [Cf. F. lupulin. See Lupuline.]
   1. (Chem.) A bitter principle extracted from hops.
      [1913 Webster]

   2. The fine yellow resinous powder found upon the strobiles
      or fruit of hops, and containing this bitter principle.
      [Written also lupuline.]
      [1913 Webster]