The Collaborative International Dictionary of English v.0.48:

bioflavinoid \bi`o*flav"in*oid\ n.
   a vitamin that maintains the resistance of cell and capillary
   walls to permeation; -- called also vitamin P and citrin.
   [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

citrin \citrin\ n.
   a vitamin that maintains the resistance of cell and capillary
   walls to permeation; -- called also vitamin P.

   Syn: vitamin P, bioflavinoid.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

citrin
    n 1: a vitamin that maintains the resistance of cell and
         capillary walls to permeation [syn: vitamin P,
         bioflavinoid, citrin]