The Collaborative International Dictionary of English v.0.48:

Juglandin \Jug"lan*din\, n. [L. juglans, -andis, a walnut: cf.
   F. juglandine.] (Chem.)
   An extractive matter contained in the juice of the green
   shucks of the walnut (Juglans regia). It is used
   medicinally as an alterative, and also as a black hair dye.
   [1913 Webster]