The Collaborative International Dictionary of English v.0.48:

Inulin \In"u*lin\, n. [From NL. Inula Helenium, the
   elecampane: cf. F. inuline.] (Chem.)
   A substance of very wide occurrence. It is found dissolved in
   the sap of the roots and rhizomes of many composite and other
   plants, as Inula, Helianthus, Campanula, etc., and is
   extracted by solution as a tasteless, white, semicrystalline
   substance, resembling starch, with which it is isomeric,
   having fructose units in place of most of the glucose units.
   It is intermediate in nature between starch and sugar, and
   replaces starch as the reserve food in Compositae. Called
   also dahlin, helenin, alantin, alant starch, etc.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Helenin \Hel"e*nin\, n. (Chem.)
   A neutral organic substance found in the root of the
   elecampane (Inula helenium), and extracted as a white
   crystalline or oily material, with a slightly bitter taste.
   [1913 Webster]