The Collaborative International Dictionary of English v.0.48:

Curcumin \Cur"cu*min\ (-m?n), n. (Chem.)
   The coloring principle of turmeric, or curcuma root,
   extracted as an orange yellow crystalline substance,
   C14H14O4, with a green fluorescence.
   [1913 Webster]

   Note: It possesses acid properties and with alkalies forms
         brownish salts. This change in color from yellow to
         brown is the characteristic reaction of tumeric paper.
         See Turmeric paper, under Turmeric.
         [1913 Webster]