I looked up some info on it at Wikipedia...
"Curcumin is the principal curcuminoid of the Indian curry spice turmeric, the other two curcuminoids being demethoxycurcumin and Bis-demethoxycurcumin.The curcuminoids are polyphenols and are responsible for the yellow color of turmeric. Curcumin can exist in at least two tautomeric forms, keto and enol. The enol form is more energetically stable in the solid phase and in solution.[1] It is also hepatoprotective.[2]
Curcumin can be used for boron quantification in the so-called curcumin method. It reacts with boric acid forming a red colored compound, known as rosocyanine.
Since curcumin is brightly colored, it may be used as a food coloring. As a food additive, its E number is E100."
There's a ton more info on the page at Wikipedia and links to more resources
Curcumin - Wikipedia, the free encyclopedia