Curcumin is the principal curcuminoid of the popular Indian curry spice turmeric, the other two curcuminoids being desmethoxycurcumin and bis-desmethoxycurcumin. 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. It is also hepatoprotective.

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.

Chemistry

Curcumin incorporates several functional groups. The aromatic ring systems, which are polyphenols are connected by two α,β-unsaturated carbonyl groups. The two carbonyl groups form a diketone. The diketone form stable enols or are easily deprotonated and form enolates, while the α,β-unsaturated carbonyl is a good Michael acceptor and undergoes nucleophilic addition.

Potential medical uses

Curcumin is known for its antitumor, antioxidant, antiarthritic, anti-amyloid, anti-ischemic and anti-inflammatory properties. Anti-inflammatory properties may be due to inhibition of eicosanoid biosynthesis. In addition it may be effective in treating malaria, prevention of cervical cancer, and may interefere with the replication of the HIV virus. In HIV, it appears to act by interfering with P300/CREB-binding protein (CBP). A 2008 study at Michigan State University showed that low concentrations of curcumin interfere with Herpes simplex virus-1 (HSV-1) replication. The same study showed that curcumin inhibited the recruitment of RNA polymerase II to viral DNA, thus inhibiting the transcription of the viral DNA. This effect was shown to be independent of effect on histone acetyltransferase activities of p300/CBP. A previous (1999) study performed at University of Cincinnati indicated that curcumin is significantly associated with protection from infection by HSV-2 in animal models of intravaginal infections.

Curcumin acts as a free radical scavenger and antioxidant, inhibiting lipid peroxidation and oxidative DNA damage. Curcuminoids induce glutathione S-transferase and are potent inhibitors of cytochrome P450.

For the last few decades, extensive work has been done to establish the biological activities and pharmacological actions of curcumin. Its anticancer effects stem from its ability to induce apoptosis in cancer cells without cytotoxic effects on healthy cells. Curcumin can interfere with the activity of the transcription factor NF-κB, which has been linked to a number of inflammatory diseases such as cancer. Indeed, when 0.2% curcumin is added to diet given to rats or mice previously given a carcinogen, it significantly reduces colon carcinogenesis (Data from sixteen scientific articles reported in the Chemoprevention Database). A 2007 report indicates that curcumin may suppress MDM2, an oncogene involved in mechanisms of malignant tumor formation.