Indian cuisine is well known for its incredible range of flavors and ingredients, a clear manifestation of the country’s rich cultural and geographic diversity. Turmeric, the bright orange-yellow spice commonly found in curry dishes and many other foods and beverages, is derived from the subterranean stems (rhizomes) of Curcuma longa, a perennial plant of the ginger family that is indigenous to the Indian subcontinent. It has also been used in a variety of herbal remedies in traditional Indian medicine and as a natural pigment in the cosmetic, textile, and food industries. Significantly, the color and biological activity of turmeric are usually ascribed to the presence (2-5%) of curcumin, a relatively simple aromatic compound in which two substituted phenols are connected by adjacent a,b‑unsaturated carbonyl groups.
It is also worth noting that India is the largest producer, consumer, and exporter of turmeric in the world, with the global market for the so-called “golden spice” continuing to grow at an accelerated pace. Perhaps even more impressive is the fact that the annual production of turmeric in India in 2012-2013 almost reached a whopping million tonnes, an amount that is comparable to its combined output of basic metals such lead and zinc.
The stamp featured in this note was issued in India on 30 January 2014 to commemorate the International Year of Crystallography. It shows a diamond in the foreground and the molecular structure of the enol form of curcumin in the background. Interestingly, the enol form of the compound, stabilized by an internal hydrogen bond, is the predominant tautomer observed in the solid state and in solutions with solvents of low polarity.
The potential medicinal applications of curcumin, including the treatment of stomach ulcers, Alzheimer’s disease, and breast, colon, and prostate cancers, are attracting a lot of attention in recent years, particularly due to its anti-inflammatory and antioxidant properties. While preliminary tests of biological activity with cell cultures and animal models are encouraging, there is a dire need for the implementation of reliable clinical trials to assess the validity of such claims.
For a recent review on the structural and biological chemistry of curcumin, see: G. Rimbach et al. Angew. Chem. Int. Ed. 2012, 51, 5308-5332.