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Curcumin is a specially gifted molecule provided by Mother-Nature to protect humans from chronic health problems. Looking at the simple chemical structure of curcumin, it is natural to presume that chemistry of curcumin is also very simple, however with increasing scientific understanding it appears to be more complex, unique and difficult to comprehend. It is a symmetric molecule abundant in turmeric with relatively high stability in natural form. It has an intense yellow color, that changes to deep red in basic pH solution. In simple aqueous and aqueous-organic solutions, it is susceptible to fast degradation, which increases as the basicity of the solutions increases, and also on exposure to sunlight. The metabolic products of curcumin are different from the degradation products, where O-conjugation and reduction are the important processes initiated through the enzymatic reactions. Interestingly unlike the degradation products, the metabolic products are much more difficult to synthesize in the laboratory. The presence of α,β-unsaturated structure makes curcumin participate in nucleophilic addition reactions with protein thiols and selenols, that play important role in modulating cellular oxidative stress. It is still not clear if these processes are reversible under physiological conditions. Future chemical research on these aspects is necessary to elucidate the kinetics and mechanism of all these reactions, so that a meaningful conclusion can be made on the role of these different processes in curcumin biology.

Recently there is a surge of activity on preparation and characterization of curcumin-metal complexes due to the strong affinity of β-diketo moiety as an efficient metal chelator. Although it is confirmed that curcumin reduces metal toxicity in living systems through complexation, the actual role of these metal complexes in curcumin biology appears to be complex and unclear. Detailed research is warranted on structure-activity evaluation of the curcumin-metal-complexes in solution.

Problems associated with curcumin bioavailability could be overcome to a great extent through formulations with natural biopolymers, which find practical application as nutritional products. Recent research is now focused on developing conjugates of curcumin with metal and metal oxide nanoparticles and some of these formulations have promising potential in nanomedicine with additional effects of inducing targeted hyperthermia in cancer cells. They are also attracting interest as diagnostic tools for Alzheimer’s disease and also as MRI contrast agents. Overall it appears that even though there has been significant progress in the chemistry of curcumin, a great deal can still be expected from chemists to exploit this divine natural product as a therapeutic remedy for many chronic diseases.