The chemistry of curcumin: from extraction to therapeutic agent

Abstract

Curcumin, a pigment from turmeric, is one of the very few promising natural products that has been extensively investigated by researchers from both the biological and chemical point of view. While there are several reviews on the biological and pharmacological effects of curcumin, chemistry reviews are comparatively scarcer. In this article, an overview of different aspects of the unique chemistry research on curcumin will be discussed. These include methods for the extraction from turmeric, laboratory synthesis methods, chemical and photochemical degradation and the chemistry behind its metabolism. Additionally other chemical reactions that have biological relevance like nucleophilic addition reactions, and metal chelation will be discussed. Recent advances in the preparation of new curcumin nanoconjugates with metal and metal oxide nanoparticles will also be mentioned. Directions for future investigations to be undertaken in the chemistry of curcumin have also been suggested.

Scheme 1

Synthesis of curcumin by the general method proposed by Pabon [29].

Scheme 2

Keto-enol tautomerism, Prototropic equilibria and degradation products of curcumin.

Scheme 3

Possible sites of attack of free radical oxidants with curcumin and stabilization of phenoxyl intermediate and its regeneration by ascorbic acid.

Scheme 4

Michael addition products of curcumin with protein thiols and selenols where, X = S or Se.

Figure 1

(a) Structure of 2:1 curcumin:metal complex; (b) Mixed ligand curcumin:metal complex.

Figure 2

Curcumin-bound mesoporous silicon nanoparticles.

Figure 3

Gold nanoparticles capping by curcumin molecules.

Figure 4

Polymer stabilized curcumin functionalized iron oxide magnetic nanoparticles.