Curcumin: A Natural Lead for Potential New Drug Candidates.

Curcumin (1) is a secondary metabolite of turmeric, derived from Curcuma longa L. and was shown to have many biological activities. One of the most interesting properties of curcumin (1) is the antitumour activity allied with the ability to act as a multidrug resistance (MDR) modulator. Several curcumin derivatives have been synthesized with the purpose of discovering more information about the mechanisms of action, to establish structure-activity relationships (SAR), and to overcome pharmacokinetic problems. Over the past few decades, more potent and more stable curcumin derivatives have emerged with potential as drug candidates. Some important SAR studies pointed out that the unstable α,β-unsaturated diketone linker present in curcumin (1) may not be necessary for the antitumour activity; generally, shorter linkers result in more potent compounds than curcumin (1); the type of substituents and their substitution pattern are crucial regarding the biological activities of interest. Overall, the structure of curcumin (1) may represent an important basis for the development of more effective therapeutic agents, particularly in chemotherapy, as reflected by ongoing clinical trials. This article aims to review the synthesis and biological activities of curcumin (1) and derivatives, highlighting the MDR modulation properties of curcumin (1), since these effects makes this natural product a promising lead compound for the development of new anticancer drugs.