Advances in β-Diketocyclisation of Curcumin Derivatives and their Antitumor Activity.

Curcumin, derived from the popular spice turmeric, is a pharmacologically active polyphenol. Curcumin's therapeutic activity has been extensively studied in recent decades, with reports implicating curcumin in many biological activities, particularly, its significant anticancer activity. However, its potential as an oral administration product is hampered by poor bioavailability, which is associated with a variety of factors, including low water solubility, poor intestinal permeability, instability, and degradation at alkaline pH. To improve its bioavailability, modifying β-diketone curcumin with heterocycles, such as pyrazole, isoxazole and triazole is a powerful strategy. Derivatives are synthesized while maintaining the basic skeleton of curcumin. The β-diketone cyclized curcumin derivatives are regulators of multiple molecular targets, which play vital roles in a variety of cellular pathways. In some literatures, structurally modified curcumin derivatives have been compared with curcumin, and the former has enhanced biological activity, improved water solubility and stability. Therefore, the scope of this review is to report the most recently synthesized heterocyclic derivatives and to classify them according to their chemical structures. Several of the most important and effective compounds are reviewed by introducing different active groups into the β-diketone position to achieve better therapeutic efficacy and bioavailability.