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Curcumin: Recent insights, novel developments, new challenges

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  2. Curcumin: Recent insights, novel developments, new challenges

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The curry spice turmeric and its major constituent curcumin have been ingested as part of the human diet for centuries and long been suspected to impart beneficial effects on human health. Curcumin was first isolated in the early 19th century, obtained in crystalline form in the 1870s, and its structure was solved in the early twentieth century. Ever since then this molecule has stimulated the curiosity of scores of biomedical scientists. In recent years the number of biomedical publications on curcumin and its progenitor plant material has been growing at a considerable pace, as reflected by a web of science search of “curcumin” generating over 900 citations for 2012 alone. The aim of this special issue is to present a “snapshot” of state-of-the-art curcumin research in 2013. It comprises five reviews and ten papers with original results. What are the insights imparted in these contributions?

“… that there is plenty of “research life” left in the old yellow molecule…”

Paper 1 reviews the astonishing multitude of biochemical mechanisms which turmeric and curcumin can engage, and both papers 1 and 2 focus on the non-curcuminoid constituents which may contribute substantially to the anticarcinogenic and anti-inflammatory effects of turmeric. The third paper presents a meticulously conducted metabolism and cell permeability study of curcumin in an in vitro model system of human intestinal cells which helps explain its poor bioavailability in vivo. Four of the contributions included here are devoted to effects of curcuminoids on disease states linked to diabetes, three to curcuminoids and arterial/vascular pathology, and three to curcuminoids in cancer/carcinogenesis. Paper 4 overviews antidiabetic effects of curcuminoids. Curcumin may ameliorate retinal diseases including those associated with diabetes (paper 5). It also lowered glucose levels in diabetic patients (paper 6). Curcumin seems capable of attenuating testicular damage in diabetic rats (paper 7). Different curcuminoid species elicit distinctly differential activities on arterial and vascular diseases (papers 8–10). Novel mechanistic aspects germane to curcumin and carcinogenesis are reviewed in papers 11 and 12, the former describing evidence suggesting that curcumin causes epigenetic alterations in neoplastic cells, i.e. changes in DNA methylation, histone acetylation and/or miRNA expression, the latter exploring the intriguing role which “cancer stem-like cells” may play in the anticarcinogenic properties of curcumin. Another potential benefit associated with exposure to curcumin is its potential to ameliorate the resistance of colon cancer cells against certain cytotoxic anticancer drugs (paper 13). Curcuminoids may improve chronic kidney disease caused by oxidative stress (paper 14). Finally, a nanoparticle formulation of curcumin was shown to protect rats against acrolein-induced neurotoxicity (paper 15). Curcumin bioavailability has long been considered a potential confounder of its pharmacological efficacy, and formulations like curcumin nanoparticles or curcumin complexes with phosphatidylcholine have been developed to improve systemic availability. Two papers in this issue (papers 4 and 15) describe the use of such formulations. New insights and developments tend to be accompanied by new challenges. Would improved bioavailability of the novel formulations engender safety issues? Thus far such problems have not been reported, but we need to be vigilant. Which would be the most suitable formulation of curcumin to advance to large definitive clinical trials? How relevant are insights obtained with novel formulations for the dietary consumption of curcuminoids? This special issue on curcumin certainly suggests that there is plenty of “research life” left in the old yellow molecule.

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Andy Gescher

Dept of Cancer Studies and Molecular Medicine

University of Leicester

UK