| Preferred IUPAC name
| Other names
Natural Yellow 3
|3D model (Jmol)||Interactive image|
|E number||E100 (colours)|
|Molar mass||368.39 g·mol−1|
|Appearance||Bright yellow-orange powder|
|Melting point||183 °C (361 °F; 456 K)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|(what is ?)|
Curcumin (//, diferuloylmethane) is a bright yellow chemical produced by some plants. It is the principal curcuminoid of turmeric (Curcuma longa), a member of the ginger family (Zingiberaceae). It is sold as an herbal supplement, cosmetics ingredient, food flavoring and food coloring. As a food additive, its E number is E100.
It was isolated in 1815 when Vogel and Pelletier reported the isolation of a “yellow coloring-matter” from the rhizomes of turmeric and named it curcumin. Although curcumin has been used historically in Ayurvedic medicine, its potential medicinal properties remain unproven and are an area of active investigation.
Chemically, curcumin is a diarylheptanoid, belonging to the group of curcuminoids, which are natural phenols responsible for turmeric's' yellow color. It is a tautomeric compound existing in enolic form in organic solvents and as a keto form in water.
Annual sales of curcumin have increased since 2012, largely due to an increase in its popularity as a dietary supplement. It is increasingly popular in skin care products that are marketed as containing natural ingredients or dyes, especially in Asia. The largest market is in North America, where sales exceeded US$20 million in 2014.
Curcumin incorporates several functional groups whose structure was first identified in 1910. The aromatic ring systems, which are phenols, are connected by two α,β-unsaturated carbonyl groups. The diketones form stable enols and are readily deprotonated to form enolates; the α,β-unsaturated carbonyl group is a good Michael acceptor and undergoes nucleophilic addition.
The biosynthetic route of curcumin is uncertain. In 1973, Roughly and Whiting proposed two mechanisms for curcumin biosynthesis. The first mechanism involves a chain extension reaction by cinnamic acid and 5 malonyl-CoA molecules that eventually arylized into a curcuminoid. The second mechanism involves two cinnamate units coupled together by malonyl-CoA. Both use cinnamic acid as their starting point, which is derived from the amino acid phenylalanine.
An experimentally backed route was not presented until 2008. This route follows both Roughley and Whiting mechanisms. However, the labeling data supported the first mechanism model in which 5 malonyl-CoA molecules react with cinnamic acid to form curcumin. However, the sequencing in which the functional groups, the alcohol and the methoxy, introduce themselves onto the curcuminoid seemed to support more strongly the second proposed mechanism. Therefore, the second pathway was accepted.
In vitro, curcumin has been shown to inhibit certain epigenetic enzymes (the histone deacetylases: HDAC1, HDAC3, and HDAC8) and transcriptional co-activator proteins (the p300 histone acetyltransferase). Curcumin also inhibits the arachidonate 5-lipoxygenase enzyme in vitro.
In Phase I clinical trials, dietary curcumin was shown to exhibit poor bioavailability, exhibited by rapid metabolism, low levels in plasma and tissues, and extensive rapid excretion, factors that make its in vivo activity poorly understood. Potential factors that limit the bioavailability of curcumin include insolubility in water (more soluble in alkaline solutions) and non-absorption. Numerous approaches to increase curcumin bioavailability are under research, including the use of absorption factors (such as piperine), liposomes, a structural analogue, or nanomaterials using specialized polymers.
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