Curcumin is a bright yellow chemical produced by the plant species Curcuma longa. 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.
Chemically, curcumin is a polyphenol, more particularly a diarylheptanoid, belonging to the group of curcuminoids, which are phenolic pigments responsible for the yellow color of turmeric.
Extensive studies have consistently failed to show any medical value for curcumin. It is difficult to study because it is both unstable and poorly bioavailable. It is unlikely to produce useful leads for drug development as a lead compound. Later, it was found to be a mixture of resin and turmeric oil. In 1910, Milobedzka and Lampe reported the chemical structure of curcumin to be as diferuloylmethane. Later in 1913, the same group accomplished the synthesis of the compound.
Although used in traditional medicine, the possible therapeutic properties of turmeric or curcumin remain undetermined.
Uses
thumb|Curcumin powder
The most common applications are as an ingredient in dietary supplement, in cosmetics, as flavoring for foods, such as turmeric-flavored beverages in South and Southeast Asia, It is also approved by the U.S. FDA to be used as a food coloring in US.
Chemistry
alt=A bright red substance in a small glass flask, held by gloved fingers|thumb|Curcumin becomes bright red when it interacts [[electrostatics|electrostatically with a phospholipid film]]
Curcumin incorporates a seven carbon linker and three major functional groups: an α,β-unsaturated β-diketone moiety and an aromatic O-methoxy-phenolic group. It is a diketone tautomer, existing in enolic form in organic solvents and in keto form in water. The diketones form stable enols and are readily deprotonated to form enolates, which bind metal ions to form acetylacetonate-like complexes. Its complexing properties are manifesting in its reaction with boric acid to give a red-colored rosocyanine.
Because of its hydrophobic nature, curcumin is poorly soluble in water Only a few identified compounds, such as anigorufone and pinosylvin, build from cinnamic acid.
500px|center|thumb|class=skin-invert-image|alt= Curcumin biosynthesis diagram|Biosynthetic pathway of curcumin in [[Curcuma longa. although some derivatives of curcumin such as EF-24 have been well-studied.
Factors that limit the bioactivity of curcumin or its analogs include chemical instability, water insolubility, absence of potent and selective target activity, low bioavailability, limited tissue distribution, and extensive metabolism. If curcumin enters plasma in reasonable amounts, there is a high risk of toxicity since it is promiscuous, and interacts with several proteins known to increase the risk of adverse effects, including hERG, cytochrome P450s, and glutathione S-transferase. Its instability, reactivity, and poor bioavailability, make curcumin an unlikely drug candidate.
Between 1995 and 2017, the US government funded US$150 million in biomedical research into curcumin through the National Center for Complementary and Integrative Health. No support was found for curcumin as a medical treatment. In high amounts, it may be unsafe for women during pregnancy. Curcumin is a contact allergen.
The intended use of curcumin as a food additive is generally recognized as safe by the U.S. Food and Drug Administration.
Research fraud
Bharat Aggarwal, a former cancer researcher at the University of Texas MD Anderson Cancer Center, had 29 papers retracted due to research fraud . Aggarwal's research had focused on potential anti-cancer properties of herbs and spices, particularly curcumin, and according to a March 2016 article in the Houston Chronicle, "attracted national media interest and laid the groundwork for ongoing clinical trials".
Aggarwal cofounded a company in 2004 called Curry Pharmaceuticals based in Research Triangle Park, North Carolina, which planned to develop drugs based on synthetic analogs of curcumin. SignPath Pharma, a company seeking to develop liposomal formulations of curcumin, licensed three patents by Aggarwal related to that approach from MD Anderson in 2013.
Warnings about dietary supplements
Between 2018 and 2023, the U.S. FDA issued 29 warning letters to American manufacturers of dietary supplements for making false claims of anti-disease effects from using products containing curcumin. In each letter, the FDA stated that the supplement product was not an approved new drug because the "product is not generally recognized as safe and effective" for the advertised uses, that "new drugs may not be legally introduced or delivered for introduction into interstate commerce without prior approval from FDA", and that the "FDA approves a new drug on the basis of scientific data and information demonstrating that the drug is safe and effective". In 2017, two serious cases of adverse events were reported from curcumin or turmeric products—one severe allergic reaction and one death The researchers used spectrophotometry and capillary electrophoresis to establish radiosensitivity of the three organic food colorants. Carmine samples were quite stable against radiation treatment, annatto showed limited stability, and curcumin was found to be unstable, particularly when diluted.