Curcumin

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Curcumin
Curcumin.svg
Enol form
CurcuminKeto.svg
Keto form
Curcumin-enol-3D-balls.png
Curcumin-keto-3D-balls.png
Names
Pronunciation /ˈkɜːrkjʊmɪn/
Preferred IUPAC name
(1E,6E)-1,7-Bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione
Other names
  • (1E,6E)-1,7-Bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione
  • Diferuloylmethane
  • Curcumin I
  • C.I. 75300
  • Natural Yellow 3
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.006.619 OOjs UI icon edit-ltr-progressive.svg
E number E100 (colours)
KEGG
PubChem CID
UNII
  • InChI=1S/C21H20O6/c1-26-20-11-14(5-9-18(20)24)3-7-16(22)13-17(23)8-4-15-6-10-19(25)21(12-15)27-2/h3-12,24-25H,13H2,1-2H3/b7-3+,8-4+ Yes check.svgY
    Key: VFLDPWHFBUODDF-FCXRPNKRSA-N Yes check.svgY
  • InChI=1/C21H20O6/c1-26-20-11-14(5-9-18(20)24)3-7-16(22)13-17(23)8-4-15-6-10-19(25)21(12-15)27-2/h3-12,24-25H,13H2,1-2H3/b7-3+,8-4+
    Key: VFLDPWHFBUODDF-FCXRPNKRBF
  • O=C(\C=C\c1ccc(O)c(OC)c1)CC(=O)\C=C\c2cc(OC)c(O)cc2
Properties
C21H20O6
Molar mass 368.385 g·mol−1
AppearanceBright 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).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Curcumin is a bright yellow chemical produced by plants of the Curcuma longa species. It is the principal curcuminoid of turmeric (Curcuma longa), a member of the ginger family, Zingiberaceae. It is sold as a herbal supplement, cosmetics ingredient, food flavoring, and food coloring. [1]

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. [2]

Laboratory and clinical research have not confirmed any medical use 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. [3]

History

Curcumin was named in 1815 when Henri Auguste Vogel and Pierre Joseph Pelletier reported the first isolation of a "yellow coloring-matter" from the rhizomes of turmeric. [4] 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. [5] 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. [3] [6] [7]

Uses

Curcumin powder Kurkumina.jpg
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, [1] and as coloring for foods, such as curry powders, mustards, butters, and cheeses. As a food additive for orange-yellow coloring in prepared foods, its E number is E 100 in the European Union. [8] [9] It is also approved by the U.S. FDA to be used as a food coloring in US. [10]

Curcumin is used as a complexometric indicator for boron. [2] [11] It reacts with boric acid to form a red-colored compound, rosocyanine.

Chemistry

Curcumin becomes bright red when it interacts electrostatically with a phospholipid film Curcumin thin lipid film.jpg
Curcumin becomes bright red when it interacts 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. [2] [5] The aromatic ring systems, which are phenols, are connected by two α,β-unsaturated carbonyl groups. [2] [12] It is a diketone tautomer, existing in enolic form in organic solvents and in keto form in water. [13] 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.[ citation needed ] Because of its hydrophobic nature, curcumin is poorly soluble in water [2] but is easily soluble in organic solvents. [5]

Biosynthesis

The biosynthetic route of curcumin is uncertain. In 1973, Peter J. Roughley and Donald A. 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 arylize 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. [14]

Plant biosynthesis starting with cinnamic acid is rare compared to the more common p-coumaric acid. [14] Only a few identified compounds, such as anigorufone and pinosylvin, build from cinnamic acid. [15] [16]

Biosynthetic pathway of curcumin in Curcuma longa. Curcumin biosynthesis.svg
Biosynthetic pathway of curcumin in Curcuma longa .

Pharmacology

Curcumin displays green fluorescence under UV light Curcumin fluorescence.jpg
Curcumin displays green fluorescence under UV light

Curcumin, which shows positive results in most drug discovery assays, is regarded as a false lead that medicinal chemists include among "pan-assay interference compounds". This attracts undue experimental attention while failing to advance as viable therapeutic or drug leads, [3] [6] [17] although some derivatives of curcumin such as EF-24 have seen a significant amount of research. [18]

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. [3] Very little curcumin escapes the GI tract and most is excreted in feces unchanged. [19] 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. [3]

Safety

As a component of turmeric, curcumin may interact with prescription drugs and dietary supplements. [20] In high amounts, it may be unsafe for women during pregnancy. [20] It may cause side effects, such as nausea, diarrhea, hives, or dizziness. [20] Between 2004 and 2022 there were ten cases of liver injury caused by curcumin herbal and dietary supplements. [21] Curcumin is a contact allergen. [22]

The intended use of curcumin as a food additive is generally recognized as safe by the U.S. Food and Drug Administration. [23]

Medical research

Although curcumin has been assessed in numerous laboratory and clinical studies, it has no medical uses established by well-designed clinical research. [24] According to a 2017 review of more than 120 studies, curcumin has not been successful in any clinical trial, leading the authors to conclude that "curcumin is an unstable, reactive, non-bioavailable compound and, therefore, a highly improbable lead". [3] Curcumin exhibits numerous interference properties which may lead to misinterpretation of results. [3] [6] [25]

The US government has supported US$150 million in research into curcumin through the National Center for Complementary and Integrative Health, and no support has been found for curcumin as a medical treatment. [3] [26]

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 as of July 2021. [27] [28] [29] 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". [30] [31] [32]

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. [31] [33] 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. [34]

FDA warnings about dietary supplements

Between 2018 and 2023, the FDA issued 29 warning letters to American manufacturers of dietary supplements for making false claims of anti-disease effects from using products containing curcumin. [35] 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". [35]

Alternative medicine

Though there is no evidence for the safety or efficacy of using curcumin as a therapy, [3] [6] some alternative medicine practitioners give it intravenously, supposedly as a treatment for numerous diseases. [36] [37] [38] In 2017, two serious cases of adverse events were reported from curcumin or turmeric products—one severe allergic reaction and one death [36] —that were caused by administration of a curcumin-polyethylene glycol (PEG40) emulsion product by a naturopath. [38] One treatment caused anaphylaxis leading to death. [36] [38]

Stability

Decontamination of food by ionizing radiation, or food irradiation, is considered a safe and efficient process for elimination of pathogenic bacteria. [39] [40] Ionizing radiation treatment can be applied to either raw materials or ready to eat foods, with some countries, like the United States, imposing limitations on its use. [39] [41] In 2016, laboratory research established and compared the radiosensitivity of three organic food colorants including curcumin, carmine, and annatto to create data to be used for application whenever food products containing these food colors were to undergo the radiation process. [39] 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. [39]

Related Research Articles

<span class="mw-page-title-main">Turmeric</span> Plant used as spice

Turmeric, ,) is a flowering plant in the ginger family Zingiberaceae. It is a perennial, rhizomatous, herbaceous plant native to the Indian subcontinent and Southeast Asia that requires temperatures between 20 and 30 °C and high annual rainfall to thrive. Plants are gathered each year for their rhizomes, some for propagation in the following season and some for consumption.

<span class="mw-page-title-main">Ginger</span> Species of plant used as a spice

Ginger is a flowering plant whose rhizome, ginger root or ginger, is widely used as a spice and a folk medicine. It is an herbaceous perennial that grows annual pseudostems about one meter tall, bearing narrow leaf blades. The inflorescences bear flowers having pale yellow petals with purple edges, and arise directly from the rhizome on separate shoots.

<span class="mw-page-title-main">Food coloring</span> Substance used to color food or drink

Food coloring, color additive or colorant is any dye, pigment, or substance that imparts color when it is added to food or beverages. Colorants can be supplied as liquids, powders, gels, or pastes. Food coloring is commonly used in commercial products and in domestic cooking.

<span class="mw-page-title-main">Medicinal plants</span> Plants or derivatives used to treat medical conditions in humans or animals

Medicinal plants, also called medicinal herbs, have been discovered and used in traditional medicine practices since prehistoric times. Plants synthesize hundreds of chemical compounds for various functions, including defense and protection against insects, fungi, diseases, and herbivorous mammals.

<span class="mw-page-title-main">Sunless tanning</span> Indoor tanning lotion

Sunless tanning, also known as UV filled tanning, self tanning, spray tanning, or fake tanning, refers to the effect of a suntan without exposure to the Sun. Sunless tanning involves the use of oral agents (carotenids), or creams, lotions or sprays applied to the skin. Skin-applied products may be skin-reactive agents or temporary bronzers (colorants).

<span class="mw-page-title-main">Gingerol</span> Chemical compound

Gingerol ([6]-gingerol) is a phenolic phytochemical compound found in fresh ginger that activates heat receptors on the tongue. It is normally found as a pungent yellow oil in the ginger rhizome, but can also form a low-melting crystalline solid. This chemical compound is found in all members of the Zingiberaceae family and is high in concentrations in the grains of paradise as well as an African Ginger species.

Natural skin care uses topical creams and lotions made of ingredients available in nature. Much of the recent literature reviews plant-derived ingredients, which may include herbs, roots, flowers and essential oils, but natural substances in skin care products include animal-derived products such as beeswax, and minerals. These substances may be combined with various carrier agents, preservatives, surfactants, humectants and emulsifiers.

<span class="mw-page-title-main">Red yeast rice</span> Type of bright reddish purple fermented rice

Red yeast rice or red rice koji is a bright reddish purple fermented rice, which acquires its color from being cultivated with the mold Monascus purpureus. Red yeast rice is what is referred to as a kōji in Japanese, meaning "grain or bean overgrown with a mold culture", a food preparation tradition going back to ca. 300 BC.

<span class="mw-page-title-main">Rosocyanine</span> Chemical compound

Rosocyanine and rubrocurcumin are two red colored materials, which are formed by the reaction between curcumin and borates.

<span class="mw-page-title-main">Pinosylvin</span> Chemical compound

Pinosylvin is an organic compound with the formula C6H5CH=CHC6H3(OH)2. A white solid, it is related to trans-stilbene, but with two hydroxy groups on one of the phenyl substituents. It is very soluble in many organic solvents, such as acetone.

<span class="mw-page-title-main">Curcuminoid</span> Class of chemical compounds

A curcuminoid is a linear diarylheptanoid, a relatively small class of plant secondary metabolites that includes curcumin, demethoxycurcumin, and bisdemethoxycurcumin, all isolated from turmeric. These compounds are natural phenols and produce a pronounced yellow color that is often used to color foods and medicines. Curcumin is obtained from the root of turmeric.

<span class="mw-page-title-main">Dibenzoylmethane</span> Chemical compound

Dibenzoylmethane (DBM) is an organic compound with the formula (C6H5C(O))2CH2. DBM is the name for a 1,3-diketone, but the compound exists primarily as one of two equivalent enol tautomers. DBM is a white solid. Due UV-absorbing properties, derivatives of DBM such as avobenzone, have found applications as sunscreen products.

Desmethoxycurcumin is a curcuminoid found in turmeric. Commercial grade curcumin contains a mixture of curcuminoids.

Bisdemethoxycurcumin is a curcuminoid found in turmeric, but absent in Javanese turmeric. Bisdemethoxycurcumin is used as a pigment and nutraceutical with antimutagenic properties. All three of the curcuminoids found in Curcuma longa have been shown to have antioxidant properties, but bisdemethoxycurcumin is more resistant than the others to alkaline degradation. It was found to be effective in sensitizing PC cells resistance against gemcitabine.

<span class="mw-page-title-main">Diarylheptanoid</span> Class of chemicals found in plants

The diarylheptanoids are a class of plant secondary metabolites. Diarylheptanoids consist of two aromatic rings joined by a seven carbons chain (heptane) and having various substituents. They can be classified into linear (curcuminoids) and cyclic diarylheptanoids. The best known member is curcumin, which is isolated from turmeric and is known as food coloring E100. Some other Curcuma species, such as Curcuma comosa also produce diarylheptanoids.

1,7-Bis(4-hydroxyphenyl)-1,4,6-heptatrien-3-one is a natural product, a curcuminoid antioxidant found in turmeric and torch ginger.

Curcumin synthase categorizes three enzyme isoforms, type III polyketide synthases (PKSs) present in the leaves and rhizome of the turmeric plant that synthesize curcumin. CURS1-3 are responsible for the hydrolysis of feruloyldiketide-CoA, previously produced in the curcuminoid pathway, and a decarboxylative condensation reaction that together comprise one of the final steps in the synthesis pathway for curcumin, demethoxycurcumin, and bisdemethoxycurcumin, the compounds that give turmeric both its distinctive yellow color, and traditional medical benefits. CURS should not be confused with Curcuminoid Synthase (CUS), which catalyzes the one-pot synthesis of bisdemethoxycurcumin in Oryza sativa.

Bharat B. Aggarwal is an Indian-American biochemist. His research has been in the areas of cytokines, the role of inflammation in cancer, and the anti-cancer effects of spices and herbs, particularly curcumin. He was a professor in the Department of Clinical Immunology, Bioimmunotherapy, and Experimental Therapeutics at University of Texas MD Anderson Cancer Center in Houston, Texas.

Turmerones are a group of related chemical compounds of the sesquiterpene class. They are found in turmeric, from which they derive their name, as well as other related plants such as Curcuma caesia. There are multiple structural types of turmerones which differ in the number and placement of double bonds including α-tumerone, β-turmerone, and ar-turmerone. Each of these types consists of multiple stereoisomers.

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