Caffeic acid

Last updated
Caffeic acid
Kaffeesaure.svg
Cafeic-acid-3D.png
CaffeicAcid3d.png
Names
IUPAC names
3-(3,4-Dihydroxyphenyl)-2-propenoic acid
3,4-Dihydroxycinnamic acid
trans-Caffeate
3,4-Dihydroxy-trans-cinnamate
(E)-3-(3,4-dihydroxyphenyl)-2-propenoic acid
3,4-Dihydroxybenzeneacrylicacid
3-(3,4-Dihydroxyphenyl)-2-propenoic acid
Preferred IUPAC name
(2E)-3-(3,4-Dihydroxyphenyl)prop-2-enoic acid
Identifiers
3D model (JSmol)
1954563
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.005.784 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 206-361-2
KEGG
PubChem CID
UNII
  • InChI=1S/C9H8O4/c10-7-3-1-6(5-8(7)11)2-4-9(12)13/h1-5,10-11H,(H,12,13)/b4-2+ Yes check.svgY
    Key: QAIPRVGONGVQAS-DUXPYHPUSA-N Yes check.svgY
  • InChI=1/C9H8O4/c10-7-3-1-6(5-8(7)11)2-4-9(12)13/h1-5,10-11H,(H,12,13)/b4-2+
    Key: QAIPRVGONGVQAS-DUXPYHPUBE
  • O=C(O)\C=C\c1cc(O)c(O)cc1
Properties
C9H8O4
Molar mass 180.16 g/mol
Density 1.478 g/cm3
Melting point 223 to 225 °C (433 to 437 °F; 496 to 498 K)
UV-vis (λmax)327 nm and a shoulder at c. 295 nm in acidified methanol [1]
Hazards
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg
Warning
H315, H319, H335, H351, H361
P201, P202, P261, P264, P271, P280, P281, P302+P352, P304+P340, P305+P351+P338, P308+P313, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Related compounds
Related compounds
 Chlorogenic acid
Cichoric acid
Coumaric acid
Quinic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Caffeic acid is an organic compound with the formula (HO)2C6H3CH=CHCO2H. It is a polyphenol. It is a yellow solid. Structurally, it is classified as a hydroxycinnamic acid. The molecule consists of both phenolic and acrylic functional groups. It is found in all plants as an intermediate in the biosynthesis of lignin, one of the principal components of biomass and its residues. [2] It is chemically unrelated to caffeine; the related name is due to its presence in coffee.

Contents

Natural occurrences

Caffeic acid can be found in the bark of Eucalyptus globulus [3] the barley grain Hordeum vulgare and the herb Dipsacus asperoides. [4] It can also be found in the freshwater fern Salvinia molesta [5] and in the mushroom Phellinus linteus . [6]

Occurrences in food

Free caffeic acid can be found in a variety of beverages, including brewed coffee at 63.1-96.0 mg per 100 ml [7] and red wine at 2 mg per 100 ml. [8] It is found at relatively high levels in herbs of the mint family, especially thyme, sage and spearmint (at about 20 mg per 100 g), and in spices, such as Ceylon cinnamon and star anise (at about 22 mg per 100 g). Caffeic acid occurs at moderate levels in sunflower seeds (8 mg per 100 g), apple sauce, apricots and prunes (at about 1 mg per 100 g). [9] It occurs at remarkably high levels in black chokeberry (141 mg per 100 g). [10] It is also quite high in the South American herb yerba mate (150 mg per 100 g based on thin-layer chromatography densitometry [11] and HPLC [12] ). It is also found at lower levels in barley and rye. [13]

Biosynthesis

Caffeic acid is biosynthesized by hydroxylation of coumaroyl ester of quinic acid (esterified through a side chain alcohol). This hydroxylation produces the caffeic acid ester of shikimic acid, which converts to chlorogenic acid. It is the precursor to ferulic acid, coniferyl alcohol, and sinapyl alcohol, all of which are significant building blocks in lignin. [2] The transformation to ferulic acid is catalyzed by the enzyme caffeate O-methyltransferase.

Caffeic acid and its derivative caffeic acid phenethyl ester (CAPE) are produced in many kinds of plants. [14] [15] [16]

In plants, caffeic acid (middle) is formed from 4-hydroxycinnamic acid (left) and is transformed to ferulic acid. CaffeicAcIn.png
In plants, caffeic acid (middle) is formed from 4-hydroxycinnamic acid (left) and is transformed to ferulic acid.

Dihydroxyphenylalanine ammonia-lyase was presumed to use 3,4-dihydroxy-L-phenylalanine (L-DOPA) to produce trans-caffeate and NH3. However, the EC number for this purported enzyme was deleted in 2007, as no evidence has emerged for its existence. [17]

Biotransformation

Caffeate O-methyltransferase is an enzyme responsible for the transformation of caffeic acid into ferulic acid.

Caffeic acid and related o-diphenols are rapidly oxidized by o-diphenol oxidases in tissue extracts. [18]

Biodegradation

Caffeate 3,4-dioxygenase is an enzyme that uses caffeic acid and oxygen to produce 3-(2-carboxyethenyl)-cis,cis-muconate.

Caffeic acid is susceptible to autoxidation. Glutathione and thiol compounds (cysteine, thioglycolic acid or thiocresol) or ascorbic acid have a protective effect on browning and disappearance of caffeic acid. [19] This browning is due to the conversion of o-diphenols into reactive o-quinones. Chemical oxidation of caffeic acid in acidic conditions using sodium periodate leads to the formation of dimers with a furan structure (isomers of 2,5-(3′,4′-dihydroxyphenyl)tetrahydrofuran 3,4-dicarboxylic acid). [20] Caffeic acid can also be polymerized using the horseradish peroxidase/H2O2 oxidizing system. [21]

Glycosides

3-O-caffeoylshikimic acid (dactylifric acid) and its isomers, are enzymic browning substrates found in dates ( Phoenix dactylifera fruits). [22]

Pharmacology

Caffeic acid has a variety of potential pharmacological effects in in vitro studies and in animal models, and the inhibitory effect of caffeic acid on cancer cell proliferation by an oxidative mechanism in the human HT-1080 fibrosarcoma cell line has recently been established. [23]

Caffeic acid is an antioxidant in vitro and also in vivo . [16] Caffeic acid also shows immunomodulatory and anti-inflammatory activity. Caffeic acid outperformed the other antioxidants, reducing aflatoxin production by more than 95 percent. The studies are the first to show that oxidative stress that would otherwise trigger or enhance Aspergillus flavus aflatoxin production can be stymied by caffeic acid. This opens the door to use as a natural fungicide by supplementing trees with antioxidants. [24]

Studies of the carcinogenicity of caffeic acid have mixed results. Some studies have shown that it inhibits carcinogenesis, and other experiments show carcinogenic effects. [25] Oral administration of high doses of caffeic acid in rats has caused stomach papillomas. [25] In the same study, high doses of combined antioxidants, including caffeic acid, showed a significant decrease in growth of colon tumors in those same rats. No significant effect was noted otherwise. Caffeic acid is listed under some Hazard Data sheets as a potential carcinogen, [26] as has been listed by the International Agency for Research on Cancer as a Group 2B carcinogen ("possibly carcinogenic to humans"). [27] More recent data show that bacteria in the rats' guts may alter the formation of metabolites of caffeic acid. [28] [29] Other than caffeic acid being a thiamine antagonist (antithiamine factor), there have been no known ill effects of caffeic acid in humans. Also, caffeic acid treatment attenuated lipopolysaccharide (LPS)-induced sickness behaviour in experimental animals by decreasing both peripheral and central cytokine levels along with oxidative stress inflicted by LPS. [30]

Other uses

Caffeic acid may be the active ingredient in caffenol, a do-it-yourself black-and-white photographic developer made from instant coffee. [31] The developing chemistry is similar to that of catechol or pyrogallol. [32]

It is also used as a matrix in MALDI mass spectrometry analyses. [33]

Isomers

Isomers with the same molecular formula and in the hydroxycinammic acids family are:

Related Research Articles

Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants are frequently added to industrial products, such as polymers, fuels, and lubricants, to extend their usable lifetimes. Foods are also treated with antioxidants to forestall spoilage, in particular the rancidification of oils and fats. In cells, antioxidants such as glutathione, mycothiol, or bacillithiol, and enzyme systems like superoxide dismutase, can prevent damage from oxidative stress.

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

Polyphenols are a large family of naturally occurring phenols. They are abundant in plants and structurally diverse. Polyphenols include phenolic acids, flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.

<span class="mw-page-title-main">Deoxycholic acid</span> Bile acid

Deoxycholic acid is a bile acid. Deoxycholic acid is one of the secondary bile acids, which are metabolic byproducts of intestinal bacteria. The two primary bile acids secreted by the liver are cholic acid and chenodeoxycholic acid. Bacteria metabolize chenodeoxycholic acid into the secondary bile acid lithocholic acid, and they metabolize cholic acid into deoxycholic acid. There are additional secondary bile acids, such as ursodeoxycholic acid. Deoxycholic acid is soluble in alcohol and acetic acid. When pure, it exists in a white to off-white crystalline powder form.

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

Chlorogenic acid (CGA) is the ester of caffeic acid and (−)-quinic acid, functioning as an intermediate in lignin biosynthesis. The term chlorogenic acids refers to a related polyphenol family of esters, including hydroxycinnamic acids with quinic acid.

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

Ferulic acid is a hydroxycinnamic acid derivative and a phenolic compound. It is an organic compound with the formula (CH3O)HOC6H3CH=CHCO2H. The name is derived from the genus Ferula, referring to the giant fennel (Ferula communis). Classified as a phenolic phytochemical, ferulic acid is an amber colored solid. Esters of ferulic acid are found in plant cell walls, covalently bonded to hemicellulose such as arabinoxylans. Salts and esters derived from ferulic acid are called ferulates.

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

Sinapinic acid, or sinapic acid (Sinapine - Origin: L. Sinapi, sinapis, mustard, Gr., cf. F. Sinapine.), is a small naturally occurring hydroxycinnamic acid. It is a member of the phenylpropanoid family. It is a commonly used matrix in MALDI mass spectrometry. It is a useful matrix for a wide variety of peptides and proteins. It serves well as a matrix for MALDI due to its ability to absorb laser radiation and to also donate protons (H+) to the analyte of interest.

<span class="mw-page-title-main">Avenanthramide</span> Type of alkaloid

Avenanthramides are a group of phenolic alkaloids found mainly in oats, but also present in white cabbage butterfly eggs, and in fungus-infected carnation. A number of studies demonstrate that these natural products have anti-inflammatory, antioxidant, anti-itch, anti-irritant, and antiatherogenic activities. Oat kernel extracts with standardized levels of avenanthramides are used for skin, hair, baby, and sun care products. The name avenanthramides was coined by Collins when he reported the presence of these compounds in oat kernels. It was later found that three avenanthramides were the open-ring amides of avenalumins I, II, and III, which were previously reported as oat phytoalexins by Mayama and co-workers.

Hydroxycinnamic acids (hydroxycinnamates) are a class of aromatic acids or phenylpropanoids having a C6–C3 skeleton. These compounds are hydroxy derivatives of cinnamic acid.

Laccases are multicopper oxidases found in plants, fungi, and bacteria. Laccases oxidize a variety of phenolic substrates, performing one-electron oxidations, leading to crosslinking. For example, laccases play a role in the formation of lignin by promoting the oxidative coupling of monolignols, a family of naturally occurring phenols. Other laccases, such as those produced by the fungus Pleurotus ostreatus, play a role in the degradation of lignin, and can therefore be classed as lignin-modifying enzymes. Other laccases produced by fungi can facilitate the biosynthesis of melanin pigments. Laccases catalyze ring cleavage of aromatic compounds.

<span class="mw-page-title-main">Folin–Ciocalteu reagent</span> Chemical mixture

The Folin–Ciocâlteu reagent (FCR) or Folin's phenol reagent or Folin–Denis reagent, is a mixture of phosphomolybdate and phosphotungstate used for the colorimetric in vitro assay of phenolic and polyphenolic antioxidants, also called the gallic acid equivalence method (GAE). It is named after Otto Folin, Vintilă Ciocâlteu, and Willey Glover Denis. The Folin-Denis reagent is prepared by mixing sodium tungstate and phosphomolybdic acid in phosphoric acid. The Folin–Ciocalteu reagent is just a modification of the Folin-Denis reagent. The modification consisted of the addition of lithium sulfate and bromine to the phosphotungstic-phosphomolybdic reagent.

Polyphenol oxidase, an enzyme involved in fruit browning, is a tetramer that contains four atoms of copper per molecule.

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

Diferulic acids (also known as dehydrodiferulic acids) are organic compounds that have the general chemical formula C20H18O8, they are formed by dimerisation of ferulic acid. Curcumin and curcuminoids, though having a structure resembling diferulic acids', are not formed that way but through a condensation process. Just as ferulic acid is not the proper IUPAC name, the diferulic acids also tend to have trivial names that are more commonly used than the correct IUPAC name. Diferulic acids are found in plant cell walls, particularly those of grasses.

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

Vanillic acid is a dihydroxybenzoic acid derivative used as a flavoring agent. It is an oxidized form of vanillin. It is also an intermediate in the production of vanillin from ferulic acid.

<span class="mw-page-title-main">Phenolic content in wine</span> Wine chemistry

Phenolic compounds—natural phenol and polyphenols—occur naturally in wine. These include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenoids, flavonols, dihydroflavonols, anthocyanins, flavanol monomers (catechins) and flavanol polymers (proanthocyanidins). This large group of natural phenols can be broadly separated into two categories, flavonoids and non-flavonoids. Flavonoids include the anthocyanins and tannins which contribute to the color and mouthfeel of the wine. The non-flavonoids include the stilbenoids such as resveratrol and phenolic acids such as benzoic, caffeic and cinnamic acids.

<span class="mw-page-title-main">Naturally occurring phenols</span> Group of chemical compounds

In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecological pressures such as pathogen and insect attack, UV radiation and wounding. As they are present in food consumed in human diets and in plants used in traditional medicine of several cultures, their role in human health and disease is a subject of research. Some phenols are germicidal and are used in formulating disinfectants.

<span class="mw-page-title-main">Grape reaction product</span> Chemical compound

The grape reaction product is a phenolic compound explaining the disappearance of caftaric acid from grape must during processing. It is also found in aged red wines. Its enzymatic production by polyphenol oxidase is important in limiting the browning of musts, especially in white wine production. The product can be recreated in model solutions.

<small>D</small>-Fructose-<small>L</small>-histidine Chemical compound

d-Fructose-l-histidine (FruHis) is a ketosamine combining the d-isomer of fructose and the l-isomer of histidine into a functional group. FruHis is present in dried fruits. In interaction with lycopene, FruHis is a potential food related antioxidant and chemopreventive agent, found abundantly in dried tomatoes.

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

Dactylifric acid is an ester derived from caffeic acid and shikimic acid. It and its isomers are enzymic browning substrates found in dates.

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

Tellimagrandin I is an ellagitannin found in plants, such as Cornus canadensis, Eucalyptus globulus, Melaleuca styphelioides, Rosa rugosa, and walnut. It is composed of two galloyl and one hexahydroxydiphenyl groups bound to a glucose residue. It differs from Tellimagrandin II only by a hydroxyl group instead of a third galloyl group. It is also structurally similar to punigluconin and pedunculagin, two more ellagitannin monomers.

References

  1. ↑ Gould, Kevin S.; Markham, Kenneth R.; Smith, Richard H.; Goris, Jessica J. (2000). "Functional role of anthocyanins in the leaves of Quintinia serrata A. Cunn". Journal of Experimental Botany. 51 (347): 1107–1115. doi: 10.1093/jexbot/51.347.1107 . PMID   10948238.
  2. 1 2 Boerjan, Wout; Ralph, John; Baucher, Marie (2003). "Lignin biosynthesis". Annual Review of Plant Biology. 54: 519–546. doi:10.1146/annurev.arplant.54.031902.134938. PMID   14503002.
  3. ↑ Santos, Sónia A. O.; Freire, Carmen S. R.; Domingues, M. Rosário M.; Silvestre, Armando J. D.; Pascoal Neto, Carlos (2011). "Characterization of Phenolic Components in Polar Extracts of Eucalyptus globulus Labill. Bark by High-Performance Liquid Chromatography–Mass Spectrometry". Journal of Agricultural and Food Chemistry. 59 (17): 9386–9393. doi:10.1021/jf201801q. PMID   21761864.
  4. ↑ Khoo, Cheang S.; Sullivan, Shaun; Kazzem, Magdy; Lamin, Franklin; Singh, Swastika; Nang, Marnilar; Low, Mitchell; Suresh, Harsha; Lee, Samiuela (2014). "The Liquid Chromatographic Determination of Chlorogenic and Caffeic Acids in Xu Duan (Dipsacus asperoides) Raw Herb". ISRN Analytical Chemistry. 2014: 1–6. doi: 10.1155/2014/968314 .
  5. ↑ Choudhary, M. Iqbal; Naheed, Nadra; Abbaskhan, Ahmed; Musharraf, Syed Ghulam; Siddiqui, Hina; Atta-Ur-Rahman (2008). "Phenolic and other constituents of fresh water fern Salvinia molesta". Phytochemistry. 69 (4): 1018–1023. Bibcode:2008PChem..69.1018C. doi:10.1016/j.phytochem.2007.10.028. PMID   18177906.
  6. ↑ Lee, Y.-S.; Kang, Y.-H.; Jung, J.-Y.; Lee, Sanghyun; Ohuchi, Kazuo; Shin, Kuk Hyun; Kang, Il-Jun; Park, Jung Han Yoon; Shin, Hyun-Kyung; Soon, Sung (October 2008). "Protein glycation inhibitors from the fruiting body of Phellinus linteus". Biological & Pharmaceutical Bulletin. 31 (10): 1968–1972. doi: 10.1248/bpb.31.1968 . PMID   18827365.
  7. ↑ Pirjo, Mittila; Kumpulainen, Jorma (19 June 2002). "Determination of free and total phenolic acids in plant-derived foods by HPLC with diode-array detection". J Agric Food Chem. 50 (13): 3660–7. doi:10.1021/jf020028p. PMID   12059140.
  8. ↑ "Showing all foods in which the polyphenol Caffeic acid is found - Phenol-Explorer".
  9. ↑ "Caffeic acid". Iarc Monographs on the Evaluation of Carcinogenic Risks to Humans. 56: 115–134. 1993. PMC   7681336 . PMID   8411618.
  10. ↑ Zheng, Wei; Wang, Shiow Y (15 January 2003). "Oxygen radical absorbing capacity of phenolics in blueberries, cranberries, chokeberries, and lingonberries". J Agric Food Chem. 51 (2): 502–9. doi:10.1021/jf020728u. PMID   12517117.
  11. ↑ Bojić, Mirza; Haas, Vicente Simon; Šarić, Darija; Maleš, Željan (4 April 2018). "Determination of Flavonoids, Phenolic Acids, and Xanthines in Mate Tea (Ilex paraguariensis St.-Hil.)". Journal of Analytical Methods in Chemistry. 2013: 658596. doi: 10.1155/2013/658596 . PMC   3690244 . PMID   23841023.
  12. ↑ Berté, Kleber A. S. (2011). "Chemical Composition and Antioxidant Activity of Yerba-Mate (Ilex paraguariensis A. St.-Hil., Aquifoliaceae) Extract as Obtained by Spray Drying". Journal of Agricultural and Food Chemistry. 59 (10): 5523–5527. doi:10.1021/jf2008343. PMID   21510640.
  13. ↑ Quinde-Axtell, Zory; Baik, Byung-Kee (2006). "Phenolic Compounds of Barley Grain and Their Implication in Food Product Discoloration". J. Agric. Food Chem. 54 (26): 9978–9984. doi:10.1021/jf060974w. PMID   17177530.
  14. ↑ "Red Clover Benefits & Information". indigo-herbs.co.uk. Retrieved 4 April 2018.
  15. ↑ "Dr. Duke's Phytochemical and Ethnobotanical Databases". Archived from the original on 2000-12-05.
  16. 1 2 Olthof, M. R.; Hollman, P. C.; Katan, M. B. (January 2001). "Chlorogenic acid and caffeic acid are absorbed in humans". J. Nutr. 131 (1): 66–71. doi: 10.1093/jn/131.1.66 . PMID   11208940.
  17. ↑ "EC 4.3.1.11". www.chem.qmul.ac.uk. Archived from the original on 3 March 2016. Retrieved 4 April 2018.
  18. ↑ Pierpoint, W. S. (1969). "o-Quinones formed in plant extracts. Their reactions with amino acids and peptides". Biochem. J. 112 (5): 609–616. doi:10.1042/bj1120609. PMC   1187763 . PMID   4980678.
  19. ↑ Cilliers, Johannes J. L.; Singleton, Vernon L. (1990). "Caffeic acid autoxidation and the effects of thiols". J. Agric. Food Chem. 38 (9): 1789–1796. doi:10.1021/jf00099a002.
  20. ↑ Fulcrand, Hélène; Cheminat, Annie; Brouillard, Raymond; Cheynier, Véronique (1994). "Characterization of compounds obtained by chemical oxidation of caffeic acid in acidic conditions". Phytochemistry. 35 (2): 499–505. Bibcode:1994PChem..35..499F. doi:10.1016/S0031-9422(00)94790-3.
  21. ↑ Xu, Peng; Uyama, Hiroshi; Whitten, James E.; Kobayashi, Shiro; Kaplan, David L. (2005). "Peroxidase-Catalyzed in Situ Polymerization of Surface Orientated Caffeic Acid". J. Am. Chem. Soc. 127 (33): 11745–11753. doi:10.1021/ja051637r. PMID   16104752.
  22. ↑ Maier, V. P.; Metzler, D. M.; Huber, A. F. (1964). "3-O-Caffeoylshikimic acid (dactylifric acid) and its isomers, a new class of enzymic browning substrates". Biochemical and Biophysical Research Communications. 14 (2): 124–128. doi:10.1016/0006-291x(64)90241-4. PMID   5836492.
  23. ↑ Rajendra Prasad, N.; Karthikeyan, A.; Karthikeyan, S.; Reddy, B. V. (Mar 2011). "Inhibitory effect of caffeic acid on cancer cell proliferation by oxidative mechanism in human HT-1080 fibrosarcoma cell line". Mol Cell Biochem. 349 (1–2): 11–19. doi:10.1007/s11010-010-0655-7. PMID   21116690. S2CID   28014579.
  24. ↑ "Nuts' New Aflatoxin Fighter: Caffeic Acid?".
  25. 1 2 Hirose, M.; Takesada, Y.; Tanaka, H.; Tamano, S.; Kato, T.; Shirai, T. (1998). "Carcinogenicity of antioxidants BHA, caffeic acid, sesamol, 4-methoxyphenol and catechol at low doses, either alone or in combination, and modulation of their effects in a rat medium-term multi-organ carcinogenesis model". Carcinogenesis. 19 (1): 207–212. doi: 10.1093/carcin/19.1.207 . PMID   9472713.
  26. ↑ "Caffeic Acid". IARC Summary & Evaluation. 1993.
  27. ↑ "Agents Classified by the IARC Monographs" (PDF). iarc.fr. International Agency for Research on Cancer. Archived from the original (PDF) on 25 October 2011. Retrieved 4 April 2018.
  28. ↑ Peppercorn, M. A.; Goldman, P. (1972). "Caffeic acid metabolism by gnotobiotic rats and their intestinal bacteria". Proceedings of the National Academy of Sciences. 69 (6): 1413–1415. Bibcode:1972PNAS...69.1413P. doi: 10.1073/pnas.69.6.1413 . PMC   426714 . PMID   4504351.
  29. ↑ Gonthier, M.-P.; Verny, M.-A.; Besson, C.; Rémésy, C.; Scalbert, A. (1 June 2003). "Chlorogenic acid bioavailability largely depends on its metabolism by the gut microflora in rats". Journal of Nutrition. 133 (6): 1853–1859. doi: 10.1093/jn/133.6.1853 . PMID   12771329.
  30. ↑ Basu, Mallik S; et al. (3 Sep 2016). "Caffeic acid attenuates lipopolysaccharide-induced sickness behaviour and neuroinflammation in mice". Neuroscience Letters. 632: 218–223. doi:10.1016/j.neulet.2016.08.044. PMID   27597761. S2CID   5361129.
  31. ↑ "Caffenol-C-M, recipe". Caffenol blog. 2 March 2010.
  32. ↑ Williams, Scott. "A Use for that Last Cup of Coffee: Film and Paper Development". Technical Photographic Chemistry 1995 Class. Imaging and Photographic Technology Department, School of Photographic Arts and Sciences, Rochester Institute of Technology.
  33. ↑ Beavis, R. C.; Chait, B. T. (Dec 1989). "Cinnamic acid derivatives as matrices for ultraviolet laser desorption mass spectrometry of proteins". Rapid Commun. Mass Spectrom. 3 (12): 432–435. Bibcode:1989RCMS....3..432B. doi:10.1002/rcm.1290031207. PMID   2520223.
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