Caffeic acid is an
organic compound with the formula (HO)2C6H3CH=CHCO2H. 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 unrelated to
caffeine,
Free caffeic acid can be found in a variety of beverages, including brewed
coffee at 0.13 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 chromatographydensitometry[11] and HPLC [12]). It is also found at lower levels in
barley and
rye.[13]
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]
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-1080fibrosarcoma cell line has recently been established.[23]
Caffeic acid is an
antioxidantin 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
stomachpapillomas.[25] In the same study, high doses of combined antioxidants, including caffeic acid, showed a significant decrease in growth of
colontumors 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]
^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.
PMID21761864.
^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.
PMID12059140.
^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.
PMID21510640.
^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.
PMID17177530.
^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.
^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.
^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.
PMID16104752.
^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.
PMID5836492.
^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.
PMID21116690.
S2CID28014579.
^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.
PMID2520223.
External links
"Chemical Land". Caffeic Acid as Carbocyclic Carboxylic Acid.