Apigenin

Apigenin (4′,5,7-trihydroxyflavone), found in many plants, is a natural product belonging to the flavone class that is the aglycone of several naturally occurring glycosides. It is a yellow crystalline solid that has been used to dye wool.

Apigenin[1]
Names
IUPAC name
5,7-Dihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one
Other names
Apigenine; Chamomile; Apigenol; Spigenin; Versulin; 4′,5,7-Trihydroxyflavone; C.I. Natural Yellow 1
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.007.540
KEGG
UNII
Properties
C15H10O5
Molar mass 270.240 g·mol−1
Appearance Yellow crystalline solid
Melting point 345 to 350 °C (653 to 662 °F; 618 to 623 K)
UV-vis (λmax) 267, 296sh, 336 nm in methanol[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sources in nature

Apigenin is found in many fruits and vegetables, but parsley, celery, celeriac, and chamomile tea are the most common sources.[3] Apigenin is particularly abundant in the flowers of chamomile plants, constituting 68% of total flavonoids.[4]

Biosynthesis

Apigenin is biosynthetically derived from the general phenylpropanoid pathway and the flavone synthesis pathway.[5] The phenylpropanoid pathway starts from the aromatic amino acids L-phenylalanine or L-tyrosine, both products of the Shikimate pathway.[6] When starting from L-phenylalanine, first the amino acid is non-oxidatively deaminated by phenylalanine ammonia lyase (PAL) to make cinnamate, followed by oxidation at the para position by cinnamate 4-hydroxylase (C4H) to produce p-coumarate. As L-tyrosine is already oxidized at the para position, it skips this oxidation and is simply deaminated by tyrosine ammonia lyase (TAL) to arrive at p-coumarate.[7] To complete the general phenylpropanoid pathway, 4-coumarate CoA ligase (4CL) substitutes coenzyme A (CoA) at the carboxy group of p-coumarate. Entering the flavone synthesis pathway, the type III polyketide synthase enzyme chalcone synthase (CHS) uses consecutive condensations of three equivalents of malonyl CoA followed by aromatization to convert p-coumaroyl-CoA to chalcone.[8] Chalcone isomerase (CHI) then isomerizes the product to close the pyrone ring to make naringenin. Finally, a flavanone synthase (FNS) enzyme oxidizes naringenin to apigenin.[9] Two types of FNS have previously been described; FNS I, a soluble enzyme that uses 2-oxogluturate, Fe2+, and ascorbate as cofactors and FNS II, a membrane bound, NADPH dependent cytochrome p450 monooxygenase.[10]

Glycosides

The naturally occurring glycosides formed by the combination of apigenin with sugars include:

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See also

References
  1. Merck Index, 11th Edition, 763.
  2. The Systematic Identification of Flavonoids. Mabry et al, 1970, page 81
  3. The compound in the Mediterranean diet that makes cancer cells 'mortal' Emily Caldwell, Medical Express, May 20, 2013.
  4. Venigalla M, Gyengesi E, Münch G (August 2015). "Curcumin and Apigenin - novel and promising therapeutics against chronic neuroinflammation in Alzheimer's disease". Neural Regeneration Research. 10 (8): 1181–5. doi:10.4103/1673-5374.162686. PMC 4590215. PMID 26487830.
  5. Forkmann, G. (January 1991). "Flavonoids as Flower Pigments: The Formation of the Natural Spectrum and its Extension by Genetic Engineering". Plant Breeding. 106 (1): 1–26. doi:10.1111/j.1439-0523.1991.tb00474.x. ISSN 0179-9541.
  6. Herrmann KM (January 1995). "The shikimate pathway as an entry to aromatic secondary metabolism". Plant Physiology. 107 (1): 7–12. doi:10.1104/pp.107.1.7. PMC 161158. PMID 7870841.
  7. Lee H, Kim BG, Kim M, Ahn JH (September 2015). "Biosynthesis of Two Flavones, Apigenin and Genkwanin, in Escherichia coli". Journal of Microbiology and Biotechnology. 25 (9): 1442–8. doi:10.4014/jmb.1503.03011. PMID 25975614.
  8. Austin MB, Noel JP (February 2003). "The chalcone synthase superfamily of type III polyketide synthases". Natural Product Reports. 20 (1): 79–110. CiteSeerX 10.1.1.131.8158. doi:10.1039/b100917f. PMID 12636085.
  9. Martens S, Forkmann G, Matern U, Lukacin R (September 2001). "Cloning of parsley flavone synthase I". Phytochemistry. 58 (1): 43–6. doi:10.1016/S0031-9422(01)00191-1. PMID 11524111.
  10. Leonard E, Yan Y, Lim KH, Koffas MA (December 2005). "Investigation of two distinct flavone synthases for plant-specific flavone biosynthesis in Saccharomyces cerevisiae". Applied and Environmental Microbiology. 71 (12): 8241–8. doi:10.1128/AEM.71.12.8241-8248.2005. PMC 1317445. PMID 16332809.
  11. Meyer H, Bolarinwa A, Wolfram G, Linseisen J (2006). "Bioavailability of apigenin from apiin-rich parsley in humans". Annals of Nutrition & Metabolism. 50 (3): 167–72. doi:10.1159/000090736. PMID 16407641.
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