3D model (JSmol)
|Molar mass||354.31 g·mol−1|
|Melting point||207 to 209 °C (405 to 408 °F; 480 to 482 K)|
|Safety data sheet||External MSDS|
|S-phrases (outdated)||S24 S25 S28 S37 S45|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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 (caffeic acid, ferulic acid and p-coumaric acid) with quinic acid.
Despite the "chloro" of the name, chlorogenic acids contain no chlorine. Instead, the name comes from the Greek χλωρός (light green) and -γένος (a suffix meaning "giving rise to"), pertaining to the green color produced when chlorogenic acids are oxidized.
Structurally, chlorogenic acid is the ester formed between caffeic acid and the 3-hydroxyl of L-quinic acid. Isomers of chlorogenic acid include the caffeoyl ester at other hydroxyl sites on the quinic acid ring: 4-O-caffeoylquinic acid (cryptochlorogenic acid or 4-CQA) and 5-O-caffeoylquinic acid (neochlorogenic acid or 5-CQA). The epimer at position 1 has not yet been reported.
Structures having more than one caffeic acid group are called isochlorogenic acids, and can be found in coffee. There are several isomers, such as 3,4-dicaffeoylquinic acid and 3,5-dicaffeoylquinic acid. and cynarine (1,5-dicaffeoylquinic acid)
Biosynthesis and natural occurrence
The biosynthetic precursor to chlorogenic acid is 4-coumaroyl-CoA, containing a single hydroxyl group on the aryl ring, which in turn is produced from cinnamic acid. The hydroxylation of the coumaryl ester, i.e. installing the second hydroxy group, is catalyzed by a cytochrome P450 enzyme.
Chlorogenic acid and the related compounds cryptochlorogenic acid, and neochlorogenic acid have been found in the leaves of Hibiscus sabdariffa. Isomers of chlorogenic acid are found in potatoes. Chlorogenic acid is present in the flesh of eggplants, peaches, and prunes.
Taken as a dietary supplement or in coffee, chlorogenic acid slightly reduces blood pressure, It has been investigated for possible anti-inflammatory effects. Chlorogenic acid has been studied as a possible chemical sensitizer involved in respiratory allergy to certain plant materials.
The atom-numbering of chlorogenic acid can be ambiguous. The order of numbering of atoms on the quinic acid ring was reversed in 1976 following IUPAC guidelines, with the consequence that 3-CQA became 5-CQA, and 5-CQA became 3-CQA. This article uses the original numbering, which was exclusive prior to 1976, (chlorogenic acid being 3-CQA, while neochlorogenic acid is 5-CQA). Thereafter researchers and manufacturers have been divided, with both numbering systems in use. Even the 1976 IUPAC recommendations are not entirely satisfactory when applied to some of the less common chlorogenic acids.[unreliable source?]
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