Chlorogenic acid (CGA) is the

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

caffeic acid Caffeic acid is an organic compound with the formula . It is a polyphenol with a key role in scavenging reactive oxygen species (ROS) generated in energy metabolism. Caffeic acid is also one major polyphenol responsible for maintaining normal le ...

and

quinic acid Quinic acid is an organic compound with the formula . The compound is classified as a cyclitol, a cyclic polyol, and a cyclohexanecarboxylic acid. It is a colorless solid that can be extracted from plant sources. Quinic acid is implicated in the p ...

, functioning as an intermediate in lignin biosynthesis. The term chlorogenic acids refers to a related

polyphenol 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 ...

family of esters, including

hydroxycinnamic acid Hydroxycinnamic acids (hydroxycinnamates) are a class of aromatic acids or phenylpropanoids having a C6–C3 skeleton. These compounds are hydroxy derivatives of cinnamic acid. In the category of List of phytochemicals in food, phytochemicals tha ...

s (

ferulic acid 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''). Cl ...

and ''p''-coumaric acid) with

. Despite the "chloro" of the name, chlorogenic acids contain no

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

. Instead, the name comes from the Greek χλωρός (khloros, light green) and -γένος (genos, a suffix meaning "giving rise to"), pertaining to the green color produced when chlorogenic acids are

oxidized Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

Structural properties

Structurally, chlorogenic acid is the

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 In stereochemistry, an epimer is one of a pair of diastereomers. The two epimers have opposite configuration at only one stereogenic center out of at least two. All other stereogenic centers in the molecules are the same in each. Epimerization is t ...

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 Coffee is a beverage brewed from roasted, ground coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content, but decaffeinated coffee is also commercially a ...

. There are several isomers, such as 3,4-dicaffeoylquinic acid and 3,5-dicaffeoylquinic acid. and

cynarine Cynarine is a hydroxycinnamic acid derivative (chemistry), derivative and a biologically active chemical constituent of artichoke (''Cynara cardunculus''). Chemically, it is an ester formed from quinic acid and two units of caffeic acid. See al ...

(1,5-dicaffeoylquinic acid)

Biosynthesis and natural occurrence

The biosynthetic precursor to chlorogenic acid is

4-coumaroyl-CoA Coumaroyl-coenzyme A is the thioester of coenzyme-A and coumaric acid. Coumaroyl-coenzyme A is a central intermediate in the biosynthesis of myriad natural products found in plants. These products include Monolignol, lignols (precursors to lignin ...

, containing a single hydroxyl group on the aryl ring, which in turn is produced from

cinnamic acid Cinnamic acid is an organic compound with the formula phenyl, C6H5-CH=CH-Carboxylic acid, COOH. It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Classified as an unsaturated carboxy ...

. The

hydroxylation In chemistry, hydroxylation refers to the installation of a hydroxyl group () into an organic compound. Hydroxylations generate alcohols and phenols, which are very common functional groups. Hydroxylation confers some degree of water-solubility ...

of the coumaryl ester, i.e. installing the second hydroxy group, is catalyzed by a

cytochrome P450 Cytochromes P450 (P450s or CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for examp ...

enzyme. Chlorogenic acid can be found in the

bamboo Bamboos are a diverse group of mostly evergreen perennial plant, perennial flowering plants making up the subfamily (biology), subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family, in th ...

Phyllostachys edulis ''Phyllostachys edulis'', the bamboo, or tortoise-shell bamboo, or (), (), () is a temperate species of giant timber bamboo native to China and Taiwan and naturalised elsewhere, including Japan where it is widely distributed from south of Hok ...

'', as well as in many other plants, such as the shoots of

common heather ''Calluna vulgaris'', common heather, ling, or simply heather, is the sole species in the genus ''Calluna'' in the flowering plant family Ericaceae. It is a low-growing evergreen shrub growing to tall, or rarely to and taller, and is found wide ...

(''

Calluna vulgaris ''Calluna vulgaris'', common heather, ling, or simply heather, is the sole species in the genus ''Calluna'' in the flowering plant family Ericaceae. It is a low-growing evergreen shrub growing to tall, or rarely to and taller, and is found wide ...

'').

In food

Chlorogenic acid and the related compounds cryptochlorogenic acid, and

neochlorogenic acid Neochlorogenic acid is a natural polyphenol found in some dried fruits and other plant sources, such as peaches. It is an isomer of chlorogenic acid Chlorogenic acid (CGA) is the ester of caffeic acid and quinic acid, functioning as an interme ...

have been found in the leaves of ''

Hibiscus sabdariffa Roselle (''Hibiscus sabdariffa'') is a species of flowering plant in the genus ''Hibiscus'' that is native to Africa, most likely West Africa. In the 16th and early 17th centuries it was spread to Asia and the West Indies, where it has since beco ...

''. Isomers of chlorogenic acid are found in potatoes. Chlorogenic acid is present in the flesh of

eggplant Eggplant (American English, US, Canadian English, CA, Australian English, AU, Philippine English, PH), aubergine (British English, UK, Hiberno English, IE, New Zealand English, NZ), brinjal (Indian English, IN, Singapore English, SG, Malays ...

peach The peach (''Prunus persica'') is a deciduous tree first domesticated and Agriculture, cultivated in China. It bears edible juicy fruits with various characteristics, most called peaches and the glossy-skinned, non-fuzzy varieties called necta ...

es,

prune A prune is a dried plum, most commonly from the European plum (''Prunus domestica'') tree. Not all plum species or varieties can be dried into prunes. Use of the term ''prune'' for fresh plums is obsolete except when applied to varieties of ...

s and coffee beans.

Research and safety

There is not enough evidence to determine whether chlorogenic acid is safe or effective for human health, and its use in high doses, such as excessive consumption of green coffee, may have

adverse effect An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term compli ...

s. Chlorogenic acid has not been approved as a

prescription drug A prescription drug (also prescription medication, prescription medicine or prescription-only medication) is a pharmaceutical drug that is permitted to be dispensed only to those with a medical prescription. In contrast, over-the-counter drugs c ...

food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used f ...

recognized as a safe ingredient for foods or beverages. Chlorogenic acid is under preliminary research for its possible biological effects, such as regulation of blood pressure, although there is insufficient evidence for its effectiveness.

Nomenclature

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 The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

guidelines, with the consequence that 3-CQA became 5-CQA, and 5-CQA became 3-CQA. Both numbering systems remain in use, as of 2016.

References

{{Authority control Hydroxycinnamic acid esters Hydroxycinnamic acid glycosides Quinic acid esters Catechols