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 ...

of caffeic acid and quinic acid, 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 acids ( caffeic acid, ferulic acid and ''p''-coumaric acid) with quinic acid. 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.

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 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 (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 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'', as well as in many other plants, such as the shoots of common heather ('' Calluna vulgaris'').

In food

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

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, prunes 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 or

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