Caffeoylquinic acids in coffee beans

Caffeic, ferulic, and p-coumaric acids are the main phenolic compounds in coffee which derive from trans-cinnamic acid.

Naturally, they may present as mono- or diesters with quinic acid, forming chlorogenic acids, which are known to be the most active antioxidant compounds. Caffeoylquinic acids and particularly 5-CQA (5-O-caffeoylquinic acid) are found to be the most abundant compounds in coffee beans, where they can form vacuolar complexes with caffeine.

Caffeoylquinic acids are cinnamate conjugates derived from the phenylpropanoid pathway. They are generally involved in plant responses to biotic and abiotic stress.

Since caffeoylquinic acids contribute to acidity, astringency, and bitterness of the brewed coffee, they are relevant to sensorial properties of the beverage.

Caffeoylquinic acid compounds are widespread in plants. They protect plants against predation and infection and may have several beneficial functions in the human diet.

Esters formed between hydroxycinnamates and quinic acid represent a major family of plant phenolics. Chlorogenic acid (5-CQA) is the most widespread of all monoesters formed between caffeic and quinic acids.

Due to their antioxidant and antibiotic properties, hydroxycinnamoylquinic acids are involved in numerous biological plant functions such as pest and disease resistance. The caffeoylquinic acids are among numerous phenolic compounds found in plants that are thought to function in defense against predation and parasitism.

In coffee trees, hydroxycinnamoylquinic acids accumulate in beans. This is particularly marked in Coffea canephora where their content can exceed 10 % of dry bean weight.

On a molecular basis, oxidative activity increases in proportion to the number of caffeoyl residues in the molecule. Other potential beneficial effects of caffeoylquinic acid compounds on humans that have been demonstrated in laboratory studies include anti-inflammatory activity; reduced skin aging by inhibiting the enzyme, collagenase; anti-spasmodic activity; antihyperglycemic activity; suppression of melanogenesis.
Caffeoylquinic acids in coffee beans

Antioxidants in coffee

Oxidative stress is a commonly used term to describe a disturbance in the balance between the production of free radicals that, upon accumulation, lead to the cellular breakdown of critical macromolecules. Prolonged oxidative stress inevitably leads to dangerous diseases—such as cancer, cardiovascular diseases, or diabetes—and premature aging. Oxidative stress can be reduced by antioxidant therapy, i.e., by consumption of certain amounts of natural antioxidants contained in food and beverages.

Coffee is one of the best sources of other bioactive compounds, such as flavonoids and phenolic acids. Beneficial health effects of coffee are usually attributed to its high antioxidant activity (ability to inhibit the process of oxidation).

Antioxidant activity of coffee is related to hydroxycinnamic acid family such as chlorogenic, ferulic, caffeic, and n-coumaric acids contained in it. Chlorogenic acid was found as the most abundant phenolic compound in coffee and thus should account for a part of global antioxidant power of the beverage. Other esters of caffeoyl-quinic acids are present in coffee, such as caffeic acid, ferulic acid and P-coumaric acid derivatives, caffeic acid esters being the most abundant.

In roasted coffee, melanoidins (brown pigments) are synthesized—these are strong antioxidants. In some publications, caffeine and trigonelline are considered to be antioxidants also. Hydroxycinnamic derivatives and their hydrolyzed forms such as caffeic acid are considered powerful antioxidant compounds, which inhibit Low Density Lipoproteins (LDL) oxidation and DNA damage, or regulate genetic expression in vitro, and are thus potent candidates for cancer and cardiovascular diseases prevention.

Phenylalanines which are formed during the roasting process show high antioxidant activity, as do heterocyclic compounds. Bioactive compounds in coffee are responsible for many biological actions, such as chemo-protective effects, antioxidant and anti-inflammatory properties, and anticancer activity. Regular brewed coffee consumption protects the human body against many chronic diseases, including cardiovascular disease, obesity, some types of cancer, and type 2 diabetes.
Antioxidants in coffee