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

Chlorogenic acid in coffee

The chlorogenic acids are ubiquitous in the plant kingdom. Although chlorogenic acids are common in vegetables foodstuffs, the relatively large quantity present in coffee make it an important dietary sources.

Chlorogenic acid and its isomers represent major coffee constituents of phenolic acid. They are family esters of quinic acid with several hydroxycinnamic acids, particularly caffeic, ferulic, p-coumaric acids.

coffee berries

In coffee they are essentially mono- and diesters and by far the prevailing acids. Other esters may occur but generally only in small amounts.

The quality of coffee depends in part on the relative proportion of mono and dichlorogenic acids, The ratio between these two acids is slightly less in robusta than in arabica. An excess of dichlorogenic acids might result in a metallic after-taste in the beverage.

Oral ingestion by man of 200 mg of chlorogenic acid was found to stimulate stomach secretion with enhancement of hydrochloric acid production. Caffeic acid had the same effect, and quinic acid, XII was inactive.
Chlorogenic acid in coffee