Chlorogenic acid, an ester of caffeic acid and quinic acid, is a major phenolic compound in coffee, but is also found widespread in plants and can be isolated from the leaves and fruit  This compound, long known as an antioxidant, also slows the release of glucose into the bloodstream after a meal.

Biological importance
This acid is an important factor in plant metabolism. It is also an antioxidant and an inhibitor of the tumor promoting activity of phorbol esters; at concentrations as high as 100 μg/L, does not inhibit the 5-lipoxygenase activity of ionophore-stimulated human polymorphonuclear leukocytes.

Chlorogenic acid and caffeic acid are antioxidants in vitro and might therefore contribute to the prevention of Type 2 Diabetes Mellitus and cardiovascular disease .