Determination of Chlorogenic Acid

Abstract

SLOTTA AND NEISSER¹ found that o-dihydroxy-phenolic compounds such as chlorogenic acid and caffeic acid could be oxidized quantitatively with an alkaline hypoiodate solution, and used this method for the determination of these acids in coffee. They found that for every mole of chlorogenic or caffeic acid, 10 gm.-atoms of iodine were required for complete oxidation and that the oxidation involved the aromatic ring only without affecting the side chain, This method has recently been used by Wilkinson. Phillips and Bacot² for the determination of chlorogenic acid in flue-cured tobacco. In their method the polyphenols were precipitated from an aqueous extract of tobacco with neutral lead acetate solution. The precipitate of lead salts was then washed with water to remove sugars, suspended in water and decomposed with hydrogen sulphide. Caffeic acid was removed by extraction with ether and chlorogenic acid estimated in the resulting solution by the above method¹. This solution may, however, contain other substances which possess o-dihydroxyphenolic groups, such as rutin^3,4, isoquercitrin^5,6 and quercetin⁵. Wilkinson et al.² state without any proof that rutin did not interfere to any appreciable extent. Since these authors used their results for drawing conclusions about the quality of flue-cured tobacco, it was decided to investigate the action of alkaline hypoiodate on pure polyphenols which contained o-dihydroxyphenolic groups.