Marius-Febi Matei

• Chlorogenic acids (CGAs) are known as common secondary plant metabolites and coffee, tea, potatoes as well as many vegetables and fruits are known to display particularly high contents of such esters. Food processing (roasting, cooking, baking, frying, steaming, microwaving, fermenting) of many dietary plants enriches the profile of the CGAs and their derivatives in a given food, which are then available to human consumption and potentially human metabolism. Even the simple exposure of phenolics to hot water at slightly acidic pH results in an astonishing number of transformation products. These newly formed CGA derivatives contribute to the desired taste, flavor, aroma and color of the foods and beverages. A series of mono-, di- and triacylated chlorogenic acids and derivatives were synthesized in the current project; the chosen cinnamoyl substituents were caffeoyl, feruloyl and dimethoxycinnamoyl. Efficient orthogonal protecting group strategies were developed and employed for the alcohols and carboxylic acid of the quinic acid moiety, and for the phenols of the hydroxycinnamate moiety. In food processing, water does not simply act as a solvent and innocent bystander but as a reactive reagent resulting in significant chemical changes of the dietary material. It was documented in the current study that water addition to the olefinic moiety of the cinnamoyl residues of CGAs, caffeoylglucoses, methyl quinates and γ-quinides takes place in a regiospecific manner. The water addition derivatives were found not only in compound model brews but also in the coffee beverage and the maté tea brew. Other transformation products were detected to form in hot water at slightly acidic pH from CGAs, including trans-cis isomerization and acyl migration products. Liquid chromatography coupled to powerful mass spectrometry techniques and authentic or synthesized standards were used for the identification and characterization of these chemical transformation products.