Structure-activity relationship of procyanidins: systematic preparation and investigation of the antioxidant effect in vitro

• Applicant: Professorin Dr. Tuba Esatbeyoglu
• Subject Area: Food Chemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 461711366

Sustainability is currently a central issue not only in politics, economy and society, but also in the food industry. Therefore, the present project intends to contribute to a more effective reuse of industrial by-products by using the zero waste strategy. Industrial by-products are still rich in valuable ingredients and can be used in the synthesis of bioactive compounds, such as procyanidins which are known to have antioxidant effects. However, a solid basis for understanding the structure-activity relationship with regard to antioxidant properties of these substances is still missing. The present project aims to investigate this basis.In order to achieve this goal, (1) the semi-synthetic approach of A- and B-type procyanidins as well as the study of the variability of the nucleophile will carried out. In this way, not only the substance class of procyanidins will be extended by new structural derivatives, but also products with possibly higher antioxidant activity will be synthesized using nucleophiles, such as quercetin and epicatechin gallate, which are well-known antioxidants. In addition, by adjusting the reaction conditions, gambiriins, which are by-products of semi-synthesis, but may also show antioxidant activity, will be synthesized as main compounds. (2) For structural characterization of the synthesized and subsequently isolated compounds, instrumental analytical methods (NMR and IMS-MS) will be used in addition to phloroglucinolysis or furanolysis to obtain valuable information on the relationship between ion mobility and their molecular structure. (3) Subsequently, for the first time, the compounds will be systematically investigated with respect to their radical scavenging and antioxidant properties using cell-free and cell-based assays. The underlying mechanisms by which procyanidins mediate antioxidant effects will be investigated using modern cell and molecular biological methods. In this context, it will be clarified whether and to what extent the flavan-3 ol units, the number of OH groups in the lower unit, the type and stereochemistry of the interflavan bond and the degree of polymerization have an influence on the bioactivity of the compounds.The obtained results in this project will help to close two knowledge gaps in different disciplines. Firstly, spectra and CCS databases will contribute to the identification of procyanidins in food based on their CCS values - without the need of isolation, phloroglucinolysis and NMR experiments. Secondly, findings on the antioxidant effects of procyanidins and their derivatives will be used to assess their actual contribution to health-promoting effects and thus their importance in the production of food supplements and/or innovative foods.

• DFG Programme: Research Grants