Plant-based phenolic acids: exploring the interaction of digestive enzyme trypsin/DNA and antioxidant potential

Plant-based phenolic acids are abundantly present in fruits, vegetables, and other plant-based sources. Their broad spectrum of biological properties has sparked substantial interest among researchers. Hence, it seems that studies are required about the effects of phenolic acids on the structure and function of biomacromolecules. This study aimed to investigate the binding interactions of two plant-derived phenolic acids, gentisic and protocatechuic acid, with calf thymus DNA (CT-DNA) and trypsin. Experimental analyses were performed using fluorescence spectroscopy, FTIR, antioxidant assays, and molecular docking techniques. Results indicated that both phenolic acids bind to CT-DNA via the minor groove and interact with trypsin, as confirmed by fluorescence quenching. Thermodynamic parameters in agreement with molecular docking results demonstrated that both phenolic acids could interact with trypsin spontaneously through hydrogen bonds and Van der Waals forces. The distance between phenolic acids and trypsin after interaction was calculated according to fluorescence resonance energy transfer (FRET) theory. Synchronous fluorescence, three-dimensional fluorescence, and FTIR analyses indicated that the conformation of trypsin was changed upon binding with both phenolic acids. Molecular docking supported these findings by showing stable binding modes with comparable energies, influenced by hydroxyl group positions. Furthermore, changes in the number and position of hydroxyl groups revealed that gentisic acid has higher antioxidant potential than protocatechuic acid. These findings provide structural insight into the potential enzyme-inhibitory and nucleic acid-binding properties of both phenolic acids. Additionally, this work contributes to the knowledge of interactions between trypsin/DNA and both phenolic acids under physiological conditions and radical scavenging activities.