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Free radical scavenging potency of dihydrocaffeic acid: Thermodynamics of 2H+/2e- processes

Thermodynamics of 2H+/2e- free radical scavenging mechanisms of dihydrocaffeic acid (3- (3’, 4’-dihydroxyphenyl)propionic acid), an abundant colon catabolite of complex dietary (poly)phenols [1], was studied by DFT method using the Gaussian 09 program package [2]. Geometry optimizations and frequency calculations were carried out using the M06- 2X/6-311++G(d, p) level of theory, in conjunction with the SMD continuum solvation model. The role of catechol moiety (reaction path a) and carboxyl moiety (reaction path b) in free radical scavenging processes was investigated by considering double hydrogen atom transfer (dHAT), double electron transfer- proton transfer (dET-PT) and double sequential proton loss electron transfer (dSPLET) mechanisms [3]. The Gibbs free energies of reactions indicate that dihydrocaffeic acid possesses potential for inactivating free radicals of different nature (HO•, HOO•, CH3O•, CH3OO•, CH2=CH–OO•, PhO• etc.) via dHAT and dSPLET mechanisms. 3’- Methylated, 3’- glucuronidated and 3’-sulfated conjugates of dihydrocaffeic acid may retain their appreciable activity via reaction path b. Because dihydrocaffeic acid is produced in colon in high concentrations (up to 90 mM) [1], and could be much more abundant in the circulation than its precursor molecules, it has potential to contribute to health benefits associated with regular intake of polyphenol- rich diet by direct scavenging of reactive oxygen species. Acknowledgments: This work has been supported by The Foundation of the Croatian Academy of Sciences and Arts, under the project No. 10- 102/244-1-2016. - “Investigations of the antioxidant mechanisms of polyphenols and their metabolites.” [1] B. Halliwell, J. Rafter, A. Jenner, Am. J. Clin. Nutr., 2005, 81, 268S. [2] M. J. Frisch, G. W. Trucks et al., Gaussian 09. Revision A.02, Gaussian, Inc., Wallingford CT, 2009. [3] A. Amić, B. Lučić, V. Stepanić, Z. Marković, S. Marković, J. M. Dimitrić Marković, D. Amić, Food Chem., 2017, 218, 144.

free radical scavenging ; dihydrocaffeic acid ; DFT ; dHAT ; dET-PT ; dSPLET

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