title: Structure-thermodynamics-antioxidant activity relationships of selected natural phenolic acids and derivatives: an experimental and theoretical evaluation.
abstract: Phenolic acids and derivatives have potential biological functions, however, little is known about the structure-activity relationships and the underlying action mechanisms of these phenolic acids to date. Herein we investigate the structure-thermodynamics-antioxidant relationships of 20 natural phenolic acids and derivatives using DPPH• scavenging assay, density functional theory calculations at the B3LYP/6-311++G(d,p) levels of theory, and quantitative structure-activity relationship (QSAR) modeling. Three main working mechanisms (HAT, SETPT and SPLET) are explored in four micro-environments (gas-phase, benzene, water and ethanol). Computed thermodynamics parameters (BDE, IP, PDE, PA and ETE) are compared with the experimental radical scavenging activities against DPPH•. Available theoretical and experimental investigations have demonstrated that the extended delocalization and intra-molecular hydrogen bonds are the two main contributions to the stability of the radicals. The C = O or C = C in COOH, COOR, C = CCOOH and C = CCOOR groups, and orthodiphenolic functionalities are shown to favorably stabilize the specific radical species to enhance the radical scavenging activities, while the presence of the single OH in the ortho position of the COOH group disfavors the activities. HAT is the thermodynamically preferred mechanism in the gas phase and benzene, whereas SPLET in water and ethanol. Furthermore, our QSAR models robustly represent the structure-activity relationships of these explored compounds in polar media.
authors: School of Mathematical Sciences, Henan Institute of Science and Technology, Xinxiang 453003, P. R. China.
authors: Yuzhen
authors: Y
authors: Chen
authors: Key Laboratory of Biorheological Science and Technology, Ministry of Education, School of Bioengineering, Chongqing University, Chongqing 400044, P. R. China.
authors: Huizhi
authors: H
authors: Xiao
authors: Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, United States of America.
authors: Jie
authors: J
authors: Zheng
authors: Key Laboratory of Biorheological Science and Technology, Ministry of Education, School of Bioengineering, Chongqing University, Chongqing 400044, P. R. China.
authors: Guizhao
authors: G
authors: Liang
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002934:Cinnamates / Q000737:chemistry; D004610:Ellagic Acid / Q000737:chemistry; D062385:Hydroxybenzoates / Q000737:chemistry*; D021281:Quantitative Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D000975:Antioxidants; D002934:Cinnamates; D062385:Hydroxybenzoates; D004610:Ellagic Acid