Methoxyphenols—antioxidant principles in food plants and spices: Pulse radiolysis, EPR spectroscopy, and density functional theory calculations*

Bors, Wolf; Kazazić, Snježana; Michel, Christa; Kortenska, Vessela D.; Stettmaier, Kurt; Klasinc̆, L.

doi:10.1002/qua.985

Cited by 19 publications

(15 citation statements)

References 22 publications

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“…Consistent with earlier observations (16,17), we always achieved better correlations between experimental and theoretical calculations for the coupling constants of the aromatic as compared to the side-chain Scheme II. Relevant mesomeric and isomeric structures of caffeic acid and dihydrocaffeic acid radicals used for DFT calculations.…”

Section: Gsupporting

confidence: 91%

“…Pulse radiolysis (12)(13)(14) was employed to study the radical scavenging effectivity and stability of the semiquinone structures. EPR spectroscopy (15) was used to identify likely radical target sites of the individual catechol structures and hybrid density-functional theory (DFT) calculation (16,17) was used to confirm the experimentally obtained isotropic coupling constants and to assign the respective hydrogen atoms.…”

Section: Introductionmentioning

confidence: 99%

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Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

et al. 2004

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Caffeic acid, rosmarinic acid and oligomers of caffeic acid with multiple catechol groups are all constituents of Salvia officinalis. Their antioxidant potential was investigated with regard to their radical scavenging activity and the stability and structure of the intermediate radicals. Pulse-radiolytic studies revealed very high rate constants with hydroxyl radicals. Evidence from kinetic modeling calculations suggested an unusual complex behavior due to the presence of both O 4 -and O 3 -semiquinones and formation and decay of a hydroxyl radical adduct at the vinyl side chain. The radical structures observed by EPR spectroscopy after autoxidation in slightly alkaline solutions were only partially identified due to their instability and generally represented dissociated O 4 -semiquinones. Hybrid density-functional calculations of the potential radical structures showed distinct differences between the resonance stabilization of the O 4 -and O 3 -semiquinones of caffeic and dihydrocaffeic acids, reflected also in the considerably faster decay of the O 3 -semiquinone observed by pulse radiolysis. No evidence was found for dimerization reactions via Cβ radicals typical for lignin biosynthesis.

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Section: Gsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

et al. 2004

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“…In a studty on the kinetics of lipid peroxidation in the presence of HCAs, sinapic acid ensured a longer oxidation stability of lipids when compared to ferulic and para-coumaric acid [128]. The higher stability of phenoxy radicals being surrounded by two methoxy groups rather than one, have been also exploited via combined kinetic and EPR studies [129].…”

Section: Introduction Of Electron Donating Substituentsmentioning

confidence: 99%

Antioxidant Properties of Hydroxycinnamic Acids: A Review of Structure- Activity Relationships

Razzaghi‐Asl¹,

Garrido²,

Khazraei³

et al. 2013

CMC

168

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Hydroxycinnamic acids (HCAs) are important phytochemicals possessing significant biological properties. Several investigators have studied in vitro antioxidant activity of HCAs in detail. In this review, we have gathered the studies focused on the structure-activity relationships (SARs) of these compounds that have used medicinal chemistry to generate more potent antioxidant molecules. Most of the reports indicated that the presence of an unsaturated bond on the side chain of HCAs is vital to their activity. The structural features that were reported to be of importance to the antioxi-dant activity were categorized as follows: modifications of the aromatic ring, which include alterations in the number and position of hydroxy groups and insertion of electron donating or withdrawing moieties as well as modifications of the car-boxylic function that include esterification and amidation process. Furthermore, reports that have addressed the influence of physicochemical properties including redox potential, lipid solubility and dissociation constant on the antioxidant activ-ity were also summarized. Finally, the pro-oxidant effect of HCAs in some test systems was addressed. Most of the investigations concluded that the presence of ortho-dihydroxy phenyl group (catechol moiety) is of significant importance to the antioxidant activity, while, the presence of three hydroxy groups does not necessarily improve the activity. Optimiza-tion of the structure of molecular leads is an important task of modern medicinal chemistry and its accomplishment relies on the careful assessment of SARs. SAR studies on HCAs can identify the most successful antioxidants that could be use-ful for management of oxidative stress-related diseases.Keywords: Antioxidant, hydroxycinnamic acids, in vitro, ROS, structure-activity relationships. OXIDATIVE STRESS AND ANTIOXIDANTSReactive oxygen species (ROS) are oxygen derived molecules that readily react with other compounds and macromolecules and oxidize them. Some representative exam-ples of these species include superoxide (O2•-), hydroxy (HO • ) and peroxy (ROO • ) radicals, hydrogen peroxide (H2O2) and singletROS are involved in important physiological processes such as immune response, gene expression, signal transduc-tion and growth regulation [5,6]; however if they are not kept under tight control by physiological antioxidant systems they will be able to oxidize and damage various biological molecules leading to a condition called oxidative stress [1,7,8]. In this regard, oxidative stress has been reported to be in-volved in the pathogenesis of diseases such as cancer [9], neurodegenerative diseases [10], stroke [11], and others [12,13].Since an important source of ROS comes from environment [14], with the industrial development and the change in life style, oxidative stress related diseases need a special attention [15].Antioxidants operate by preventing or slowing the progression of oxidative damage reactions [16,17]. An antioxidant has been defined as "any substance that delays, p...

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“…Structure-activity relationship studies using theoretical methods are gaining interest among scientists for the prediction or elucidation of differences in the activity of series of molecules. Phenolic antioxidants are the most intensively examined category because of their broadly accepted biological activity [16][17][18][19][20][21][22]. The aim of this article is to present a comparative analysis of the activity of antioxidants as radical scavengers and chainbreaking antioxidants as well as their structure-activity relationships, using various experimental and theoretical methods.…”

Section: Introductionmentioning

confidence: 99%

“…1). They were separated into the following groups: group A: hydroxy cinnamic acids (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15); group B: standard antioxidants (16)(17)(18); group C: flavonoids and related compounds (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33); group D: hydroxy chalcones (34)(35)(36)(37)(38); group E: dihydroxy coumarins (39)(40)(41)(42); and group F: binary mixtures of two antioxidants (43)(44)(45)(46)(47)(48)(49)(50). Correlations between ...…”

Section: Introductionmentioning

confidence: 99%

Phenolic antioxidants – radical‐scavenging and chain‐breaking activity: A comparative study

Kancheva

2009

Euro J Lipid Sci & Tech

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Fifty phenolic antioxidants (AH) (42 individual compounds and 8 binary mixtures of two antioxidants) were chosen for a comparative analysis of their radical-scavenging (H-donating) and chain-breaking (antioxidant) activity. Correlations between experimental (antiradical and antioxidant) and predictable (theoretical) activities of 15 flavonoids, 15 hydroxy cinnamic acid derivatives, 5 hydroxy chalcones, 4 dihydroxy coumarins and 3 standard antioxidants (butylated hydroxytoluene, hydroquinone, DL-atocopherol) were summarized and discussed. The following models were applied to explain the structureactivity relationships of phenolic antioxidants of natural origin: (a) model 1, a DPPH assay used for the determination of the radical-scavenging capacity (AH 1 DPPH . ? A . 1 DPPH-H); (b) model 2, chemiluminescence of a model substrate RH (cumene or diphenylmethane) used for the determination of the rate constant of a reaction with model peroxyl radicals (AH 1 RO 2 . ? ROOH 1 A . ); (c) model 3, lipid autoxidation used for the determination of the chain-breaking antioxidant efficiency and reactivity (AH 1 LO 2 . ? LOOH 1 A . ; A . 1 LH (1O 2 ) ? AH 1 LO 2 . ); and (d) model 4, theoretical methods used for predicting the activity (predictable activity). The highest lipid oxidation stability was found for antioxidants with a catecholic structure and for their binary mixtures with DL-a-tocopherol, as a result of synergism between them.

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Methoxyphenols—antioxidant principles in food plants and spices: Pulse radiolysis, EPR spectroscopy, and density functional theory calculations*

Cited by 19 publications

References 22 publications

Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

Antioxidant Properties of Hydroxycinnamic Acids: A Review of Structure- Activity Relationships

Phenolic antioxidants – radical‐scavenging and chain‐breaking activity: A comparative study

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