Antioxidants

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12 pages, 1570 KiB

Open AccessArticle

Effect of Ultrasound-Treated Arabinoxylans on the Oxidative Stability of Soybean Oil

by Mayra A. Mendez-Encinas, Elizabeth Carvajal-Millan, Jesús Ortega-García, Lubitza B. Santiago-Gómez, Yubia De Anda-Flores, Karla G. Martínez-Robinson and Dora E. Valencia-Rivera

Antioxidants 2020, 9(2), 147; https://doi.org/10.3390/antiox9020147 - 10 Feb 2020

Cited by 10 | Viewed by 2721

Abstract

Arabinoxylans (AX) are polysaccharides with antioxidant activity and emulsifying properties, which make them an attractive alternative for its potential application as a natural antioxidant in oils. Therefore, this work aimed to investigate the effect of ultrasonic treatment of AX on their antioxidant capacity [...] Read more.

Arabinoxylans (AX) are polysaccharides with antioxidant activity and emulsifying properties, which make them an attractive alternative for its potential application as a natural antioxidant in oils. Therefore, this work aimed to investigate the effect of ultrasonic treatment of AX on their antioxidant capacity and its ability to improve the oxidative stability of soybean oil. For this purpose, AX were exposed to ultrasonic treatment at 25% (100 W, AX-1) and 50% (200 W, AX-2) power and an operating frequency of 20 KHz during 15 min, and their macromolecular properties (weight average molecular weight (Mw), polydispersity index and intrinsic viscosity) were evaluated. The antioxidant capacity of AX was determined by the DPPH assay and Rancimat test. Results showed that ultrasonic treatment did not affect the molecular identity of the polysaccharide but modified its Mw distribution. AX-1 showed the highest antioxidant activity (75% inhibition) at 533 µg/mL by the DPPH method compared to AX and AX-2. AX at 0.25% (w/v) and AX-1 at 0.01% (w/v) exerted the highest protective effects on oxidative stability of soybean oil with induction periods of 7.69 and 5.54 h, respectively. The results indicate that AX could be a good alternative for the potential application as a natural antioxidant in oils. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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16 pages, 2505 KiB

Open AccessArticle

Hydroxycinnamyl Derived BODIPY as a Lipophilic Fluorescence Probe for Peroxyl Radicals

by Jaroslaw Kusio, Kaja Sitkowska, Adrian Konopko and Grzegorz Litwinienko

Antioxidants 2020, 9(1), 88; https://doi.org/10.3390/antiox9010088 - 20 Jan 2020

Cited by 7 | Viewed by 4820

Abstract

Herein, we describe the synthesis of a fluorescent probe NB-2 and its use for the detection of peroxyl radicals. This probe is composed of two receptor segments (4-hydroxycinnamyl moieties) sensitive towards peroxyl radicals that are conjugated with a fluorescent reporter, dipyrrometheneboron difluoride (BODIPY), [...] Read more.

Herein, we describe the synthesis of a fluorescent probe NB-2 and its use for the detection of peroxyl radicals. This probe is composed of two receptor segments (4-hydroxycinnamyl moieties) sensitive towards peroxyl radicals that are conjugated with a fluorescent reporter, dipyrrometheneboron difluoride (BODIPY), whose emission changes depend on the oxidation state of the receptors. The measurement of the rate of peroxidation of methyl linoleate in a micellar system in the presence of 1.0 µM NB-2 confirmed its ability to trap lipid peroxyl radicals with the rate constant k_inh = 1000 M⁻¹·s⁻¹, which is ten-fold smaller than for pentamethylchromanol (an analog of α-tocopherol). The reaction of NB-2 with peroxyl radicals was further studied via fluorescence measurements in methanol, with α,α′-azobisisobutyronitrile (AIBN) used as a source of radicals generated by photolysis or thermolysis, and in the micellar system at pH 7.4, with 2,2′-azobis(2-amidinopropane) (ABAP) used as a thermal source of the radicals. The reaction of NB-2 receptors with peroxyl radicals manifests itself by the strong increase of a fluorescence with a maximum at 612–616 nm, with a 14-fold enhancement of emission in methanol and a 4-fold enhancement in the micelles, as compared to the unoxidized probe. Our preliminary results indicate that NB-2 behaves as a “switch on” fluorescent probe that is suitable for sensing peroxyl radicals in an organic lipid environment and in bi-phasic dispersed lipid systems. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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18 pages, 1991 KiB

Open AccessArticle

Antioxidant Activity of Metal Nanoparticles Coated with Tocopherol-Like Residues—The Importance of Studies in Homo- and Heterogeneous Systems

by Adrian Konopko, Jaroslaw Kusio and Grzegorz Litwinienko

Antioxidants 2020, 9(1), 5; https://doi.org/10.3390/antiox9010005 - 19 Dec 2019

Cited by 19 | Viewed by 4274

Abstract

Functionalized nanoparticles (NPs) attract great attention in pharmacy, diagnostics, and biomedical areas due to benefits like localization and unique interactions of NPs with biocomponents of living cells. In the present paper, we prepared and characterized two kinds of gold nanoparticles (AuNPs) coated with [...] Read more.

Functionalized nanoparticles (NPs) attract great attention in pharmacy, diagnostics, and biomedical areas due to benefits like localization and unique interactions of NPs with biocomponents of living cells. In the present paper, we prepared and characterized two kinds of gold nanoparticles (AuNPs) coated with α-tocopherol-like residues: 1A were soluble in non-polar solvents and their antioxidant activity was tested during the peroxidation of a model hydrocarbon in a homogeneous system, whereas nanoparticles 1B were soluble in polar solvents and were applied as antioxidants in micellar and liposomal systems. The effectiveness of 1A is comparable to 2,2,5,7,8-pentamethylchroman-6-ol (PMHC, an analogue of α-tocopherol). Taking the results of the kinetic measurements, we calculated an average number of 2150 chromanol residues per one NP, suggesting a thick organic coating around the metal core. In heterogeneous systems, the peroxidation of methyl linoleate dispersed in Triton X-100 micelles or DMPC liposomes resulted in the observation that 1B (545 chromanol residues per one NP) was active enough to effectively inhibit peroxidation in a micellar system, but in a liposomal system, 1B behaved as a retardant (no clear induction period). The importance of microenvironment in heterogeneous systems on the overall antioxidant activity of nanoparticles is discussed. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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17 pages, 3505 KiB

Open AccessArticle

Synthesis, DFT Calculations, and In Vitro Antioxidant Study on Novel Carba-Analogs of Vitamin E

by Aneta Baj, Jakub Cedrowski, Ewa Olchowik-Grabarek, Artur Ratkiewicz and Stanislaw Witkowski

Antioxidants 2019, 8(12), 589; https://doi.org/10.3390/antiox8120589 - 26 Nov 2019

Cited by 22 | Viewed by 4598

Abstract

Vitamin E is the most active natural lipophilic antioxidant with a broad spectrum of biological activity. α-Tocopherol (α-T), the main representative of the vitamin E family, is a strong inhibitor of lipid peroxidation as a chain-breaking antioxidant. Antioxidant and antiradical properties of vitamin [...] Read more.

Vitamin E is the most active natural lipophilic antioxidant with a broad spectrum of biological activity. α-Tocopherol (α-T), the main representative of the vitamin E family, is a strong inhibitor of lipid peroxidation as a chain-breaking antioxidant. Antioxidant and antiradical properties of vitamin E result from the presence of a phenolic hydroxyl group at the C-6 position. Due to stereoelectronic effects in the dihydropyranyl ring, the dissociation enthalpy for phenolic O–H bond (BDE_OH) is reduced. The high chain-breaking reactivity of α-T is mainly attributed to orbital overlapping of the 2p-type lone pair on the oxygen atom (O1) in para position to the phenolic group, and the aromatic π-electron system. The influence of the O1 atom on the antioxidant activity of vitamin E was estimated quantitatively. The all-rac-1-carba-α-tocopherol was synthesized for the first time. Along with model compounds, 1-carba-analog of Trolox and its methyl ester were screened for their in vitro antioxidant activity by inhibition of styrene oxidation, and for the radical-reducing properties by means of 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging assay. To study the antioxidant activity, density functional theory (DFT) was also applied. Reaction enthalpies related to HAT (hydrogen atom transfer), SET–PT (sequential electron transfer—proton transfer), and SPLET (sequential proton loss—electron transfer) mechanisms were calculated. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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13 pages, 2734 KiB

Open AccessArticle

Coordination Complex Formation and Redox Properties of Kynurenic and Xanthurenic Acid Can Affect Brain Tissue Homeodynamics

by Lenka Kubicova, Franz Hadacek, Gert Bachmann, Wolfram Weckwerth and Vladimir Chobot

Antioxidants 2019, 8(10), 476; https://doi.org/10.3390/antiox8100476 - 11 Oct 2019

Cited by 25 | Viewed by 3614

Abstract

Reactive oxygen species (ROS) are known for their participation in various physiological and pathological processes in organisms, including ageing or degeneration. Kynurenine pathway metabolites, such as kynurenic (KYNA) or xanthurenic (XA) acid, can affect neurodegenerative diseases due to their ROS scavenging and Fe [...] Read more.

Reactive oxygen species (ROS) are known for their participation in various physiological and pathological processes in organisms, including ageing or degeneration. Kynurenine pathway metabolites, such as kynurenic (KYNA) or xanthurenic (XA) acid, can affect neurodegenerative diseases due to their ROS scavenging and Fe ion coordination complex formation but insights are still incomplete. Therefore, we investigated the formation and antioxidant capabilities of KYNA– and XA–Fe complexes by nano-electrospray−mass spectrometry, differential pulse voltammetry, deoxyribose degradation and Fe^II autoxidation assays. XA formed coordination complexes with Fe^II or Fe^III ions and was an effective antioxidant. By contrast, only Fe^II–KYNA complexes could be detected. Moreover, KYNA showed no antioxidant effects in the FeCl₃/ascorbic acid deoxyribose degradation assay variant and only negligible activities in the Fe^II autoxidation assay. Coordination complexes of Fe ions with KYNA probably stabilize KYNA in its keto tautomer form. Nevertheless, both KYNA and XA exhibited sufficient antioxidant activities in some of the employed assay variants. The results provide evidence that both have the potential to alleviate neurodegenerative diseases by helping to maintain tissue redox homeodynamics. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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14 pages, 2268 KiB

Open AccessArticle

Evaluation of the Antioxidant Activity of Cis/Trans-N-Phenyl-1,4,4a,5,8,8a-Hexahydro-3,1-Benzoxazin-2-Imines

by Guadalupe Firpo, María L. Ramírez, Martín S. Faillace, Maria dos R. Mendes de Brito, Ana P. S. Correia Lima e Silva, Jessica Pereira Costa, Marcela C. Rodríguez, Gustavo A. Argüello, Zsolt Szakonyi, Ferenc Fülöp and Walter J. Peláez

Antioxidants 2019, 8(6), 197; https://doi.org/10.3390/antiox8060197 - 25 Jun 2019

Cited by 13 | Viewed by 4450

Abstract

The growing interest in the chemistry of unsaturated ring-fused 1,3-heterocycles, in this particular case 1,3-oxazines, arise in part from their versatile pharmacological applications. In the present article, the evaluation of the in vitro and ex vivo antioxidant activity of two cyclohexene-fused oxazines is [...] Read more.

The growing interest in the chemistry of unsaturated ring-fused 1,3-heterocycles, in this particular case 1,3-oxazines, arise in part from their versatile pharmacological applications. In the present article, the evaluation of the in vitro and ex vivo antioxidant activity of two cyclohexene-fused oxazines is discussed. The in vitro antioxidant activity was evaluated by trapping the ABTS and hydroxyl radicals as well as the inhibition of the enzyme acetyl-cholinesterase and hemolysis of erythrocytes by 2,2’-Azobis(2-amidinopropane) dihydrochloride (AAPH). The results suggest that both unsaturated 1,3-oxazines are auspicious sources of biologically active compounds with good antioxidant properties. In addition, a comprehensive analysis of the interaction between these heterocycles with 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals, as well as the measurements of redox potential, provided evidence for a mechanism of antioxidant activity that takes place through electron transfer (ET) processes. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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11 pages, 2661 KiB

Open AccessArticle

Effect of Side Chain Functional Groups on the DPPH Radical Scavenging Activity of Bisabolane-Type Phenols

by Kazuya Ichikawa, Ryosuke Sasada, Kosuke Chiba and Hiroaki Gotoh

Antioxidants 2019, 8(3), 65; https://doi.org/10.3390/antiox8030065 - 16 Mar 2019

Cited by 25 | Viewed by 6573

Abstract

Methods for improving the antioxidant activity of phenolic compounds have been widely investigated; however, most studies have focused on the structure–activity correlations of substituents on the aromatic rings of catechols or flavonoids. We investigated the influence of side chain functional groups on the [...] Read more.

Methods for improving the antioxidant activity of phenolic compounds have been widely investigated; however, most studies have focused on the structure–activity correlations of substituents on the aromatic rings of catechols or flavonoids. We investigated the influence of side chain functional groups on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of xanthorrhizol and curcuphenol analogues. These compounds were synthesised by the side chain functional group conversion of curcumene, followed by direct oxidation of the aromatic ring. We determined the DPPH radical scavenging activity from the half-maximal effective concentration (EC₅₀) obtained from a DPPH assay in methanol. The positional relationships of the side chain with the aromatic ring and phenolic OH group were determined using density functional theory calculations, and the stability of different conformations was compared. Electron transfer-proton transfer was determined to be the dominant mechanism in the DPPH reaction with xanthorrhizol analogues, based on the correlation between the EC₅₀ and ionisation potential. The radical cation was greatly stabilised in the structure where the side chain functional group was close to the aromatic ring. Stabilisation also depended on the phenolic OH group position. In future antioxidant design, aromatic ring substituent conversion and the use of functional groups far from the OH group or ring should be explored. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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17 pages, 3258 KiB

Open AccessArticle

Enhanced Antioxidant Activity under Biomimetic Settings of Ascorbic Acid Included in Halloysite Nanotubes

by Andrea Baschieri, Riccardo Amorati, Tiziana Benelli, Laura Mazzocchetti, Emanuele D’Angelo and Luca Valgimigli

Antioxidants 2019, 8(2), 30; https://doi.org/10.3390/antiox8020030 - 27 Jan 2019

Cited by 27 | Viewed by 5869

Abstract

Antioxidant activity of native vitamin C (ascorbic acid, AH₂) is hampered by instability in solution. Selective loading of AH₂ into the inner lumen of natural halloysite nanotubes (HNT) yields a composite nanoantioxidant (HNT/AH₂), which was characterized and investigated [...] Read more.

Antioxidant activity of native vitamin C (ascorbic acid, AH₂) is hampered by instability in solution. Selective loading of AH₂ into the inner lumen of natural halloysite nanotubes (HNT) yields a composite nanoantioxidant (HNT/AH₂), which was characterized and investigated for its reactivity with the persistent 1,1-diphenyl-2-picrylhydrazyl (DPPH•) radical and with transient peroxyl radicals in the inhibited autoxidation of organic substrates, both in organic solution (acetonitrile) and in buffered (pH 7.4) water in comparison with native AH₂. HNT/AH₂ showed excellent antioxidant performance being more effective than native ascorbic acid by 131% in acetonitrile and 290% (three-fold) in aqueous solution, under identical settings. Reaction with peroxyl radicals has a rate constant of 1.4 × 10⁶ M⁻¹ s⁻¹ and 5.1 × 10⁴ M⁻¹ s⁻¹, respectively, in buffered water (pH 7.4) and acetonitrile, at 30 °C. Results offer physical understanding of the factors governing HNT/AH₂ reactivity. Improved performance of HNT/AH₂ is unprecedented among forms of stabilized ascorbic acid and its relevance is discussed on kinetic grounds. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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Review

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22 pages, 2897 KiB

Open AccessReview

Chain Breaking Antioxidant Activity of Heavy (S, Se, Te) Chalcogens Substituted Polyphenols

by Caterina Viglianisi and Stefano Menichetti

Antioxidants 2019, 8(10), 487; https://doi.org/10.3390/antiox8100487 - 16 Oct 2019

Cited by 15 | Viewed by 6114

Abstract

Polyphenols are probably the most important family of natural and synthetic chain-breaking antioxidants. Since long ago, chemists have studied how structural (bioinspired) modifications can improve the antioxidant activity of these compounds in terms of reaction rate with radical reactive oxygen species (ROS), catalytic [...] Read more.

Polyphenols are probably the most important family of natural and synthetic chain-breaking antioxidants. Since long ago, chemists have studied how structural (bioinspired) modifications can improve the antioxidant activity of these compounds in terms of reaction rate with radical reactive oxygen species (ROS), catalytic character, multi-defence action, hydrophilicity/lipophilicity, biodistribution etc. In this framework, we will discuss the effect played on the overall antioxidant profile by the insertion of heavy chalcogens (S, Se and Te) in the phenolic skeleton. Full article

(This article belongs to the Special Issue The Chemistry of Antioxidant Activity)

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