Kinetic Study of the Quenching Reaction of Singlet Oxygen by Common Synthetic Antioxidants (tert-Butylhydroxyanisol, tert-di-Butylhydroxytoluene, and tert-Butylhydroquinone) as Compared with α-Tocopherol

ABSTRACT: Effects of synthetic phenolic antioxidants (BHA, BHT, and TBHQ) on the methylene blue (MB) sensitized photooxidation of linoleic acid as compared with that of α‐tocopherol have been studied. Their antioxidative mechanism was studied by both ESR spectroscopy in a 2,2,6,6‐tetramethylpiperidone (TMPD)‐methylene blue (MB) system and spectroscopic analysis of rubrene oxidation induced by a chemical source of singlet oxygen. Total singlet oxygen quenching rate constants (k_ox?Q+k_q) were determined using a steady state kinetic equation. TBHQ showed the strongest protective activity against the MB sensitized photooxidation of linoleic acid, followed by BHA and BHT. TBHQ (1 × 10^?3 M) exhibited 86.5% and 71.4% inhibition of peroxide and conjugated diene formations, respectively, in linoleic acid photooxidation after 60‐min light illumination. The protective activity of TBHQ against the photosensitized oxidation of linoleic acid was almost comparable to that of α‐tocopherol. The data obtained from ESR and rubrene oxidation studies clearly showed the strong singlet oxygen quenching ability of TBHQ. The k_ox?Q+k_q of BHA, BHT, and TBHQ were determined to be 3.37 × 10⁷, 4.26 × 10⁶, and 1.67 × 10⁸ M^?1 s^?1, respectively. The k_ox?Q+k_q of TBHQ was within the same order of magnitude of that of α‐tocopherol, a known efficient singlet oxygen quencher. There was a high negative correlation (r² = ?0.991) between log (k_ox?Q+k_q) and reported oxidation potentials for the synthetic antioxidants, indicating their charge‐transfer mechanism for singlet oxygen quenching. This is the 1st report on the kinetic study on k_ox?Q+k_q of TBHQ in methanol as compared with other commonly used commercial synthetic antioxidants and α‐tocopherol.     

Kinetic study on the singlet oxygen quenching activity of nordihydroguaiaretic acid (NDGA) using methylene blue sensitized photooxidation of α-terpinene

Singlet oxygen is highly reactive and can therefore induce rapid oxidation of a range of biological molecules, causing cell damages. The effects of nordihydroguaiaretic acid (NDGA) on the photochemical singlet oxygen oxidation of α-terpinene in methanol were studied. NDGA showed strong protective activity on the singlet oxygen oxidation of α-terpinene in methanol in a dose dependent manner. The protective activity of NDGA was considerably higher than that of butylated hydroxytoluene and 1,4-diazabicyclo[2.2.2]octane. Total singlet oxygen quenching rate constant (k _r +k _q ) of NDGA was determined by a steady state kinetic equation. The total singlet oxygen quenching rate constant of NDGA was 9.81×10⁷ M^?1 sec^?1. The result showed that NDGA possessed strong singlet oxygen quenching activity, indicating its potential for the protection of molecules, cells and nutrients from the highly reactive singlet oxygen. To the best of our knowledge, this is the first report on the singlet oxygen quenching rate constant of NDGA.     

Evaluation of silicon intake through consumption of Takju,Soju, and wine

The protective activities of 6 different catechins on the singlet oxygen induced photooxidation of α-terpinene in methanol were studied to find out the relation between their structure and singlet oxygen quenching activity. The total singlet oxygen quenching abilities (k _r +k _q values) in the same system were also calculated by using a Stern-Volmer plot. The protective activities were in order of epigallocatechin gallate (EGCG)=epigallocatechin (EGC) > gallocatechin gallate (GCG) > epicatechin gallate (ECG) > epicatechin (EC) > catechin (C). The k _r +k _q values of EGCG and C were 1.31×10⁸ and 1.66×10⁷/M·s, respectively. The pyrogallol (B) ring structure was the most influencing factor for the k _r +k _q values. Stereospecific configuration also provided a considerable influence on the values. The G-ring structure did not show significant influence in the value for EGCG and EGC. The k _r values of the catechins were 3.23×10⁵–1.64×10⁶/M·s.     

Migration analysis,antioxidant, and mechanical characterization of polypropylene-based active food packaging films loaded with BHA,BHT, and TBHQ

Polypropylene (PP) based active composite films were prepared by adding butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylated hydroquinone (TBHQ) antioxidants using the extrusion molding process. All concentrations of BHT, 2% to 3% BHA, and 3% TBHQ significantly increased the tensile strength (TS) of the composite films compared with control films. Increasing antioxidant concentration decreased TS values for BHT films, whereas an opposite trend was observed for BHA and TBHQ films. BHA at < 2%, BHT at > 2%, and TBHQ at all added concentrations significantly reduced elongation at break (E_b) of the composite films compared to control films. Water vapor permeability (WVP) of 1% BHT film was not significantly different from control. However, other antioxidants especially at increased concentrations significantly increased WVP values. TBHQ films with 300% to 662% increase had the highest WVP and BHT films with 5% to 81% increase had the lowest WVP among composite films. All three antioxidants had a negative effect on the transparency of the films; however the effect of BHA at higher concentrations was greater. The antioxidants did not change the color attributes of the films. Films containing all antioxidants showed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, which increased with increase in their concentration, especially for those containing 3 wt.% BHT and TBHQ. Overall, incorporating BHA and BHT into a PP matrix improved mechanical, barrier, antioxidant properties, and film appearance and consequently were proposed for the development of antioxidant active PP films. TBHQ film is not recommended for food packaging because of its weak mechanical properties (lower E_b and TS values, higher WVP, and greater migration).     

Synthetic antioxidants determination in lard and vegetable oils by the use of voltammetric methods on disk ultramicroelectrodes

Voltammetry on ultramicroelectrodes was used to determine antioxidants tert-butylhydroxyanisole (BHA), tert-butylhydroxytoluene (BHT) and propyl gallate (PG) in vegetable oils or lard. The present work demonstrates the advantages of using not only the conventional three electrode configuration but also the non-conventional two electrode configuration cell system, with respect to the determination of antioxidants. Different ways of performing the determinations are compared either through step by step extractive procedures or through direct measurements using standard addition. Detection limits in the range of (0.20–1.25)×10⁻⁵ mol dm⁻³, (1.00–1.25)×10⁻⁵ mol dm⁻³ and (0.60–1.00)×10⁻⁵ mol were obtained for BHA and BHT in vegatable oil and PG in lard determinations, respectively, depending upon the medium composition. Relative standard deviations for antioxidants concentration were about 6–7% for most of media studied and can be compared with those reported for HPLC from collaborative studies, i.e. 4.54, 6.61 and 3.18% for BHT, BHA and PG, respectively.     

SYNERGISTIC ACTIVITY OF CAPELIN PROTEIN HYDROLYSATES WITH SYNTHETIC ANTIOXIDANTS IN A MODEL SYSTEM

Capelin protein hydrolysates (CPHs) were examined in a β-carotene-linoleate model system together with synthetic antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tert-butyl hydroquinone (TBHQ). Addition of CPHs was at 0.25 and 1 mg per 5 mL in the above emulsion. BHA and BHT were added at levels of 2.5 and 5 μg and TBHQ at 5 and 10 μg. Absorbance of model emulsion system at 470 nm was recorded every 30 min for 2 h. CHPs and synthetic antioxidants inhibited oxidation of linoleic acid effectively. In the experiment with BHA, the influence of CPHs was significant (p<0.01) for the samples incubated for 60, 90, and 120 min; and in experiments with BHT and TBHQ during the entire incubation period. The influence of added BHA and BHT on inhibition of bleaching of β-carotene in the emulsion system was significant (p <0.01) during the incubation period and after 60, 90 and 120 min when TBHQ was used. A synergistic effect was observed only for CPHs and TBHQ when incubation time was 60, 90, and 120 min.     

Determination of synthetic phenolic antioxidants in soft drinks by stir-bar sorptive extraction coupled to gas chromatography-mass spectrometry

The synthetic phenolic antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butyl hydroquinone (TBHQ) were pre-concentrated by stir-bar sorptive extraction and thermally desorbed (SBSE-TD) before analysis by GC-MS. Several parameters affecting the derivatisation step and both SBSE extraction and thermal desorption were carefully optimised. When the analyses of BHA and TBHQ in their acetylated, silylated and underivatised forms were compared, the best results were obtained when the in-situ derivatisation procedure with acetic anhydride was employed. Quantification was carried out using carvacrol as the internal standard, providing quantification limits of between 0.11 and 0.15 ng ml^?1, depending on the compound. Recovery assays for samples spiked at two concentration levels, 1 and 5 ng ml^?1, provided recoveries in the 81–117% range. The proposed method was applied in the analysis canned soft drinks and the analytes were found in five of the 10 samples analysed.     

Oxidative stability of palm‐ and soybean‐based medium‐ and long‐chain triacylglycerol (MLCT) oil blends

BACKGROUND: Medium‐ and long‐chain triacylglyerols (MLCT) enzymatically esterified using Lipozyme RM IM lipase has very low oxidative stability as it does not contain any antioxidants. The aim of this work was to study the ability of various antioxidants to increase the oxidative stability of palm‐ and soybean‐based MLCT blends which assist to bring up the oxidative stability of both MLCT blends. In this study, the effectiveness of rosemary extracts, sage extracts, tert‐butylhydroquinone (TBHQ) and mixtures of tert‐butyl‐4‐hydroxyanisole (BHA) and tert‐butyl‐p‐hydroxytoluene (BHT) in protecting against oxidation of various MLCT blends was investigated. RESULTS: Blending of MLCT oil with either palm olein or soybean oil improved its smoke point values and oxidative stability. TBHQ addition to both palm‐ and soybean‐based MLCT blends increased oxidative stability. Combination of BHA and BHT showed no significant improvement (P > 0.05) in ability to protect blends from oxidation compared to natural antioxidants such as sage or rosemary extracts. CONCLUSION: Blended oils with 500 g kg^?1 MLCT and 500 g kg^?1 palm olein (MP5) were the most suitable for use at high temperature based on the fatty acid composition of the MLCT blends, which subsequently had an effect on thermal oxidative stability. In general, addition of either natural or synthetic antioxidant assisted in improving the antioxidative strength of both MLCT blends. MLCT blends with added TBHQ showed the highest thermal oxidative stability among the antioxidants used. Copyright © 2008 Society of Chemical Industry     

Qualitative and Quantitative Effects of Antioxidants on the Flavor Stability of Oil

Qualitative and quantitative effects of the common antioxidants, BHA, BHT, PG and TBHQ on the rate of dissolved free oxygen disappearance in soybean oil during storage were studied. The order of effectiveness was BHA, BHT, PG and TBHQ with TBHQ as the most effective. Statistical analyses of the results showed that the effects of BHA and BHT were not significantly different from each other at the 5% level, but BHA or BHT was different from PG or TBHQ, and PG was different from TBHQ. The antioxidant effectiveness of levels of 0, 50, 100, 150 and 200 ppm BHA, BHT, PG or TBHQ was significantly different from one another at the 5% level. The higher the amounts of antioxidants added, the slower the rate of dissolved oxygen disappearance in the oil.     

Autoxidation of methyl linolenate. The effect of antioxidants on product distribution

Studies on autoxidation of polyunsaturated fatty acids in the presence of antioxidants have shown that there can be significant differences in the proportions and types of products produced in ‘inhibited’ autoxidations, as compared with control autoxidations, in the absence of an antioxidant. The autoxidation of methyl linolenate has been used as a model system with which to study the effects of different concentrations of both natural and synthetic antioxidants on the proportions of the various types of oxidation product formed. The antioxidants studied included α-, γ-, and δ-tocopherol, α-tocotrienol, 2,2,5,7,8-pentamethylhydroxychroman (PMHC), 2,6-di-tert-butyl-4-methylphenol (BHT), 3-tert-butyl-4-hydroxyanisole (BHA), and mono-tert-butylhydroquinone (TBHQ). In order to investigate the effect of the antioxidants, the oxidation products were analysed for the proportions of diperoxides and monohy-droperoxides present, and the monohydroperoxide class was further analysed for the proportions of cis, trans and trans, trans dienes and ‘inner’ and ‘outer’ hydroperoxides. In all cases where any significant oxidation occurred the extent of the change in product distribution caused by the antioxidant increased as the antioxidant concentration increased. In many cases the extent of methyl linolenate oxidation occurring under standard conditions (after 100 h at 40°C) also increased as the antioxidant concentration increased, but this was not so for δ-tocopherol, BHT and TBHQ. The importance of these findings in relation to food systems and to the understanding of antioxidant behaviour is discussed.     

Effect of BHA, BHT, TBHQ and PG on Growth and Toxigenesis of Selected Aspergilli

The antifungal effect of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary butylhydroquinone (TBHQ) and propyl gallate (PC) alone or in combination on three toxigenic strains of aspergilli (NRRL 2999, NRRL 4123, NRRL 5835) and three nontoxigenic strains of aspergilli (NRRL 5521, NRRL 5917, NRRL 5918) was examined in a solid medium and in salami. BHT and PG (0.001,0.005,0.01,0.02g per plate) did not inhibit growth, sporulation, and toxigenesis of all six cultures. Aflatoxin production by toxigenic aspergilli (B₁, B₂, G₁ and G₂) in the presence of BHA, TBHQ, and a combination of BHA and TBHQ was reduced significantly (P < 0.05). In salami BHA, TBHQ alone or in combination at 100 ppm significantly (P < 0.05) decreased the aflatoxin production by aspergilli when compared to control samples. A combination of BHA and TBHQ showed synergistic inhibition in both studies (solid medium and salami studies).     

Antioxidants Release from Solvent-Cast PLA Film: Investigation of PLA Antioxidant-Active Packaging

The release study of natural antioxidants, i.e., ascorbyl palmitate and α-tocopherol, and synthetic phenolic antioxidants including butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate, and tert-butylhydroquinone (TBHQ) from polylactic acid (PLA) film into food simulants were accomplished. PLA antioxidant films were placed in contact with 95, 50, and 10 % ethanol at 40 and 20 °C. Released antioxidants were regularly measured by high-performance liquid chromatography system for 60 days. Ascorbyl palmitate was completely degraded during film preparation and is not a suitable antioxidant for PLA antioxidant-active packaging. The diffusion coefficient (D) and partition coefficient (K) of antioxidants were calculated based on obtained data. Diffusion of the antioxidants from PLA to the simulants showed a Fick’s behavior with the diffusion coefficient (D) value between 10^?9 and 10^?11 cm² s^?1 with 0–100 % of release. Faster and higher release of antioxidants occurred at 40 °C according to Arrhenius law. At 40 °C, TBHQ in 95 % ethanol decomposed to 2-tert-butyl-1,4-benzoquinone and other quinone derivatives, and α-tocopherol in 50 % ethanol decomposed to some unknown neoformed compounds. Antioxidants molecular weight, Log P, simulant polarity, and temperature were the most influencing factors on antioxidants release rate from PLA films in contact with food simulants. The D and K coefficients of studied antioxidants from PLA in three food simulants and two temperatures can be used to create PLA antioxidant-active packaging to continually control the oxidation reactions in diverse foodstuffs to ensure higher food qualities. The PLA antioxidant-active packaging approach also permits to reduce the amounts of directly added antioxidants in foods to provide safer foods.     

一种新的儿茶素类食用植物油抗氧化剂

以大豆色拉油和精炼菜籽色拉油为实验油，采用活性氧法(AOM)研究了儿茶素EGCG的长链脂肪酸酯EGCG单棕榈酸酯的抗氧化活性，并与合成抗氧化剂特丁基-4-羟基茴香醚(BHA)、2，6-二特丁基对甲酚(B肿)、叔丁基对苯二酚(TBHQ)的抗氧化活性进行了比较，结果表明脂溶性的EGCG单棕榈酸酯的抗氧活性与TBHQ相当，而比BHA、BHT有更强的活性，是食用植物油很好的抗氧化剂。     

Scirpusin A,a hydroxystilbene dimer from Xinjiang wine grape,acts as an effective singlet oxygen quencher and DNA damage protector

BACKGROUND: Grapes and red wines are rich sources of phenolic compounds such as anthocyanins, catechins, flavonols and stilbenes, most of which are potent antioxidants showing cardioprotective properties. We first isolated scirpusin A, a hydroxystilbene dimer, from a wine grape of Xinjiang, and studied its antioxidant activity. RESULTS: Reactive oxygen species scavenging effects and the protection against reactive singlet oxygen‐induced DNA damage of scirpusin A have been investigated in our experiments. The concentration of scirpusin A required to inhibit 50% of ¹O₂ generation was 17 µmol L^?1, while addition of scirpusin A at 140 µmol L^?1 caused complete inhibition. Further kinetic study revealed that the reaction of Scirpusin A with singlet oxygen has an extremely high rate constant (k_a = 4.68 × 10⁹ L mol^?1 s^?1). Scirpusin A (140 µmol L^?1) exhibited significant inhibition effects on pBR322 DNA breakage. However, scavenging effects of scirpusin A on superoxide anion O₂^?? and hydroxyl radical ·OH were not potent as the inhibitor rates at a concentration of 1400 µmol L^?1 were 28.83% and 19.5%, respectively. CONCLUSION: The present study shows that scirpusin A is a selective quencher of singlet oxygen and a protector against reactive singlet oxygen‐induced pBR322 DNA damage at very low concentrations. Copyright © 2010 Society of Chemical Industry     

Detection of Singlet Oxygen Generation by Chlorophyll using Electron Paramagnetic Resonance Spectroscopy

Electron paramagnetic resonance (EPR) spectroscopy was used to detect the photosensitized generation of singlet oxygen (¹O₂) by chlorophyll b. Illumination of a chlorophyll b solution containing a spin trap (2,2,6,6-tetramethyl-4-piperidone, TMPD) yielded pronounced EPR signals for TAN (2,2,6,6-tetramethyl-4-piperidone-N-oxyl) suggesting the presence of ¹O₂. N,N,N′,N′-tetramethylethylene diamine (TMEDA, a ¹O₂quencher) and a combination of TMEDA with a free radical scavenger (butylated hydroxyanisole, BHA) completely eliminated the TAN signal. BHA alone did not exert this inhibitory effect.     

Effectiveness of antioxidants on the stability of banana chips

The effectiveness of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) in improving the stability of banana chips stored at 65°C were compared. Criteria used in the assessment of the stability of the chips included the determinations of peroxide, p-anisidine, acid and iodine values, E_1cm ^1% at 232 amd 268 nm and the C18:2/C16:0 ratio of oil extracted from banana chips. It was found that chips fried in refined, bleached and deodorised (RBD) olein containing BHA or BHT were more stable than chips fried in RBD olein without antioxidants. BHT was more effective than BHA in prolonging the shelf-life of of banana chips. The same order of effectiveness of the antioxidants was observed at 65°C and at room temperature (25°C).     

Gas Chromatographic Determination of Butylated Hydroxyanisole, Butylated Hydroxytoluene and Tertiarybutyl Hydroquinone in Soybean Oil

Oils containing different levels of the most common phenolic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiarybutyl hydroquinone (TBHQ) from 0–200 ppm were analyzed by a new gas chromatographic method. The antioxidants in oils were isolated by nitrogen gas purging, collected on Tenax GC coated with polymetaphenoxylene, and then separated and quantitated by gas chromatography. This method requires neither extraction of antioxidants from oil nor derivatization of antioxidants. The correlation coefficients (r) between gas chromatographic peak heights or peak area and their concentrations in oils were 0.99 for BHA, BHT, and TBHQ. This simple gas chromatographic method can determine as little as 10 ppm pf BHA, BHT, or TBHQ in oils in an hour.     

Kinetics of Growth and Inhibition of Listeria monocytogenes in the Presence of Antioxidant Food Additives

Listeria monocytogenes strain Scott A in Tryptose Broth was treated with 100-300 ppm butylated hydroxyanisole (BHA), 300-700 ppm butylated hydroxytoluene (BHT) and 10-30 ppm tertiary butylhydroquinone (TBHQ). Resulting growth curves were fitted using the logistic model, and growth parameters [lag period (LP), generation time (GT), and maximum growth (MG)] were calculated. BHA and BHT inhibited Listeria monocytogenes by increasing LP and GT and decreasing MG. Extent of inhibition was concentration-dependent for cultures with BHA, but not with BHT. TBHQ at 10-30 ppm increased LP but did not affect other parameters. LP increased exponentially with increased BHA or TBHQ in Listeria culture. Concentrations of additive required to increase LP by one order of magnitude were 240 ppm for BHA and 26 ppm for TBHQ.     

PG、TBHQ、BHA和BHT4种常见抗氧化剂部分稳定性的研究

研究PG、TBHQ、BHA和BHT 4种常见抗氧化剂在不同溶荆、酸碱中稳定性为检测工作者及科研工作者在试验过程中储存或者提取时提供参考依据。采用高效液相色谱法(HPLc),以4种抗氧化剂的保留率为指标,考察4种抗氧化剂的稳定性。从试验结果来看:PG、TBHQ、BHA和BHT在甲醇以及酸性条件下具有较好的稳定性。     

Singlet molecular oxygen quenching by the antioxidant dimethylmethoxy chromanol in solution and in ex vivo porcine skin

Singlet‐oxygen is a non‐radical reactive oxygen species believed to play a major role in many photooxidation processes in connection with diverse photo‐biological processes such as skin ageing or photocarcinogenesis. Dimethylmethoxy chromanol (3,4‐dihydro‐6‐hydroxy‐2,2‐dimethyl‐7‐methoxy‐1(2H)‐benzopyran) is a potent antioxidant used in cosmetic and pharmaceutical formulations. We have assessed the singlet oxygen quenching ability of dimethylmethoxy chromanol, by monitoring the near‐IR phosphorescence of singlet‐oxygen in solution and in ex vivo porcine skin samples. Dimethylmethoxy chromanol quenches singlet oxygen with a rate constant of (1.3 ± 0.1) × 10⁸ M^?1 s^?1 in solution. Consistent with this, a clear reduction in the singlet oxygen lifetime and emission intensity was observed when ex vivo porcine skin samples were treated with dimethylmethoxy chromanol.