Ultrasensitive SERS quantitative detection of antioxidants via diazo derivatization reaction and deep learning for signal fluctuation mitigation

Synthetic antioxidants serve as essential protectors against oxidation and deterioration of edible oils, however, prudent evaluation is necessary regarding potential health risks associated with excessive intake. The direct adsorption of antioxidants onto conventional surface-enhanced Raman scattering (SERS) substrates is challenging due to the presence of phenolic hydroxyl groups in their molecular structures, resulting in weak Raman scattering signals and rendering direct SERS detection difficult. In this study, a diazo derivatization reaction was employed to enhance SERS signals by converting antioxidant molecules into azo derivatives, enabling the amplification of the weak Raman scattering signals through the strong vibrational modes induced by the N = N double bond. The resulting diazo derivatives were characterized using UV-visible absorption and infrared spectroscopy, confirming the occurrence of diazo derivatization of the antioxidants. The proposed method successfully achieved the rapid detection of three commonly used synthetic antioxidants, namely butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), and propyl gallate (PG) on interfacial self-assembled gold nanoparticles. Furthermore, rapid predictions of BHA, PG, and TBHQ within the concentration range of 1 × 10-6 to 2 × 10-3 mol/L were achieved by integrating a convolutional neural network model. The predictive range of this model surpassed the traditional quantitative method of manually selecting characteristic peaks, with linear coefficients (R2) of 0.9992, 0.9997, and 0.9997, respectively. The recovery of antioxidants in real soybean oil samples ranged from 73.0 % to 126.4 %. Based on diazo derivatization, the proposed SERS method eliminates the need for complex substrates and enables the analysis and determination of synthetic antioxidants in edible oils within 20 min, providing a convenient analytical approach for quality control in the food industry.

Colorimetric sensor array based on CoOOH nanoflakes for rapid discrimination of antioxidants in food

The identification of synthetic antioxidants has considerable significance in food safety. Here, we described the development of a colorimetric sensor array for rapid detection of eight antioxidants in food through the redox reaction between CoOOH and antioxidants in the presence of colorimetric signal indicators. The CoOOH nanoflakes exhibited high catalytic oxidation activity and can independently catalyze oxidation signal indicators showing different colors. The color reaction was inhibited to different degrees in the presence of antioxidants, which resulted in distinct signal response patterns for their discrimination. The method showed good linearity in the range from 50 to 1000 nM for butylated hydroxytoluene (BHT), butylhydroxyanisole (BHA), propyl gallate (PG) and tert-butyl hydroquinone (TBHQ). Moreover, different proportions of antioxidants were located in the middle pattern of each single antioxidant, and showed certain linear relationships among different concentration ratios. Finally, the proposed colorimetric sensor array was used for practical applications where TBHQ and BHT were detected in biscuits and sausages, and BHA and PG were detected in fried pork kebabs, respectively. The results were further confirmed by high-performance liquid chromatography, which demonstrated the great potential of the colorimetry sensor array for practical applications.

Identification of In Vitro Metabolites of Synthetic Phenolic Antioxidants BHT, BHA, and TBHQ by LC-HRMS/MS

Butylated hydroxytoluene (BHT) and its analogs, butylated hydroxyanisole (BHA) and tert-butyl-hydroquinone (TBHQ), are widely used synthetic preservatives to inhibit lipid oxidation in the food, cosmetic and pharmaceutical industries. Despite their widespread use, little is known about their human exposure and related biotransformation products. The metabolism of these compounds was investigated using in vitro incubations with human and rat liver fractions. Liquid chromatography coupled to high-resolution tandem mass spectrometry was employed to detect and characterize stable and reactive species formed via oxidative metabolism, as well as phase II conjugates. Several oxidative metabolites have been detected, as well as glutathione, glucuronide, and sulfate conjugates, many of which were not previously reported. A combination of accurate mass measurements, MS/MS fragmentation behavior, and isotope-labeling studies were used to elucidate metabolite structures.

Properties and Application of Multifunctional Composite Polypropylene-Based Films Incorporating a Combination of BHT, BHA and Sorbic Acid in Extending Donut Shelf-Life

To extend the shelf-life of packaged donut without the addition of preservative, polypropylene-based active composite films loaded with a combination of sorbic acid, BHA and BHT were prepared by the extrusion moulding method: T1 (Control-pure PP-film), T2 (PP-BHT1%-SA2%), T3 (PP-BHA3%-SA2%) and T4 (PP-BHT1%-BHA1%-SA2%). The incorporation of active additives enhanced water vapour permeability (WVP) and increased oxygen permeability of films. Active films had higher antioxidant activity than pure PP in the order T4 > T2 > T3 (89.11, 83.40 and 79.16%). In vitro examinations demonstrated a significant antibacterial effect on Escherichia coli and S. aureus growth. Overall migration was not significantly different for watery food simulants, while in acidic and fatty foods increased it significantly. The effect of the active films on the fried and packaged donut samples showed significantly higher moisture contents and peroxide values, while acidity was lower. T2 film is proposed due to the preservation of the intrinsic properties of the film, increasing the storage period up to 25 to 50 days.

Electrochemical sensor for determination of butylated hydroxyanisole (BHA) in food products using poly O-cresolphthalein complexone coated multiwalledcarbon nanotubes electrode

In this study, we have reported an electrochemical sensor for the determination of butylated hydroxyanisole (BHA) by electropolymerization of O-cresolphthalein complexone (OC) over the multiwalled carbon nanotubes (MWCNTs). In order to confirm the surface morphology, oxidation states, functional groups and charge transfer property of POC/MWCNTs electrode, the resulting POC film with MWCNTs electrode was characterized by spectroscopy, microscopy, and electrochemical techniques. The fabricated electrode was evaluated for its electrochemical performance in oxidation of BHA and the study showed that at POC/MWCNTs electrodes BHA oxidation occurred at 0.27 V. POC/MWCNTs electrode has shown a linear range for the detection of BHA from 0.33 µM to 110 µM with the detection limit of 0.11 µM (S/N = 3). Amperometric determination of BHA was also done using chronoamperometric techniques and the result was found to be linear. The real time analysis of sensors is also validated by analysing the packed potato chips samples.

Alkylated Sesamol Derivatives as Potent Antioxidants

Sesamol is a phenolic derivative. Its antioxidant activity is low than that of Trolox and depends on benzodioxole moiety. Thus, a molecular modification strategy through alkylation, inspired by natural and synthetic antioxidants, was studied by molecular modeling at the DFT/B3LYP level of theory by comparing the 6-31+G(d,p) and 6-311++G(2d,2p) basis sets. All proposed derivatives were compared to classical related antioxidants such as Trolox, t-butylated hydroxytoluene (BHT) and t-butylated hydroxyanisole (BHA). According to our results, molecular orbitals, single electron or hydrogen-atom transfers, spin density distributions, and alkyl substitutions at the ortho positions related to phenol moiety were found to be more effective than any other positions. The trimethylated derivative was more potent than Trolox. t-Butylated derivatives were stronger than all other alkylated derivatives and may be new alternative forms of modified antioxidants from natural products with applications in the chemical, pharmaceutical, and food industries.

Antioxidant Activity of Pastinaca sativa L. ssp. sylvestris [Mill.] Rouy and Camus Essential Oil

In the last decade, there has been growing interest in the food industry in replacing synthetic chemicals with natural products with bioactive properties. This study's aims were to determine the chemical composition and the antioxidant properties of the essential oil of Pastianica sylvestris. The essential oil was isolated with a yield of 0.41% (w/v) by steam distillation from the dried seeds and subsequently analysed by GC-MS. Octyl acetate (78.49%) and octyl hexanoate (6.68%) were the main components. The essential oil exhibited an excellent activity for the inhibition of primary and secondary oxidation products for cold-pressed sunflower oil comparable with butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), which were evaluated using peroxide and thiobarbituric acid values. The antioxidant activity of the essential oil was additionally validated using DPPH radical scavenging (0.0016 ± 0.0885 mg/mL), and β-carotene-linoleic acid bleaching assays. Also, the amounts of total phenol components (0.0053 ± 0.0023 mg GAE/g) were determined.

Herbal Extracts Incorporated into Shortbread Cookies: Impact on Color and Fat Quality of the Cookies

This study aimed at determining the effect of aqueous ethanolic extracts from lemon balm, hyssop and nettle, and butylated hydroxyanisole (BHA) on properties of shortbread cookies. This was achieved by instrumental measurements of color and sensory properties of the cookies directly after baking and by determination of peroxide (PV) and p-anisidine (p-AnV) values, and specific extinction coefficients (K₂₃₂ and K₂₆₈ values) for fat extracted from the cookies stored for 3 months at room temperature. Increase of the herbal extracts’ concentration from 0.02% to 0.2% in the cookies caused a reduction of L* (the brightness) and a* values (the red coordinate), while b* values (the yellow coordinate) increased when the cookies were enriched with lemon balm and nettle extracts. Among the cookies studied, those prepared with BHA and 0.1 and 0.2% addition of lemon balm extracts were characterized by the highest scores for aroma, taste, and overall acceptability. Incorporation of BHA and 0.02% hyssop extract into the cookies caused a decrease of PV values (the peroxide value) for fat extracted from the cookies after 3 months of their storage compared to a (control) sample without additives and produced the lowest K₂₃₂ values. Changes in the p-AnV values for the fat samples studied occurred gradually and slowly during the storage and the obtained values were lower compared to the control sample. All of the studied fat samples also showed a higher ability to scavenge DPPH radicals than the control sample. Considering both PV and p-AnV values as indicators of fat oxidation, BHA protected fat extracted from cookies against oxidation better than the herbal extracts used.

Butylated hydroxyanisole isomers induce distinct adipogenesis in 3T3-L1 cells

Butylated hydroxyanisole (BHA) isomers, as the widely used anthropogenic antioxidants in food, have been revealed to induce endocrine disrupting effects, while the mechanism how BHA isomers regulate the lipogenic differentiation remains to be elucidated. Using 3T3-L1 differentiation model, the effects of BHA isomers, including 2-tert-butyl-4-hydroxyanisole (2-BHA), 3-tert-butyl-4-hydroxyanisole (3-BHA) and their mixture (BHA), on adipogenesis were tested. The results showed that 3-BHA and BHA promoted adipocyte differentiation and enhanced the cellular lipid accumulation through the regulation of the transcriptional and protein levels of the adipogenetic biomarkers, while 2-BHA had no effect. The effective window for 3-BHA induced lipogenesis was the first four days during 3T3-L1 differentiation. BHA isomers showed no binding affinities for peroxisome proliferator activated receptor γ (PPARγ). Instead, the upstream of PPARγ signaling pathway, i.e. the phosphorylation of cAMP-response element binding protein (CREB), upregulation of CAAT/enhancer-binding proteins β (C/EBPβ) and elevated cell proliferation during postconfluent mitosis stage were induced by 3-BHA exposure. Altogether, this study revealed the adipogenic effect of 3-BHA through interference with the upstream events of the PPARγ signaling pathway. The authorized usage of BHA as food additives and its occurrence in human sera can potentially contribute to the incidence of obesity, which is of high concern.

Microencapsulated food-grade antioxidant applied as a preservative of peanut seed quality in microcosm- and pilot-scale trials

BACKGROUND

In Argentina, peanuts are stored for 3-6 months. It is important to avoid proliferation of fungi and insect pests during this period. In this study, the potential of butylated hydroxyanisole (BHA) microcapsules to conserve peanut kernels was evaluated in microcosms and on a pilot scale.

RESULTS

In microcosm assays, microcapsules containing BHA at a dose of 1802 µg g^-1 reduced 37% of total fungal count. Higher reductions (77-100%) were obtained with a combined treatment with BHA formulation (1802 µg g^-1 ) plus fungicide (methyl thiophanate 0.0100 g L^-1  and metalaxyl 0.0133 g L^-1 ). However, germination levels of peanut seeds treated with the BHA formulation were less than 6% throughout the incubation time. In pilot-scale trials, the storage conditions allowed the control of fungal development and insect proliferation. Quantifiable levels of BHA were also detected throughout the entire storage period. The combined treatment significantly reduced fungal contamination at 2 months of storage (C1-2015: 37.41%; C1-2016: 28.48%; C2-2016: 45.02%). Seed germination of unshelled stored peanuts was not affected by the formulation.

CONCLUSION

The application of the BHA formulation during storage combined with pre-seeding treatment could be an appropriate strategy to maintain the quality of the peanut kernels destined for seed. © 2018 Society of Chemical Industry.

Impact of antioxidant additives on the performance and emission characteristics of C.I engine fuelled with B20 blend of rice bran biodiesel

This manuscript presents the impact of addition of antioxidant additives to rice bran biodiesel blend on the performance and emission characteristics of compression ignition (C.I) engine. Rice bran methyl ester (RBME) was produced from rice bran oil by transesterification using sodium hydroxide as catalyst. An experimental investigation was conducted on a single-cylinder four-stroke C.I engine to analyze the performance and emission characteristics of rice bran methyl ester (RBME) blended with diesel at 20% by volume (B20) with and without addition of 1000 ppm of two monophenolic antioxidant additives, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The results showed that the BHA- and BHT-treated B20 blend decreased the brake specific fuel consumption (BSFC) by 2.1 and 1.2% and increased the brake thermal efficiency (BTE) by 1.04 and 0.5% compared to B20. The BHA- and BHT-treated B20 blend produced mean reductions in NOx emission of 12.2 and 9.6%, respectively, compared to B20. The carbon monoxide (CO) and hydrocarbon (HC) emissions of BHA- and BHT-treated B20 were increased by 14.8-16.6% and 10.6-11.2%, respectively, compared to B20. However the emission levels were lower than those of diesel.

Anti-inflammatory activity of the artificial antioxidants 2-tert-butyl-4-methoxyphenol (BHA), 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,4,6-tri-tert-butylphenol (TBP), and their various combinations

BACKGROUND/AIM

The artificial complex phenols, 2-tert-butyl-4-methoxyphenol (BHA), 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,4,6-tri-tert-butylphenol (TBP) exert efficient antioxidant activity; however, they are considerable toxic and potentially tumor-promoting. These phenols, particularly in combinations, have enhanced antioxidant activity due to synergistic interactions and produce bioactive intermediates such as quinone methide. We investigated the anti-inflammatory activity of BHA, BHT and TBP, and combinations of BHT/BHA (in molar ratios of 1:1, 1:2, 1:3 and 2:1), BHT/TBP (1:1), and BHA/TBP (1:1), using gene-expression systems for cyclooxygenase-2 (Cox2) and tumor necrosis facto-alpha (Tnfa) in RAW264.7 cells.

MATERIALS AND METHODS

The inhibitory effects of BHA, BHT and TBP on expression of Cox2 and Tnfa genes upon stimulation with Escherichia coli lipopolysaccharide (LPS) or Porphyomonas gingivalis (Pg) fimbriae were determined using real-time polymerase chain reaction.

RESULTS

The inhibitory effect on expression of Cox2 and Tnfa genes upon stimulation with LPS and fimbriae was greatly enhanced by the combination of two antioxidants (molar ratio 1:1), BHT/BHA. In addition, that of the Cox2 gene, but not of Tnfa gene was slightly enhanced by a combination of equimolar BHT/TBP and BHA/TBP. None of the antioxidants alone exerted any anti-inflammatory activity upon stimulation with LPS, but a slight anti-inflammatory activity was observed upon stimulation with Pg fimbriae. The inhibitory effect of the BHT/BHA combination on expression of Cox2 mRNA upon stimulation with LPS was investigated at afferent molar ratios, and a molar ratio of 1:1 was found to have considerably less effect than a molar ratio of 1:2 or 2:1. The 1:3 combination had no effect.

CONCLUSION

The combination of BHT and BHA at a molar ratio of 0.5-2 exerts potent anti-inflammatory activity. This anti-inflammatory activity on the generation of inflammatory mediators in LPS-activated RAW264.7 cells may be attributable to complex synergistic antioxidant activity of the combination of BHT and BHA. Our results suggest the potential usefulness of the BHT/BHA combination at an appropriate molar ratio as an antioxidant in foods and pharmaceuticals, whereas either antioxidant alone is unlikely to be effective.

Conformational stability, vibrational and NMR analysis, chemical potential and thermodynamical parameter of 3-tert-butyl-4-hydroxyanisole

The FT-IR and FT-Raman spectra of 3-tert-butyl-4-hydroxyanisole (TBHA) molecule have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. Optimized geometrical structure, harmonic vibrational frequencies has been computed by B3LYP level using 6-31G (d,p) and 6-311+G (d,p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the first-order hyperpolarizability of the investigated molecule were computed using DFT calculations. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and analyzed. The isotropic chemical shift computed by (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the TBHA calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations.

Molecular structure, quantum mechanical calculation and radical scavenging activities of (E)-4,6-dibromo-2-[(3,5-dimethylphenylimino)methyl]-3-methoxyphenol and (E)-4,6-dibromo-2-[(2,6-dimethylphenylimino)methyl]-3-methoxyphenol compounds

In this study, (E)-4,6-dibromo-2-[(3,5-dimethylphenylimino)methyl]-3-methoxyphenol and (E)-4,6-dibromo-2-[(2,6-dimethylphenylimino)methyl]-3-methoxyphenol compounds have been synthesized and characterized by using X-ray crystallographic method, FT-IR and Density functional method. The molecular geometry, vibrational frequencies of the title compounds in the ground state have been calculated by using B3LYP with the 6-31G(d,p) basis set. The tautomeric form of the compounds has been demonstrated by using single crystal X-ray method, FT-IR spectrometer and DFT method. In addition, HOMO-LUMO energy gap, molecular electrostatic potential map and NBO analysis of the compounds are performed at B3LYP/6-31G(d,p) level. It may be remarked that the free radical scavenging activities of the title compounds were assessed using DPPH, DMPD+, and ABTS+ assays. The obtained results show that especially compound 2 has effective DPPH (SC50 1.52±0.14 μg/mL), DMPD+ (SC50 1.22±0.21 μg/mL), and ABTS+ (SC50 3.32±0.17 μg/mL) scavenging activities compared with standards (BHA, rutin, and trolox).

Quantum mechanical study and spectroscopic (FT-IR, FT-Raman, UV-Visible) study, potential energy surface scan, Fukui function analysis and HOMO-LUMO analysis of 3-tert-butyl-4-methoxyphenol by DFT methods

This study represents an integral approach towards understanding the electronic and structural aspects of 3-tert-butyl-4-methoxyphenol (TBMP). Fourier-transform Infrared (FT-IR) and Fourier-transform Raman (FT-Raman) spectra of TBMP was recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The molecular structures, vibrational wavenumbers, infrared intensities and Raman activities were calculated using DFT (B3LYP and LSDA) methods using 6-311++G (d,p) basis set. The most stable conformer of TBMP was identified from the computational results. The assignments of vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of TBMP have been discussed. The stability and charge delocalization of the molecule was studied by Natural Bond Orbital (NBO) analysis. UV-Visible spectrum and effects of solvents have been discussed and the electronic properties such as HOMO and LUMO energies were determined by time-dependent TD-DFT approach with B3LYP/6-311++G (d,p) level of theory. The molecule orbital contributions are studied by density of energy states (DOSs). The reactivity sites are identified by mapping the electron density into electrostatic potential surface (MEP). Mulliken analysis of atomic charges is also calculated. The thermodynamic properties at different temperatures were calculated, revealing the correlations between standard heat capacities, standard entropy and standard enthalpy changes with temperatures. Global hardness, global softness, global electrophilicity and ionization potential of the title compound are determined.

Spectroscopic studies on the antioxidant activity of ellagic acid

Ellagic acid (EA, C14H6O8) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anticarcinogenesis and anti-oxidation properties. In vitro radical scavenging and antioxidant capacity of EA were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. EA inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 μg/mL concentration. On the other hand, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), α-tocopherol and ascorbic acid displayed 69.8%, 66.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, EA had an effective DPPH• scavenging, ABTS+ scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that EA can be used in the pharmacological, food industry and medicine because of these properties.

Spectroscopic studies on the antioxidant activity of p-coumaric acid

p-coumaric acid (4-hydroxycinnamic acid), a phenolic acid, is a hydroxyl derivative of cinnamic acid. It decreases low density lipoprotein (LDL) peroxidation and reduces the risk of stomach cancer. In vitro radical scavenging and antioxidant capacity of p-coumaric acid were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe(2+)) chelating activity and ferric ions (Fe(3+)) reducing ability. p-Coumaric acid inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45μg/mL concentration. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and ascorbic acid displayed 66.8%, 69.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, p-coumaric acid had an effective DPPH scavenging, ABTS(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe(3+)) reducing power and ferrous ions (Fe(2+)) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that p-coumaric acid can be used in the pharmacological and food industry because of these properties.

Stability and antioxidant activity of semi-synthetic derivatives of 4-nerolidylcatechol

4-nerolidylcatechol (4-NC) is an unstable natural product that exhibits important antioxidant, anti-inflammatory and other properties. It is readily obtainable on a multi-gram scale through straightforward solvent extraction of the roots of cultivated Piper peltatum or P. umbellatum, followed by column chromatography on the resulting extract. Semi-synthetic derivatives of 4-NC with one or two substituent groups (methyl, acetyl, benzyl, benzoyl) on the O atoms have been introduced that have increased stability compared to 4-NC and significant in vitro inhibitory activity against the human malaria parasite Plasmodium falciparum. Antioxidant and anti-inflammatory properties may be important for the antiplasmodial mode of action of 4-NC derivatives. Thus, we decided to investigate the antioxidant properties, cytotoxicity and stability of 4-NC derivatives as a means to explore the potential utility of these compounds. 4-NC showed high antioxidant activity in the DPPH and ABTS assays and in 3T3-L1 cells (mouse embryonic fibroblast), however 4-NC was more cytotoxic (IC₅₀ = 31.4 µM) and more unstable than its derivatives and lost more than 80% of its antioxidant activity upon storage in solution at −20 °C for 30 days. DMSO solutions of mono-O-substituted derivatives of 4-NC exhibited antioxidant activity and radical scavenging activity in the DPPH and ABTS assays that was comparable to that of BHA and BHT. In the cell-based antioxidant model, most DMSO solutions of derivatives of 4-NC were less active on day 1 than 4-NC, quercetin and BHA and more active antioxidants than BHT. After storage for 30 days at −20 °C, DMSO solutions of most of the derivatives of 4-NC were more stable and exhibited more antioxidant activity than 4-NC, quercetin and BHA and exhibited comparable antioxidant activity to BHT. These findings point to the potential of derivatives of 4-NC as antioxidant compounds.

The characteristics of performance and exhaust emissions of a diesel engine using a biodiesel with antioxidants

The aim of this study is to investigate the effects of antioxidants on the oxidation stability of biodiesel fuel, the engine performance and the exhaust emissions of a diesel engine. Biodiesel fuel used in the study was derived from soybean oil. The results show that the efficiency of antioxidants is in the order TBHQ>PrG>BHA>BHT>alpha-tocopherol. The oxidative stability of biodiesel fuel attained the 6-h quality standard with 100 ppm TBHQ and with 300 ppm PrG in biodiesel fuel. Combustion characteristics and exhaust emissions in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. The BSFC of biodiesel fuel with antioxidants decreased more than that of biodiesel fuel without antioxidants, but no trends were observed according to the type or amount of antioxidant. Antioxidants had few effects on the exhaust emissions of a diesel engine running on biodiesel.

Sorption behavior of a synthetic antioxidant, polycyclic musk, and an organophosphate insecticide in wastewater sludge

Emerging contaminants (ECs) are chemicals that are currently unregulated due to limited understanding of health effects and limited data regarding occurrence. Wastewater treatment plants (WWTP) receive many ECs as components of influent waste and the removal of organic contaminants, such as ECs, occurs primarily by sorption to sludge. Therefore, it is important to develop measures of sorption behavior by ECs to sludge. This study evaluates sorption of three ECs: 3-tert-butyl-4-hydroxyanisole (BHA) a synthetic antioxidant, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta(g)-2-benzopyrane (HHCB) a polycyclic musk, and chlorpyrifos a organophosphate insecticide. Twenty-four hour laboratory-scale sorption experiments were conducted for each compound individually and then in combination, which allowed the quantification of sorption onto wastewater sludge and the affects of multiple compounds. ECs in both the liquid and solid phases were analyzed using a gas chromatograph with flame ionization detector (GC/FID). Isotherms of individual sorption behavior followed a linear trend (R2 > 0.9) for individual ECs, while K(d) averaged 2,689 L kg(-1), 27,786 L kg(-1) and 31,402 L kg(-1) for BHA, chlorpyrifos and HHCB, respectively. Sorption behavior for BHA was linear during combined studies with K(d) of 1,766 L kg(-1) or a decrease of 34%, while HHCB and chlorpyrifos followed non-linear isotherm models. Synergistic effects were observed with spike concentrations > or =25 mg L(-1) for HHCB and > or =20 mg L(-1) for chlorpyrifos. K(d) values ranged from 16,984-6,000,000 L kg(-1) for HHCB and 19,536-3,000,000 L kg(-1) for chlorpyrifos. These distribution coefficients differed substantially from previously published values, mainly because few studies used sludge as the sorption media. Results suggest that HHCB and chlorpyrifos may be contained in the sludge unlike BHA, which is more available in the aqueous phase. Future investigations should evaluate WWTP processes for degrading ECs to harmless products and releases of ECs from sludge.

Comparative study of the alkyl and peroxy radical-scavenging activity of 2-t-butyl-4-methoxyphenol (BHA) and its dimer, and their theoretical parameters

BACKGROUND

2-t-Butyl-4-methoxyphenol (BHA) has considerable toxicity and undesirable potential tumor-promoting activities. To clarify the free radical mechanism of BHA-induced toxicity, the comparative radical-scavenging activity of BHA and its dimer (bis-BHA, 3,3'-ditert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diol) with or without 2-mercapto-1-methylimidazole (MMI) was studied using the induction period method.

MATERIALS AND METHODS

The induction period and propagation rate (Rp) were determined by differential scanning calorimetry (DSC) monitoring of polymerization of methyl methacrylate, initiated by the thermal decomposition of benzoyl peroxide (a source of the peroxy radical, PhCOO*) or 2,2'-azobisisobutyronitrile (a source of the alkyl radical, R*) under nearly anaerobic conditions. The anti-1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical- and O2(-)-scavenging activities were also investigated. Furthermore, theoretical parameters were calculated from the DEFT/B3LYP and HF/6-31G*//B3LYP levels.

RESULTS

For both PhCOO* and R* the inhibition rate constant (k(inh)) for BHA and bis-BHA was almost identical, but a marked decrease in the Rp(inh)/Rp(con) was found for the former. The BHA/MMI mixture (1:1 molar ratio) oxidized by R* reduced the total radical-scavenging activity by approximately 20% . BHA showed lower anti-DPPH radical- and higher O2(-)-scavenging activity.

CONCLUSION

Upon PhCOO* or R* scavenging, BHA with a lower BDE, IP(koopman's), electronegativity, and electrophilicity value, but not bis-BHA with higher corresponding values, highly suppressed propagation. This may be due to the formation of highly reactive free-radical intermediates, which are potentially toxic.

A novel method to measure both the reductive and the radical scavenging activity in a linoleic acid model system

The aim of this study was to develop a combined method for measuring the total antioxidant activity, the reductive and the radical scavenging activity. Linoleic acid was used as the substrate for an iron-initiated lipid peroxidation to measure the total antioxidant activity. In addition, methyl esters of linoleic acid hydroperoxides were used as substrates to measure the reductive antioxidant activity. The radical scavenging antioxidant activity was calculated by subtracting the reductive antioxidative activity from the total antioxidative activity. As representative examples, the antioxidants alpha-tocopherol, ascorbic acid, trans-resveratrol and L-glutathione as well as commonly used food additives such as 2(3)-tert-butyl-4-hydroxyanisole (BHA) and 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT) were analyzed. The results for the novel antioxidation test showed that alpha-tocopherol, BHA and BHT are primarily acting as radical scavengers, whereas ascorbic acid and L-glutathione show a strong reductive capacity. As linoleic acid as well as its hydroperoxides both are present in foods and in the organism, the test presented here can be considered representative of radical reactions occurring in food matrixes and in vivo. Further experiments are required to document the comprehensive applicability in foods and in vivo.

A rapid technique to evaluate the oxidative stability of a model drug

The objective of the current study was to investigate the oxidative induction time (OIT) as a measurement of the stability of an oxygen-sensitive model drug. The OIT was determined by differential scanning calorimetry and represents the time required for oxidative decomposition to occur at a given temperature. Samples were heated to a specific temperature under a nitrogen blanket then held isothermal while exposed to oxygen. The experiment proceeded until oxidative degradation of the sample was apparent from the real-time heat flow graphs. Variables investigated in this study included different lots and suppliers of a model drug as well as the addition of antioxidants. Results demonstrated that the stability of the drug was dependent on the supplier. All antioxidants investigated in this study improved oxygen stability of the model compound, as evidenced by a longer OIT. Butylated hydroxyanisole (BHA) was found to better stabilize the drug than butylated hydroxytoluene at equivalent concentrations. The combination of ascorbic acid and BHA provided the greatest protection against oxidation of the model compound. The results of this study demonstrate the usefulness of OIT to investigate the oxygen stability of pharmaceutical compounds.

Ozonation of endocrine disrupting chemical BHA under the suppression effect by salt additive--with and without H(2)O(2)

The oxidation of fresh and saline wastewater containing an endocrine disrupting chemical (butylated hydroxyanisole, BHA) under different reaction conditions by ozonation and O(3)/H(2)O(2) was investigated at various pH levels. The observed pseudo-first-order reaction kinetics was justified through a combined direct ozone and indirect radical oxidation approach for the ozonation process. The BHA decay rates increased with the increase of the solution pH, but decreased as the NaCl concentration increased because of the consumption of ozone by chloride. A kinetic model was therefore derived for predicting BHA degradation at various initial pH levels and NaCl concentrations. For the O(3)/H(2)O(2) and O(3)/H(2)O(2)/Cl(-) processes, the rate of BHA removal was investigated at hydrogen peroxide concentration ranged from 0.5 to 5mM at pH 7. Different optimal H(2)O(2) dosages and decay rates were found for both processes due to the participation of reactions among O(3), H(2)O(2), OH* and Cl(-) as discussed in the paper.

Reaction pathways and kinetics of butylated hydroxyanisole with UV, ozonation, and UV/O(3) processes

The chemical degradation of the endocrine disrupting chemical, butylated hydroxyanisole (BHA), was investigated by different treatment processes including ultraviolet (UV) irradiation, ozonation (O(3)), and UV/O(3). O demethylation, dimerization, and oxidation have been found to be the main degradation mechanisms. A systematic decay pathway was proposed based on ten identified intermediates in the studied processes, including a unique pathway leading to the formation of precipitates in the ozonation process. An unconventional minimum-type variation of BHA decay rate constants from acidic to caustic range has been found for both ozonation and UV/O(3) processes. The precipitates formed during ozonation can be removed during the process to optimize the treatment, while the UV/O(3) process can offer a relatively fast and clean process to degrade BHA and its associated intermediates.

The aqueous degradation of butylated hydroxyanisole by UV/S2O8(2-): study of reaction mechanisms via dimerization and mineralization

Three distinctive phases of BHA reactivity toward UV/ S2O8(2-) at acidic, neutral, and basic pH range were examined, where 80-100% mineralization has been observed within an hour of irradiation under 254 nm. A reduction in solution pH during the reaction was observed mainly due to the complete conversion of S2O8(2-) to sulfate ion together with proton generation. Seven measurable intermediates were found via an oxidation and dimerization process at all tested pH levels. The BHA decay mechanisms are quite different in acidic condition and at other pH levels. There are three unique intermediates that are only detectable at pH 3 via two additional pathways. This is due to the generation of weaker oxidants or radicals which results in a slower degradation of the BHA, and therefore, the accumulation of these intermediates to detectable levels. The rate of BHA decay generally increases from low to high pH levels; however, the corresponding mineralization at higher pH is retarded due to the futile process of recombining radicals and involvement of intermediates. Therefore, neutral pH was suggested to be the optimum condition in terms of mineralization and moderate efficiency in removing BHA.

Antioxidant activities of various extracts of lotus (Nelumbo nuficera Gaertn) rhizome

Lotus rhizome powder was extracted with solvents of different polarities. Antioxidant activities of the extracts were evaluated by a 2, 2'-diphenylpicrylhydrazyl (DPPH) assay and a beta-carotene bleaching assay, and compared with that of butylated hydroxyanisole (BHA) and ascorbic acid. Methanol showed the highest extract yield among all of solvents. Although acetone extract had the highest total phenolics content, methanol extract had the highest total phenolics recovery from lotus powder (20.1 mg catechin equivalents/100g lotus powder). Extract of either methanol or acetone demonstrated the highest DPPH scavenging activity at both 66.7 mg/L and 133.3 mg/L. All extracts exhibited higher antioxidant activity coefficient (AAC) than that of ascorbic acid, furthermore, dichloromethane and petroleum extracts had comparable AAC with BHA by the beta-carotene bleaching assay. The properties of the extracting solvents significantly affected the yield, total phenolics content and antioxidant activity of lotus rhizome extracts.

Antioxidant Properties of Methanolic Extracts from Leaves of Rhazya stricta

Because of increased safety concerns about synthetic antioxidants, exploitation of cheaper and safer sources of antioxidants based on natural origin is the focus of research nowadays. Rhazya stricta is a medicinally important plant native to South Asia. Extraction of antioxidants was carried out in different solvent systems, i.e., water, 80% methanol, 70% ethanol, and diethyl ether. The methanolic extract exhibited the highest total phenolic content among the extracts; therefore for further studies the methanolic extract was employed. Antioxidant activity measurement in the linoleic acid system, metal chelating activity, reducing power, scavenging effect on 1,1-diphenyl-2-picrylhydrazyl free radical, and superoxide anion radical scavenging activity were taken as the parameters for assessment of antioxidant potential of methanolic extracts. Results were compared with alpha-tocopherol and the synthetic antioxidant butylated hydroxyanisole. The antioxidant potential of methanolic extracts of R. stricta leaves was comparable with previously exploited potent antioxidants and is strongly concentration dependent.

An ortho dimer of butylated hydroxyanisole inhibits nuclear factor kappa B activation and gene expression of inflammatory cytokines in macrophages stimulated by Porphyromonas gingivalis fimbriae

Butylated hydroxyanisole, BHA, is widely used as a potent antioxidant, but its adverse effects such as carcinogenesis and proinflammatory activity have been reported, which are possibly due to the prooxidant property of this compound. We recently demonstrated that the dimer of 2-methoxyphenols exhibits cyclooxygenase-2 inhibition, because of lessening of its prooxidant property caused by the dimerization. In the present study, toward our goal of developing a chemopreventive agent for chronic periodontal diseases, we examined whether 2-BHA (2-tert-butyl-4-methoxyphenol) and its synthetic ortho dimer, bis-BHA (3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diol) could inhibit the Porphyromonas gingivalis fimbria-stimulated inflammatory reaction. The fimbria-induced expression of interleukin-1beta and neutrophil chemoattractant KC genes in RAW264.7 murine macrophages was strongly inhibited by bis-BHA. In contrast, 2-BHA showed only slight inhibition. bis-BHA also significantly inhibited the fimbria-stimulated phosphorylation-dependent degradation of the alpha inhibitor of nuclear factor-kappaB and the transcriptional activity of this factor in the cells. These findings suggest that bis-BHA possesses anti-inflammatory activity against chronic periodontal diseases.

Simultaneous analysis of antioxidants and preservatives in cosmetics by supercritical fluid extraction combined with liquid chromatography-mass spectrometry

This study evaluated supercritical fluid extraction (SFE) combined with liquid chromatography-mass spectrometry (LC-MS) to determine trace preservatives and antioxidants including methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol (alpha-t) and alpha-tocopherol acetate (alpha-ta) in cosmetic products. A supercritical fluid extraction procedure was used to isolate four paraben preservatives and four antioxidants from the cosmetic matrix before quantitative analysis. The optimum extraction condition was performed with static extraction for 5 min, then dynamic extraction for 20 min by using carbon dioxide supercritical fluid at 14,000 kPa and 65 degrees C. Methanol was used as collection solvent and the sea sand was chosen as a filling material. The analytes were separated on a C18 reversed-phase column using methanol-water as mobile phase and quantified by measuring its mass spectrometry. The linearity range is from 10 to 20,000 ng/g with RSD values below 18%. Detection limits are achieved at the level of 4.7-142 ng/g. It was successfully applied to the determination of paraben preservatives and antioxidants in cosmetics without tedious pretreatment.

[Comparative characteristics of the antioxidants of plant origin introduced in fat emulsion foods]

One of the methods of increasing the quality of fatty products is including in their composition antioxidants, which provide the time of their conservation and improvement of their biological value. From this point of view calls concern a new drug epigallocatechina gallate. On the basis of these studies the prospects of usage were shown epigallocatechina gallate in fatty products and the paths of further applying in creation of food products.

Kinetic studies of the radical-scavenging activity of ebselen, a seleno-organic compound

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) is now under active investigation as a neuroprotective and anticancer agent. In the present study, the induction period method was used to investigate the antioxidant activity of ebselen in the radical polymerization of methyl methacrylate (MMA) at 70 degrees C. The reaction of ebselen with growing MMA radicals (lipid radicals) showed a k(inh) of 4 x 10(4) M(-1)s(-1). This value was similar to that for mercaptomethylimidazole (MMI, a thiol) and 10-fold greater than that for butylated hydroxyanisole (BHA). The ratio of the rate of chain inhibition to that of chain propagation (CI/CP) for ebselen, MMI and BHA was 0.1, 0.01 and 0.001, respectively, whereas the stoichiometric factor (n, the number of free radicals trapped by one mole of antioxidant moiety) for the corresponding compounds was 0.02, 0.2 and 2, respectively. Ebselen preferentially affected CP rather than CI, indicating that it was an effective scavenger (suppressor) of growing MMA radicals. These results suggest that ebselen is a potent suppressor of polyunsaturated fatty acid (PUFA) radicals, which are harmful radicals in biological systems.

Kinetic evaluation of polyamines as radical scavengers

To clarify whether polyamines scavenge alkyl (carbon-centered) and peroxy (oxygen-centered) radicals, we analyzed their effects on the kinetics of polymerization of methyl methacrylate (MMA) induced by 2,2'-azobisisobutyronitrile (AIBN, a R* radical) and benzoyl peroxide (BPO, a PhCOO* radical) under nearly anaerobic conditions. Stoichiometric factors (n; number of free radicals trapped by one mole of antioxidant moiety) were determined by the induction period method. The n value for polyamines (putrescine, spermidine and spermine) was 0.1-0.7, whereas that for conventional synthetic antioxidants, BHA and BHT, was about 2. These n values were not different between the AIBN and BPO systems. The n value for polyamines declined in the order spermine > spermidine > putrescine. The K(inh)/K(p) value for polyamines (20-115) was greater than that (4-7) for BHT or BHA. Radical-scavenging activity largely depends on the stoichiometric factor of antioxidants rather than their effects on initial rate of polymerization, a rate of propagation. Polyamines may scavenge alkyl or peroxy radicals derived from polyunsaturated fatty acids in biological systems.

Solid-State Nuclear Magnetic Resonance Determination of the Physical Form of BHA on Common Pharmaceutical Excipients

PURPOSE

The purpose of this study was to evaluate the physical form of 2-tert-butyl-4-methoxy-phenol (BHA) following wet granulation onto common pharmaceutical excipients.

METHODS

A 13C label was incorporated into the methoxy group of BHA, the major isomer in synthetic butylated hydroxyanisole. Solutions of the labeled BHA were used to load the labeled BHA onto common pharmaceutical excipients. After air drying under ambient conditions, the mixtures were examined by 13C MAS and CP/MAS nuclear magnetic resonance (NMR) spectroscopy to evaluate the physical form of the BHA.

RESULTS

The data suggested that BHA could exist as either a crystalline or an amorphous component and that amorphous material was either bound to excipients or relatively mobile during the time of the NMR experiment. At 0.1% loading, BHA appeared to be amorphous and mobile in the freshly prepared blends. At 0.5% loading, BHA was shown to be amorphous on microcrystalline cellulose (MCC) and hydroxypropylmethylcellulose (HPMC) while remaining crystalline on lactose, mannitol, calcium phosphate dihydrate, and croscarmellose sodium.

CONCLUSIONS

Solid-state NMR spectroscopy has been used to probe the physical forms of 13C-labeled BHA granulated onto common pharmaceutical excipients. The techniques described in this paper may be applied to help explain stability changes in formulations containing BHA.

In vitro antioxidant properties of morphine

Morphine is implicated in diverse functions, from development to immune modulation in the central and peripheral nervous systems. It has also been used extensively in the clinical management of pain due to its potent analgesic effect. This study was designed to evaluate the in vitro antioxidant capacity of morphine using different antioxidant tests, including total antioxidant activity, reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities. Morphine exhibited strong total antioxidant activity. The concentrations of 25, 50 and 75 microgml(-1) of morphine showed 79.1, 84.3 and 92.3% inhibition on peroxidation of linoleic acid emulsion, respectively. On the other hand, at 75 microgml(-1) concentration of standard antioxidant, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and alpha-tocopherol, exhibited 88.7, 94.5 and 70.4% inhibition on peroxidation of linoleic acid emulsion, respectively. In addition, morphine had effective reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities at the same concentrations (25, 50 and 75 microgml(-1)). These various antioxidant activities were compared to standard antioxidants such as BHA, BHT and alpha-tocopherol.

Evaluation of antioxidant potential of aloe vera (Aloe barbadensis miller) extracts

The polysaccharide and flavonoid concentrations of two-, three-, and four-year-old Aloe vera were determined, and their antioxidant activities were evaluated compared to BHT and alpha-tocopherol by the DPPH radical scavenging method and the linoleic acid system at 100 microg of soluble solids per mL of ethanol. The results showed that three-year-old Aloe vera contained significantly higher levels of polysaccharides and flavonoids than two- and four-year-old Aloe vera, and no significant differences in flavonoid levels were found between three- and four-year-old Aloe vera. All the aloe extracts showed significant antioxidant activity. The antioxidant activity of Aloe vera extracts and reference compounds followed the order: three-year-old Aloe vera > BHT > four-year-old Aloe vera > alpha-tocopherol > two-year-old Aloe vera. The three-year-old extract exhibited the strongest radical scavenging activity of 72.19%, which is significantly higher than that of BHT at 70.52% and alpha-tocopherol at 65.20%. These data suggest that the growth stage plays a vital role in the composition and antioxidant activity of Aloe vera.

Modeling the Co-Antioxidant Behavior of Monofunctional Phenols. Applications to Some Relevant Compounds

A study on the regeneration of alpha-tocopherol (vitamin E) by phenolic co-antioxidants in homogeneous hydrocarbon solution is reported. The behavior of some relevant phenols such as BHA, BHT, and trans-resveratrol appears to be nicely predicted by a model based on the knowledge of kinetic and thermochemical data concerning the various reactants. Despite its good reputation as an antioxidant, trans-resveratrol was found only moderately effective (k(inh) = 2.0 x 10(5) M(-1) s(-1) in chlorobenzene at 303 K) and unable to recycle vitamin E.

Reversal of dentin bonding to bleached teeth

Many studies have shown a considerable reduction in enamel bond strength of resin composite restorations when the bonding procedure is carried out immediately after bleaching. These studies claim that a certain waiting period is needed prior to restoration to reach the original bond strength values prior to bleaching. This study determined the effect of anti-oxidant applications on the bond strength values of resin composites to bleached dentin. Ninety human teeth extracted for orthodontic purposes were used in this study. The labial surface of each tooth was ground and flattened until dentin appeared. The polished surfaces were subjected to nine different treatments: 1) bleaching with gel (35% Rembrandt Virtuoso); 2) bleaching with gel + 10% sodium ascorbate (SA); 3) bleaching with gel + 10% butylhydroxyanisole (BHA); 4) bleaching with sol (35% hydrogen peroxide); 5) bleaching with sol + 10% sodium ascorbate; 6) bleaching with sol + 10% BHA; 7) bleaching with gel + immersed in artificial saliva for seven days; 8) bleaching with sol + immersed in artificial saliva for seven days; 9) no treatment. After bonding application, the resin composite in standard dimensions was applied to all specimens. The teeth were stored in distilled water at 37 degrees C for 24 hours and a universal testing machine determined their resistance to shear bond strength. The data was evaluated using ANOVA and Duncan tests. Bond strength in the bleached dentin group significantly decreased compared to the control group. On the other hand, the antioxidant treatment had a reversal effect on the bond strength to dentin. After the bleaching treatment, the 10% sodium ascorbate application was effective in reversing bond strength. In the samples where antioxidant was applied after the bleaching process, bonding strength in dentin tissue was at the same level as those teeth kept in artificial saliva for seven days.

Comparison of antioxidant activity between aromatic indolinonic nitroxides and natural and synthetic antioxidants

In view of the possible employment of nitroxide compounds in various fields, it is important to know how they compare with other synthetic antioxidant compounds currently used in several industries and with naturally occurring antioxidants. To address this issue, the antioxidant activity of two aromatic indolinonic nitroxides synthesized by us was compared with both commercial phenolic antioxidants (BHT and BHA) and with natural phenolic antioxidants (alpha-hydroxytyrosol, tyrosol, caffeic acid, alpha-tocopherol). DPPH radical scavenging ability and the inhibition of both lipid and protein oxidation induced by the peroxyl-radical generator, AAPH, were evaluated. The results obtained show that overall: (i) the reduced forms of the nitroxide compounds are better scavengers of DPPH radical than butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BLT) but less efficient than the natural compounds; (ii) the nitroxides inhibit both linolenic acid micelles and bovine serum albumin (BSA) oxidation to similar extents as most of the other compounds in a concentration-dependent fashion. Since the aromatic nitroxides tested in this study are less toxic than BHT, these compounds may be regarded as potential, alternative sources for several applications. The mechanisms underlying the antioxidant activity of nitroxides were further confirmed by UV-Vis absorption spectroscopy experiments and macroscale reactions in the presence of radicals generated by thermolabile azo-compounds. Distribution coefficients in octanol/buffer of the nitroxides and the other compounds were also determined as a measure of lipophilicity.

A chiral ligand-mediated asymmetric addition of a lithium BHA ester enolate to an aldehyde

The asymmetric reaction of a lithium enolate generated from a BHA (2, 6-di-tert-buty-4-methoxyphenyl) propanoate was allowed to react with benzaldehyde in the presence of a diether-type chiral ligand affording the corresponding anti-aldol product in a moderate enantioselectivity. A tetradentate ligand induced better enantioselectivity albeit relative loss of anti-selectivity. A variation of lithiating amide agent affected the selectivity, indicating involvement of an amine as a component of the mixed aggregate. Absolute configuration of some of the aldol products was determined by standard transformations.

In vitro antioxidant properties of dantrolene sodium

Dantrolene sodium is a skeletal muscle relaxant, which inhibits intracellular Ca2+ release from the sarcoplasmic reticulum. The aim of this study is to examine possible in vitro antioxidant effects of dantrolene sodium. For this reason, the in vitro antioxidant effects of dantrolene sodium were studied using thiocyanate methods. Additionally, the reducing power and free radical scavenging activity were determined. Dantrolene sodium showed strong antioxidant activity in the linoleic acid emulsion system. The antioxidant activity increased with an increasing amount of dantrolene sodium (50, 100, 250 microg). The 50, 100 and 250 microg samples of dantrolene sodium showed 55%, 70% and 82% inhibition on peroxidation of linoleic acid, respectively. On the other hand, the 250 microg sample of alpha-tocopherol showed 62% inhibition of peroxidation of linoleic acid. Like antioxidant activity, the reducing power of dantrolene sodium increased in a dose-dependent manner. The reducing power of dantrolene was statistically significant vs control, but lower than butylated hydroxytoluene (BHT) and quercetin. Although dantrolene sodium had free radical scavenging activity this was not statistically significant. In contrast to dantrolene sodium, quercetin and butylated hydroxyanisole (BHA) had highly potent free radical scavenging activities and those were statistically significant. According to the these results, it may be said that antioxidant effect of dantrolene sodium is more related to its antioxidant activity in linoleic acid emulsion and reducing power, than to its free radical scavenging activity. These properties may be major reasons for the inhibition of lipid peroxidation.

Catalytic activity of anion-exchange resins modified with metal-porphine in oxidative reactions of phenols

Anion-exchange resins modified with metal-porphine (M-Pr) have been investigated to develop a solid catalyst in the oxidative reaction of phenols by O2 in air. Co-Pr, which is easily prepared and separable from the reaction mixture, has been proved to accelerate the oxidative reaction of phenols such as 3,5-di-tertbutyl-4-hydroxyanisole. The resulting main oxidative products were identified to be quinones by using the GC-MS method.

Radical intensity and cytotoxicity of butylated hydroxyanisole and its orthobisphenol dimer

The radical intensity of BHA (4-Hydroxy-3-t-butylanisole) and its dimer (3,3'-Di-t-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diol, Bis-BHA) were compared with their cytotoxic activity. ESR spectroscopy showed that BHA produced characteristic five peaks of radicals under alkaline conditions (pH > 9.5). At higher pH, BHA radical rapidly disappeared, and progressively transformed into new radical species, as detected by the splitting of the ESR signal. BHA showed higher cytotoxic activity against salivary gland tumor cell line than against normal human gingival fibroblast. On the other hand, Bis-BHA did not produce any detectable amounts of radicals at wide ranges of pH, corresponding with its weaker cytotoxic activity as compared with BHA. BHA scavenged DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical and superoxide anion, more efficiently than Bis-BHA. The present study demonstrated that BHA is more cytotoxic, produces higher amounts of radicals and more efficiently scavenges various radical species, as compared with Bis-BHA. This suggests the possible link between the cytotoxic activity and radical generation/scavenging activity in BHA-derived compounds.

Antioxidant properties of melatonin: a pulse radiolysis study

Various one-electron oxidants such as OH*, tert-BuO*, CCl3OO*, Br2*- and N3*, generated pulse radiolytically in aqueous solutions at pH 7, were scavenged by melatonin to form two main absorption bands with lambda(max) = 335 nm and 500 nm. The assignment of the spectra and determination of extinction coefficients of the transients have been reported. Rate constants for the formation of these species ranged from 0.6-12.5x10(9) dm3 mol(-1) s(-1). These transients decayed by second order, as observed in the case of Br2*- and N3* radical reactions. Both the NO2* and NO* radicals react with the substrate with k = 0.37x10(7) and 3x10(7) dm3 mol(-1) s(-1), respectively. At pH approximately 2.5, the protonated form of the transient is formed due to the reaction of Br2*- radical with melatonin, pKa ( MelH* <=> Mel* + H+) = 4.7+/-0.1. Reduction potential of the couple (Mel*/MelH), determined both by cyclic voltammetric and pulse-radiolytic techniques, gave a value E(1)7 = 0.95+/-0.02 V vs. NHE. Repair of guanosine radical and regeneration of melatonin radicals by ascorbate and urate ions at pH 7 have been reported. Reactions of the reducing radicals e(aq)- and H* atoms with melatonin have been shown to occur at near diffusion rates.

Interaction between eugenol-related compounds and radicals

The radical modulating activity of 2-methoxy-4-(2-propenyl)phenol (eugenol), 2-t-butyl-4-methoxy-phenol (BHA), and their dimers (bis-eugenol, bis-BHA) was investigated, using ESR spectroscopy. Eugenol produced radicals in alkaline solutions, and enhanced the radical intensity of both sodium-L-ascorbate and sodium 5,6-benzylidene-L-ascorbate. BHA has similar, but slightly lower activity, and their dimers were inactive. Their ability to scavenge the superoxide anion (O2-), generated by hypoxanthine and xanthine oxidase reaction, was in the order of eugenol > bis-eugenol > BHA > bis-BHA. The relative radical intensity among these compounds was paralleled by their cytotoxic activity. The present study demonstrates that eugenol and BHA were very reactive with radicals and their reactivity was considerably reduced by dimerization. The applicability of the dimerized eugenol in dentistry was discussed.

Hydroxylamine and phenol-induced formation of methemoglobin and free radical intermediates in erythrocytes

As previously shown with isolated oxyhemoglobin, methemoglobin formation can also be induced in intact erythrocytes by hydroxylamine compounds and substituted phenols such as butylated hydroxyanisole (BHA). Electron spin resonance investigations revealed that, accordingly, free radical intermediates were formed in erythrocytes from hydroxylamine, N,N-dimethylhydroxylamine, and N-hydroxyurea. Due to the low stability of the dihydronitroxyl radicals, their detection required the use of a continuous flow system and relatively high amounts of the reactants. As has already been demonstrated with the solubilized hemoglobin system, hemoglobin of intact erythrocytes also reacts with the more hydrophilic xenobiotics such as hydroxylamine. However, the reaction rate was slightly reduced, indicating the existence of an incomplete permeability barrier for these compounds. The limited solubility of phenolic compounds in the aqueous buffer of suspended erythrocytes (in combination with the strict requirement of osmolarity in order to prevent hemolysis) impeded the direct detection of the respective phenoxyl radicals previously reported in hemoglobin solutions. However, in accordance with earlier findings in homogeneous reaction systems, chemiluminescence was observed as well, indicating the existence of a further reaction intermediate, which was also obtained in pure hemoglobin solutions when mixed with the respective reactants. As has recently been demonstrated, this light emission is indicative of the existence of highly prooxidative compound I intermediates during methemoglobin formation. Prooxidant formation in erythrocytes is reflected by a significant decrease in thiol levels even with those compounds where free radical formation was not directly detectable by ESR spectroscopy. The use of the spin-labeling technique revealed membrane effects as a result of oxidative stress. Oxidative metabolism of hemoglobin with hydroxylamine caused a release of low molecular weight iron. The marked hemolysis observed in the presence of BHA results from a direct membrane effect of this compound rather than a consequence of free radical-induced oxidative stress. A correlation of the different results is discussed in terms of possible toxicological consequences.

Formation of 8-hydroxydeoxyguanosine in calf thymus DNA treated with tert-butylhydroquinone, a major metabolite of butylated hydroxyanisole

Oxidative DNA damage caused by butylated hydroxyanisole (BHA), 2-tert-butyl(1,4)hydroquinone (TBHQ, a metabolite of BHA) and 2,5-di-tert-butyl(1,4)hydroquinone (DTBHQ), as well as 2,6-di-tert-butyl(1,4)benzoquinone (BHTQ, a metabolite of butylated hydroxytoluene), was evaluated by measuring the formation of 8-hydroxydeoxyguanosine (8OHdG) in calf thymus DNA. 8OHdG formation was greatly increased by TBHQ in a concentration-dependent manner. This effect was strongly enhanced by CuCl2 and suppressed by EDTA, bathocuproinedisulfonic acid disodium salt, methionine, glutathione reduced form or catalase, but was not affected by mannitol, sodium benzoate or sodium azide. Thus, TBHQ-induced 8OHdG formation may be mediated by copper. DTBHQ also induced the formation of 8OHdG, though to a much lesser extent than TBHQ, and its effect was stimulated by CuCl2. BHA had a small enhancing effect at high concentration, only in the presence of CuCl2, whereas in the case of BHTQ, it occurred both in the presence of CuCl2 and FeCl2.