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Reactivity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in methanol, ethanol, isopropanol, isooctane, and ethyl acetate, was evaluated to assess the antioxidant capabilities in medium chain triacylglycerol. DPPH loss values were obtained over 30 min, with sampling every 5 min. Even the same concentration of antioxidants showed different DPPH reactivity depending on solvent. In methanol, 5 min was enough for α-tocopherol to react with DPPH, whereas BHT did not react with DPPH even after 30 min. Gallate series showed higher DPPH reactivity than TBHQ, sesamol, or BHA in methanol, while lower reactivity in isooctane. Antioxidants in ethanol and isopropanol reacted with DPPH less efficiently compared to those in methanol, the exception being sesamol. DPPH reactivity of gallate series in isooctane was lower than that of sesamol, TBHQ, and α-tocopherol. Combinatorial usage of methanol and isooctane for DPPH reactivity could provide reliable information on the antioxidant capacities of chemicals in edible oils. [ABSTRACT FROM AUTHOR]

This study investigates the antioxidant components (total carotenoids, lycopene, β-carotene, total phenols, flavonoids, ascorbic acid and total vitamin C) as well as the hydrophilic and lipophilic antioxidant activities (HAA and LAA) of tomato genotypes consisting of one ordinary cultivar Rio Grande and the two high-lycopene breeding lines HLT-F71 and HLT-F72. The correlation of nutritional value to L∗, a∗, b∗ colour indexes and a∗/b∗ ratio was also investigated in whole and fresh cut tomato fruits. Except for β-carotene content, significant differences were found among cultivars for antioxidants. The berries of both HLT-lines recorded higher antioxidant contents, HAA and LAA (TEAC and FRAP assays) than Rio Grande. Under controlled conditions, HLT-F72 reached the highest levels of total carotenoids (165.5 mg β-ca Eq per kg fw), lycopene (150.1 mg per kg fw) and total phenolics (549.7 mg GAE per kg fw). However, HLT-F72 exhibited the highest levels of ascorbic acid (193.3 mg per kg fw), total vitamin C (271.6 mg per kg fw) and flavonoids (450.5 mg RE per kg fw). Line HLT-F71 showed the highest HAA (148.0 µM Trolox per 100 g fw and 4.2 mM FRAP per g fw) and LAA values (258.5 µM Trolox per 100 g fw and 3.2 mM FRAP per g fw respectively). Colour readings in red ripe fresh cut tomato berries particularly a∗, b∗ and the ratio a∗/b∗ could represent an indicator not only for lycopene but also for other phytochemicals and resulting antioxidant activities. HLT-Lines may serve as a starting point for the development of semi-determinate growth habit tomato cultivars with higher functional quality.

Pyrogallol, as an important chemical raw material and reagent, has been prepared by the decarboxylation reaction of gallic acid hydrolyzing tannin acid extracted from Chinese gall, but the decarboxylation reaction is known to cause serious environmental pollution. To obtain efficient strains to degrade gallic acid, a screening study was carried out to explore different strains and optimal fermentation conditions of single impact factors, as well as using response surface methodology. The antioxidant bioactivity of products containing pyrogallol in the fermentation medium was also estimated. The results indicated that Enterobacter aerogenes could degrade gallic acid into pyrogallol with 77.86% average yield under the optimal fermentation conditions of an inoculum size of 5%, substrate concentration of 0.32%, incubation period of 60 h, fermentation temperature of 32 °C, content of phosphate buffer at 25%, and an initial pH of 6.0 in fermentation medium. The products contained 66.5% pyrogallol and were tested for their antioxidant capacity. They proved to have stronger antioxidant capacity compared with ABTS, BHT, and even Vc. In conclusion, the study provided a simple, highly efficient method, superior to complex genetic engineering technologies, to degrade gallic acid into pyrogallol, suggesting the possibility of large-scale production in the future.

The effect of traditional stir-frying process at different heating temperatures (50–150 °C) and time periods (5–20 min) on hydrophilic part (total and individual phenolics), lipophilic part (tocopherol and phytosterol compounds) and their corresponding antioxidant capacities in pine nut kernels were investigated. The concentrations of total phenolics, phenolic acids, tocopherols and phytosterols in raw pine nut kernels were 15.76 mg gallic acid equivalents/100 g dry weight (mg GAE/100 g DW), 12.15 mg/100 g DW, 28.67 mg/100 g DW and 198.81 mg/100 g DW, respectively. Stir-frying at low temperatures over short time periods led to an increase of phenolics, phytosterols and hydrophiliic antioxidant capacities. However, these values decreased under the longer heating time and the higher temperature. Tocopherols and lipophilic antioxidant capacities did not show clear changes at lower heating temperatures or shorter heating times, while they had an apparent decreasing trend at higher heating temperatures or longer heating times. Gallic acid might be the main component, which is responsible for the hydrophilic antioxidant capacity (R2 = 0.84, 0.81 and 0.81 using DPPH, FRAP and H-ORAC assays), and tocopherols might be the main antioxidant components in the lipophilic part (R2 = 0.87 and 0.89 using DPPH and L-ORAC assays). [ABSTRACT FROM PUBLISHER]

Antioxidative or prooxidative properties of α-tocopherol, Trolox, ascorbic acid, and ascorbyl-palmitate at the concentration of 0.1 and 1.0 mM were determined in oil-in-water (O/W) emulsions under chlorophyll photosensitization. Headspace oxygen depletion, lipid hydroperoxides, and headspace volatile analyses were conducted to determine the oxidative stability of O/W emulsions. For 32 h visible light irradiation, depleted headspace oxygen content in O/W emulsions were in the order of samples containing Trolox, ascorbic acid, ascorbyl palmitate, α-tocopherol, without antioxidants under light, and samples in the dark, which implies that all the added compounds acted prooxidant. These prooxidative properties of added compounds can be observed in the results of lipid hydroperoxides and headspace volatiles. Samples containing ascorbic acid and ascorbyl palmitate retained higher chlorophyll content than those containing Trolox up to 16 h. Increases of concentration of Trolox, ascorbic acid, and ascorbyl palmitate from 0.1 to 1.0 mM increased the lipid oxidation products whereas α-tocopherol decreased the degree of lipid oxidation implying α-tocopherol may not share the same prooxidant mechanisms compared to other compounds in chlorophyll sensitized O/W emulsions. [ABSTRACT FROM AUTHOR]

• Effects of DOPC on lipophilic and hydrophilic antioxidants were determined in bulk oils. • DPPH reactivity of ascorbyl palmitate increased by 10.22 times with DOPC addition. • DOPC significantly enhanced antioxidant activity of ascorbyl palmitate in corn oil. • Synergic effects of DOPC were not observed in bulk oils with α-tocopherol or ascorbic acid. Effects of 1,2-dioleoyl- sn - glycero -3-phosphocholine (DOPC) and moisture on the solubility of hydrophilic and lipophilic antioxidants were evaluated in medium-chain triacylglycerol (MCT) by 2,2-diphenyl-1-picrylhydrazyl (DPPH) reactivity. Next, we assessed the oxidative stability of antioxidant-containing corn oil depending on the presence of DOPC. The critical micelle concentration (CMC) of DOPC decreased when the moisture content was increased from 300 to 495 mg/kg oil and gradually increased when the moisture was further increased to 2122 mg/kg oil. As the DOPC concentration increased, the DPPH reactivity of ascorbyl palmitate in the control MCT increased by 10.23-fold, whereas that of the ascorbic acid and α-tocopherol was slightly affected both by the DOPC and moisture content. Presence of DOPC significantly increased the oxidative stability of ascorbyl palmitate-containing corn oil (p < 0.05), whereas these synergistic antioxidant effects were not observed in ascorbic acid-or α-tocopherol-containing corn oil. In conclusion, DOPC displays a synergistic antioxidant effect with ascorbyl palmitate in bulk oil. [ABSTRACT FROM AUTHOR]

Scavenging rate constants of eight hydrophilic antioxidants, including caffeic acid, chlorogenic acid, genistein, glutathione, N-acetylcysteine, rutin, trolox, and uric acid against multiple ROS, namely superoxide anion, hydroxyl radical, singlet oxygen, and alkoxyl radical were determined with the electron spin resonance method. Direct flash photolysis measurement of the second-order rate constant in the reaction of alkoxyl radical plus the spin trap 5,5-dimethyl-pyrroline N-oxide made it possible to evaluate scavenging rate constants in antioxidants. The magnitudes of scavenging rate constants were notably dependent on the character of each ROS and the overall rate constants were highest in hydroxyl radical scavenging and the lowest in superoxide anion. The highest scavenging rate constant against superoxide anion was obtained by chlorogenic acid (2.9 × 10(5) M(-1) s(-1)) and the lowest was by N-acetylcysteine (5.0 × 10(2) M(-1) s(-1)). For singlet oxygen, the highest was by glutathione (9.4 × 10(8) M(-1) s(-1)) and the lowest was by uric acid (2.3 × 10(6) M(-1) s(-1)). All other numbers are listed and illustrated. Redox potential measurements of the antioxidants indicated that the antioxidants are likely to react with superoxide anion and singlet oxygen through electron transfer processes.