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Generation of reactive oxidative species from thermal treatment of sugar solutions
... At fixed times (0, 4, 8, 24, 28, and 32 h) the experimental units were sampled and analyzed for glucose consumption. At intermediate sampling times (4,8,24, and 28 h), the depleted glucose concentration was restored by immediately adding additional glucose to guarantee that all experimental units had their corresponding initial glucose concentrations (4, 8, and 12 mM). In addition to glucose concentration, experimental units were analyzed at all sampling times for tryptophan depletion, and formation of allysine, α-AA, advanced glycation end-products (AGEs), and yellowness. ...
... In line with the present experiment, Arcanjo et al. [16] reported the oxidative damage caused to HSA by biologically relevant concentrations of GO and MGO (0.4 mM/37 °C/48 h) proving that this mechanism may occur in vivo, explaining the increased carbonylation levels in plasma proteins from animals and humans with impaired glucose metabolism. It is worth highlighting that the radical-mediated pathway of protein carbonylation (represented in Figure 2 as pathway B) cannot be ruled out since the oxidative decomposition of glucose in the presence of transition metals such as iron leads to the formation of a variety of reactive oxygen species (ROS) and hydrogen peroxide [24]. This Maillard-mediated mechanism of carbonylation has been replicated by authors by using Maillard α-dicarbonyl such as glyoxal (GO) and methylglyoxal (MGO) as reactants, proving that these species are active promoters of allysine formation in proteins. ...
... In line with the present experiment, Arcanjo et al. [16] reported the oxidative damage caused to HSA by biologically relevant concentrations of GO and MGO (0.4 mM/37 • C/48 h) proving that this mechanism may occur in vivo, explaining the increased carbonylation levels in plasma proteins from animals and humans with impaired glucose metabolism. It is worth highlighting that the radical-mediated pathway of protein carbonylation (represented in Figure 2 as pathway B) cannot be ruled out since the oxidative decomposition of glucose in the presence of transition metals such as iron leads to the formation of a variety of reactive oxygen species (ROS) and hydrogen peroxide [24]. The role of Fe 3+ in such degradation is well-known and involves the acceptance of the electrons lost by glucose and Maillard intermediates such as Amadori products. ...
Understanding the molecular basis of the disease is of the utmost scientific interest as it contributes to the development of targeted strategies of prevention, diagnosis, and therapy. Protein carbonylation is a typical feature of glyco-oxidative stress and takes place in health disorders such as diabetes. Allysine as well as its oxidation product, the α-amino adipic acid (α-AA) have been found to be markers of diabetes risk whereas little is known about the chemistry involved in its formation under hyperglycemic conditions. To provide insight into this issue, human serum albumin was incubated in the presence of FeCl3 (25 μM) and increasing glucose concentrations for 32 h at 37 °C. These concentrations were selected to simulate (i) physiological fasting plasma concentration (4 mM), (ii) pathological pre-diabetes fasting plasma concentration (8 mM), and pathological diabetes fasting plasma concentration (12 mM) of glucose. While both allysine and α-AA were found to increase with increasing glucose concentrations, the carboxylic acid was only detected at pathological glucose concentrations and appeared to be a more reliable indicator of glyco-oxidative stress. The underlying chemical mechanisms of lysine glycation as well as of the depletion of tryptophan and formation of fluorescent and colored advanced glycation products are discussed.
... Lipids, proteins, and nucleic acids are subject to oxidative damage by ROS due to interaction and electron/hydrogen reduction [5]. Given that it has been shown to impair macromolecules, oxidative stress is harmful to the structure and function of cells [6]. Oxidative stress has been demonstrated to limit the activity of endogenous antioxidants, reducing the cell's antioxidant defenses and increasing the cell's susceptibility to oxidative damage [7]. ...
Oxidative stress has been linked to a wide array of health-debilitating diseases. To alleviate oxidative stress, antioxidants especially of plant origin are desired due to their potency and low toxicity. The current study, therefore, evaluated the antioxidant properties and cytoprotective effects of Terminalia prunioides pods. Hexane, chloroform, ethyl acetate and methanol extracts from Terminalia prunioides pods were evaluated for flavonoid and total phenol contents. Their effects on 2, 2-diphenyl-1-picryl hydrazyl (DPPH), 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), Superoxide dismutase (SOD), Catalase (CAT), reduced glutathione (GSH) and Ferric reducing antioxidant power (FRAP) were evaluated. The extracts were also tested for their cytoprotective effects on HeLa cells against H2O2, using 4-[−3(4-Iodophenyl)-2-(4-nitro-phenyl)-2 H-5-tetrazolio]-1,3-benzene sulfonate (WST-1) assay. The methanol extract possessed 67.8 ± 10.4 mg QE/g and 113.2 ± 7.6 mg GAE/g of total flavonoid (TFC) and total phenolic contents (TPC) respectively. Methanol extracts from Terminalia prunioides pods recorded IC50 values of 0.06 mg/mL, 0.07 mg/mL, and 0.24 mg/mL for DPPH, FRAP and ABTS assays respectively. Catalase (CAT), reduced glutathione (GSH) and Superoxide Dismutase (SOD) activities were significantly increased (p < 0.05) in HeLa cells treated with Terminalia prunioides pods extracts. The current study’'s findings indicate the high antioxidant activity of Terminalia prunioides pods extracts and cytoprotection of HeLa cells from H2O2 induced cell death.
... The oxidation levels found in GLU systems are consistent with the formation of ROS and furthermore, the combination of glucose with Mb intensified both, ROS generation and the subsequent oxidative damage. The generation of ROS through the autoxidation of reducing sugars under physiological conditions, have been experimentally documented by Wang et al. (2016). The present results originally emphasize the relevant role of glucose as inducers of ROS-mediated degradation of biomolecules during gastric digestion of proteins and shows that such effect is enhanced by heme iron. ...
The severe pro-oxidative environment in the stomach promotes oxidation of dietary components. The pro-oxidant molecular mechanisms of reducing sugars on this environment are unknown. To investigate the mechanisms involved in protein oxidation and nitration during a simulated gastric digestion (porcine pepsin, 37°C, 2h) of meat proteins, these were exposed to several dietary reactive components namely myoglobin, glucose, glyoxal, myoglobin+glucose and myoglobin+glyoxal. Two versions of each experimental unit were prepared depending on the addition or absence of nitrite. Compared to control (only meat proteins), myoglobin+glucose showed the highest pro-oxidative and pro-nitrosative effect (p<0.001), likely caused by an increase in ROS derived from the degradation of glucose during assay. Nitrite promoted the occurrence of protein nitration but decreased protein oxidation in myoglobin-added groups (p<0.001) by, plausibly, stabilizing heme iron. These results indicate the relevant role of glyco-oxidation during digestion of red meat with other dietary components such as reducing sugars.
... Therefore, fructose sensors such as fluorescent sensors with operational simplicity and sensitivity are still required at the forefront. Notably, fructose is prone to react with O 2 and then generate reactive oxygen species (ROS) like H 2 O 2 , hydroxyl radical (•OH), and superoxide anion (O 2 ⋅-) [34][35][36]. ...
A surge of nanozymes with oxidase-like activities is emerging in various fields, whereas nanozymes with the ability to catalyze the oxidation of saccharides have less been explored. Herein, CuO nanoparticles (NPs) with phosphate-supported fructose oxidase-like activity have been reported. Notably, reactive oxygen species (ROS) have been confirmed as the products during the process. By coupling the fructose oxidase-like activity with the peroxidase-like activity of CuO NPs, a tandem catalysis-based fructose sensor can be fabricated. In detail, CuO NPs can catalyze the fructose oxidation under O2 to yield ROS (e.g., H2O2, •OH, and O2·-) and effectively decompose H2O2 into ·OH. After that, terephthalic acid can be oxidized by •OH produced from the tandem catalysis to generate a fluorescent product. This sensor shows a linear range toward fructose (0.625–275 μМ) with a low limit of detection (0.5 μМ), which can be successfully conducted to detect fructose from real samples. Overall, this work aims to expand the catalytic types of nanozymes and provide a desirable fructose sensor.
... The possibility that lysine catalyzes formation of dioxetane 69 suggests that proteins can promote formation of toxic aldehydic lipid oxidation products. It also indirectly supports the feasibility of cyclization of fatty acid peroxyl radicals into dioxetanyl radicals as shown in Figure 8. Wang et al. [91] recently found that thermal treatment of pure glucose or fructose solutions up to 70 ∘ C led to formation of both hydrogen peroxide and singlet oxygen. Using glucose as an example, the potential mechanism for singlet oxygen generation during heating of such solutions is suggested in Figure 15. ...
Recent studies have shown that exposing antibodies or amino acids to singlet oxygen results in the formation of ozone (or an ozone-like oxidant) and hydrogen peroxide and that human neutrophils produce both singlet oxygen and ozone during bacterial killing. There is also mounting evidence that endogenous singlet oxygen production may be a common occurrence in cells through various mechanisms. Thus, the ozone-producing combination of singlet oxygen and amino acids might be a common cellular occurrence. This paper reviews the potential pathways of formation of singlet oxygen and ozone in vivo and also proposes some new pathways for singlet oxygen formation. Physiological consequences of the endogenous formation of these oxidants in human tissues are discussed, as well as examples of how dietary factors may promote or inhibit their generation and activity.
This study compared a hydroxyl radical-generating system (HRGS) (0.05-0.2 mM Fe³⁺ + 0.6 mM H2O2) and a glycation system (GLY) (0.05-0.2 mM Fe³⁺ + 0.05 M glucose) for their ability to promote protein carbonylation and tryptophan depletion in myofibrillar proteins, ovalbumin, β-lactoglobulin, soy protein and human serum albumin. Animal-source were more susceptible to protein carbonylation than soy proteins and globular were more susceptible than fibrillar proteins. Both systems promoted tryptophan loss and the formation of protein carbonyls and iron had a clear dose-effect in most systems and proteins. In the tested conditions, the GLY environment was more effective than the HRGS system in promoting the oxidative damage to food proteins. According to the results, glucose and H2O2 may compete for iron for the production of glycosylative and oxidative species, respectively. This study provides original insight into the chemical mechanisms implicated in the oxidative and glycosylative damage to food proteins.
The antioxidative and prooxidative activities of sugars and sugar analogs were investigated on the autoxidation of methyl linoleate and saffower oil. Autoxidation of methyl linoleate was conducted in either the dry state or aqueous emulsion state. Although all sugars and sugar analogs inhibited the autoxidation of methyl linoleate in the dry system, the reducing sugars accelerated oxidation in the aqueous emulsion system. When glyceraldehyde, dihydroxyacetone and glycerol were added in the oxidation system, glyceraldehyde and dihydroxyacetone with water accelerated the formation and decomposition of methyl linoleate monohydroperoxide. On the other hand, glycerol inhibited the formation and decomposition of hydroperoxide. These results indicate that the carbonyl group of sugars accelerates lipid peroxidation and the hydroxy group of sugars and sugar analogs inhibits the oxidation. The effect of sugars in the safflower oil-sugar-cellulose oxidation system was also examined. Sugars at low humidity inhibited the autoxidation of safflower oil, but reducing sugars at high humidity accelerated the oxidation.
There is compelling evidence that long-term intake of excessive fructose can have deleterious side effects in different experimental models. However, the role of fructose in vivo remains controversial, since acute temporary application of fructose is found to protect yeast as well as animal tissues against exogenous oxidative stress. This review suggests the involvement of reactive carbonyl and oxygen species in both the cytotoxic and defensive effects of fructose. Potential mechanisms of the generation of reactive species by fructose in the nonenzymatic reactions, their implication in the detrimental and protective effects of fructose are discussed.
Peroxide bleaching is significantly affected by transition and alkaline earth metals. Isolating the effects of different transition and alkaline earth metals on the reactions of peroxide with different representative lignin structures allows the separation of the positive from the negative contributions of these metal ions. In this work, five monomeric or dimeric phenolic lignin model compounds were treated with alkaline hydrogen peroxide in the absence or presence of Mn2+, Cu2+, Fe3+, and Mg2+. We followed the disappearance of the starting material and the progress of demethylation, radical coupling and oxalic acid formation were followed. Transition metals increased the reactivities of all the lignin model compounds with hydrogen peroxide in the order Mn2+ > Cu2+ > Fe3+, which is the same as the order of activity toward peroxide decomposition while Mg2+ stabilized the system. Demethylation, radical coupling, and oxalic acid formation were all increased by the presence of transition metals in the system and decreased by the addition of Mg2+. The acceleration of the total degree of reaction and of the demethoxylation reactions improves peroxide bleaching, but the increase in the radical coupling reactions can affect the further bleachability of pulp while the increase in the formation of oxalic acid could lead to a greater probability of scaling.Key words: lignins, hydrogen peroxide, peroxide bleaching, reactivity, chemical pulps, metal compounds, alkali treatment, transition metals, delignification.
The purpose of this study is to investigate the feasibility for quantitative measurement of singlet oxygen ((1)O(2)) generation by using a newly developed (1)O(2)-specific fluorescence probe Singlet Oxygen Sensor Green reagent (SOSG). (1)O(2) generation from photoirradiation of a model photosensitizer Rose Bengal (RB), in initially air-statured phosphate buffered saline (PBS) was indirectly monitored with SOSG. In the presence of (1)O(2), SOSG can react with (1)O(2) to produce SOSG endoperoxides (SOSG-EP) that emit strong green fluorescence with the maximum at 531 nm. The green fluorescence of SOSG-EP is mainly dependent on the initial concentrations of RB and SOSG, and the photoirradiation time for (1)O(2) generation. Furthermore, kinetic analysis of the RB-sensitized photooxidation of SOSG is performed that, for the first time, allows quantitative measurement of (1)O(2) generation directly from the determination of reaction rate. In addition, the obtained (1)O(2) quantum yield of porphyrin-based photosensitizer hematoporphyrin monomethyl ether (HMME) in PBS by using SOSG is in good agreement with the value that independently determined by using direct measurement of (1)O(2) luminescence. The results of this study clearly demonstrate that the quantitative measurement of (1)O(2) generation using SOSG can be achieved by determining the reaction rate with an appropriate measurement protocol.
Carboxylic and hydroxycarboxylic acids are an important family of products formed during oxida-tion of reducing sugars and/or carbonyls produced by their degradation. During thermal treatment of foods, the oxidation processes play an important role in the sugar transformations providing that either final oxidation products and/or key intermediates undergo subsequent reactions (oxidative degrada-tion). The extent of sugar oxidation depends mainly on pH value, temperature, the type of sugar, and the presence and type of oxidising agents. Many papers reported on sugar oxidation proceeding under different conditions such as oxidation by enzymes (Geigert et al. 1983), free oxygen (Samuelson Supported by the Ministry of Education, Youth and Sports of the Czech Republic (Projects COST 927, and MSM 6046137305). Department of Food Chemistry and Analysis, Faculty of Food and Biochemical technology, Institute of Chemical technology in prague, prague, Czech Republic Abstract Novotný O., Cejpek K., Velíšek J. (2008): Formation of carboxylic acids during degradation of mono-saccharides. Czech J. Food Sci., 26: 117–131.
Glyceraldehyde and other simple monosaccharides autoxidise under physiological conditions generating 1-hydroxyalkyl (carbon-centred) free radicals and intermediates of dioxygen reduction: superoxide, hydrogen peroxide and hydroxyl radicals. The major glyceraldehyde-derived product is the alpha-ketoaldehyde, hydroxypyruvaldehyde. Close similarities between the temperature dependence of the kinetics of glyceraldehyde autoxidation and glyceraldehyde enolisation to an ene-diol indicates that enolisation is the rate-determining step in the autoxidative process. Inspection of a wide range of carbonyl compounds showed that the monosaccharide moiety -CH(OH)-C- is conserved in carbonyl compounds reactive towards autoxidation, indicating that the ability to form an ene-diol is a prerequisite to monosaccharide autoxidation. The ene-diol intermediate autoxidises rapidly to the products: hydrogen peroxide, water and alpha-ketoaldehydes: beta-hydroxypyruvaldehyde is produced from glyceraldehyde and dihydroxyacetone, glyoxal from glycolaldehyde autoxidation. Ene-diol autoxidation is catalysed by hydrogen peroxide and trace metal ion contaminants; removal of either of these factors sufficiently retards ene-diol autoxidation such that ene-diol autoxidation rather than enolisation becomes the rate determining step in the overall autoxidative process. Under enolisation control, the rate of monosaccharide autoxidation is influenced by pH and the buffer system used for pH control.
The influence of different non-electrolytes (fructose, xylitol, glucose/mannitol mixture) and electrolytes (NaCl, KCl) on anaerobic L-ascorbic acid (AA) degradation in an aqueous model system (pH 3.5, aw 0.94) was studied to assess the effect on that reaction of substances commonly used to diminish the water activity of fruit or vegetable juices, as well as its relation with non-enzymatic browning (NEB) development, at processing (70, 80, 90 °C) and storage (24, 33, 45 °C) temperatures. AA degraded as a function of time with a behaviour that could be described by first-order kinetics at all temperatures studied, and activation energies could be calculated using the Arrhenius law. The presence of humectants enhanced AA destruction, with D-fructose promoting the fastest L-ascorbic acid destruction and browning development at processing temperatures. The influence of humectants on NEB seemed to determine differences between their influence on AA degradation. Water activity decrease by humectant addition produced higher AA stability in solution at storage temperatures. The differential effect of each humectant used to decrease the water activity seemed to be related to its influence on solvent structure.© 2001 Society of Chemical Industry
To detect singlet oxygen ((1)O2), the commercially available fluorescent sensor named Singlet Oxygen Sensor Green (SOSG) has been the most widely used from material studies to the medical application, for example, photodynamic therapy. In light of the previous studies, SOSG is a dyad composed of fluorescein and anthracene moieties. In the present study, we carried out quantitative studies on photochemical dynamics of SOSG for the first time, such as the occurrence of intramolecular photoinduced electron transfer (PET), (1)O2 generation, and two-photon ionization. It was revealed that these relaxation pathways strongly depend on the irradiation conditions. The visible-light excitation (ex. 532 nm) of SOSG induced intramolecular PET as a major deactivation process (kPET = 9.7 × 10(11) s(-1)), resulting in fluorescence quenching. In addition, intersystem crossing occurred as a minor deactivation process that gave rise to (1)O2 generation via the bimolecular triplet-triplet energy transfer (kq = 1.2 × 10(9) M(-1) s(-1)). Meanwhile, ultraviolet-light excitation (355 nm) of SOSG caused the two-photon ionization to give SOSG cation (Φion = 0.003 at 24 mJ cm(-2)), leading to SOSG decomposition to the final products. Our results clearly demonstrate the problems of SOSG, such as photo-decomposition and (1)O2 generation. In fact, these are not special for SOSG, but common drawbacks for most of the fluorescein-based sensors.
Effects of temperature, pH and phosphate buffer on volatiles formed by heating model solutions of fructose, glucose, sucrose, lactose or starch were investigated by selected ion flow tube-mass spectrometry (SIFT-MS). Among the carbohydrates studied, the monosaccharide reducing sugars fructose and glucose were more reactive than macro molecular starch, lactose and sucrose, which are not reducing sugars. Furan was formed from fructose heated at 120, 100 and 80 °C at pH 5–7 in phosphate buffer and at 100 °C in unbuffered solution. Glucose did not yield furan in unbuffered solution at 100 °C but glucose did yield furan in phosphate buffer solution at a similar pH. Furan formation increased as temperature and pH increased. As temperature, pH value, and buffer components changed, furan formation may occur by different reactive pathways. Both of the buffer components, NaH2PO4 and citric acid, enhanced the formation of thermal degradation products from fructose. The enhancing effect of NaH2PO4 was stronger than citric acid. Formic and acetic acids were concomitantly formed with furan. More formic acid was produced from fructose than glucose, and more acetic acid was produced from glucose than fructose.
The solubility of oxygen in pure and in saline water between 2°and 40°has been determined by using a modification of the Winkler titration technique. The values found have, in some cases, been lower than those generally accepted by as much as 4%. On applying these new solubilities to the determination of rates of solution in well mixed water, satisfactory agreement with the Adeney & Becker law of aeration is obtained.
The anaerobic destruction of L-ascorbic acid in sweet aqueous model systems (water activity = 0.94) of pH 3.5 was studied. Ascorbic acid degraded as a function of time and temperature with a behaviour that, in general, could be described by first order kinetics. The influence of the humectants tested (glucose, sucrose, sorbitol) on nutrient destruction depended on the temperature studied: at lower temperatures (24, 33 and 45 °C), humectants protected L-ascorbic acid from destruction, sugars being the most effective due to the structure-forming effect they have; at higher temperatures characteristic of processing (70, 80 and 90 °C), humectants with active carbonyls (glucose and sucrose) promoted ascorbic acid destruction, non-enzymic browning reactions probably being responsible for these results. The effect of sodium bisulphite presence was only significant at the lower temperature range producing inhibition of destruction; at higher temperatures the prevalence of nonenzymatic browning seemed to nullify the effect of this additive. It is concluded that not only water activity or additive effect but also solute–solvent interaction and other reactions taking place must be considered when analysing the effect of humectants and additives on ascorbic acid degradation.
The influence of different non‐electrolytes (fructose, xylitol, glucose/mannitol mixture) and electrolytes (NaCl, KCl) on anaerobic L ‐ascorbic acid (AA) degradation in an aqueous model system (pH 3.5, a w 0.94) was studied to assess the effect on that reaction of substances commonly used to diminish the water activity of fruit or vegetable juices, as well as its relation with non‐enzymatic browning (NEB) development, at processing (70, 80, 90 °C) and storage (24, 33, 45 °C) temperatures. AA degraded as a function of time with a behaviour that could be described by first‐order kinetics at all temperatures studied, and activation energies could be calculated using the Arrhenius law. The presence of humectants enhanced AA destruction, with D ‐fructose promoting the fastest L ‐ascorbic acid destruction and browning development at processing temperatures. The influence of humectants on NEB seemed to determine differences between their influence on AA degradation. Water activity decrease by humectant addition produced higher AA stability in solution at storage temperatures. The differential effect of each humectant used to decrease the water activity seemed to be related to its influence on solvent structure.
© 2001 Society of Chemical Industry
Singlet oxygen is a highly reactive, electrophilic, and nonradical molecule. It is different from diradical triplet oxygen in its electron arrangement. Photosensitizers can form singlet oxygen from triplet oxygen in the presence of light. The reaction rate of singlet oxygen with foods is much greater than that of triplet oxygen due to the low activation energy. Singlet oxygen oxidation produces undesirable compounds in foods during processing and storage. However, carotenoids and tocopherols in foods can minimize singlet oxygen oxidation. The in-depth scientific knowledge on the formation, reactions, quenching mechanisms, and kinetics of singlet oxygen can greatly improve the quality of foods by minimizing the oxidation during processing and storage. The single oxygen oxidation of foods has contributed to the explanation of several important chemical reactions in the reversion flavor in soybean oil, sunlight flavor in milk products, and the rapid losses of vitamin D, riboflavin, and ascorbic acid in milk under light storage.
Autoxidation of methyl linoleate emulsions in aqueous phosphate buffer solutions in the presence of glucose, fructose, and
sucrose has been studied by the rate of oxygen uptake. Oxidation rates increased with increasing concentration of sugars in
the system. At comparable molar ratios of sugar to methyl linoleate the rate of oxidation in the presence of fructose was
greater than with glucose which, in turn, was greater than with sucrose. Oxidation rates increased with pH until a maximum
rate was reached at pH 8.00. There was less conjugation and more CO2 with fructose than with glucose at a comparable level of oxygen uptake and pH value. This suggested concurrent oxidation
of methyl linoleate and sugars; fructose is the most readily oxidized of those studied.
Sugars seemed to be effective only in combination with the resulting methyl linoleate hydroperoxide. The effect of sugars
rests in an activation of the decomposition of the linoleate hydroperoxide, and on the acceleration of the autocatalysis.
The activation energy values for the autoxidation of methyl linoleate emulsions in the presence of sucrose, glucose, and fructose
are 14.9, 10.6, and 10.6 K. Cal./mol. at pH 5.50; 16.0, 10.8, and 10.4 K. Cal./mol. at pH 7.00; and 14.4, 10.2, and 8.8 K.
Cal. at pH 8.00, respectively.
Addition of ascorbic acid to the system at zero time or after 2 hrs. increased oxygen absorption. It appeared that oxidized
methyl linoleate caused co-oxidation of the ascorbic acid. Additions of nordihydroguaiaretic acid, propyl gallate, and hydroquinone
to the system were ineffective in stopping oxidation when they were added after oxidation had commenced. They reduced effectively
the rate of oxidation when added at zero time.
This study aimed to elucidate how the major intrinsic factors, such as ascorbic acid (AA), flavonoids and sugars affected
the thermal degradation of blood orange anthocyanins. The results in our study indicated that AA and sugars significantly
accelerated anthocyanins degradation while flavonoids had a protective effect on degradation of anthocyanins. Flavonoids and
AA could reduce the influence of temperature on anthocyanins degradation rate. However, the promoting effects of sugars on
anthocyanins degradation correlated with the temperature. Moreover, the degradation of anthocyanins in the presence of sugars
followed complex reaction kinetics when temperature was above 70°C, and the promoting effects of sugars on anthocyanins degradation
were glucose<sucrose<fructose. The results also indicated that flavonoids had a protective effect against either AA or
sugars accelerated the degradation of anthocyanins, and this protective effect played a more important role in the degradation
of anthocyanins comparing to the negative effect of AA or sugars. In addition, AA and sugars showed a synergistic effect on
the degradation of anthocyanins at all our investigation temperatures except 90°C.
Anthocyanin-rich concentrates from different fruits can be used as natural food colourants. The pigments' stability is comparatively low and dependent on the composition of food matrices. Food ingredients relevant for soft drinks, jelly fruits and salad dressings were tested in model systems regarding their influence on the colour stability of elderberry and black currant concentrate determined by colour measurement (CIE L
*
a
*
b
*). In aqueous solutions food-grade organic acids and salt were found to influence anthocyanin stability: colour stability increased with increasing pK
a of acids and decreased with increasing salt concentrations. This may be attributed to altered solvation characteristics of aqueous solutions. A stabilizing influence was found for sugars presumably by reducing water activity. However, when heat treatment was applied, e.g. in the production of hydrocolloid gels, fructose was shown to accelerate anthocyanin decay due to the formation of sugar degradation products. Comparing hydrocolloids, alginate was shown to increase colour stability in aqueous solution and pectin displayed overall highest colour stability in a gel model system, suggesting that polyuronic acids may improve anthocyanin stability by intermolecular association.
The production of free radicals during the autoxidation of simple monosaccharides at 37° has been studied by the electron spin resonance (e.s.r.) technique of spin trapping. In the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), monosaccharides undergoing autoxidation produced hydroxyl and 1-hydroxyalkyl radical-derived spin adducts, indicating that hydroxyl and hydroxyalkyl free-radicals are involved in the autoxidation of monosaccharides. The pH profile for the production of free radicals from monosaccharides undergoing autoxidation revealed the formation of both hydroxyl and hydroxyalkyl radicals at relatively high pH, whereas at low pH, only the formation of hydroxyalkyl radicals was observed; the transition between these routes for the production of free radicals occurred at pH 8.0–8.5. Glycoaldehyde, glyceraldehyde, dihydroxyacetone, and erythrose are relatively rapidly enolised (to an ene-diol) and autoxidised with the concomitant production of free radicals. Ribose and glucose enolise and autoxidise very slowly without detectable production of free radicals. A comparison of the pH profiles of the rates of enolisation and the pH dependence of the production of free radicals from glyceraldehyde during autoxidation suggests that a change in reaction mechanism occurs at pH 8.2. Below pH 8.2, the rates of enolisation and autoxidation increase with increasing pH, with a concomitant increase in the formation of hydroxyalkyl spin-adducts. Above pH 8.2, glyceraldehyde undergoing autoxidation shows a much higher rate of enolisation than of autoxidation and, although the formation of hydroxyalkyl radicals is decreased, the production of hydroxyl radicals is also observed. A free-radical mechanism for the autoxidation of monosaccharides is proposed, to account for the pH-dependent characteristics of the production of free radicals and the relationships between the production of free radicals, autoxidation, and enolisation of the monosaccharides.
Nine black currant varieties cultivated in Lithuania were studied. The highest amount of ascorbic acid was established in fresh berries from cv Minaj Smyriov and Kupoliniai: these varieties contained 220.5 and 186.7 mg 100 g−1 of ascorbic acid in berries. The highest amount of anthocyanins was found in cake produced from berries cv Kupoliniai and Kriviai: 14.65 and 15.42 mg g−1, respectively. The major pigment determined in Kupoliniai variety was delphinidin-3-rutinoside; in Ben Lomond, Minaj Smyriov, Kriviai and Gagatai cultivars, cyanidin-3-rutinoside. The composition of the identified pigments was the following: cyanidin-3-rutinoside (33–38%), delphinidin-3-rutinoside (27–34%), cyanidin-3-glucoside (8–10%) and delphinidin-3-glucoside (8–10%). Impact of storage, thermal treatment and addition of sweeteners were studied. Cyanidin-3-rutinoside was the most stable to the effect of thermal treatment at 95 °C, while cyanidin and delphinidin rutinosides were the most stable during storage for 12 months at 8 °C. Fructose has a greater effect on anthocyanin degradation compared with glucose and aspartame.
The food processing industry has matured over the years with an impressive record on safety and a vibrant marketplace for new product development. Consumer demands for high-quality products has inspired researchers and the food industry to explore alternative methods as replacement for traditional processing methods. The food industry is poised to adopt cost effective technologies that offer better quality and safe products. Given the impressive safety record associated with traditional systems, one may be tempted to conclude that there is little room for advancement and innovation to meet current consumer demands. Process optimization will continue to evolve to enhance quality and overall energy utilization either in traditional or novel systems. The need for efficient operations will certainly drive system automation, control and monitoring systems that can handle complex mathematical routines in real-time. Such systems would certainly require vigorous validation and verification for industry to embrace them. It truly sounds illogical for industry to re-evaluate existing process schedules based on studies that demonstrate non-linearity of survival curves. However, the need to optimize quality and operating costs could potentially prompt re-evaluating existing systems to capture additional benefits. New processing concepts such as the application of variable retort temperature have received attention from processing experts and promises to improve both the economy and quality of thermally processed foods.
The development of efficient and selective luminescent probes for reactive oxygen species, particularly for singlet molecular oxygen, is currently of great importance. In this study, the photochemical behavior of Singlet Oxygen Sensor Green(®) (SOSG), a commercially available fluorescent probe for singlet oxygen, was examined. Despite published claims to the contrary, the data presented herein indicate that SOSG can, in fact, be incorporated into a living mammalian cell. However, for a number of reasons, caution must be exercised when using SOSG. First, it is shown that the immediate product of the reaction between SOSG and singlet oxygen is, itself, an efficient singlet oxygen photosensitizer. Second, SOSG appears to efficiently bind to proteins which, in turn, can influence uptake by a cell as well as behavior in the cell. As such, incorrect use of SOSG can yield misleading data on yields of photosensitized singlet oxygen production, and can also lead to photooxygenation-dependent adverse effects in the system being investigated.
We present data for H2O2 production at eight different materials tested as electrocatalysts for the oxygen reduction reaction (ORR) in 0.5 M H2SO4 (Hg, Au, Ag, Cu, Pt, Pd, Pd80Co20, and Au60Cu40) using scanning electrochemical microscopy (SECM) as an alternative to the widely used rotating ring-disk electrode (RRDE) method. The amount of H2O2 is related to the total number of electrons, n, found in the O2 reduction reaction, with n = 2 showing only H2O2 production and n = 4 showing no H2O2 formation. From the SECM study Hg shows n close to 2, whereas Pt and Pd80Co20 show n-values near 4. The other materials show intermediate n-values as a function of potential.
The fluorescent probe Singlet Oxygen Sensor Green is able to produce singlet oxygen under exposure to UV or visible radiation.
The accumulation of hydrogen peroxide (H2O2) during incubations of protein with glucose (experimental glycation) has previously been too low for direct measurement although it is suggested to be the precursor of protein-damaging hydroxylating agents. We have thus developed a simple H2O2-measuring technique which relies upon the rapid peroxide-mediated oxidation of Fe2+ to Fe3+ (catalysed by sorbitol) under acidic conditions followed by reaction of the latter cation with the dye, xylenol orange. We have used the method to demonstrate that incubation mixtures of protein and glucose generates nanomolar levels of hydrogen peroxide in the presence of protein under physiological conditions of pH and temperature.
Protein exposed to glucose is cleaved, undergoes conformational change and develops fluorescent adducts ('glycofluorophores'). These changes are presumed to result from the covalent attachment of glucose to amino groups. We have demonstrated, however, that the fragmentation and conformational changes observed are dependent upon hydroxyl radicals produced by glucose autoxidation, or some closely related process, and that antioxidants dissociate structural damage caused by the exposure of glucose to protein from the incorporation of monosaccharide into protein. We have also provided further evidence that glycofluorophore formation is dependent upon metal-catalysed oxidative processes associated with ketoaldehyde formation. If experimental glycation is an adequate model of tissue damage occurring in diabetes mellitus, then these studies indicate a therapeutic role for antioxidants.
Monosaccharide autoxidation (a transition metal-catalysed process that generates H2O2 and ketoaldehydes) appears to contribute to protein modification by glucose in vitro. The metal-chelating agent diethylenetriaminepenta-acetic acid (DETAPAC), which inhibits glucose autoxidation, also reduces the covalent attachment of glucose to bovine serum albumin. A maximal 45% inhibition of covalent attachment was observed, but this varied with glucose and DETAPAC concentrations in a complex fashion, suggesting at least two modes of attachment. The extent of inhibition of the metal-catalysed pathway correlated with the extent of inhibition of glycosylation-associated chromo- and fluorophore development. DETAPAC also inhibited tryptophan fluorescence quenching associated with glycosylation. Conversely, ketoaldehydes analogous to those produced by glucose autoxidation, but generated by 60Co irradiation, bound avidly to albumin and accelerated browning reactions. It is therefore suggested that a component of protein glycosylation is dependent upon glucose autoxidation and subsequent covalent attachment of ketoaldehydes. The process of glucose autoxidation, or ketoaldehydes derived therefrom, appear to be important in chromophoric and fluorophoric alterations. It is noted, consistent with these observations, that the chemical evidence for the currently accepted 'Amadori' product derived from the reaction of glucose with protein amino groups is consistent also with the structure expected for the attachment of a glucose-derived ketoaldehyde to protein. The concept of 'autoxidative glycosylation' is briefly discussed in relation to oxidative stress in diabetes mellitus.
Characteristic chemiluminescence emission of singlet (1 delta g) molecular oxygen at 1268 nm is reported from a Haber-Weiss reaction. The reaction consists of mixing aqueous hydrogen peroxide with a solution of potassium superoxide, solubilized by 18-crown-6 ether in carbon tetrachloride or in dry acetonitrile at room temperature. Since the discovery of the enzyme superoxide dismutase by J.M. McCord and I. Fridovich [(1968) J. Biol. Chem. 243, 5733-5760], the identity of the reactive oxidant in superoxide-generating systems in biology has remained a chemical mystery. The results presented here suggest strongly that the reactive species is singlet oxygen generated via the Haber-Weiss reaction and not, as usually assumed, the hydroxyl radical, .OH, generated by the same reaction.
To determine the relative ranking of autoxidative potential of various sugars the fluorescence of phycoerythrin was monitored in the presence of various concentrations of sugars incubated at 37 degrees C with or without CuSO4. The antioxidative properties of these sugars was assayed in the presence of a peroxy radical generator 2,2' azobis(2 amidinopropane) AAPH. The results indicate that 25 mM D-glucose, but not 5 mM D-glucose solution can significantly potentiate CuSO4-induced free radical damage after 32 h of incubation. This weak effect was comparable to that seen with lactose or maltose and was in contrast to the high potency of fructose and ribose in potentiating phycoerythrin damage through oxidation. 2-Deoxyribose had an antioxidant effect in this assay. In the presence of AAPH, 25 mM D-glucose, and to a lesser extent, 5 mM D-glucose, had statistically significant free radical quenching effect (61.5 +/- 0.7% and 44.9 +/- 2.4% inhibition of oxidation, respectively). The corresponding free radical quenching effect expressed as percentage inhibition of oxidation for 5 mM fructose, maltose, lactose, ribose, and deoxyribose and ascorbate were 30.2 +/- 1.9%, 49.1 +/- 1.2%, 53.5 +/- 1.6%, 64.7 +/- 1.8%, 68.8 +/- 1.7%, and 69.5 +/- 1.0%, respectively. It is concluded that autoxidative potential of simple sugars is highly diverse. Whereas some sugars have no oxidative potential, others are potent prooxidants in the presence of Cu++, and some can have antioxidant properties. However, the autoxidative potential of reducing sugars is extremely weak compared with that of the free copper ions. All sugars tested have antioxidant effect in the presence of peroxy radical generator. In this assay, the antioxidant potency of deoxyribose was comparable to that of ascorbate.
We examined the role of fructose in the development of diabetic complications. Compared with glucose, fructose increased the fluorescence intensity and the cross-linking of glycated collagen, and promoted the polymerization of proteins. Therefore fructose accelerated the production of advanced glycation end-products more than glucose. In addition, fructose enhanced the reactive oxygen or oxygen radical generation and the associated degeneration of proteins and lipids. These actions of fructose appeared to be due to the formation of dicarbonyl compounds such as 3-deoxyglucosone, a highly reactive intermediate product formed in the advanced glycation stage. These results suggest that fructose is closely involved not only in glycation but also in the polyol pathway and peroxidation reactions through free radical formation. Thus, fructose is considered to be a more critical reducing sugar associated with the progression of diabetic complications than it has been thought until now.
A sensitive chemiluminescent probe that selectively reacts with singlet oxygen in the presence of superoxide and hydrogen peroxide has been used to quantify the production of singlet oxygen in the reaction of superoxide with hydrogen peroxide. The yield of singlet oxygen from this reaction was found to be low (0.2% relative to the initial superoxide concentration). No evidence for the formation of hydroxyl radical was observed in this reaction, ruling out the Haber-Weiss mechanism as a major singlet oxygen formation pathway. No singlet oxygen production was observed in the reaction of superoxide with 2-nitrobenzoic acid, which has a pKa similar to that of hydrogen peroxide, rendering the protonation of superoxide, followed by its disproportionation, an unlikely explanation for the formation of singlet oxygen in this system. The low yields of singlet oxygen and hydroxyl radical suggest that their formation in this reaction should be relatively unimportant in biological systems.
Although the oxidative destruction of glucose and fructose has been studied by several investigators over the past century, the mechanism by which phosphate promotes these oxidation reactions is not known. A wide range of oxidation products have been used to monitor the oxidation of sugars and free radicals have been shown to be involved. The influence of phosphate concentration on the rate of production of free radicals and several sugar oxidation products has been studied. It was found that fructose is much more susceptible to autoxidation than glucose, galactose, or sucrose. The promotion of sugar oxidation by phosphate was found to be iron dependent. Addition of the iron chelators, diethylenetriaminepentaacetic acid (DTPA) and desferrioxamine completely suppressed the oxidation reactions, even at high concentrations of phosphate. Formaldehyde was positively identified as a product of fructose oxidation by HPLC analysis of its acetylacetone adduct. A mechanism is proposed in which phosphate cleaves the oxo bridges of the iron(III)-fructose complex, based on UV spectral analysis and magnetic susceptibility measurements, and thereby catalyzes the autoxidation of fructose.
Singlet molecular oxygen in the Haber-Weiss reaction
- A U Khan
- M Kasha
Khan, A. U., & Kasha, M. (1994). Singlet molecular oxygen in the Haber-Weiss
reaction. Proceedings of the National Academy of Sciences of the United States of
America, 91(26), 12365-12367.