Dehydroascorbic Acid Content Research Articles

Effect of light intensity and wavelengths on ascorbic acid content and the antioxidant system in tomato fruit grown in vitro

The ascorbic acid (ASA) content of tomatoes is regulated by culture practices and environmental conditions such as light. However, in tomatoes, little is known about the direct effect of lighting conditions on ASA content in the absence of natural environmental fluctuations. The aim of this study was to determine the direct light regulation of ASA and dehydroascorbic acid (DHA) contents and the antioxidant system in tomato fruits grown in vitro using two different cultivars (high- and low-ASA cultivars), different light intensities [darkness, low light (∼249 μmol m−2 s−1), and high light (∼961 μmol m−2 s−1)], and different light spectra light emitting diodes (LEDs) under the same light intensity (226–249 μmol m−2 s−1): control (eight-peak LED), red LED light (peaks at 625 and 660 nm), and blue LED light (peaks at 420 and 450 nm). Results indicate that the effect of light on ASA and DHA content may be universal regardless of whether the cultivar is designated as a high- or low-ASA cultivar. ASA content was enhanced by an increase in light intensity and by blue (but not red) LED light. Our results also indicate that stimulation of the antioxidant system (ascorbate peroxidase and dehydroascorbate reductase activity) enhances ASA content under high light intensity, and underlying differences in mechanisms in response to blue and red LED light were observed. Therefore, we conclude that the direct light regulation of ASA content and the antioxidant system occurs in tomato fruits grown in vitro. In addition, our findings provide useful information for improving agricultural techniques to develop high-ASA tomatoes by controlling lighting conditions and by applying LED light.

Hormonal regulation of prooxidant-antioxidant homeostasis in gilts

The results of research on the features of cyclic lability of homeostasis in gilts are highlighted. In the experiments it has been used gilts of the Red White belted breed of meat pigs at different phases of the reproductive cycle: luteal phase, estrus, on the 15th, 20th, 30th, 60th, 90th, 104th, 113th day of pregnancy and in 12 hours after farrowing. The dynamics of the content of thyroid and steroid hormones, as well as the peculiarities of the formation of prooxidant-antioxidant homeostasis were determined in blood serum. It was found out that the amount of steroid hormones in blood of gilts is labile and is determined by the physiological state, namely the onset of estrus, relative to the luteal phase, it is increased the level of thyroxine (30.0 %), triiodothyronine (26.3 %), estradiol-17 β (by 22.8 %, P < 0.01) testosterone (15.2 %), as well as a decrease in progesterone (by 37.2 %). Such changes are accompanied by the acceleration of peroxidation processes, xanthine oxidase activity increases, it is increased the content of diene conjugates (P < 0.05) and TBA-active compounds. This is accompanied by a probable increase in the level of antioxidant protection – the activity of superoxide dismutase (P < 0.05), vitamin A (P < 0.05) and vitamin E (P < 0.05). During two months of pregnancy, the concentration of thyroxine (P < 0.05), triiodothyronine, progesterone (P < 0.01), testosterone (P < 0.05) and estradiol-17β increases. Such metabolic shifts cause changes in the state of prooxidant-antioxidant homeostasis in the direction of reducing the intensity of peroxidation processes. In gilts before farrow there is a decrease in thyrocoxin, triiodothyronine and progesterone. The intensification of peroxidation was found: the increase in SOD activity (P < 0.05), the dehydroascorbic acid content (P < 0.05), diene conjugates and TBA-active complexes, as well as the decrease in the concentration of reduced glutathione and vitamin A (P < 0.05) and vitamin E (P < 0.05). In blood of sows after farrowing, the concentration of thyroxine increases on 1.3 times, triiodothyronine – on 2.7 times, and progesterone and estradiol-17β decreases on 1.8 and 8.7 times, respectively. It was revealed that the intensity of lipid peroxidation processes decreased: DC content by 16.3 % and TBA-active complexes by 13.3%. It was determined that the concentration of ascorbic acid decreased by 32.8 % and vitamin E – 18.9 %.

The nutritional value and vitamin C content of different raspberry cultivars from organic and conventional production

Raspberry fruit is a source of vitamin C. Vitamin C has antioxidant properties and can neutralize the negative effects of oxidative stress. The aim of this study was therefore to compare the content of vitamin C, sugars and organic acids in organic vs. conventional raspberries and to determine the effects of harvest time and cultivar on the contents of these compounds. The experiment was carried out in 2013–2014. Fruits from four raspberry cultivars ('Laszka', 'Glen Ample', 'Glen Fine' and 'Tulameen') were collected in the summer, and fruits of the 'Polka' cv. were collected in the autumn. The experiment was carried out on three organic farms and three conventional farms. The vitamin C, sugars and organic acids contents were determined using the HPLC method. The conventional raspberries grown in 2013 contained a significantly greater vitamin C (40.5 mg/100 g FW) and dehydroascorbic acid (35.8 g/100 g FW) content compared to organic raspberries (33.7 mg/100 g FW and 29.2 mg/100 g FW, respectively). We observed an effect of the cultivar on the total organic acids and citric acid content in raspberry fruit in 2013 and 2014. ‘Laszka’ cv. (1720 mg/100 g FW and 1650 mg/100 g FW) and ‘Glen Fine’ cv. (1740 mg/100 g FW and 1710 mg/100 g FW) fruits contained significantly more total organic acids and citric acid (1680 mg/100 g FW and 1610 mg/100 g FW) as well (1680 mg/100 g FW and 1670 mg/100 g FW) compared to the other experimental cultivars. However, the 2014 ‘Tulameen’ cv. was characterized by the highest levels of total sugars (14.9 g/100 g FW) and sucrose (5.0 g/100 g FW) content. The conventional raspberry fruits (55.4 mg/100 g FW) harvested in the autumn of 2014 contained a significantly greater malic acid content compared to organic fruits (46.2 mg/100 g FW).

Iodosalicylates and iodobenzoates supplied to tomato plants affect the antioxidative and sugar metabolism differently than potassium iodide

Abstract Iodine is considered as a beneficial element for plants. As compared to the mineral form of iodine, the effect of organoiodine compounds on physiological and biochemical processes in plants is weakly recognized. This study describes the influence of different forms of iodine – mineral as KI and organic as iodosalicylates and iodobenzoates on the antioxidative and sugar metabolism of tomato plants. Plants were treated with KI and with the following organoiodine compounds: 5-iodosalicylic acid (5-ISA), 3,5-diiodosalicylic acid (3,5-diISA), 2-iodobenzoic acid (2-IBeA) and 4-iodobenzoic acid (4-IBeA). The effect of salicylic acid (SA) and benzoic acid (BeA) on plants was also tested. The plants revealed a lower tolerance to 3,5-diISA, 4-IBeA and slightly to BeA as compared to control. Tested compounds did not affect the content of ascorbic (AA) and dehydroascorbic (DHA) acid. All tested compounds, with the exception of 2-IBeA, did not affect the content of phenols, phenylpropanoids and anthocyanins in leaves. Tested compounds variously modified the activity of catalase (CAT), ascorbic peroxidase (APX) and peroxidase (POX) in leaves and roots. The content of soluble sugars in tomato leaves and roots varied depending on the combination, with a noticeable tendency to increase after the application of organoiodine compounds.

Development and validation of a differential pulse polarography method for determination of total vitamin C and dehydroascorbic acid contents in foods

The objective of the study was to develop a new method for the determination of total vitamin C and dehydroascorbic acid contents in food using the differential pulse polarography technique, and to compare achieved results to those obtained with the proposed reference method applying HPLC with spectrophotometric detection. Dithiothreitol was used to reduce dehydroascorbic acid into l-ascorbic acid. Interference due to the presence of dithiothreitol during polarographic determination of l-ascorbic acid was efficiently eliminated by clarification of the sample solution with Carrez reagent. Validation of the polarographic method indicates its usefulness for the analysis of foods products that do not contain isoascorbic acid. The coefficient of variation for the analysis of l-ascorbic acid and total vitamin C content ranges from 1.86% to 6.98%, Horrat values from 0.41 to 0.89 and average recovery of l-ascorbic acid ranges from 98% to 104%. Results obtained using the developed method are characterised by high compatibility with those obtained with the HPLC reference method, indicating equivalence of both methods, and in conclusion, the method was deemed fit for purpose for measuring total vitamin C and dehydroascorbic acid in foods.

The Effect of Sodium Chloride on Ion Association of Lysine and Arginine Ionizable Side Chains Amino Acids with Dehydro-L-ascorbic Acid in Aqueous Solution at Different Temperatures

Molar conductance (Λ) of ionizable side chains amino acids, lysine (Lys) and arginine (Arg) with dehydroascorbic acid (DHA) in water and in NaCl solutions was measured at temperatures range 298 K to 313 K. The limited molar conductance (Λo) and the constant of the ions association (KA) are calculated using the Shedlovsky techniques. The dynamic radius of the concerned ion (R) is calculated by used Stokes–Einstein relation. The heat of association, the Gibbs free energy, the change of entropy and activation energy (ΔHo/ kJ mol-1, ΔGo/ kJ mol-1, ΔSo/J K-1 mol-1, and ΔES/ kJ mol-1) respectively), also calculated. The data show increases the molar conductance with increase in temperature and decreasing in values at addition of DHA to Lys and Arg solutions. The association ions in NaCl solutions appear to increase in radius and decrease in diffusion coefficient relative to water solutions.ΔES, shows in most samples a positive value for the association and the values in NaCl solutions has lower relative to the water solutions. ΔGo is a trend to decrease with an increase in DHA concentration in water and NaCl solutions. The ion association is exothermic reaction relative to the negative value of ΔHo. The ΔSo andΔHo results, for Lys and Arg solutions, show decreasing in values at increase in DHA concentration in water and NaCl solutions. ΔGo (kJ mol-1), ΔSo (J K-1 mol-1), ΔHo (kJ mol-1), and ΔEs (kJ mol-1)

Comparison of Effects of Potassium Iodide and Iodosalicylates on the Antioxidant Potential and Iodine Accumulation in Young Tomato Plants

Iodine (I) is classified as a beneficial element for plants. Until now, there have been only hypotheses regarding the uptakes of organic iodine compounds by plant roots. The purpose of our research was to compare the uptakes and effects of the application of the following mineral and organic iodine compounds on young tomato plants: KI, 5-iodosalicylic (5-ISA), and 3,5-diiodosalicylic (3,5-diISA) acids. An additional control combination included the treatment with salicylic acid (SA) alone. All compounds were introduced into the nutrient solution in 5, 10, 25, and 50 μM I concentrations. It was established that after the application of 5-ISA and 3,5-diISA, iodine is taken up to a smaller extent than from KI. The tested KI, 3,5-diISA, and 5-ISA doses had no negative impact on the growth and development of plants, apart from the reduction of shoot biomass after the application of 3,5-diISA in 10 and 25 µM I doses. All applied compounds, except for SA, caused a reduction of ascorbic acid (AA) content and increase of dehydroascorbic acid (DHA) content in leaves. A significant increase of APX activity was noted only for the highest doses of KI and 5-ISA. None of the iodine compounds, in most tested doses, have substantially increased the CAT and POX activities in tomato leaves. Application of KI decreased the levels of all analyzed sugars in tomato leaves. The effect of iodosalicylates on sugar content varied depending on the compound: when applied in the highest dose 5-ISA increased, while 3,5-diISA decreased the sugar accumulation in tomato plants. In all tested treatments, a reduction of SA content in leaves was noted. We conclude that organic iodine compounds, i.e., 3,5-diISA and 5-ISA, can be taken up by the roots of tomato plants at an early stage of development.

The Effect of Processing on Ascorbic Acid and Dehydroascorbic Acid in Different Varieties of Yam

The effect of some processing method on the ascorbic acid and dehydroascorbic acid content of two cultivars of yam (Dioscorea rotundata and D. cayenensis) were investigated. The processing method adopted were cooking, frying and roasting. The assay of ascorbic acid in the two cultivars ranged from (5.0 – 9.2 mg / 100 g fresh tissue). The moisture contents of the processed samples ranged from 40-55% for D. rotundata and 48-60% for D.cayenensis except for roasted samples which had a moisture content of 30% for the two cultivars of yam. The pH values were similar in all the varieties examined. The level of ascorbic acid after 0 - 8 days of storage ranged from 5.2 - 7.3 mg / 100 g fresh tissue on a moisture -free basis (mfb). The dehydroascorbic acid content varied from 5.0 - 9.2 mg / 100 g fresh tissue on a moisture- free basis. The retention in ascorbic acid and dehydroascorbic acid of the various treatments ranged from 4.9 - 6.2 mg / 100 g and 5.2 - 8.9 mg / 100 g respectively. Thus, different processing methods has contributed to the loss of ascorbic acid with the highest loss observed when the yam samples were roasted and least loss when they were fried.

New UHPLC-QqQ-MS/MS Method for the Rapid and Sensitive Analysis of Ascorbic and Dehydroascorbic Acids in Plant Foods.

A new method using ultra high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS) methodology was developed for the determination of ascorbic acid (AA) and dehydroascorbic acid (DHAA) contents in liquid and solid vegetable samples. The advantages of this method are speed, high sensitivity and practical application. In accordance with these advantages, the present method allows the simultaneous determination of AA and DHAA without previous reduction/derivatization of DHAA and without the use of internal standards in the samples. This is of high interest in routine analysis, providing a simpler sample preparation, as well as enhanced accuracy and robustness. Its validation included selectivity, sensitivity and linearity, precision and accuracy, matrix effect, and recovery. The results showed high selectivity and sensitivity, with calibration curves ranging from 10 to 500 ng mL−1 and from 50 to 500 ng mL−1 for AA and DHAA, respectively. Appropriate dilutions for each sample are necessary to avoid the matrix effect with accepted recoveries.

Appropriate Handling, Processing and Analysis of Blood Samples Is Essential to Avoid Oxidation of Vitamin C to Dehydroascorbic Acid.

Vitamin C (ascorbate) is the major water-soluble antioxidant in plasma and its oxidation to dehydroascorbic acid (DHA) has been proposed as a marker of oxidative stress in vivo. However, controversy exists in the literature around the amount of DHA detected in blood samples collected from various patient cohorts. In this study, we report on DHA concentrations in a selection of different clinical cohorts (diabetes, pneumonia, cancer, and critically ill). All clinical samples were collected into EDTA anticoagulant tubes and processed at 4 °C prior to storage at −80 °C for subsequent analysis by HPLC with electrochemical detection. We also investigated the effects of different handling and processing conditions on short-term and long-term ascorbate and DHA stability in vitro and in whole blood and plasma samples. These conditions included metal chelation, anticoagulants (EDTA and heparin), and processing temperatures (ice, 4 °C and room temperature). Analysis of our clinical cohorts indicated very low to negligible DHA concentrations. Samples exhibiting haemolysis contained significantly higher concentrations of DHA. Metal chelation inhibited oxidation of vitamin C in vitro, confirming the involvement of contaminating metal ions. Although EDTA is an effective metal chelator, complexes with transition metal ions are still redox active, thus its use as an anticoagulant can facilitate metal ion-dependent oxidation of vitamin C in whole blood and plasma. Handling and processing blood samples on ice (or at 4 °C) delayed oxidation of vitamin C by a number of hours. A review of the literature regarding DHA concentrations in clinical cohorts highlighted the fact that studies using colourimetric or fluorometric assays reported significantly higher concentrations of DHA compared to those using HPLC with electrochemical detection. In conclusion, careful handling and processing of samples, combined with appropriate analysis, is crucial for accurate determination of ascorbate and DHA in clinical samples.

Effect of fermentation and storage on the nutritional value and contents of biologically-active compounds in lacto-fermented white asparagus (Asparagus officinalis L.)

In this study we determined contents of dry matter, ash, total protein, total sugars, lipids, B-group vitamins and vitamin C, polyphenolic compounds, and flavonoids, as well as active acidity, pH value, and antioxidant activity against ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)), DPPH (1,1-Diphenyl-2-picrylhydrazyl radical, 2,2-Diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl) radicals, FRAP (ferric ion reducing antioxidant power) in fresh and lacto-fermented white asparagus stored for 1 and 3 months. In addition, we analyzed the microbiological quality of fermented asparagus. The nutritional value and contents of biologically-active compounds were affected by both the fermentation process and the storage of fermented products. Fermentation had no significant effect on dry matter, total protein and fat contents, but contributed to an increase in ash content and a decrease in total sugars content. Fermentation caused a significant decrease in contents of B-group vitamins, polyphenolic compounds, and dehydroascorbic acid, whereas enhanced ability to reduce iron ions and decreased vitamin content were determined in fermented white asparagus during storage. Fermentation and storage did not affect the radical scavenging ability against DPPH and ABTS nor contents of total polyphenols and total flavonoids.

Non-enzymatic antioxidant accumulations in BR-deficient and BR-insensitive barley mutants under control and drought conditions.

Drought is one of the most adverse stresses that affect plant growth and yield. Disturbances in metabolic activity resulting from drought cause overproduction of reactive oxygen species. It is postulated that brassinosteroids (BRs) regulate plant tolerance to the stress conditions, but the underlying mechanisms remain largely unknown. An involvement of endogenous BRs in regulation of the antioxidant homeostasis is not fully clarified either. Therefore, the aim of this study was to elucidate the role of endogenous BRs in regulation of non-enzymatic antioxidants in barley (Hordeum vulgare) under control and drought conditions. The plant material included the 'Bowman' cultivar and a group of semi-dwarf near-isogenic lines (NILs), representing mutants deficient in BR biosynthesis or signaling. In general, accumulations of 11 compounds representing various types of non-enzymatic antioxidants were analyzed under both conditions. The analyses of accumulations of reduced and oxidized forms of ascorbate indicated that the BR mutants contain significantly higher contents of dehydroascorbic acid under drought conditions when compared with the 'Bowman' cultivar. The analysis of glutathione accumulation indicated that under the control conditions the BR-insensitive NILs contained significantly lower concentrations of this antioxidant when compared with the rest of genotypes. Therefore, we postulate that BR sensitivity is required for normal accumulation of glutathione. A complete accumulation profile of various tocopherols indicated that functional BR biosynthesis and signaling are required for their normal accumulation under both conditions. Results of this study provided an insight into the role of endogenous BRs in regulation of the non-enzymatic antioxidant homeostasis.

Mitochondrial Uptake and Accumulation of Vitamin C: What Can We Learn from Cell Culture Studies?

The mitochondrial fraction of l-ascorbic acid (AA) is of critical importance for the regulation of the redox status of these organelles and for cell survival. Recent Advances: Most cell types take up AA by the high-affinity sodium-dependent vitamin C transporter 2 (SVCT2) sensitive to inhibition by dehydroascorbic acid (DHA). DHA can also be taken up by glucose transporters (GLUTs) and then reduced back to AA. DHA concentrations, normally very low in biological fluids, may only become significant next to superoxide-releasing cells. Very little is known about the mechanisms mediating the mitochondrial transport of the vitamin. Information on AA transport is largely derived from studies using cultured cells and is therefore conditioned by possible cell culture effects as overexpression of SVCT2 in the plasma membrane and mitochondria. Mitochondrial SVCT2 is susceptible to inhibition by DHA and transports AA with a low affinity as a consequence of the restrictive ionic conditions. In some cells, however, high-affinity mitochondrial transport of AA is observed. Mitochondrial uptake of DHA may take place through GLUTs, an event followed by its prompt reduction to AA in the matrix. Intracellular levels of DHA are, however, normally very low. We need to establish, or rule out, the role and significance of mitochondrial SVCT2 in vivo. The key question for mitochondrial DHA transport is instead related to its very low intracellular concentrations.

Role of Zucchini and Its Distinctive Components in the Modulation of Degenerative Processes: Genotoxicity, Anti-Genotoxicity, Cytotoxicity and Apoptotic Effects.

Zucchini (Cucurbita pepo subsp. pepo) is a seasonal vegetable with high nutritional and medical values. Many useful properties of this fruit are attributed to bioactive compounds. Zucchini fruits (“Yellow” and “Light Green” varieties) and four distinctive components (lutein, β-carotene, zeaxanthin and dehydroascorbic acid) were selected. Firstly, the lutein, β-carotene, zeaxanthin and dehydroascorbic acid contents were determined in these fruits. Then, in order to evaluate the safety and suitability of their use, different assays were carried out: (i) genotoxicity and anti-genotoxicity tests to determine the safety and DNA-protection against hydrogen peroxide; (ii) cytotoxicity; and (iii) DNA fragmentation and Annexin V/PI (Propidium Iodide) assays to evaluate the pro-apoptotic effect. Results showed that: (i) all the substances were non-genotoxic; (ii) all the substances were anti-genotoxic except the highest concentration of lutein; (iii) “Yellow” zucchini epicarp and mesocarp exhibited the highest cytotoxic activity (IC50 > 0.1 mg/mL and 0.2 mg/mL, respectively); and (iv) “Light Green” zucchini skin induced internucleosomal DNA fragmentation, β-carotene being the possible molecule responsible for its pro-apoptotic activity. To sum up, zucchini fruit could play a positive role in human health and nutrition due to this fruit and its components were safe, able to inhibit significantly the H2O2-induced damage and exhibit anti-proliferative and pro-apoptotic activities toward HL60 (human promyelocytic leukemia cells) tumor cells. The information generated from this research should be considered when selecting potential accessions for breeding program purposes.

Ascorbate degradation in tomato leads to accumulation of oxalate, threonate and oxalyl threonate.

Ascorbate content in plants is controlled by its synthesis from carbohydrates, recycling of the oxidized forms and degradation. Of these pathways, ascorbate degradation is the least studied and represents a lack of knowledge that could impair improvement of ascorbate content in fruits and vegetables as degradation is non-reversible and leads to a depletion of the ascorbate pool. The present study revealed the nature of degradation products using [14 C]ascorbate labelling in tomato, a model plant for fleshy fruits; oxalate and threonate are accumulated in leaves, as is oxalyl threonate. Carboxypentonates coming from diketogulonate degradation were detected in relatively insoluble (cell wall-rich) leaf material. No [14 C]tartaric acid was found in tomato leaves. Ascorbate degradation was stimulated by darkness, and the degradation rate was evaluated at 63% of the ascorbate pool per day, a percentage that was constant and independent of the initial ascorbate or dehydroascorbic acid concentration over periods of 24h or more. Furthermore, degradation could be partially affected by the ascorbate recycling pathway, as lines under-expressing monodehydroascorbate reductase showed a slight decrease in degradation product accumulation.

Physiological Responses to Cadmium, Nickel and their Interaction in the Seedlings of Two Maize (Zea mays L.) Cultivars

Abstract In the leaves of maize seedlings, cultivars Premia and Blitz, the relatively low 2 μmol/L concentration of cadmium (Cd), nickel (Ni), or both metals acting simultaneously (Cd +Ni) for 72 h, induced a significant metal accumulation, decrease in total K+ content, reduction of light-induced membrane electrical potential (EM) repolarisation in mesophyll cells and changes of ascorbic acid (AsA), dehydroascorbic acid (DHA) and glutathione (GSH) content. Shoot growth and the values of resting EM did not change significantly. Increased K+ leakage, from the leaves, and lipid peroxidation accompanied by increase of TBA-reactive substances (TBARS) were found only in cv. Blitz exposed to Cd + Ni. This indicates a capability of high leaf-cell anti-oxidant pool to ameliorate the toxic effects on plasma membrane of single ions in both cultivars, and of Cd + Ni only in cv. Premia. The decreased total content of K+ in leaves in all variants indicated repressing the K+ uptake and/or distribution to the shoots. Under anoxia, the magnitude of the repolarisation obtained after switching on the light was smaller in Cd-treated cultivar Premia than in the controls, and this also occurred in Ni- and Cd + Ni-treated cultivar Blitz.

Effects of exogenous spermidine on antioxidant system of tomato seedlings exposed to high temperature stress

The effects of foliar spraying with spermidine (Spd) on antioxidant system in tomato (Lycopersicon esculentum Mill.) seedlings were investigated under high temperature stress. The high temperature stress significantly inhibited plant growth and reduced chlorophyll (Chl) content. Application of exogenous 1 mM Spd alleviated the inhibition of growth induced by the high temperature stress. Malondialdehyde (MDA), hydrogen peroxide (H2O2) content and superoxide anion (O2) generation rate were significantly increased by the high temperature stress, but Spd significantly reduced the accumulation of reactive oxygen species (ROS) and MDA content under the stress. The high temperature stress significantly decreased glutathione (GSH) content and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), but increased contents of dehydroascorbic acid (DHA), ascorbic acid (AsA), and oxidized glutathione (GSSG) in tomato leaves. However, Spd significantly increased the activities of antioxidant enzymes, levels of antioxidants and endogenous polyamines in tomato leaves under the high temperature stress. In addition, to varying degrees, Spd regulated expression of MnSOD, POD, APX2, APX6, GR, MDHAR, DHAR1, and DHAR2 genes in tomato leaves exposed to the high temperature stress. These results suggest that Spd could change endogenous polyamine levels and alleviate the damage by oxidative stress enhancing the non-enzymatic and enzymatic antioxidant system and the related gene expression.

Ascorbate pool, sugars and organic acids in black currant (Ribes nigrum L.) berries are strongly influenced by genotype and post‐flowering temperature

Marked effects of the climatic environment on fruit chemical composition have often been demonstrated in field experiments. However, complex covariations of several climatic factors in the natural environment complicate the interpretation of such experiments and the identification of the causal factors. This can be better achieved in a phytotron where the various climatic factors can be varied systematically. Therefore, we grew four black currant cultivars of contrasting origin in a phytotron under controlled post-flowering temperature and photoperiod conditions and analysed the berries for their ascorbic acid, sugar and organic acid contents. The analyses revealed significant effects of genotype on all investigated compounds. Particularly large cultivar differences were observed in the concentrations of l-ascorbic acid (AA) and sucrose. The concentrations of both AA and dehydroascorbic acid (DHAA), as well as the concentrations of all major sugars, decreased consistently with an increasing temperature over the temperature range 12-24 °C. Fructose and glucose were the predominant sugars with concentrations several fold higher than that for sucrose. AA was the main contributor to the total ascorbate pool in black currant berries. The AA/DHAA ratio varied from 5.6 to 10.3 among the studied cultivars. The concentration of citric acid, which was the predominant organic acid in black currant berries, increased with an increasing temperature, whereas the opposite trend was observed for malic and shikimic acid. Quninic acid was always present at relatively low concentrations. By contrast, photoperiod had no significant effect on berry content of any of the investigated compounds. It is concluded that the post-flowering temperature has marked effects on the concentration of important chemical compounds responsible for taste and nutritional value of black currant berries, whereas photoperiod has no such effect in the studied cultivars. © 2016 Society of Chemical Industry.

A comparison of plasma glucose and oxidative status in lactating dairy cows in summer and autumn.

The objective of this study was to investigate the effects of the hot summer season on plasma glucose and oxidative stress markers. For two 14-day experimental periods, namely periods 1 (July-August) and 2 (October-November), 12 and 14 lactating dairy cows, respectively, that were milked using an automatic milking system, were fed diets containing similar ingredients, and their milk production, plasma metabolites and oxidative status markers were investigated. Dry matter intake and milk yield were not affected by the experimental period. Rectal temperature at 18.00 hours and milk protein concentration in period 1 were higher and lower, respectively, than in period 2 (P < 0.05), suggesting that the hot summer season had an effect on the experimental dairy cows. Plasma glucose and the ascorbic acid + dehydroascorbic acid (AA) concentrations in period 1 were lower than in period 2 (P < 0.01). The plasma malondialdehyde (MDA) concentration did not differ between the experimental periods. The increase in the cellular AA uptake in peripheral tissues in period 1 might be a possible compensatory mechanism to balance the occurrence of reactive oxygen species and the antioxidant capacity in the cells, resulting in the absence of an effect of the hot summer season on plasma MDA concentration. © 2016 Japanese Society of Animal Science.

HPLC-UV method for the simultaneous determinations of ascorbic acid and dehydroascorbic acid in human plasma

A high performance liquid chromatography (HPLC) paired with UV-vis detection method to determine ascorbic acid and its oxidation product, dehydroascorbic acid, in human plasma was developed. Ascorbic acid in human plasma was extracted and stabilized using 10% metaphosphoric acid, and was analyzed by a Symmetry C18 column with 5 mM Hexadecyltrimethylammonium bromide and 50 mM KH2PO4 solution as the mobile phase (1.0 mL/min flow rate). Isoascorbic acid served as the internal standard and ultraviolet detector wavelength was 254 nm and 265 nm. Dehydroascorbic acid concentration was calculated from the differences in ascorbic acid concentration before and after reduction by dithiothreitol reagent. Quantification for ascorbic acid in human plasma was linear from 1–100 μg/mL. The interand intra-day precisions and accuracy were determined and the results were found to be within ±15%. This method was successfully applied to a human pharmacokinetic study of ascorbic acid as well as dehydroascorbic acid after oral administration of 4,000 mg vitamin C tablets to healthy Korean volunteers.