Reduced Form Of Ascorbic Acid Research Articles

SLC23 family of ascorbic acid transporters in GtoPdb v.2021.3

Predicted to be 12 TM segment proteins, members of this family transport the reduced form of ascorbic acid (while the oxidized form may be handled by members of the SLC2 family (GLUT1/SLC2A1, GLUT3/SLC2A3 and GLUT4/SLC2A4). phloretin is considered a non-selective inhibitor of these transporters, with an affinity in the micromolar range [1].

SLC23 family of ascorbic acid transporters (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Predicted to be 12 TM segment proteins, members of this family transport the reduced form of ascorbic acid (while the oxidized form may be handled by members of the SLC2 family (GLUT1/SLC2A1, GLUT3/SLC2A3 and GLUT4/SLC2A4). phloretin is considered a non-selective inhibitor of these transporters, with an affinity in the micromolar range.

VARIABILITY OF BIOCHEMICAL PARAMETERS OF AMARANTH PLANTS DURING CULTIVATION TO OBTAIN THE NATURAL FOOD COLORANT WITH A HIGH CONTENT OF BIOLOGICALLY ACTIVE SUBSTANCES

Amaranth leaves can be used in salads, soups, sauces enriching them with biologically active substances (in particular, ascorbic acid and phenolic compounds), as well as giving them an original taste and color. Plants were grown on the experimental field of VNIISSOK in the Moscow region. The experiment was laid on sod-podzolic soil. For the period of 2013-2016 years, biochemical parameters were investigated: total content of water-soluble antioxidants, ascorbic acid content, dry matter content, amarantine content in three amaranth varieties (Valentina, Don Pedro and Fakel) and two green leaf varieties (Pamyati Kovasa and Eku 17020) of FSBSI FSVC (formerly VNIISSOK) and INIAP selection and a correlation analysis was performed, which showed a relationship between the relative concentration of amarantine in the leaves and other biochemical parameters at different stages of plant development. The maximum accumulators of antioxidants according to the TAC parameter were the Valentina and Don Pedro varieties - up to 2.9 mg gallic acid equivalents/g. The situation was similar in terms of the content of the reduced form of ascorbic acid. So also the Valentina and Don Pedro varieties were leading with values of about 140 mg%. A positive correlation between the content of ascorbic acid and the sum of hydrophilic antioxidants was confirmed. Pamyati Kovasa and Eku 17020 varieties can be recommended as a source of green mass of leaves with a high content of ascorbic acid, red colored varieties Don Pedro, Valentina, Fakel – for obtaining red dye enriched with antioxidants.

Biochemical and Visual Changes in Cactus Stems (Opuntia ficus-indica Mill.) Stored at 4, 12 and 26C

The purpose of this study was to identify visible and microscopic symptoms as well as certain biochemical changes associated with chilling injury (CI) in “Atlixco” cactus stems. Cladodes were harvested, disinfected, minimally processed and stored at 4, 12 and 26C for 14–21 days. Results indicated that cactus stems were sensitive to CI at 4 and 12C and exhibited pitting and bronzing as visible symptoms of this disorder. Confocal microscopy showed that mitochondrial integrity was maintained at 4C whereas a deterioration of these organelles occurred at 12 and 26C. Electrolyte leakage, together with an increase in the levels of Adenosine triphosphate (ATP), glutathione and the reduced form of ascorbic acid were associated with CI. In spite of the presence of CI at 4C, cactus stems were still able to preserve their taste quality and no adverse effects were observed on either firmness or color for 21 days. Practical Applications Minimally processed products should be refrigerated at ≤4C in order to maintain their quality and prevent the growth of harmful microorganisms. However, the refrigeration of cactus stems at suboptimal temperatures causes the appearance of chilling injury (CI). Previous studies have mentioned the general symptoms of this physiological disorder in cactus stems, but no one has described the symptomatology in detail and there is yet to be reported histological and biochemical characterization that might serve to confirm or diagnose its presence. This study describes the symptoms of CI and provides histological and biochemical indicators for its early identification during storage. It also constitutes the preliminary stage to the future application of postharvest technologies that induce tolerance to CI, preventing browning and preserving the quality of minimally processed cactus stems in order to expand their domestic and international markets.

Oxidative stress and formation and maintenance of root stem cells

The hypothesis of L. Feldman and his coworkers, according to which a more oxidizing environment in the cells of root quiescent center results from high activity of ascorbate oxidase activated by indoleacetic acid (IAA) accumulating in these cells, is discussed. The high activity of ascorbate oxidase is responsible for lowered concentrations of the reduced form of ascorbic acid and glutathione and high content of reactive oxygen species in quiescent center cells. The oxidative stress represses proliferation of the cells. Inhibitors of IAA transport attenuate the oxidative stress, thus suggesting a role of IAA as an activator of ascorbate oxidase. Interestingly, the high concentration of IAA in dividing cap cells adjacent to the quiescent center cells did not cause retardation of cell proliferation and oxidative state in these cells.

Immunohistochemical study of the distribution of sodium‐dependent vitamin C transporters in adult rat brain

Sodium-dependent vitamin C transporters (SVCTs) is known to transport the reduced form of ascorbic acid into the cell, whereas the oxidized form of vitamin C (VC) is moved through a facilitative sugar transporter, such as glucose transporter (GLUT). With regard to the distribution of SVCT1 and -2 within the various organs, they were reported to be expressed in different types of cells. Especially in the central nervous system, only SVCT2 mRNA was expressed mainly in neurons and some types of neuroglial cells. However, data on the expression of SVCT proteins in the brain are scant. Therefore, we tried to develop comprehensive data on the distribution of SVCT proteins in adult rat brain by using immunohistochemical techniques for the first time. In our study, SVCT2 immunoreactivities (IRs) were intensely localized in the neurons of cerebral cortex, hippocampus, and Purkinje cells of cerebellum, and much weaker SVCT2 IRs were found in the other brain regions. Judging from double-immunohistochemical data, most of the cells expressing SVCT2 IRs were likely to be neurons or microglia, even though the cells in choroids plexus or ependymal cells around the ventricles also exhibited SVCT2 IRs. Complete mapping of the distribution of SVCT2 IRs was available by using a semiquantitative method. The subcellular localization of SVCT proteins is necessary for understanding the exact role of the protein, so the current overall mapping of SVCT IRs in the rat brain could be the basis for further studies on related subjects.

Chondrocyte transport and concentration of ascorbic acid is mediated by SVCT2

Collagen II is the major protein component of articular cartilage and forms the collagen fibril network, which provides the tensile strength of cartilage. Collagen II synthesis is enhanced by ascorbic acid (vitamin C) at both a transcriptional and post-transcriptional level. While the importance of ascorbic acid in the synthesis of collagen has been established, the mechanism by which this essential nutrient is transported into chondrocytes has not been investigated previously. We have characterized the transport of the reduced form of ascorbic acid in passaged primary human chondrocytes to discern the physiologically relevant pathways of ascorbic acid transport in cartilage. We have found that chondrocytes are robust concentrators of ascorbic acid, capable of transporting the reduced form, and concentrating total ascorbic acid, in the reduced form and its metabolites, 960-fold over the concentration in the extracellular milieu. Chondrocyte transport of ascorbic acid was sodium and temperature dependent, stereoselective for the L-forms, and inhibited by the anion transport inhibitor, sulfinpyrazone. Chondrocytes preferentially expressed the full-length and functional isoform of sodium-dependent vitamin C transporter 2 (SVCT2). When this transcript was suppressed with sequence-specific siRNAs, the active transport component of ascorbic acid was abolished. Thus, we provide the first evidence that SVCT2 mediates the secondary active and concentrative transport of ascorbic acid in human chondrocytes.

Short-term ascorbic acid deficiency induced oxidative stress in the retinas of young Guinea pigs.

We examined whether short-term ascorbic acid deficiency induces oxidative stress in the retinas of young guinea pigs. Four-week-old guinea pigs were given a scorbutic diet (20 g/animal/day) with and without adequate ascorbic acid (400 mg/animal/day) in drinking water for 3 weeks. The serum concentrations of the reduced form of ascorbic acid and the oxidized form of ascorbic acid in the deficient group were 14.1 and 4.1%, respectively, of those in the adequate group. The retinal contents of the reduced form of ascorbic acid and the oxidized form of ascorbic acid in the deficient group were 6.4 and 27.3%, respectively, of those in the adequate group. The retinal content of thiobarbituric acid-reactive substances, an index of lipid peroxidation, was 1.9-fold higher in the deficient group than in the adequate group. Retinal reduced glutathione and vitamin E contents in the deficient group were 70.1 and 69.4%, respectively, of those in the adequate group. This ascorbic acid deficiency did not affect serum thiobarbituric acid-reactive substances and reduced glutathione concentrations but increased serum vitamin E concentration. These results indicate that short-term ascorbic acid deficiency induces oxidative stress in the retinas of young guinea pigs without disrupting systemic antioxidant status.

Short-Term Ascorbic Acid Deficiency Induced Oxidative Stress in the Retinas of Young Guinea Pigs

We examined whether short-term ascorbic acid deficiency induces oxidative stress in the retinas of young guinea pigs. Four-week-old guinea pigs were given a scorbutic diet (20 g/animal/day) with and without adequate ascorbic acid (400 mg/animal/day) in drinking water for 3 weeks. The serum concentrations of the reduced form of ascorbic acid and the oxidized form of ascorbic acid in the deficient group were 14.1 and 4.1%, respectively, of those in the adequate group. The retinal contents of the reduced form of ascorbic acid and the oxidized form of ascorbic acid in the deficient group were 6.4 and 27.3%, respectively, of those in the adequate group. The retinal content of thiobarbituric acid-reactive substances, an index of lipid peroxidation, was 1.9-fold higher in the deficient group than in the adequate group. Retinal reduced glutathione and vitamin E contents in the deficient group were 70.1 and 69.4%, respectively, of those in the adequate group. This ascorbic acid deficiency did not affect serum thiobarbituric acid-reactive substances and reduced glutathione concentrations but increased serum vitamin E concentration. These results indicate that short-term ascorbic acid deficiency induces oxidative stress in the retinas of young guinea pigs without disrupting systemic antioxidant status.

Prolonged marginal ascorbic acid deficiency induces oxidative stress in retina of guinea pigs.

We examined whether prolonged marginal ascorbic acid deficiency induces oxidative stress in the retina of guinea pigs. Male guinea pigs aged four weeks were given a scorbutic diet (20 g/animal per day) with either marginally deficient ascorbic acid (0.5 mg/animal per day) or adequate ascorbic acid (1 g/animal per day) in drinking water for three and six months. The retinal contents of the reduced form of ascorbic acid in the deficient group at three and six months were 68.1 and 43.5%, respectively, of that in the corresponding adequate group. The retinal contents of the oxidized form of ascorbic acid in the deficient group at three and six months were 1.9- and 2.7-fold, respectively, higher than that in the corresponding adequate group. The content of retinal thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, in the deficient group was 2.5-fold higher than that in the adequate group at six months. The retinal contents of reduced glutathione (GSH) in the deficient group at three and six months were 84.8 and 66.7%, respectively, of that in the corresponding adequate group. The deficient group had 37.5% of retinal vitamin E content of the adequate group at six months. The deficient group had higher serum vitamin E concentration than the adequate group in both experimental periods. There were no differences in serum TBARS and GSH concentrations between the groups at both periods. These results indicate that prolonged marginal ascorbic acid deficiency induces oxidative stress in the retina of guinea pigs without systemic oxidative stress.

Human HL-60 Myeloid Leukemia Cells Transport Dehydroascorbic Acid Via the Glucose Transporters and Accumulate Reduced Ascorbic Acid

The cellular accumulation of vitamin C, a substance critical to human physiology, is mediated by transporters located at the cell membrane, and is regulated in a cell-specific manner. Neoplastic cells may have special needs for vitamin C. Therefore, we investigated the transport of vitamin C in a human myeloid leukemia cell line (HL-60). The HL-60 cells lacked the capacity to transport the reduced form of vitamin C, ascorbic acid, but they showed a remarkable ability to transport the oxidized form of vitamin C, dehydroascorbic acid (DHA). Uptake-accumulation studies indicated that the HL-60 cells accumulated ascorbic acid when provided with DHA. Kinetic analysis showed the presence of two functional activities involved in the uptake of DHA, one with low affinity and one with high affinity. Cytochalasin B and phloretin, which inhibit the passage of glucose through the facilitative glucose transporters, also inhibited the transport of DHA by HL-60 cells. Transport of DHA was completed by D- but not L-hexoses, and was sensitive to D-hexose-dependent counter transport acceleration. These data support the concept that HL-60 myeloid leukemic cells transport DHA through the facilitative hexose transporters (glucose transporters) and accumulate the reduced form of ascorbic acid.

Human HL-60 myeloid leukemia cells transport dehydroascorbic acid via the glucose transporters and accumulate reduced ascorbic acid

The cellular accumulation of vitamin C, a substance critical to human physiology, is mediated by transporters located at the cell membrane, and is regulated in a cell-specific manner. Neoplastic cells may have special needs for vitamin C. Therefore, we investigated the transport of vitamin C in a human myeloid leukemia cell line (HL-60). The HL-60 cells lacked the capacity to transport the reduced form of vitamin C, ascorbic acid, but they showed a remarkable ability to transport the oxidized form of vitamin C, dehydroascorbic acid (DHA). Uptake- accumulation studies indicated that the HL-60 cells accumulated ascorbic acid when provided with DHA. Kinetic analysis showed the presence of two functional activities involved in the uptake of DHA, one with low affinity and one with high affinity. Cytochalasin B and phloretin, which inhibit the passage of glucose through the facilitative glucose transporters, also inhibited the transport of DHA by HL-60 cells. Transport of DHA was completed by D- but not L-hexoses, and was sensitive to D-hexose-dependent counter transport acceleration. These data support the concept that HL-60 myeloid leukemic cells transport DHA through the facilitative hexose transporters (glucose transporters) and accumulate the reduced form of ascorbic acid.

Changes of superoxide dismutase activity and ascorbic acid in focal cerebral ischaemia in rats.

Free radical reactions are supposed to cause ischaemic brain damage, and active oxygens can initiate these chains reaction. If active oxygens play important roles in ischaemic brain damage, the activity of superoxide dismutase, scavenger of superoxide anion, is supposed to decrease in ischaemic brain. The reduced form of ascorbic acid also scavenges superoxide anion. In rat middle cerebral artery focal ischaemia, we investigated the changes in superoxide dismutase activity and the concentration of reduced ascorbate up to 48 hours. Middle cerebral artery territory of each cerebral hemisphere was homogenized. The supernatant was divided into two aliquots; one was dialysed to remove ascorbate and the other was not. The enzyme activity of the dialysed specimen from the ischaemic hemisphere did not decrease within 4 h after the arterial occlusion. The activity of the dialysed specimen from the nonischaemic side remained unchanged during the examination. Reduced ascorbate levels in nondialysed samples showed similar changes to the superoxide dismutase activities in the dialysed samples. Our data suggest that ascorbic acid may exert the enzyme activity and that the enzyme activity remains at the normal level in the early phase of ischaemia despite the irreversible ischaemic changes that take place within 4 h after the onset of ischaemia.

Transport and metabolism of ascorbic acid in human placenta.

The role of human placenta in cellular transport and metabolism of the potentially toxic oxidized form and the useful reduced form of ascorbic acid was examined in surviving tissue fragments in vitro. At the end of a 60-min incubation with the 14C label nominally present in the reduced form, a tissue-to-medium ratio in excess of unity was reached. The importance of evaluating uptake of the ascorbic acid metabolites is evident from a careful assay of 14C label present in the bathing media. Significant spontaneous oxidation occurs, which is slowed or reversed to a limited extent by the presence of placental tissue. Uptake of the oxidized substrate, dehydro-L-ascorbic acid, proceeds much more rapidly than uptake of ascorbic acid. At the end of a 15-min incubation, most of the substrate taken up was in the reduced form. From an additional evaluation of 14C label in the bath it is calculated that 25% of ascorbic acid formed by the tissue is released within 15 min. The cellular uptake mechanism for dehydro-L-ascorbic acid is not shared by glucose and is not dependent on the presence of Na+ but is dependent on intact cellular metabolism. The finding of avid cellular uptake and reduction of the oxidized form of ascorbic acid supports the concept that the placenta helps to clear the toxic molecule from the maternal circulation, metabolizes it, and delivers the useful reduced form to the fetus.

Physiological and morphological studies on potato plants : Part 11. On the variation of ascorbic acid content of potato plants in irregular tuber formation.

The present investigation is one of a series of experiments carried out under the title of physiological and morphological studies on potato plants. In the previous papers (1949, 1951), the authors have reported some assumptions concerning the mechanism of sprout tuber formation due to the senility of mother tubers. Judging from the results described in the above papers, it seems very reasonable to assume, therefore, that the irregular tuber formation of potato plants, such as sprout tuber, might be attributable to the changes of the reserve substances in the mother tuber and of the respiration rate of the sprout and tuber according to their storage conditions. In recent studies on the tuber formation of potato plants, the authors (1952) have made it obvious that the accumulation of ascorbic acid and the variations of carbohydrates contents in the potato tuber stand physiologically in a close interrelationship, namely, that the ascorbic acid may serve as an activator in the formation of starch in the potato tuber. The purpose of the present, investigation was chiefly to determine the relation between the variations of ascorbic acid and carbohydrate contents in the abnormal tuberization of potato plants under the various conditions, with a view to narrowing the problem whether the ascorbic acid may also act as an activator in the formation of starch in the abnormal tuberization of potatoes. The variety Irish Cobbler was used as material. The fractions analysed in the present experiments were similar to those described in the previous papers, so full descriptions are omitted here. The experimental results obtained may be summarized as follows ; (1) Under the storage conditions of dried and high temperature, the accumulation of starch and the rapid acceleration of growth in thickness of the sprout were recognized. With regard to the ascorbic acid content in the sprout tuber under these conditions, the content of oxidized form was much greater than that of the reduced form of ascorbic acid. The low content of the latter may be attributable to the oxidation of reduced ascorbic acid due to the high temperature condition. Accordingly, the accumulation of starch in the sprout tuber was less than that in the control tuber. (2) Being accompanied with the development of sprout tuber arose directly on the mother tuber, due to its senility resulting from long storage in a cellar. The accumulation of starch and the increase of ascorbic acid, especially of the reduced form, in the sprout tuber ran parallel. Accordingly the increase of the ratio of reduced from/oxidized form of ascorbic acid was one result. (3) When the seedlings of potatoes were placed in the dark, the ascorbic acid content in the tips of etiolated sprouts was much higher than the content in other parts of the sprouts. In the new tubers formed on the axils of the sprouts, however, the highest amounts of ascorbic acid and starch contents were recognized. (4) Judging from the results described above, if may be concluded that the localization of ascorbic acid in the tissue of potato plants tends to be parallel to that of the starch. Hence, in the case of the tuberization of potato plant, it seems very probable that the ascorbic acid, especially in the reduced form, plays an important role in the accumulation of starch and in the development of the tuber.