scholarly journals Farmacologia e toxicologia do ácido ascórbico: uma revisão

2000 ◽  
Vol 22 (22) ◽  
pp. 103
Author(s):  
Maria Caroline Jacques da Silva
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Daily Intake ◽  
Nutritional Supplement ◽  
Vitamin Supplement ◽  
Human Beings ◽  
Green Pepper ◽  
Oxidation Reduction ◽  
Enzymatic Systems ◽  
Gulonolactone Oxidase

L-Ascorbic acid (AA) or vitamin C is a six carbon cetolactone, structurally related to glucose and other hexoses. The major sources of AA are citrus fruits, strawberry, melon, green pepper, potato, tomato and leafy green vegetables. AA interferes with a broad spectrum of oxidation-reduction reactions, acting in at least 10 enzymatic systems. In this way, vitamin C influences the synthesis of collagen, carnitine, and neurotransmitters; the transformation of cholesterol into bile acids; biotransformation of xenobiotics substances; absorption of iron; and formation and scavenging of oxygen free radicals. AA is used as food addictive because of its antioxidant properties.Therapeutically, it is used as nutritional supplement during scurvy. Human beings and other primates, as well as guinea pigs and some species of bats are mammals that are unable to synthesize AA; thus, they need AA in the diet to prevent scurvy. Rats are able to synthesize AA using glucose, through intermediary formation of D-glucuronic acid, L-gulonic acid and gulonolactone.Homo sapiens lack the hepatic enzyme gulonolactone oxidase, which catalyses the last reaction of the biosynthesis pathway (L-gulonolactone conversion to ascorbic acid). The functions of central nervous, immune, and cardiovascular systems, and the periodontal tissue, as well as the detoxification function of the liver, are negatively influenced by vitamin C deficiency. In this way, it has been described several benefits of vitamin supplement ingestion, as decreasing of LDL cholesterol, including mega doses that can reach as much as 18g daily. Although there have been raised many literatures about vitamin C use in a wide variety of diseases, there is a lack of clinical efficiency of mega doses; besides, some side effects can come up, as diarrhea and oxalate stones in the kidneys. However, the ideal daily intake of vitamin C is still unknown. This happen because the recommended daily intake is based in a single role of AA, the scurvy prevention. Daily ingestion of AA should be the same quantity excreted or destroyed by oxidation, taking into consideration AA actions on the enzymatic systems. Actually, vitamin C is necessary for health in little quantities and is harmful in large doses. It happens because the cells are always walking a balance between oxidation and reduction processes, and AA in great quantities assume oxidative characteristics, interfering in this balance. Although the existence of several evidences indicating AA toxicity in large doses, there are some authors who believe that the ingestion of large doses is safe, but they admit that the disposable data are very contradictory.

scholarly journals Comparison of Vitamin C Content of Commercially Available Fresh Fruits

2019 ◽  
pp. 1-6
Author(s):  
Aneta Popova
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Study Design ◽  
Acid Level ◽  
Design Research ◽  
Current Paper ◽  
Ascorbic Acid Level ◽  
Daily Consumption ◽  
Oxidation Reduction ◽  
Reported Data

Aims: The aim of the current paper is to identify the ascorbic acid level in ten commercially available fruits in order to expand the existing database about fruits rich in Vitamin C and to promote their daily consumption. Study Design:  Research was conducted experimentally. Place and Duration of Study: University of food technologies, Plovdiv, Bulgaria, October 2019. Methodology: Ascorbic acid levels were determined with the use of two oxidation-reduction titration methods – Dichlorophenoliodophenol (DCPIP) and N-Bromosuccinimide (NBS). Results: All studies samples possessed different amounts of ascorbic acid. Both DCPIP and NBS assay resulted in determining strawberries as the fruit with the highest ascorbic acid levels – 55.1 ± 1.6 mg/100 g and 59.8 ± 2.2 mg/100 g respectively. Lowest values were obtained for fig. All results are commensurable to those obtained in other studies. Ascorbic acid levels were as follows: strawberries > grapefruit > pear > green apple > blueberries > quince > banana > plum > white grapes > fig. Conclusion: In this study, ten commercially available fruits were studied for their ascorbic acid levels. Comparison between two titration methods showed moderate differences in the results confirming that the NBS method is more sensitive. All reported data confirms that differences occur, but fruits can be considered sources of vitamin C.

On the Genetic Etiology of Scurvy

1966 ◽  
Vol 15 (4) ◽  
pp. 345-350 ◽  
Author(s):  
Irwin Stone
Keyword(s):  
Human Physiology ◽  
Ascorbic Acid ◽  
Vitamin C ◽  
Genetic Disease ◽  
Gene Defect ◽  
Nutritional Disorder ◽  
Genetic Etiology ◽  
Gulonolactone Oxidase ◽  
Mammalian Liver ◽  
Food Constituent

SummaryScurvy, now regarded as a nutritional disorder due to the lack of the trace food constituent, vitamin C, is shown to be the end result of a typical genetic disease. This genetic disease syndrome has been namedHypoascorbemia. Its primary cause is the hereditary lack of — or defect in — the gene controlling the synthesis of the enzyme, L-gulonolactone oxidase. This is a mammalian liver enzyme, the last one in the series for converting glucose into ascorbic acid. Man is one of the few mammals that lacks this enzyme and hence is unable to sythesize his own ascorbic acid. The gene defect occurred during the course of evolution by a conditional lethal mutation. The replacement of the present vitamin C theory regarding the etiology of scurvy by this genetic concept gives important new viewpoints to the quantitative aspects of ascorbic acid in human physiology and also provides new rationales for the use of high levels of ascorbic acid in normal physiology and in the therapy of clinical entities other than scurvy.

scholarly journals Vitamin C biochemistry: From scurvy to COVID-19 treatment

2020 ◽  
Vol 61 (2) ◽  
pp. 59-70
Author(s):  
Tamara Zakić ◽  
Marta Budnar ◽  
Anđelika Kalezić ◽  
Aleksandra Korać ◽  
Aleksandra Janković ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Immune System ◽  
Vitamin C ◽  
Mechanism Of Action ◽  
Mechanisms Of Action ◽  
System Function ◽  
Physiological Conditions ◽  
Immune System Function ◽  
Oxidation Reduction ◽  
New Challenges

The story of vitamin C (L-ascorbic acid) as an antioxidant and a cofactor in numerous biochemical reactions is a part of its long history and it is well known today. However, many questions of its mechanism of action and the benefits that it has on human health are still emerging. This applies not only to the recommended doses but also to the route of its administration. Besides, there are numerous questions about the therapeutic efficacy of vitamin C in various human (infectious) diseases, as well as its immune system function and antiviral potential. The fact that vitamin C can act as a reductant (antioxidant) and a prooxidant further emphasizes its oxidation-reduction (redox) potential in real physiological conditions. Today, the question of the intravenous administration of vitamin C effect in patients with SARS-CoV-2 requires special attention. This review aims to showcase known facts about vitamin C and its mechanisms of action to better understand the current new challenges related to vitamin C.

Analysis of Heavy Metal in Water used for Irrigation, Soil and Some Vegetables grown around Tin Mine Areas of Heipang District, Barkin-Ladi Local Government of Plateau State

2019 ◽  
pp. 111-119
Author(s):  
Agustina Onyebuchi Ijeomah ◽  
Rebecca Ngoholve Vesuwe ◽  
Bitrus Pam
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Food Safety ◽  
Safety Concern ◽  
Human Beings ◽  
Green Beans ◽  
Green Pepper ◽  
Transfer Factors ◽  
Mining Areas ◽  
Plateau State

Vegetables growing in mining areas have become a serious food safety concern because of the high levels of heavy metals always associated with mining. In this study, water used for irrigation, soil, cabbage, green pepper and green beans grown in tin mine areas of Heipang District, Barkin-Ladi LGA of Plateau State were analyzed for lead, cadmium and zinc, using Atomic Absorption Spectrophotometer (AAS). The concentrations of the heavy metals in water, soil, vegetables were all in the order Pb, >> Cd > Zn. In the vegetables, the order was: Pb → cabbage > green beans > green pepper; Cd → green beans > cabbage > green pepper; Zn → cabbage > green pepper = green beans. The transfer factors for all the metals (heavy metal in plant / heavy metal in soil) ranged from 0.95 to 1.48. There were high levels of Pb and Cd in all the vegetables, which may be attributed to the metals in the water used for irrigation. Whilst the concentration of Zn in all the samples were lower than recommended limits, the levels of Pb and Cd in the water, soil and vegetables were higher than the WHO/FEPA standard recommended limits reported for vegetables. The Cd concentrations of the vegetables also exceeded the tolerance thresholds for animals and human beings and therefore consumption of vegetable from the area would endanger the health of the population.

Influence of Ascorbic Acid on the Structure and Function of Alpha-2- macroglobulin: Investigations using Spectroscopic and Thermodynamic Techniques

2020 ◽  
Vol 27 (3) ◽  
pp. 201-209
Author(s):  
Syed Saqib Ali ◽  
Mohammad Khalid Zia ◽  
Tooba Siddiqui ◽  
Haseeb Ahsan ◽  
Fahim Halim Khan
Keyword(s):  
Ascorbic Acid ◽  
Conformational Changes ◽  
Structural Changes ◽  
The Body ◽  
Titration Calorimetry ◽  
Spectroscopic Techniques ◽  
Human Beings ◽  
Plasma Ascorbic Acid ◽  
Dietary Antioxidant ◽  
And Function

Background: Ascorbic acid is a classic dietary antioxidant which plays an important role in the body of human beings. It is commonly found in various foods as well as taken as dietary supplement. Objective: The plasma ascorbic acid concentration may range from low, as in chronic or acute oxidative stress to high if delivered intravenously during cancer treatment. Sheep alpha-2- macroglobulin (α2M), a human α2M homologue is a large tetrameric glycoprotein of 630 kDa with antiproteinase activity, found in sheep’s blood. Methods: In the present study, the interaction of ascorbic acid with alpha-2-macroglobulin was explored in the presence of visible light by utilizing various spectroscopic techniques and isothermal titration calorimetry (ITC). Results: UV-vis and fluorescence spectroscopy suggests the formation of a complex between ascorbic acid and α2M apparent by increased absorbance and decreased fluorescence. Secondary structural changes in the α2M were investigated by CD and FT-IR spectroscopy. Our findings suggest the induction of subtle conformational changes in α2M induced by ascorbic acid. Thermodynamics signatures of ascorbic acid and α2M interaction indicate that the binding is an enthalpy-driven process. Conclusion: It is possible that ascorbic acid binds and compromises antiproteinase activity of α2M by inducing changes in the secondary structure of the protein.

Amperometric assay of vitamin C using an ascorbate oxidase enzyme electrode

1979 ◽  
Vol 44 (11) ◽  
pp. 3395-3404 ◽  
Author(s):  
Pavel Posádka ◽  
Lumír Macholán
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Oxygen Electrode ◽  
Ascorbate Oxidase ◽  
Current Response ◽  
Reaction Conditions ◽  
Long Term Storage ◽  
Oxidase Enzyme ◽  
Optimal Reaction

An oxygen electrode of the Clark type, coated by a thin, active layer of chemically insolubilized ascorbate oxidase from squash peelings specifically detects by measuring oxygen uptake 10 to 400 μg of ascorbic acid in 3 ml of phosphate buffer. The record of current response to substrate addition lasts 1-2 min. The ascorbic acid values determined in various samples of fruit juices are in good agreement with the data obtained by titration and polarography. The suitable composition of the membrane and its lifetime and stability during long-term storage are described; optimal reaction conditions of vitamin C determination and the possibilities of interference of other compounds are also examined. Of the 35 phenols, aromatic amines and acids tested chlorogenic acid only can cause a positive error provided that the enzyme membrane has been prepared from ascorbate oxidase of high purity.

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