Why is ascorbic acid an acid

Therefore, citric acid is recommended when canning tomatoes to lower the pH or increase acidity. It is a small amount that works effectively. It would take a lot more ascorbic acid to equal the power of citric acid to acidify tomatoes properly. Then flavor would be compromised. Ascorbic acid is not as acidic as citric acid. I investigated vitamin C degradation in lemon juice cooked for various lengths of time.

I used juice squeezed that day and compared the concentrations of raw samples to those cooked for minutes. The acidity in lemon juice seems to really help preserve ascorbic acid, so be sure to take some with you on your next long sea voyage! Great to hear you find the article useful and really like the experiment you did with lemon juice! During ascorbic titration there is addition of oxalate ammonium. What is the role of this compound?

Thank you for your question and apologies for the late answer. I have been working on a bigger update of this post to better reflect your answer, but also several of the reaction mechanisms. Hopefully the updated article will answer most of your questions! What were your observations when you did your titration experiment? Did you see more or less vitamin C in the orange juice? Remember that the main effect of temperature on chemical reactions is that it increases the movement of molecules so generally speeds reactions up.

I recently did the same experiment, but had some unexpected results. The heated OJ had less ascorbic acid than the unheated, but the ascorbic acid levels increased in the heated sample as it cooled. Why would this be? We also mixed an OJ sample with milk. Those are some interesting results indeed, would any of the following be possible?

As long as DHAA does not react further, it can react back into ascorbic acid. If your drink contains reducing agents, these might be oxidized before the vitamin C gets oxidized. That would help determine whether the hypothesis above is correct. Keep in mind also that vitamin C ascorbic acid is very unstable. For a more advanced method for determining vitamin C content and some more background, you might be interested in this article. You are completely correct, and thank you for noticing this! That was a typo from our side.

I have one question about the loss of Vitamin C. By adding the salt of Ascorbic Acid, that can be found commercially, to my orange juice, will I increase the quantity of Vitamine C lost during oxydation?

Yes, you can increase the vitamin C concentration again by adding some back, as a matter of fact, it is what juice manufacturers do in their production process.

However, I would not recommend adding it back yourself since orange juice is such an unstable system. Powders on the other hand are very stable. The lack of water prevents most chemical reactions from occurring. Well-written article, but I think that something should have been said about the amount of sugar in orange juice, as we are now aware that this BY FAR creates the most clinical problems that are otherwise avoidable.

Thanks for the suggestion! Hi, I had a question about vitamin c when mixed with ground eggshell. I take the eggshell as a calcium supplement. Eggshell is mostly calcium carbonate which reacts with the citric acid.

My question is: is the vitamin c still present for the body after this? Or does the reaction oxidize it? I want to be certain the C is still usable. For them to react there will have to be enough water.

As soon as you dissolve them in water reactions will indeed occur and can likely lead to loss of vitamin C. Hi and thanks for the reply.

Foams up like crazy. Does that kill the bioavailability of the c? As described in the post, once the ascorbic acid has reacted it will become ascorbate. Thanks for the reply. I can always take the eggshells by themselves with my meal. I just thought the acid soak would help break them down better for absorption.

So, the baking soda reaction is fairly quick. Couple minutes tops. You think if I buffered it that way, most of the c would be useful still? So if I consume it right away, I should get most of the benefit. Am I getting that correctly? Scientifically, your assumptions at the bottom seem correct to me. Personally, I get all my vitamin C from fruits and vegetables which contain a lot of it.

Thanks for coming by and hope we could at least help you with the food science part of your question! I was wondering what types of compounds can be added to a fruit juice orange, grape, whatever. I would guess something like Calcium or Sodium. What form would I add it to the juice in so that it actually has some sort of effect on the Vitamin C content? As a response for high doses, vitamin C excretion from kidneys and sweat occur. The antiviral and anti-bacterial effect of vitamin C protects skin and kidneys from infection [ 1 ].

Also in extra doses, the oxidation components were used as an anticancer effect more the vitamin C itself [ ]. This percent decreases in diseased patients due to higher consumption. Repeated low doses about mg are highly recommended in diseased individuals due to theses low doses saturate the body.

Therefore, limited renal clearance of ascorbic acid is usually detected. This level controls the excretion of the ascorbic acid through kidneys. The intravenous route exerts 30—70 folds of vitamin C plasma levels than the oral route [ 19 ]. The rapid excretion due to its water soluble nature limits its harmful effect and makes it totally safe product in normal doses. It also found that the upper tolerable limit UL is 2 g. Depending on the depletion-repletion study, it was found that the RDA is 75 mg for women and 90 mg for men.

It was modified by Levine et al. The maximum bioavailability and absorption of vitamin C achieved at mg [ 20 ]. In , Marinesco et al. Plaut and Billow detected the ascorbic acid lowering not only in the organs but also in body fluids as CSF, blood and urine. They also detected this deficiency in neural diseases and alcoholism. Many reasons were thought to be the cause of vitamin C deficiency in old people. Decreased intestinal absorption and dietary deficiency are the main causes.

In , Yavorsky et al. Vitamin C has an important role in the maintenance of a healthy immune system and its deficiency causes immune insufficiency and multiple infections. The ascorbic acid level is lowered in various body fluids during bacterial infections. Thus, it is commonly used as adjunctive treatment in many infectious diseases such as hepatitis, HIV, influenza and periodontal diseases [ 22 ].

Vitamin C administration modifies and enhances both the innate and adaptive immune response. It neutralizes the bacterial toxins especially endotoxins by blocking the essential signal for lipopolysaccharides LPS formation. On the other hand, LPS block the passage of ascorbic acid through blood brain barrier and inhibits its uptake by various cells [ 22 ].

Ascorbic acid improves the phagocytic properties and activity of various immune cells including neutrophils, natural killer cells, macrophages and lymphocytes. Vitamin C increases lymphocytes proliferation and antibody production [ 23 , 24 ]. The ROS are classified into 3 classes; the first are reactive free radicals as oxygen related radicals superoxide, hydroxyl radical or peroxyl radicals. The second class is reactive species but not free radicals as hypochlorous acid.

The third class is radicals resulted from the reaction with ascorbic acid [ 26 ]. Antioxidants are also classified into enzymatic and non-enzymatic. The enzymatic antioxidants include catalase enzyme, thiol-containing agents cysteine, methionine, taurine , glutathione and lipoic acid [ 27 ]. Vitamin C is one of the nutrient non-enzymatic anti-oxidants [ 28 , 29 , 30 ].

Its antioxidant effect is by electron donation process where vitamin C easily donates two electrons reduction reaction to other compounds in order to prevent its oxidation. When ascorbic acid donates the first electron, it is transformed into a free radical called ascorbyl radical semi-dehydroascorbic acid.

It is a relatively stable, unreactive free radical with unbound electron in its outer shell but it has a short life time 10—15 s.

The unreactivity of this radical makes it unharmful to the surrounding cells. This process is called free radical scavenging or quenching. When it donates the second electron, it transformed into dehydroascorbic acid. Its stability may only last for few minutes [ 28 , 31 ]. As a general rule, it was detected that vitamin C acts as a pro-oxidant at low doses and acts as an antioxidant in high doses. It was also detected that the level of vitamin C in the skin usually exposed to ultraviolet radiation is lower than that exposed lesser.

The antioxidant activity of vitamin C enhances the epidermal turn over, and the movement of young cells to the surface of the skin where they replace old cells [ 32 ]. The study conducted by Frank in [ ] showed that RNA improved the ability of the skin cells to utilize oxygen. Ascorbyl radical and dehydroascorbic acid are reversible agents which can easily rebound into ascorbic acid.

These reversible agents can irreversibly transformed into 2,3-diketogulonic acid which is further metabolized into xylose, xylonate, lyxonate and oxalate Figure 2 [ 34 ]. Redox metabolism of ascorbic acid [ 33 ]. Vitamin C is considered as a strong anti-inflammatory agent as it inhibits many types of inflammatory mediators as tumor necrosis factor alpha [ 35 ]. This property is commonly used in the treatment of postoperative erythema formed after CO 2 laser in skin resurfacing [ 36 ].

In , Halliwell [ 37 ] detected significant reduction of plasma levels of ascorbic acid in association with elevated histamine in inflammatory diseases as ulcerative colitis and rheumatoid arthritis.

This was explained by the discovery of the anti-histaminic effect of vitamin C. It was also found that the higher ascorbic acid content in joints, the higher protection levels against damage which directed many physicians to use ascorbic acid in combination therapy with drugs aiming to joint protection as glucosamine [ 37 , 38 ].

It was discovered that vitamin C has an efficient chemotherapeutic effect. The cytotoxic effect of vitamin C is dose and route dependent. The tumor cells are more sensitive to high intravenous cytotoxic levels of vitamin C than the normal ones [ ].

On the contrary to the cancer cells, normal cells can compensate the damage occurred by these oxidative species [ ]. It was also found that these mega doses of vitamin C are essential in other diseases as diabetes, cataracts, glaucoma, macular degeneration, atherosclerosis, stroke and heart diseases [ 40 ]. Vitamin C improves the immune system and its deficiency causes immune insufficiency and multiple infections.

It was found that vitamin C modifies the behavior and activity of the immune cells; it also improves the phagocytic properties of neutrophils and macrophages. In addition, vitamin C increases the antibody production, concentration of antibodies and the activity of lymphocytes [ 41 ].

It was detected that the level of vitamin C in leukocytes is higher than its level in plasma because they have the ability to store it [ ]. Vitamin C is commonly used as an adjunctive treatment in many infectious diseases as hepatitis, HIV, common cold and influenza. It has an important role in the antibacterial reactions performed in our body by neutralization of the bacterial toxins especially endotoxins [ 42 ].

Sufficient amount of vitamin C causes blockage of the signaling essential for lipopolysaccharides LPS formation. It also stops the production of ROS especially reactive nitrogen species which is mainly produced during infection [ 42 ]. In bacterial infections, the level of ascorbic acid in various body fluids is lower than usual which perform further depression due to the action of LPS in blocking the passage of ascorbic acid through blood brain barrier.

LPS also inhibits the uptake of various cells to ascorbic acid [ ]. The anti-aging effect of vitamin C is regarding to its potent antioxidant effect, its stimulatory effect of enhancing the collagen formation, protection of the persistent collagen especially elastin against damage and finally, inhibits the cross-linking effect formed in wrinkles [ ]. It was found that the amount of ascorbic acid changes with age.

The younger the age, the higher the ascorbic acid level present. It was found that the higher the ROS is, the deeper the pigmentation produced. Anti-oxidants act a great role in lowering the melanin formation [ 43 ]. Vitamin C is considered a potent depigmenting agent which is used in the treatment of various cases of skin hyperpigmentation [ 44 , 45 , 46 , 47 , 48 ]. It can be used as an adjunctive treatment in melasma and severe cases of hyperpigmentation and as a treatment in mild and moderate cases [ 49 ].

Vitamin C inhibits melanogenesis in different steps via more than one mechanism [ ]. Being an anti-oxidant, ascorbic acid prevents production of free radicals which triggers melanogenesis [ 50 ].

It reduces o-dopaquinone back to dopa, preventing dopachrome of 5,6-DHICA [ 51 ] and reduces oxidized melanin changing the pigmentation from jet black to light tan [ 52 ]. Furthermore, the direct suppression of tyrosinase enzyme exhibits a great property [ 53 ].

The higher the ROS is, the deeper the pigmentation produced. Antioxidants act a great role in lowering the melanin formation [ 43 ]. Other mechanisms of blocking melanogenesis include inhibition of tyrosinase activity by interacting with copper ions at active sites of the enzyme [ 51 , 53 ]. In , Pauling and Cameron [ ] discovered that vitamin C has an efficient chemotherapeutic effect. The cytotoxic effect of vitamin C is due to the action of the ascorbyl free radical and it is dose as well as route dependent [ 55 ].

The tumor cells are more sensitive to high intravenous cytotoxic levels of vitamin C than the normal ones [ 23 , 56 ]. A synergistic effect is detected between the intravenous vitamin C administrations accompanying the tumor cytotoxic agent in patients suffering from advanced cancer [ 57 ]. Melanoma is the most commonly treated malignant tumors using vitamin C due to the high susceptibility and sensitivity of its cells to vitamin C.

It induces sodium ascorbate induced apoptosis of melisma. The lethal effect of ascorbic acid is attributed to inhibiting the production of IL essential for melanoma proliferation , change the intracellular iron level [ 56 , 58 ]. Besides the antioxidant role, ascorbic acid also acts as an electron donor for eight enzymes. Three of these enzymes are involved in collagen formation [ 34 ]. Other two enzymes are responsible for carnitine formation, one enzyme is responsible for epinephrine production from dopamine, and the other is responsible for the addition of the amide groups into peptide hormones.

Finally, it is essential for tyrosine metabolism and melanin production. The anti-tyrosinase enzyme occurs at 0. The role of vitamin C in collagen formation is well known. Vitamin C is an essential factor for the hydroxylation of proline, cofactor during collagen processing, activation of pro-collagen messenger RNA, inhibition of matrix metalloproteinases MMPs that are responsible for collagen fibers degradation and fibroblast activation intended for new and proper collagen formation [ 12 , 59 , 60 , 61 ].

As regards the effect of ascorbic acid on periodontal ligament, it enhances the periodontal ligament maturation and renewal by induction of the collagen formation especially collagen III young collagen and keeps the balance between collagen I mature collagen and III for tissue maturation. It was detected that thicker periodontal ligament were detected near the CEJ and narrower ones were detected in the middle one third of the root due to the effect of vitamin C in keeping the collagen bundles, well organized and more resistant to tension.

Furthermore, it also activates the fibroblast itself; proliferation, production and differentiation. By the vitamin C role in modifying the produced collagen type IV through its role as a cofactor in hydroxyproline synthesis and improving the endothelial cell vitality, its role in angiogenesis could not be forgotten.

Oxidation and reduction always occur simultaneously. As vitamin C is oxidized, the DCP is reduced and gains the two hydrogen atoms lost by the vitamin.

As the DCP is reduced, it changes from red to colorless. Since the reaction between the DCP and vitamin C is very fast, this color change can be used to indicate the point in a titration at which all of the DCP has just been consumed by the vitamin. This visual observation in a titration is called the end point of the procedure.

An equation showing the reaction of vitamin C with the DCP is shown below. During the analysis for vitamin C, the solution to be analyzed juice, beverage or tablet is added from a micro buret to multiple wells of a well tray. Next the solution in each well will be acidified the acidity is used to stabilize the vitamin C solutions that are being analyzed..

Then a measured volume of DCP solution will be added in a serial titration scheme: to the first well containing acidified vitamin C, one drop of DCP is added; to the next well, two drops of DCP are added; to the third well, three drops of DCP; etc.

As obtained from the laboratory supply, the DCP solution is blue, but when it is added to the acidic solution, you will notice its color changes.