Vitamin C also known as ascorbic acid is a water soluble vitamin Zumreoglu-Karan, 2006. During the mid-18th century a disease called scurvy was a major problem it included symptoms such as bleeding gums and … James Lind established that juice from fruits had the ability to cure and prevent this disease scurvy. A chemical derived from the sugar glucose was found to be in control of curing and preventing scurvy. Szent-Gygory found out that this chemical was hexuronic acid this was in respononsible for the antiscorbutic activity. It was renamed ascorbic acid.( the controversial place of vitamin c)
In most animals and plants ascorbic acid is made from the sugar glucose figure 1 shows the pathway that glucose takes to synthesis ascorbic acid.
Glucose→UDP glucuronic acid→D-gulonic acid→L gulono-y-lactone→2keto-L-gulonolactone→ascorbic acid. (Aspect of ascorbic acid biosyntheseHumans do not contain gulonolactone oxidase this is the enzyme which is in charge of converting the gulonolactone to the ascorbic acid. So people are required to eat food containing vitamin C.( Vitamin C and genomic stability) For Vitamin C to move into tissues it is oxidised to dehydroascorbic acid. Transporters of glucose move the deydroascorbic acid into the intracellular compartment it is then reduced back to ascorbic acid. Sodium dependent active transporters are the transporters which are involved in absorption of vitamin C. (The controversial place of vitamic c in cancer treatment).
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Vitamin C has various different functions, the main one being it is required for the formation of collagen because it helps by donating electrons to metal ion cofactors in hydroxylase enyzmes. So when collagen is being made, vitamin c transforms the proline and lysine to hydroxlyproline. It also has a role in carntine synthesis where it oxidises side chains of lysine to make carntine. Another function is it helps to absorb iron as it stops the effects of metal chelators which reduce bioavailability of iron( Controversial place of vitamin C in cancer treatment) . As ascorbic acid has redox reactions, it aids the reduction of the reactive oxygen species through oxidation of dihydroascorbic acid, so ascorbic acid contains anti-apoptotic activity?
As mentioned earlier scurvy is the main deficiency disease of vitamin C. It affects the tissues in the body with the main symptoms being bleeding gums and tissues and spots forming on the skin. Vitamin C plays a big part in forming collagen as discussed. The instability of the tissues is down to a defect in the hydroxylation of proline step in making collagen where vitamin c is required. The defect in collagen synthesis leads to (scurvy historical revienw current diagnostic approach).
There are numerous different ways for measuring vitamin C content in items including colometric methods, volumetry, flurometery, and titrimetry which is used in this experiment. 2,6 dichloroindophenol (DCIP) us used, Oxidation of the ascorbic acid to dehydroascorbic acid is normally how the vitamin C content is quantified . This technique involves the reduction of the DCIP. No indicator is required as the titrant is a self-indicator. A mixture of ascorbic acid and acetic acid is titrated with the DCIP. When Ascorbic acid is present the reagent is reduced the solution remains colourless. When the ascorbic is oxidised to dehydroascorbic acid the solution changes to a pink colour so the ascorbic acid can be identified. (Non spectrophotometric methods for determination of vitamin C
Aim of the project: To Determine the content of vitamin C in an assortment of different items in particular in this project tesco apple juice
Materials and reagents
Tesco apple juice (for other experiments different fruits and vegetables were used also cereals and vitamin supplement
10% acetic acid
20mg/L of standard ascorbic acid in 10% acetic acid solution
A 1 in 10 dilution of the apple juice was made up with the acetic acid solution 1ml of apple juice was pipetted in to a beaker with 9mls of acetic acid.
10mls of the solution is pipetted into a conical flask.
Slowly add 1ml of DCIP to the conical flask and observe the approach of the change in colour(changes to pink) which signals the end point of the titration.
Always on Time
Marked to Standard
Write down the exact amount of DCIP that was added.
Repeat the titration three times.
Titrate 10mls of the blank solution (acetic acid solution)
Titrate 10mls of the standard ascorbic acid solution 3 times.
For solid samples this protocol was used but before it was carried out, 40g of fruit or vegetable was weighed out. 100ml of acetic acid is added and the mixture is blended. The homogenate is filtered through the cheesecloth.
DCIP - Blank(ml)
Mg ascorbic acid/10ml
Total extract volume(ml)
Total mg ascorbic acid/sample
Mean of Std
Mean of samples
0.02mg ascorbic acid= 0.45ml std DCIP
Mg of test sample = 1.71mls
So mg of test sample= 1.71-0.02/0.45
0.0076mg/ml x 10 (dilution factor)
So in the apple juice sample there is 0.076mg of vitamin C per every ml. 789mls of the apple juice would be required for a person to receive their RDA.
Ascorbic acid (mg/ml)
Amount Requried for RDA
Vitamin C tablet
In this experiment the main item of interest was apple juice it was found that it contained 0.076 mg/ml. An apple contains 0.06 mg/g of ascorbic acid these results are similar with a slight difference this could be due to the fact the apple juice is processed so different substances are added and subtracted compared to the normal apple which is not processed. According to the experiment 789mls of apple juice are required to meet the RDA of vitamin C. Therefore it may not be realistic to depend on the apple juice to receive the RDA of vitamin C as 789 mls is quite a lot to drink of just apple juice in one day.
The orange juice was measured at 6.05mg/ml which is far too high of amount it would mean that a person would only require 9.09 mls while oranges are an excellent source of Vitamin C they are not that good. The expected amount of vitamin C in an orange is 0.53mg/g a figure that is vastly different from the 6.05mg/mls calculated in this experiment, this figure may have been reached by a miscalculation or else there were experimental errors when titrating. To Receive the RDA of vitamin C 113mls of orange juice must be drank this is a lot more attainable than apple juice as people will normally have a glass or two of orange juice with their breakfast.
The vitamin C tablet as expected yielded the most ascorbic acid it was found there was 110mg in the tablet although on the packet it was stated it contained 500mg there could be a few reasons again for the difference in figures as the tablet had to be grinded up with mortar and pestle some of it could be lost because of this also other experimental errors may have occurred or miscalculations. The packaging may have been false and there may never have been 500mg of vitamin C in the tablet. Even at 110mg per tablet this is nearly twice the RDA so it is a quick and convenient way to intake vitamin C.
The kiwi was another item where the vitamin C content was measured. It was found that a kiwi contained 23.23mg of ascorbic acid per ml this is once again a major difference compared to the normal value of 0.98mg/g this could be due to errors already discussed. In this experiment just 2.57mg of kiwi would be required for the RDA which is not realistic the true amount of required is 61.22mgs of the kiwi. One kiwi contains 74 mg of vitamin C so that is all that is required to receive ones RDA. Out of the 4 sources tested in this experiment excluding the vitamin C tablet, the kiwi is the best source of vitamin C this is surprising as everyone expects oranges to be the best source of Vitamin C.
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