VITAMINS | Water-Soluble: Thin-Layer (Planar) Chromatography

J.C. Linnell , in Encyclopedia of Separation Science, 2000

Ascorbic Acid (Vitamin C)

Ascorbic acid occurs abundantly in fresh fruit, especially blackcurrants, citrus fruit and strawberries, and in most fresh vegetables; good sources are broccoli and peppers. It is destroyed by heat and is not well stored in the body. Ascorbic acid is a good reducing agent and facilitates many metabolic reactions and repair processes.

In pharmaceutical preparations and fruit juices, ascorbic acid is readily separated from other compounds by TLC on silica gel and quantitated directly by absorption at 254   nm. Serum and plasma may be deproteinized with twice the volume of methanol or ethanol. Various ascorbic acid compounds in plant extracts and foods have been separated on cellulose layers and detected by spraying with 2,5-dichlorophenol indophenol. Heulandite, a natural zeolite (particle size 45   μm) has successfully been employed as an adsorbent and ascorbic acid and other hydrophilic vitamins have separated within 5   cm by ascending chromatography in dimethylformamide. HPTLC and OPLC methods have been developed to improve the separation of ascorbic acid from other water-soluble vitamins, with some success.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B0122267702030210

Vitamin C

Robert B. Rucker , Francene Steinberg , in Encyclopedia of Biological Chemistry, 2004

Summary

Ascorbic acid usually carries out redox reactions by mechanisms dependent upon free-radical processes. Ascorbate metabolism is linked to the metabolism of glutathione. Ascorbic acid is also required in animals that lack or have mutations in the gene for l-gulonolactone oxidase. Ascorbic deficiency results in reduced mono- and dioxygenase activities. The consequences of severe deficiency are profound, since growth, extracellular matrix, and hormonal regulation are impaired. Recent data suggest optimal intakes of ascorbic acid, based on a range of criteria, should be as high as 75–90 mg per day for adult humans.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B0124437109007419

Bioactive Components from Leaf Vegetable Products

Francisco J. Barba , ... Ana Frígola , in Studies in Natural Products Chemistry, 2014

Ascorbic Acid

Ascorbic acid has an enediol structure conjugated with the carbonyl group in the lactone ring. The two enolic hydrogen atoms are the ones that give this compound its acid quality and provide the electrons for its function as an antioxidant. In the presence of oxygen, ascorbic acid is transformed into dehydroascorbic acid, which has the same vitamin activity ( Fig. 2).

Figure 2. Chemical structure of ascorbic acid and its derivatives.

Ascorbic acid is considered one of the most effective natural antioxidants and is necessary for normal functioning of the organism because it is involved in many physiological functions [11–14]. Studies that have been conducted suggest that a daily intake of 90–100   mg of vitamin C reduces the risk of suffering chronic diseases in nonsmoking men and women [15]. Ascorbic acid has also proved to be effective in the therapeutic reduction of serum cholesterol levels [16] and various forms of cancer [17–19].

Table 1 summarizes ascorbic acid content of some leafy vegetable products. Overall, leafy vegetables can be considered a good source of ascorbic acid [20–27]. Among the most consumed leafy vegetables in Western countries, broccoli (96.7   mg/100   g), kale (52–67   mg/100   g), spinach (35.67–75.00   mg/100   g), and mustard greens (36.20   mg/100   g) have considerable ascorbic acid content. Therefore, these products can be a useful tool in order to provide the daily intake recommended for adults, which is 90   mg [14]. However, the amount in foods of plant origin depends on the precise variety of the plant, soil condition, climate where it grew, length of time since it was picked, storage conditions, and method of preparation.

Table 1. Ascorbic Acid Content (mg/100   g) of Leaf Vegetable Products

Sample Ascorbic Acid (mg/100   g) Reference
African mango leaves (Irvingia gabonensis) 23.30 [20]
Amaranth globe leaves (Gomphrena globosa) 97.49 [20]
Arcyptera (Arcypteris irregularis) 69.85 [21]
Basil leaves (Ocimum basilicum) 8–37 [22]
Bitter leaf (Vernonia cinerea) 32.15 [20]
Broccoli (Brassica oleracea) 96.7 [23]
Cabbage (Brassica oleracea var. capitata) 23.05–42.30 [20,23]
Cashew (Anacardium occidentale L.) 494.43 [21]
Chayote (Sechium edule (Jacq.) Swartz) 29.16 [21]
Climbing black pepper leaves (Piper nigrum) 181.19 [20]
Collards (Brassica oleracea acephala group) 92.7 [23]
Cosmos (Cosmos caudatus H.B.K.) 108.83 [21]
Curry (Helichrysum italicum) 140.50 [20]
Fluted pumpkin (Telfairia occidentalis) 129.39 [20]
Hoary basil (Ocimum americanum L.) 146.37 [21]
Indian camphorweed (Pluchea indica) 15.44 [21]
Jute mallow leaves (Corchorus) 89.94 [20]
Kale (Brassica oleracea acephala group) 52–67 [24]
Katuk (Sauropus androgynus (L.) Merr.) 190.83 [21]
Lemon grass leaves (Cymbopogon) 9.37 [20]
Lettuce leaves (Lactuca sativa) 22.27 [20]
Mint leaf (Mentha longifolia) 52.75 [20]
Miracle berry leaves (Gymnema sylvestre) 28.67 [20]
Myriantus leaves (Myrianthus arboreus) 15.93 [20]
Mustard greens (Brassica juncea) 36.2 [23]
Polyscias (Polyscias pinnata) 12.03 [21]
Spinach (Spinacia oleracea) 35.67–75.00 [20,25]
Stevia a (Stevia rebaudiana Bertoni) 14.98 [26]
Swiss chard (Beta vulgaris subsp. cicla) 45 [25]
Turnip greens (Brassica rapa subsp. rapa) 27 [27]
Water lettuce (Pistia stratiotes) 21.02 [20]
a
mg/mL.

Among the different samples, the highest content of vitamin C (494.43   mg/100   g) was found in Anacardium occidentale L. [21]. Some other products such as collards, turnip greens, Swiss chard, lettuce, and cabbage, which are normally present in our diet, have medium–high ascorbic acid content. However, it is necessary to take into account that these products are often consumed in larger quantities than the other samples and thus significant quantities of ascorbic acid will be present in our diet.

Moreover, several studies in the published literature have reported that ascorbic acid is present in fresh and dried herbs such as basil, curry, Stevia rebaudiana Bertoni, mint, thyme, and parsley [20,26], which can be used as food additives in almost any soup, stew, or as the main ingredient to a salad, enhancing the organoleptic and nutritional properties of these products.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780444632944000115

Titanium

P G JEFFERY , D HUTCHISON , in Chemical Methods of Rock Analysis (Third Edition), 1981

Reagents:

Ascorbic acid solution, dissolve 10 g of the reagent in 100 ml of water.

Diantipyrylmethane solution, dissolve 5 g of the reagent and 5 g of ascorbic acid in 150 ml of 2 N sulphuric acid and dilute to 500 ml with water. Transfer to a dark glass bottle and store in the dark.

Standard titanium working solution, pipette 10 ml of the stock solution containing 0.5 mg TiO2 per ml into a 500-ml volumetric flask, add 83 ml of concentrated hydrochloric acid and dilute to volume with water. This solution contains 10 μg TiO2 per ml.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978008023806750049X

Pyrolysis of Various Derivatives of Carboxylic Acids

Serban C. Moldoveanu , in Pyrolysis of Organic Molecules (Second Edition), 2019

Ascorbic Acid

Ascorbic acid, also known as vitamin C, is ( R)-3,4-dihydroxy-5-(S)-1,2-dihydroxyethyl-furan-2(5H)-one. The compound has acidic properties that are not from a carboxyl group but from an enol. Formally, ascorbic acid can be considered the γ-lactone of 2,3,4,5,6-pentahydroxy-2-hexenoic acid, which is a sugar acid. The fact that ascorbic acid is a sugar-type compound can be confirmed by its synthesis starting with sorbose, (3S,4R,5S)-1,3,4,5,6-pentahydroxyhexan-2-one (a keto hexose). In this synthesis, sorbose is oxidized to 2-keto-l-gluconic acid, followed by esterification with sodium methoxide when the ketone group is also transformed into an enol, and further lactonization with HCl to generate ascorbic acid.

Pyrolysis products of ascorbic acid were generated from 1.0   mg at T eq   =   900°C, β   =   10°C/ms, THt  =   10   s, and housing temperature T hou   =   280°C. The analysis of pyrolyzate was done exclusively by GC/MS under conditions given in Table 1.4.1. The pyrogram is shown in Fig. 14.3.2, and the peak assignment is given in Table 14.3.2 as a function of peak retention time. The relative molar content of different compounds in 100   moles of pyrolyzate shown in Table 14.3.2 was obtained exclusively from the peak areas in the pyrogram. As for other pyrograms presented in this book, compounds with MW below 28   a.u. were not analyzed. Also, pyrolysis of ascorbic acid generates a considerable proportion of char, which is not accounted for in mole %.

Fig. 14.3.2

Fig. 14.3.2. Pyrogram obtained at 900°C for ascorbic acid.

Table 14.3.2. Peak Identification as a Function of Retention Time for the Pyrogram of Ascorbic Acid Shown in Fig. 14.3.2

No. Compound Retention Time (Min) MW CAS# Moles %
1 Carbon dioxide 4.15 44 124-38-9 56.66
2 Formaldehyde 4.58 30 50-00-0 1.25
3 Acetaldehyde 5.71 44 75-07-0 1.21
4 Furan 7.51 68 110-00-9 1.68
5 2-Propenal (acrolein) 8.54 56 107-02-8 1.48
6 Acetone 8.99 58 67-64-1 1.03
7 2-Methylfuran 11.93 82 534-22-5 0.26
8 2,5-Dihydrofuran 13.06 70 1708-29-8 0.38
9 Methyl vinyl ketone 14.11 70 78-94-4 0.10
10 2,3-Butanedione (diacetyl) 14.32 86 431-03-8 0.14
11 Benzene 16.29 78 71-43-2 0.09
12 2-Butenal (Z) 19.26 70 15798-64-8 7.95
13 2-Methyl-2-propenal 19.35 70 78-85-3 2.90
14 Acetic acid 19.89 60 64-19-7 2.76
15 1-Hydroxy-2-propanone (acetol) 22.35 74 116-09-6 0.50
16 Toluene 22.94 92 108-88-3 0.12
17 Propionic acid 25.08 74 79-09-4 0.23
18 1-Hydroxy-2-butanone 27.49 88 5077-67-8 0.13
19 1,4-Dioxadiene 28.77 84 N/A 0.25
20 3-Methylcyclopentanone 28.80 98 1757-42-2 0.52
21 Furancarboxaldehyde (furfural) 30.27 96 98-01-1 12.05
22 Crotonic acid 31.24 86 3724-65-0 0.05
23 5-Methyl-2(3H)-furanone 31.93 98 591-12-8 0.04
24 2-Methyl-2-cyclopentene-1-one 32.52 96 1120-73-6 0.09
25 1-(2-Furanyl)ethanone 33.05 110 1192-62-7 0.19
26 2-Methyl-2-propenoic acid vinyl ester? 33.51 112 4245-37-8 0.12
27 2-Methyl-2-cyclopentene-1-one 33.81 96 1120-73-6 0.04
28 Dihydro-3-methylene-2(3H)-furanone 34.29 98 547-65-9 0.11
29 2-Hydroxy-2-cyclopenten-1-one 34.40 98 10493-98-8 0.49
30 5-Methyl-2(5H)furanone (angelica lactone) 35.27 98 591-11-7 0.24
31 Benzofuran 34.98 118 271-89-6 0.03
32 3-Methyl-2-cyclopenten-1one 36.23 96 2758-18-1 0.12
33 Furan-2-carboxylic acid 36.41 112 88-14-2 0.15
34 2-5(H)-Furanone? 36.75 84 497-23-4 0.16
35 2H-Pyran-2-one 37.90 96 504-31-4 0.55
36 2H-Pyran-2,6(3H)-dione 37.98 112 5926-95-4 0.91
37 Phenol 38.56 94 108-95-2 0.15
38 2-Methylphenol (o-cresol) 40.14 108 95-48-7 0.08
39 3,4-Epoxy-4-methyldihydro-2(3H)-furanone 40.60 114 98291-94-2 0.07
40 4-Methylphenol (p-cresol) 41.22 108 106-44-5 0.09
41 3-Methylphenol (m-cresol) 41.27 108 108-39-4 0.15
42 4-Methylene-1,2-dioxolan-3-one? 41.81 114 N/A 0.17
43 Benzofuran-3-carbaldehyde? 42.18 146 N/A 0.10
44 Mixture 45.02 166 N/A 0.06
45 3,4-Dihydroxytetrahydro-2-furanone 50.19 118 N/A 2.83
46 Unknown 52.45 102 N/A 0.19
47 2-Deoxy-d-erythtropentose? 53.18 134 533-67-5 0.21
48 3-Hydroxy-5-(2-hydroxyacetyl)-3,5-dihydrofuran-2,4-dione 57.76 174 N/A 0.90

Note: Bold numbers indicate major component in the pyrolyzate.Note: "?" indicates uncertain compound identification.

Pyrolysis of ascorbic acid generates compounds typical for a carbohydrate. Furfural and several furanones are among the main pyrolysis products. 2-Butenal and CO2 are also major constituents of the pyrolyzate. The formation of 2-butenal associated with CO2 production is shown in the reaction below:

(14.3.15)

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780444640000000147

O-Nitrosation

D.L.H. WILLIAMS , in Nitrosation Reactions and the Chemistry of Nitric Oxide, 2004

6.3 Nitrosation of ascorbic acid

Ascorbic acid reacts readily with nitrous acid in mildly acidic solution (and also with other nitrosating species) to give dehydroascorbic acid, Eq. (239). Under anaerobic conditions the other product is nitric oxide, which will

(239)

react further in the presence of oxygen. The reaction was first reported in 1934 [382]. It is a reaction which is much used in the laboratory to generate solutions of nitric oxide, when great care must be taken to eliminate all traces of oxygen.

The results of a detailed mechanistic study carried out anaerobically were reported in a series of papers by Bunton and Loewe [383]. Reaction pathways via N2O3 and also H 2 NO 2 + /NO+ were identified kinetically and there was catalysis by halide ion. At acidities in the range (0.1-1 M) the reactive species is the neutral form of ascorbic acid (pK a values 4.25 and 11.75), but at lower acidities there is evidence of reaction via the monoanion. In air-saturated solutions the nitric oxide product is reoxidised to nitrous acid, so its concentration is effectively unchanged during the experiment, [384]. If [ascorbic acid] ≫ [HNO2] under these conditions, then complete decomposition of the ascorbic acid occurs. The autoxidation of nitric oxide then becomes rate-limiting. A numerical integration analysis [384] generates the mechanism outlined in Eq. (240-4) which accounts quantitatively for the

(240) 2 HNO 2 ⇄ NO 2 + NO + H 2 O

(241) 2 NO + O 2 → 2 NO 2

(242) H 2 A + HNO 2 → NO + HA • + H 2 O

(243) HA • + O 2 → A + HO 2 •

(244) HA • + HO 2 • → A + H 2 O 2

experimental observations. Here H2A is the undissociated ascorbic acid molecule, A the dehydroascorbic acid product and HA· the radical generated from the O-nitrosated species, which itself is not kinetically significant in this Scheme.

Alkyl nitrites also react readily with ascorbate in neutral or alkaline conditions in a 2:1 stoichiometry as does nitrous acid, to given nitric oxide. Measurements in the pH range 11-13 showed that the ascorbate dianion is the only reactive form here [317]. S-Nitrosothiols also react readily with ascorbate. Analysis over a wide pH range 4-14 revealed that both the mono-and dianion forms of ascorbic acid can react, with the latter as expected being the more reactive and the major reactant at high pH values [385]. This reaction will be discussed in more detail later, in Chapter 8.

Since ascorbic acid is so reactive towards nitrous acid and it is also nontoxic in low concentrations, it has been much used as a trap or scavenger for nitrous acid. It can be very effective in the prevention of potentially carcinogenic nitrosamines when added to secondary amine/nitrous acid situations, for example see [386]. Ascorbic acid added to consumer products such as cured meats and cosmetics has had a big effect in the reduction of nitrosamine by-products in these preparations. It has been suggested that ascorbic acid be included in drug preparations which include secondary (and tertiary) amine features, such as propranolol (one of the top drugs used worldwide as a beta-blocker to reduce blood pressure), to avoid any risk of nitrosamine formation. There are many results of statistical studies which show that animals fed amines (or amides) and nitrite concurrently, generate fewer tumors if ascorbic acid is also introduced. There are also reports of inverse correlations between incidence of gastric cancer and diets containing high levels of ascorbic acid, so the situation is more complex in vivo.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780444517210500074

Biological systems

Edwin N. Frankel , in Lipid Oxidation (Second Edition), 2012

(e) Non-enzymatic peroxide destroyers

Ascorbic acid has multiple antioxidant effects in biological systems. It is an active reducing agent that can scavenge singlet oxygen, superoxide, hydrogen peroxide, hydroperoxyl radicals, hydroxyl radicals and hypochlorous acid, to give semidehydroascorbate. One of the multiple actions of ascorbic acid is to reduce lipid hydroperoxides to stable hydroxy lipids. It is regarded as the most effective water-soluble antioxidant in plasma. However, it can also reduce Fe 3+ to Fe2+, which can participate in the Fenton reaction by producing damaging hydroxy radicals in the presence of hydrogen peroxide, and stimulate iron-catalysed lipid peroxidation. This prooxidant effect is counterbalanced under certain conditions by the scavenging properties of ascorbic acid toward hydroxyl radicals. The main protective role of ascorbic acid may be the regeneration of vitamin E after its oxidation in plasma proteins (Section B.6).

Uric acid is a water-soluble antioxidant found in relatively high concentrations in plasma. It inhibits lipid peroxidation by tightly binding iron and copper ions into inactive forms, and by scavenging various oxidants such as hydroxyl radicals, peroxyl radicals, singlet oxygen and hypochlorous acid. By complexing with iron, uric acid stabilizes ascorbic acid in human serum.

Ubiquinol-10 (reduced form of ubiquinone-10, or coenzyme Q10) is a reactive lipid-soluble antioxidant that may act like ascorbic acid by regenerating vitamin E by reducing the vitamin E radicals produced during lipid peroxidation.

(f) Radical chain breakers. α-Tocopherol (vitamin E) is considered the major lipid-soluble antioxidant in membranes, acting by several mechanisms, including: by scavenging free radicals (superoxide, hydroxyl radicals), which can initiate and propagate lipid peroxidation, by reacting with nitric oxide, and by deactivating singlet oxygen. Vitamin E reacts with lipid peroxyl and alkoxyl radicals by donating labile hydrogen and terminating the lipid peroxidation sequence (Chapter 9). The resulting α-tocopherol radical is stabilized by electron delocalization around the phenol ring structure. We shall see later that α-tocopherol is important in protecting lipoproteins against oxidation. To be effective in vivo, the α-tocopherol radicals are reduced back to α-tocopherol by ascorbic acid or other reducing agents, such as cysteine, or glutathione. This synergistic effect is assumed to take place at the membrane interface because the hydrophilic reducing agent, in solution in the aqueous phase, would have an affinity for the membrane phospholipids at the surface.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978095319498850014X

Batch injection analysis for amperometric determination of ascorbic acid at ruthenium dioxide screen-printed electrodes

David Hernández-Santos , ... María Begoña González-García , in Laboratory Methods in Dynamic Electroanalysis, 2020

10.4.3.1 Optimization of the potential of detection (hydrodynamic curve)

Ascorbic acid presents an irreversible process on ruthenium electrodes around +0.09  V (vs. silver pseudo-reference). When working in a BIA system, as well as in an FIA system, it is necessary to optimize the potential applied to detect a redox species.

With this aim, using a concentration of 0.02   mM of ascorbic acid in 0.04   M PBS pH 7.4, vary the detection potential between 0.0 and +0.4   V (for example, 0   V, +0.1   V, +0.2   V, +0.3   V, and +0.4   V). For this study fix an injection volume and a speed of 40   μL and 4, respectively. Put the stirrer speed selector in position 2 (1500   rpm). Make 3 injections for each potential.

Caution: For each potential applied, it is necessary to obtain a stable background before the first injection. After the last injection, wait until the background achieves a stable level and then stop recording. Save the amperogram. Select the next potential and start recording again, applying a new potential.

Plot the mean of peak height versus the potential applied. Include also the deviation for each measurement using error bars. From this graph (hydrodynamic curve), select the optimum detection potential.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128159323000103

Zirconium and Hafnium

P G JEFFERY , D HUTCHISON , in Chemical Methods of Rock Analysis (Third Edition), 1981

Reagents:

Ascorbic acid solution, dissolve 2.5 g of the reagent in 50 ml of water. Prepare freshly as required.

Xylenol orange solution, dissolve 50 mg of the reagent in water and dilute to 100 ml.

Standard zirconium stock solution, dissolve 3.9 g of zirconium sulphate Zr(SO4)2.4H2O in dilute sulphuric acid and dilute to 1 litre with a final acid concentration of 1 M. Standardise by back titration with bismuth (after adding an excess of EDTA) using xylenol orange as indicator. This solution contains 1 mg Zr per ml.

Standard zirconium working solution, transfer 5 ml of the stock zirconium solution to a 1 litre volumetric flask, add 200 ml of 6 N hydrochloric acid, dilute to volume with water and mix well. This solution contains 5 μg Zr per ml.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780080238067500531

Composition of Wine

In Enological Chemistry, 2012

2.6 Vitamins

Vitamins can be classified into two main groups: water-soluble vitamins and fat-soluble vitamins (K, A, D, and E). Only vitamins from the first group are found in must and wine. They include vitamins B1, B2, B3, B5, B6, B8, B9, and B12, vitamin C (ascorbic acid), and vitamin P (flavonoids). myo-Inositol, which used to be referred to as vitamin B7, is also present. The essential fatty acids linoleic acid and linolenic acid (vitamin F) are found in must but they oxidize in the presence of lipoxygenase, giving rise to C6-alcohols.

Ascorbic acid oxidizes rapidly when it comes in contact with oxygen in the atmosphere and therefore disappears almost completely during must extraction. Its use as an antioxidant in musts and wines is permitted but its levels are regulated. Between 75% and 90% of thiamin is used by yeasts, and riboflavin, which appears during alcoholic fermentation, is a growth factor for bacteria (but not for yeast), and therefore plays an essential role in malolactic fermentation. Thiamin and riboflavin levels increase when fermented must is left to rest on the lees, as the yeasts transfer practically all their vitamins to the liquid; this phenomenon has also been observed in biologically aged wines. Because riboflavin is photosensitive, its levels in wine can become quickly depleted. Pyridoxine is a growth factor for yeasts. The

TABLE 4.2. Vitamin Levels in Musts and Wines (μg/L)

Vitamins Musts White Wine Red Wine
Thiamin (B1) 160–450 2–58 103–245
Riboflavin (B2) 3–60 8–133 0.47–1.9
Pantothenic acid (B5) 0.5–1.4 0.55–1.2 0.13–0.68
Pyridoxine (B6) 0.16–0.5 0.12–0.67 0.13–0.68
Biotin (B8) 1.5–4.2 1–3.6 0.6–4.6
Folic acid (B9) 0.0–1.8 0.4–4.5 0.4–4.5
Cobalamin (B12) 0.0–0.20 0.0–0.16 0.04–0.1
Ascorbic acid (C) 30–50 mg/L 1–5 mg/L 1–5 mg/L

remaining vitamins undergo few changes throughout fermentation and are found in similar concentrations in musts and wines.

Of the different clarifying agents used, such as bentonite, gelatin, kaolin and even potassium ferrocyanide, only bentonite appears to negatively affect B-vitamin content.

In brief, vitamins play an essential role in fermentation as they are growth factors for the yeast and bacteria responsible for alcoholic fermentation and malolactic fermentation, respectively. Although thiamin disappears almost entirely and ascorbic acid and pyridoxine levels decrease, wine is still a valuable potential source of vitamins.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780123884381000042