Profile of Ascorbic Acid

Sep 1, 2011 | Contact Author | By: Michael J. Fevola, PhD, Johnson & Johnson
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Title: Profile of Ascorbic Acid
ascorbic acidx vitamin Cx antioxidantx pH adjusterx skin conditionerx
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Keywords: ascorbic acid | vitamin C | antioxidant | pH adjuster | skin conditioner

Abstract: L-Ascorbic acid (AscA), more commonly referred to as vitamin C, is best known for its vital role in human health and nutrition, where it functions as a cofactor in enzymatic reactions, such as collagen synthesis, and as an antioxidant.

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M Fevola, Profile of Ascorbic Acid, Cosm & Toil 126(9) 622 (2011)

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L-Ascorbic acid (AscA), more commonly referred to as vitamin C, is best known for its vital role in human health and nutrition, where it functions as a cofactor in enzymatic reactions, such as collagen synthesis, and as an antioxidant. This compound earned its notoriety in the mid-1930s, when Nobel laureate Albert Szent-Györgyi established the link between AscA and the prevention of scurvy, a debilitating disease caused by vitamin C deficiency. As the importance of antioxidants in health and nutrition has become more widely publicized, the addition of AscA and its derivatives to products ranging from food and beverages to nutritional supplements and cosmetics has become increasingly common.

Chemistry and Manufacture

AscA (INCI: Ascorbic Acid) is a six-carbon organic acid with molecular formula C6H8O6, corresponding to a molecular weight of 176.13 g/mol.1, 2 The predominant structure of AscA is shown in Figure 1; however, AscA can exist as a variety of keto-enol tautomers, i.e., isomers resulting from the migration of a proton accompanied by inter- conversion of a C=C or C=O double bond with an adjacent C–O or C–C bond, respectively (Figure 2).

The ability of AscA to undergo intramolecular rearrangements and to delocalize electron density over its structure render AscA an acidic molecule (pKa = 4.17, even though it lacks a carboxylic acid group), a strong reducing agent and a potent free-radical scavenger (antioxidant).2 AscA is a chiral (optically active) molecule with stereocenters at C4 (D-configuration) and C5 (L-configuration). The stereochemistry of AscA is critical to its activity as vitamin C. For example, erythorbic acid, the stereoisomer of AscA with a D-configuration at C5, exhibits only 5% of the vitamin C activity of AscA.3

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Figure 1. Chemical structure of L-Ascorbic acid (AscA)

Figure 1. Chemical structure of L-Ascorbic acid (AscA)

The predominant structure of AscA is shown in Figure 1; however, AscA can exist as a variety of keto-enol tautomers, i.e., isomers resulting from the migration of a proton accompanied by inter- conversion of a C=C or C=O double bond with an adjacent C–O or C–C bond, respectively (Figure 2).

Figure 2. Keto-enol tautomerization in L-Ascorbic acid

Figure 2. Keto-enol tautomerization in L-Ascorbic acid

The predominant structure of AscA is shown in Figure 1; however, AscA can exist as a variety of keto-enol tautomers, i.e., isomers resulting from the migration of a proton accompanied by inter- conversion of a C=C or C=O double bond with an adjacent C–O or C–C bond, respectively (Figure 2).

Figure 3. Synthesis of AscA via the Reichstein and Grüssner route

Figure 3. Synthesis of AscA via the Reichstein and Grüssner route

Figure 3 depicts a representative synthesis of AscA via this route.

Figure 4. Derivatives of AscA commonly employed in cosmetic and personal care products

Figure 4. Derivatives of AscA commonly employed in cosmetic and personal care products

The functionality of AscA is readily improved by synthesizing simple derivatives of the molecule (see Figure 4 for examples) to enhance its stability, delivery, and/or compatibility with nonpolar media, e.g., oil phases and lipid bilayers.

Biography: Michael J. Fevola, PhD, Johnson & Johnson

Michael J. Fevola, PhD, is a manager in the New Technologies group at Johnson & Johnson Consumer and Personal Products Worldwide in Skillman, NJ, where he leads R&D in polymer and surface chemistry. Fevola has authored 12 peer-reviewed articles and book chapters, is an inventor on six US patents, and is a member of the Personal Care Product Council’s International Nomenclature Committee and the Society of Cosmetic Chemists.

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