Sodium Ascorbyl Phosphate

Sodium ascorbyl phosphate is a stable precursor of vitamin C that is not only helpful in treating acne, but can also lighten the skin and protect it from sun damage.


Grade Level of Evidence
A Multiple double-blind, controlled clinical trials.
B 1 double-blind, controlled clinical trial.
C At least 1 controlled or comparative clinical trial.
D Uncontrolled, observational, animal or in-vitro studies only.
Grade Effect Size of Effect Comments




Inhibits lipid oxidation on the skin and has the ability to scavenge hydroxyl radicals.


Acne treatment


Improves acne by killing P. acnes and preventing the production of squalene oxides on the skin.


Skin lightening


Whitens the skin and lIghtens age spots on the face.


Wrinkle treatment


Stimulates collagen production in human fibroblasts, and thus may help efface wrinkles.




Prevents sunburn cell formation, DNA fragmentation, lipid peroxidation and reactive oxygen species generation induced by UV light.

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Table of contents:

1. Sources

Sodium ascorbyl phosphate is a precursor of ascorbic acid (vitamin C). It is generated from ascorbic acid by the introduction of a phosphate group into the second position of the cyclic ring.[1] In cosmetic products, it is used at concentrations ranging from 0.01% to 3%.[2]

2. Bioavailability

Sodium ascorbyl phosphate has improved stability over ascorbic acid, making it well-suited for use as an active ingredient in cosmetic preparations. It is also significantly more stable than magnesium ascorbyl phosphate and ascorbyl palmitate, 2 other derivatives of vitamin C.[3] Neutral or basic solutions guarantee the highest stability, whereas in acid solution sodium ascorbyl phosphate may be easily hydrolyzed to ascorbic acid and inorganic phosphate.[4]

Ex vivo experiments on pig ear skin and human skin show that sodium ascorbyl phosphate is able to penetrate through the epidermis.[5][6] The carrier system matters, for sodium ascorbyl phosphate penetrates the epidermis significantly better from liposome dispersions than from aqueous solution.[6] Microemulsions are also suitable carrier systems for the topical application of sodium ascorbyl phosphate.[1]

In addition, laser pretreatment and electrotreatment can increase the delivery of sodium ascorbyl phosphate to the skin.[7][8]

To achieve favourable effects on the skin, ascorbic acid has to be liberated from sodium ascorbyl phosphate by enzymatic degradation in the skin.[1] There is evidence that this does occur. When mouse skin was cultured in a medium containing sodium ascorbyl phosphate, the concentration of ascorbic acid in the skin tissue increased and remained elevated for up to 24 hours, even though intact sodium ascorbyl phosphate was not detected in the skin cells. It has therefore been suggested that skin cells continuously take up sodium ascorbyl phosphate and convert it to ascorbic acid through dephosphorylation via the action of acid phosphatase in the epidermis.[9] Human skin treated with 2% sodium ascorbyl phosphate also had markedly higher epidermal ascorbic acid content than skin treated with 2% ascorbyl glucoside, indicating that the hydrolysis rate of sodium ascorbyl phosphate is much higher.[5]

3. Effects on the skin

3.1 Antioxidant effect

A human skin cell culture model pretreated with 200 mM sodium ascorbyl phosphate for 2 hours reduced the amount of generated hydroxyl radicals to 25% of that in a non-treated control.[5] Sodium ascorbyl phosphate has also been shown to inhibit lipid oxidation on the skin.[10]

Since the introduction of a phosphate group in the second position of the cyclic ring protects the enediol system of the molecule against oxidation, sodium ascorbyl phosphate cannot directly act as an antioxidant.[11] It stands to reason, therefore, that the observed antioxidant effects are due to its conversion to free ascorbic acid by enzymes in the skin.[1][5]

3.2 Acne vulgaris treatment

Acne vulgaris is the most common inflammatory skin disorder and it has a complex and multifactorial pathogenesis.[12] 1% sodium ascorbyl phosphate exerted a strong antimicrobial effect against Proprionibacterium acnes in vitro, and 3% sodium ascorbyl phosphate in a oil-in-water formulation prevented up to 40% of UVA-induced sebum oxidation in humans in vivo.[10] These indicate that sodium ascorbyl phosphate can potentially be useful in acne treatment, as both bacterial colonization by P. acnes and the oxidation of squalene, a major sebum component, are contributors to acne.[13][14]

Several clinical trials on the use of sodium ascorbyl phosphate in acne therapy have been conducted. One open-label study had 18 acne patients apply a 10% sodium ascorbyl phosphate lotion twice daily to lesions on one side of the face, leaving the other side untreated. After 8 weeks, clinical improvements of inflammation and papules-pustules were obtained in 83% and 94% of the treated side, compared to 6% and 17% in the untreated side.[15] A 3-month randomized, double-blind and vehicle-controlled study suggested that a 5% sodium ascorbyl phosphate lotion may be a good adjunct therapy for acne regimens, as it led to subjective improvements in acne scores and statistically significant declines from baseline in the counts of inflammatory and non-inflammatory lesions over 12 weeks. However, the vehicle led to a greater decrease in non-inflammatory lesions compared to the active group, and whether the differences between the active group and the vehicle group were statistically significant was not reported.[16]

The effectiveness of topical 5% sodium ascorbyl phosphate formulations in treating acne has been compared to that of other agents. 5% sodium ascorbyl phosphate was demonstrated to be superior to 5% benzoyl peroxide monotherapy, 1% clindamycin phosphate monotherapy and 0.1% adapalene monotherapy in 3 separate open trials.[10][17][18] 5% sodium ascorbyl phosphate was also about as effective as 0.2% retinol, but combination treatment with 5% sodium ascorbyl phosphate + 0.2% retinol was more effective than either treatment alone. This is due to synergistic effects on lipid peroxidation, sebaceous gland function and P. acnes inhibition in addition to the enhancement of sodium ascorbyl phosphate permeability by desquamation of stratum corneum influenced by retinol, keratin plug removal as well as the anti-inflammatory effect of retinol.[19]

Sodium ascorbyl phosphate stimulates collagen synthesis in human dermal fibroblasts, though it requires a 10-fold greater concentration to produce the same effect as ascorbic acid or magnesium ascorbyl phosphate.[20]

1.5% sodium ascorbyl phosphate has also been shown to fade age pigment spots and whiten the skin of Caucasian women after 6 weeks, with the effect significantly enhanced by the addition of the peptide PKEK. In Asian women, 1.5% sodium ascorbyl phosphate alone was not sufficient to improve pre-existing skin pigmentation or lentigines, but reduced skin pigmentation by 26% and lentigines by 18% after 8 weeks when combined with PKEK.[21]

3.4 Photoprotection

Sodium ascorbyl phosphate can protect against damage induced by UV exposure. It prevented sunburn cell formation, DNA fragmentation and lipid peroxidation caused by a single dose of UVB irradiation in cultured mouse skin,[9] and appreciably reduced the UV susceptibility of mouse epidermal keratinocytes.[22] Adding sodium ascorbyl phosphate to sunscreen formulations also quenched the formation of reactive oxygen species in ex vivo breast skin by 50%, (though the percentage decrease was lower for ex vivo facial skin) thereby improving sunscreen photoprotection.[23]

4. Side Effects

Sodium ascorbyl phosphate is considered safe as used in cosmetic products, according to the Cosmetic Ingredient Review Expert Panel.[2]

Indeed, formulations containing sodium ascorbyl phosphate have been variously described as having no side effects,[10] and having excellent cutaneous tolerability[18] similar to that of a vehicle[16] in clinical studies.

Scientific References

  1. Spiclin P, et. al. Sodium ascorbyl phosphate in topical microemulsions. Int J Pharm. (2003)
  2. Elmore AR. Final report of the safety assessment of L-Ascorbic Acid, Calcium Ascorbate, Magnesium Ascorbate, Magnesium Ascorbyl Phosphate, Sodium Ascorbate, and Sodium Ascorbyl Phosphate as used in cosmetics. Int J Toxicol. (2005)
  3. Smaoui S, Ben Hlima H, Kadri A. Application of l-Ascorbic Acid and its Derivatives (Sodium Ascorbyl Phosphate and Magnesium Ascorbyl Phosphate) in Topical Cosmetic Formulations: Stability Studies. J Chem Soc Pak. (2013)
  4. Segall AI, Moyano MA. Stability of vitamin C derivatives in topical formulations containing lipoic acid, vitamins A and E. Int J Cosmet Sci. (2008)
  5. Akagi K, et. al. Permeablity of sodium ascorbic acid-2-O-phosphate into the human skin and its scavenging of intradermal free radicals. J Invest Dermatol. (2003)
  6. Foco A, Gasperlin M, Kristl J. Investigation of liposomes as carriers of sodium ascorbyl phosphate for cutaneous photoprotection. Int J Pharm. (2005)
  7. Huang CH, et. al. Transdermal delivery of three vitamin C derivatives by Er:YAG and carbon dioxide laser pretreatment. Lasers Med Sci. (2013)
  8. Marra F, et. al. In vitro evaluation of the effect of electrotreatment on skin permeability. J Cosmet Dermatol. (2008)
  9. Nayama S, et. al. Protective effects of sodium-L-ascorbyl-2 phosphate on the development of UVB-induced damage in cultured mouse skin. Biol Pharm Bull. (1999)
  10. Klock J, et. al. Sodium ascorbyl phosphate shows in vitro and in vivo efficacy in the prevention and treatment of acne vulgaris. Int J Cosmet Sci. (2005)
  11. Austria R, Semenzato A, Bettero A. Stability of vitamin C derivatives in solution and topical formulations. J Pharm Biomed Anal. (1997)
  12. Bellew S, Thiboutot D, Del Rosso JQ. Pathogenesis of acne vulgaris: what's new, what's interesting and what may be clinically relevant. J Drugs Dermatol. (2011)
  13. Dessinioti C, Katsambas AD. The role of Propionibacterium acnes in acne pathogenesis: facts and controversies. Clin Dermatol. (2010)
  14. Saint-Leger D, et. al. A possible role for squalene in the pathogenesis of acne. I. In vitro study of squalene oxidation. Br J Dermatol. (1986)
  15. NIshikawa T, et. al. Clinical evaluation of topical sodium L-ascorbyl-2-phosphate lotion (10%W/V) in patients with acne. J Invest Dermatol. (2003)
  16. Woolery-Lloyd H, Baumann L, Ikeno H. Sodium L-ascorbyl-2-phosphate 5% lotion for the treatment of acne vulgaris: a randomized, double-blind, controlled trial. J Cosmet Dermatol. (2010)
  17. Ikeno H, et. al. An open study comparing efficacy of 5% sodium L-ascorbyl-2-phosphate lotion versus 1% clindamycin phosphate lotion and vehicle lotion in the treatment of acne vulgaris. J Invest Dermatol. (2003)
  18. Ikeno H, Ohmori K. Open Study Comparing Sodium L-Ascorbyl-2-Phosphate 5% Lotion Versus Adapalene 0.1% Gel for Acne Vulgaris. Cosmet Dermatol. (2007)
  19. Ruamrak C, Lourith N, Natakankitkul S. Comparison of clinical efficacies of sodium ascorbyl phosphate, retinol and their combination in acne treatment. Int J Cosmet Sci. (2009)
  20. Geesin JC, Gordon JS, Berg RA. Regulation of collagen synthesis in human dermal fibroblasts by the sodium and magnesium salts of ascorbyl-2-phosphate. Skin Pharmacol. (1993)
  21. Marini A, et. al. Modulation of skin pigmentation by the tetrapeptide PKEK: in vitro and in vivo evidence for skin whitening effects. Exp Dermatol. (2012)
  22. Kanatate T, et. al. Differential susceptibility of epidermal keratinocytes and neuroblastoma cells to cytotoxicity of ultraviolet-B light irradiation prevented by the oxygen radical-scavenger ascorbate-2-phosphate but not by ascorbate. Cell Mol Biol Res. (1995)
  23. Hanson KM, Clegg RM. Bioconvertible vitamin antioxidants improve sunscreen photoprotection against UV-induced reactive oxygen species. J Cosmet Sci. (2003)