Challenges and Available Solutions in Stabilizing Vitamin C for Effective Skin Treatments

Maria Fernanda Gonzalez Prato | Biochemistry Researcher

September 27, 2024

Edited by Pierre Trinh (Sustainability Researcher)

Keywords: vitamin; ascorbic acid; cosmetic; skincare; stability; efficacy; testing; stabilization; technique

Vitamin C has been widely considered in the global cosmetic sector as a hydrating hero because of its superb ability to stimulate collagen synthesis and act as an antioxidant protector against photodamage induced by UV (ultraviolet) rays; however, as with many other vitamins used in cosmetics, maintaining its stability and delivery to the active site has been proven difficult. In this article, our biochemistry researcher, Maria Fernanda Gonzalez Prato, will delve at the stability of vitamin C and its most potent forms, its mechanisms of action in the skin, and current industry methods for finding stable compounds to combine and make it more effective while ensuring consumer safety.

How is vitamin C used for cosmetic purposes?

What is Vitamin C?

Vitamin C (or Vit C) is a water-soluble and highly potent antioxidant that plays a key role in protecting the human skin from reactive oxygen species (ROS), which are highly reactive chemicals formed from diatomic oxygen, water, and hydrogen peroxide. Biologically speaking, the human body lacks the enzyme L-glucono-gamma lactone oxidase, making it almost impossible to have vitamin C synthesized and biologically available (1). Therefore, we rely on external supplementation, one of these being topical application, making it a versatile micronutrient to include in cosmetics.??

Typically, this vitamin is available in several active forms, including L-ascorbic acid, which is the most studied and recognized, ascorbyl-6-palmitate, and magnesium ascorbyl phosphate (MAP). L-ascorbic acid is the purest form of Vitamin C; it works as a potent antioxidant and a buffering agent in cosmetics, but it is also the most unstable since it is a hydrophilic molecule, and so it becomes repelled by the epithelial cells of the skin (2). Other derivatives might not degrade as rapidly, but they will have a lower concentration, ranging from a half to a sixth of the equivalent concentration of L-ascorbic acid.?

Vitamin C’s mechanisms of action and applications

Vitamin C is essential for collagen synthesis by acting as a cofactor of the proline and lysine hydroxylase molecules that stabilize and strengthen the collagen structure while also stimulating qualitative changes in the collagen structure and finally, directly activating collagen synthesis transcription (3). Clinical studies have shown that the topical use of Vitamin C does indeed increase collagen production in young skin but also in aged human skin by showing the high dependence collagen has on these hydroxylase enzymes provided by Vitamin C and a decrease in synthesis overall when Vitamin C is absent (4). In certain skincare formulations, vitamin C-derived ascorbic acid can be applied together with retinol, alpha- (AHAs) and beta-hydroxy acids (BHAs), vitamin E, or ferulic acid.

And, as an antioxidant, vitamin C is water-soluble, in which it can function in the aqueous compartments of the cell. Environmental factors such as pollution, smoking, and skin exposure to UV light can generate ROS, reactive oxygen species that can generate a cascade reaction that can cause direct chemical damage to the cells, cell proteins, and cellular DNA (5). With the upregulation of matrix metalloproteinases (MMPs) as an example, their excessive production can reduce collagen production and lead to the common manifestations of aging, including pigmentation, wrinkles, and textured skin (5). Vitamin C has the ability to neutralize these radicals.

However, the synthesis of this powerful vitamin never undergoes without difficulty. According to Yin et al., the main challenge in the development of AA-based products is their high instability and reactivity, mostly due to the photosynthesis of vitamin C. In specific, ascorbic acid is reversibly oxidized into dehydroascorbic acid (DHA) upon exposure to light, heat, transition metal ions, and pH. (6)

Analysis

In order to determine the stability of a cosmetic ingredient, it is crucial to first analyze the chemical stability of its most potent form. In this case, ascorbic acid (AA, or L-enantiomer), commonly known as vitamin C, is composed of six carbons and related to the C6 sugars. It is the aldono-1,4-lactone of a hexonic acid with an enediol group on carbons 2 and 3 (7). Although D-isoascorbic acid is the stereoisomer of ascorbic acid, such analogues hardly express the activity of ascorbic acid. Mammalian cells (such as those of the human body) cannot synthesize ascorbic acid de novo due to the lack of L-gulono-1,4 lactone oxidase, which is an essential enzyme for the production of ascorbic acid (8). Then, in case the stability profile of the vitamin C ingredients is limited, there is a necessity to consider available techniques for their further stabilization.

Efficacy studies

A notable type of experiment that should be carefully taken into account while developing highly stable Vit C ingredients is the efficacy test. Current clinical studies on the efficacy of different formulations of topical vitamin C in human skin remain limited. Even the available databases nevertheless face certain scientific challenges, which lie with developing a stable formulation and finding the most efficient transepidermal delivery method for the specific esterified derivatives of vitamin C, including ascorbic acid, to maximize the concentration of the active vitamin in the skin (9). Recent studies have shown that nanoparticles, multi-layered microemulsions for graded delivery, ultrasound, iontophoresis, laser resurfacing, and microdermabrasion can help to enhance penetration of vitamin C. (9)

From a clinical point of view, an Indian dermatologist, Dr. Pumori Saokar Telang, argued that the efficacy of the vitamin C serum is proportional to the concentration, but only up to 20%, a very limited level, while the half-life in the skin after achieving maximum concentration is 4 days. A persistent reservoir of vitamin C is important for adequate photoprotection and can be achieved by regular 8-hourly applications. (10)

Stability studies

As already stated, the instability of ascorbic acid in sensitive environments poses a significant difficulty in the development of cosmetic formulations. In specific, the prominent phenomena associated with the physical instability of emulsions are creaming, coalescence, breaking, and maintenance of elegance with respect to appearance, odor, or color. An emulsion is a dynamic system; however, any flocculation and resultant creaming represent potential steps towards complete coalescence of the internal phase. The stability of ascorbic acid in thixotropic emulsions may be improved by its use in the form of a fatty acid ester such as palmitate. Preliminary experiments have shown that ascorbic acid-based antioxidants could be slowly released from the starch-oil emulsion matrix. (11)

When it comes to chemical stability, many unsaturated oils are prone to oxidation, and their degree of exposure to oxygen may be highly influenced by factors that affect the extent of molecular dispersion, such as droplet size. However, the data on these contents’ chemical stability remains limited, and further research is needed.?

Availability and fundamental efficiency of solutions for stabilizing vitamin C content with the products

Certainly, the high instability of AA contents leads to the necessity of their stabilization in sensitive environments. Recently, scientists have attempted to encapsulate AA within layers of micro-scale material using numerous advanced delivery technologies such as microfluidic, melt extrusion, and spray chilling. However, their actual efficiency and ethics vary by method. Under certain conditions, nano-encapsulation of ascorbic acid can be realized through ion gelation of chitosan or complex coacervation with anionic polymers (12). On the other hand, bioactive compounds with low molecular weight can protect AA content by scavenging its pro-degradation factors in the solution (13). In contrast, although spray chilling techniques can be as effective as other methods, they may involve certain unethical essential oils derived from palm byproducts (14). Therefore, when comparing the ultimate efficiency of each protecting solution, one should rather integrate their socio-environmental impacts into the research model than solely consider their functions.

Conclusions

Vitamin C has been widely deemed one of the most effective antioxidants in the skin. Due to its antioxidant, neocollagenesis, and skin-lightening properties, its clinical applications range from photoprotection and antiaging to anti pigmentation. With an excellent safety profile, it has become a popular cosmetic agent. However, clinical studies on the efficacy of topical formulations of vitamin C remain limited and meet a number of challenges in finding the most stable and permeable formulation for achieving optimal results.

Recommendations

Based on our analysis, we have specific recommendations for companies and consumers to ensure not only an effective but a safe use of vitamin C.?

Recommendations for companies

• Investment in Research and Development: By allocating the right resources to develop or explore more stable forms of Vitamin C, such as ascorbyl glucoside or sodium ascorbyl phosphate, that also involves collaborating with researchers to improve the formulations.
• Transparency in Testing: It is essential for companies to share information about their stability testing protocols, especially when offering cosmetics with vitamin content; consumers need to be aware of the preservative efficacy of the ingredients added to the formulation, while also building consumers trust and an industry standard.

Recommendations for Consumers

When purchasing cosmetics that promote benefits to the skin and its appearance with Vitamin C, it’s critical to learn about the different forms of Vitamin C and their stability. Resources, including skincare blogs or scientific articles, can provide guidance for purchasing the most adequate product. It’s also important to check the packaging; products that come in an airtight and opaque container are more likely to protect the product from environmental factors that can reduce its effectiveness, while also following usage guidelines, which include keeping products in a cool, dry place and avoiding mixing products unless recommended, as certain ingredients can destabilize vitamin C.?

References

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3. Ivanov. (2016). Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate. American Journal of Cardiovascular Disease, 6(2). https://pubmed.ncbi.nlm.nih.gov/27335688/
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