Formulation Challenges: Achieving an Effective and Natural Vitamin C Serum

The objective was to create a Vitamin C serum that had exceptional skin feel, was effective over its shelf life, without synthetic ingredients where possible - while staying within a set budget.

Some of the biggest challenges in formulating a Vitamin C serum were:

• Stability: Ensuring the Vitamin C remained stable throughout the product's shelf life as exposure to light, air, and heat could degrade the Vitamin C, rendering it ineffective.
• pH levels: Maintaining pH levels as Vitamin C is only effective at a low pH (3.5), however, a low pH can be irritating to the skin, especially for sensitive skin types.
• Compatibility: Ensuring all ingredients in the formulation were compatible and did not destabilize the vitamin C or reduce its efficacy.
• Natural ingredients: Replacing synthetic stabilizers, preservatives, and other ingredients with natural or naturally derived alternatives without compromising on the product's performance.

Initially, I used simple formulations with L-Ascorbic Acid (L-AA) dissolved in a water-based gel. These formulations were unstable, oxidizing within days despite being stored in amber glass bottles. 

I then experimented with different natural solvents and pH adjustments to stabilize the L-AA. Lowering the pH below 3.5 helped somewhat, but introduced new challenges like potential skin irritation and compatibility issues with other natural ingredients. I found some success in stabilizing L-AA with ferulic acid and tocopherol in a glycol base, but high levels of glycols did not provide the desired sensory experience, and the serum still oxidized after about six months.

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Mitigating oxidative stress

The oxidation issue necessitated exploring alternatives. I looked at several alternatives that would be suitable including water soluble and oil soluble derivatives. I could use a known combination to get around the stability issue, but I’d need to look at other antioxidants to ensure I didn’t possibly infringe on a patent. I also knew if I changed my formulation base from a gel serum to an emulsified serum that I could possibly incorporate an oil soluble derivative. 

I looked at several alternatives including water soluble derivatives like Sodium Ascorbyl Phosphate (SAP), Magnesium Ascorbyl Phosphate (MAP), 3-O-Ethyl Ascorbic Acid and Ascorbyl Glucoside, as well as oil soluble derivatives like Tetrahexyldecyl Ascorbate, Ascorbyl Tetraisopalmitate and Ethyl Ascorbic Acid. 

After extensive research, I decided that I needed to explore derivatives of ascorbic acid to address the stability issue. The first option was to combine a water soluble derivative with an oil soluble derivative, or to use a more expensive stabilized version of L-AA (NV Ascorbic Acid, Nanovetores) or a novel delivery system. 

Safeguarding Vitamin C against degradation with nanotechnology

Advancements in encapsulation technologies, such as micro and nanoencapsulation, have significantly improved the stability and bioavailability of Vitamin C. These techniques protect Vitamin C from environmental degradation while ensuring its antioxidant properties are maintained for effective delivery to the targeted body or skin area, as highlighted in numerous studies. Additionally, innovative delivery systems like liposomes, microemulsions, and nanoparticles enhance Vitamin C's penetration through biological barriers, increasing its bioavailability and effectiveness. Liposomal systems, for example, encapsulate Vitamin C in lipid layers, safeguarding it against degradation and boosting absorption through the skin. NanoVec are using phospholipids to deliver Vitamin C along with tocopherol with LIP-66 and LIP-67, Evonik have ROVISOME® C NG (Water, Glycerin, Lecithin, Lonicera Caprifolium (Honeysuckle) Flower Extract, Lonicera Japonica (Honeysuckle) Flower Extract, Benzyl Alcohol, Benzoic Acid, Dehydroacetic Acid) and Tagra Biotechnologies have CelluCap™ C (Ascorbyl Tetraisopalmitate, Cellulose Acetate Butyrate, Pentaerythrityl Tetra-di-tbutyl Hydroxyhydrocinnamate). These newer delivery systems often offer other benefits too, including enhanced sensory applications. There are quite a few interesting options here which are well worth exploring.

Exploring the first option, I opted for a combination of Sodium Ascorbyl Phosphate (SAP) and Tetrahexyldecyl Ascorbate (THDA). SAP offered water solubility and stability, while THDA provided oil solubility and deeper skin penetration. I did look at other combinations, but because both THDA and SAP are more stable in a similar pH range (5-7), I decided to use these two derivatives. 

In my original serum, I was using a basic gelled serum with Xanthan Gum and Tara (Caesalpinia Spinosa) gum, with some humectants (glycerin and pentylene glycol), an antioxidant/stabilizing agent, a chelating agent, as well as a preservative (Euxyl K940). Simplicity would dictate just changing the polymer to a synthetic polymer that is tolerant to low pH and electrolytes; however, I needed to keep it as close to natural as possible and my synthetic Vitamin C derivative choices meant I really needed to stick to natural polymers for this reason. 

Options that presented themselves included using Xanthan Gum synergistically with another gum, or to use a polymer that is already modified, like Solagum AX, Luxamul, Ecogel etc. I decided that Siligel™ (Xanthan Gum, Lecithin, Sclerotium Gum, Pullulan) by Lucas Meyer Cosmetics would allow the addition of a small oil phase while still providing a serum consistency. It has the added bonus of having an exceptional sensory profile, soft and silky skin-feel. 

As using Siligel™ as my base allowed me to incorporate a small oil phase, I chose to add some Floraesters K-100® Jojoba (Hydrolyzed Jojoba Esters, Jojoba Esters, Water/Aqua) by Cargill for its rich emollience without being heavy on the skin. 

Effisin™ PG (Pentylene Glycol) and Glycerin (derived from sustainable palm oil) were added as humectants to hydrate and moisturize the skin. 

Incorporating additional antioxidants like Cosroma® Natural VE70 (Tocopherol) and Ferulic Acid Natural (Vigon) helped stabilize the Vitamin C by reducing oxidation. These antioxidants also provided synergistic skin benefits, enhancing the overall efficacy of the serum. dermofeel® PA-12 (Sodium Phytate) was used as a chelating and additional stabilizing agent. 

To maintain a pH level conducive to Vitamin C stability without causing skin irritation, pH was adjusted to 6.0. Both SAP and THDA prefer a higher pH than LAA with optimal pH being around 6 for both. 

Euxyl™ k 940 preservative (Phenoxyethanol, Benzyl Alcohol,Ethylhexylglycerin, Tocopherol) by Ashland was used to preserve the product and maintain its shelf life and efficacy. 

Using airless pump bottles and opaque packaging minimized exposure to light and air, further protecting the stability of the Vitamin C.

From concept to a robust Vitamin C serum

The formulation went through multiple iterations, each addressing specific challenges and improving the overall product. Stability testing under various conditions (temperature, light, and humidity) was conducted to ensure the serum maintained its efficacy and stability over time. 

Formulating a Vitamin C serum that is both effective and natural presents a unique challenge. Balancing budget constraints with the need for high-quality, sustainable ingredients requires careful consideration. In this case, the combination of Sodium Ascorbyl Phosphate and Tetrahexyldecyl Ascorbate, along with additional antioxidants and appropriate packaging, proved successful in maintaining the stability and efficacy of the Vitamin C. By using a higher pH, the product remained gentle on the skin without sacrificing effectiveness. 

One of the biggest hurdles was finding the right Vitamin C derivative. With numerous options available due to the inherent instability of Vitamin C, extensive research, iterations, and testing were necessary. Covalo is a great resource for sourcing ingredients, particularly for finding natural and sustainable alternatives.

Staying within budget was another significant challenge. While liposomal systems offered a promising solution, their higher cost, coupled with the expense of natural and sustainable ingredients, made them unfeasible. Ultimately, the gelling agent and derivatives proved to be the most expensive components of the formulation.

Balancing stability, efficacy, and user experience while adhering to natural and sustainable principles added layers of complexity. Sensory issues were addressed by selecting a multifunctional gelling agent, adding emollience and hydration without feeling heavy on the skin. 

Throughout the formulating journey, valuable lessons were learned. The importance of stability testing became evident, as extensive testing is crucial for developing a stable and effective product, especially with natural ingredients.

I also learnt the importance of being flexible. I really wanted to leverage the advantages of the liposomal delivery systems, due to enhanced skin penetration, however, I had to compromise on my delivery system. Being flexible in adapting to new ingredients and innovative techniques proved essential for success. 

Formulating a Vitamin C serum that remains stable for a minimum of two years is undeniably challenging but achievable. By leveraging scientific research, innovative techniques, and a commitment to sustainability, a product that delivers on its promises can be created.

For brands and formulators facing similar challenges, this case study highlights the importance of perseverance, rigorous testing, and a willingness to adapt and innovate.

The journey may be complex, but the result is a product that meets consumer demands for efficacy, safety, and sustainability, ultimately standing out in a competitive market.

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