Which Vitamin C Derivative Is Most Effective? Comparing Differences with Pure Vitamin C Using Medical Literature: Part 3 of the 'Choosing Essential Serums Based on Medical Literature' Series

It happened when I was picking up a Vitamin C serum at a drugstore and comparing the ingredient lists.

One was labeled 'Pure Vitamin C.' The other was labeled 'Stable Vitamin C Derivative,' 'High-Penetration Type,' or 'Oil-Soluble.'

The prices and concentrations are different. However, the crucial question remains.

In the end, which one is the most effective?

I will give you the conclusion first.

At present, the most accumulated clinical research on humans is for pure Vitamin C, L-ascorbic acid. On the other hand, while Vitamin C derivatives have the advantages of stability and ease of use, there are few high-quality studies that fairly compare the derivatives against each other, and we are not in a situation where we can conclude that 'this derivative is the strongest' [1-4].

What is the difference between pure Vitamin C and derivatives?

Pure Vitamin C generally refers to L-ascorbic acid.

It is in a form that can work directly on the skin, and is expected to provide antioxidant effects, support collagen synthesis, and act on melanin production.

Its weakness is that it is easily degraded by the influence of water, oxygen, light, and heat. Also, products adjusted to be acidic to deliver it to the skin can sometimes cause stinging or redness.

That is why Vitamin C derivatives were developed. They are designed to increase stability by changing part of the molecule, with the goal of working as Vitamin C after entering the skin.

However, if the derivative is not converted properly within the skin, even if it shows excellent results in a test tube, it does not necessarily mean the same effect will be obtained on actual skin.

L-ascorbic acid has the most proven track record

In a 2023 systematic review, 7 randomized controlled trials using topical Vitamin C, involving a total of 139 people, were examined.

As a result, the possibility of improvements in skin tone, fine lines, and surface smoothness was shown. On the other hand, the formulations, concentrations, and usage methods differed for each study, and there was not enough evidence to determine the optimal concentration [1].

What is important is that many of the clinical studies included in this review target L-ascorbic acid itself or formulations containing it.

In a 2025 review as well, stability, skin penetration, and tolerance to irritation were considered the main issues for Vitamin C products, and L-ascorbic acid is still treated as the standard ingredient for clinical evaluation [2].

Therefore, if you prioritize a track record of effectiveness, L-ascorbic acid is the first candidate.

However, this does not mean that 'higher concentration is always more effective.' The amount that actually reaches the skin changes depending not only on the concentration but also on the pH, solvent, combination with antioxidant ingredients, container, and storage conditions.

Water-soluble derivatives have the advantage of low irritation and stability

Representative water-soluble derivatives include the following:

Magnesium Ascorbyl Phosphate (MAP)

Sodium Ascorbyl Phosphate (SAP)

Ascorbyl Glucoside (AA-2G)

These are more stable than L-ascorbic acid and may be easier to use for those who struggle with acidic formulations.

There are basic research studies and some clinical studies regarding MAP and AA-2G related to pigmentation and collagen. However, because the concentration, formulation, and concomitant ingredients of derivatives vary by product, there is a lack of large-scale direct comparative studies proving they are superior to L-ascorbic acid [2-4].

SAP is also used in products for acne-prone skin, but it cannot be said that 'if it contains SAP, acne will be cured.' Beauty serums are not pharmaceuticals, and if inflammatory acne persists, dermatological treatment should be prioritized over adding more cosmetics.

Are oil-soluble derivatives truly highly penetrative?

Representative examples of oil-soluble types include Ascorbyl Tetraisopalmitate (THDA) and Ascorbyl Tetraisopalmitate (Note: The source text lists two names for the same chemical class; translated as written).

Because they blend easily with oil, it is sometimes explained that they pass through the stratum corneum easily. Another advantage is that they do not require a low pH, making it easier to create products with a gentle feel.

However, it has not been proven that they 'reach the dermis in large quantities because they are oil-soluble' or that they are 'more powerful than pure Vitamin C.'

In a 2024 randomized double-blind study, 5% THDA alone was compared with a formulation containing THDA plus another antioxidant ingredient in 44 people. However, this study was not a comparison between THDA and L-ascorbic acid, nor was it a study showing that THDA itself is superior to other Vitamin C derivatives [5].

While oil-soluble derivatives are an attractive option, it is necessary to distinguish between the term 'high penetration' used in advertisements and the clinical efficacy of actually improving facial spots and wrinkles.

3-O-Ethyl Ascorbic Acid is a promising newcomer

3-O-Ethyl Ascorbic Acid is attracting attention as a derivative that blends easily with both water and oil to a certain extent and has improved stability.

While there are basic research studies and small-scale trials showing effects on pigmentation, as of 2023 and beyond, there are almost no high-quality clinical trials comparing it under the same conditions as L-ascorbic acid, MAP, AA-2G, or THDA.

In 2024, research on formulations to improve skin delivery was reported, but this was primarily a study examining the release and skin permeability of the formulation. It does not directly prove the improvement of spots or wrinkles when using commercial beauty serums over a long period [6].

Although promising, at this stage, it is prudent to view it as an ingredient where expectations are ahead of the evidence.

In the end, which one should you choose?

For those who prioritize research track records of efficacy

L-ascorbic acid is the primary candidate.

If using it for the first time, do not start with the highest concentration; begin with a lower, less irritating concentration. Choose a container with light-shielding and airtight properties, and reconsider using products where the color or odor has changed significantly.

For those with sensitive or dry skin

Water-soluble derivatives such as MAP and AA-2G may be easier to use.

However, 'being a derivative' does not mean it will never cause irritation. Irritation can also be caused by the overall product formulation, fragrances, or preservatives.

For those who prioritize usage feel and stability

Oil-soluble derivatives such as THDA are also an option.

Whether an oil-based vehicle suits your skin depends on your skin type, so try a small amount first.

Products where the derivative name is not listed

If a product only states 'contains Vitamin C derivatives' without specifying the ingredient name or concentration, scientific evaluation becomes difficult.

At the very least, it is more rational to choose products where you can verify the type of Vitamin C in the full ingredient list.

The real answer to 'which is most effective'

Based on current research, it can be summarized as follows:

L-ascorbic acid has the most accumulated clinical research

Various derivatives have advantages in stability and lower irritation

The superiority of one derivative over another has not yet been settled

Even in the 2025 expert consensus, it is pointed out that while derivatives improve stability, there is a lack of research directly comparing their clinical efficacy to L-ascorbic acid [3].

Therefore, you cannot determine the 'strongest' based solely on the ingredient name.

Being able to continue using a proven ingredient without irritation, in a formulation and container that resists degradation.

This is the most reliable way to choose a Vitamin C serum at this time.

Furthermore, no matter which vitamin C you choose, it is not a substitute for sunscreen. Vitamin C is an ingredient that supplements UV protection, and daily sun protection and moisturizing are the foundation of skincare.

Next time, we will compare another classic ingredient.

How do the strength of effects and side effects differ between retinol, retinal, and tretinoin?

We will clarify realistic ways to choose while avoiding the misconception that "the stronger, the better."

Click here for Part 4☟.

References

[1] Correia G, Magina S. Efficacy of topical vitamin C in melasma and photoaging: A systematic review. Journal of Cosmetic Dermatology. 2023;22(7):1938-1945. doi:10.1111/jocd.15748.

[2] Singh N, Brown AN, Oscherwitz M, Gold MH. Vitamin C: Its role in cosmeceuticals. Dermatological Reviews. 2025;6(1):e70012. doi:10.1002/der2.70012.

[3] Addor FAS, Esposito ACC, Lima EA, Portilho L, Yamaguchi EM, Ypiranga S. Multidisciplinary consensus on the benefits of topical vitamin C. Surgical & Cosmetic Dermatology. 2025;17:e20250366. doi:10.5935/scd1984-8773.2025170366.

[4] Enescu CD, Bedford LM, Potts G, Fahs F. A review of topical vitamin C derivatives and their efficacy. Journal of Cosmetic Dermatology. 2022;21(6):2349-2359. doi:10.1111/jocd.14465.

[5] Afzal N, Nguyen N, Min M, Egli C, Afzal S, Chaudhuri RK, et al. Prospective randomized double-blind comparative study of topical acetyl zingerone with tetrahexyldecyl ascorbate versus tetrahexyldecyl ascorbate alone on facial photoaging. Journal of Cosmetic Dermatology. 2024;23(9):2943-2952. doi:10.1111/jocd.16201.

[6] Costa R, Santos D, Machado R, et al. Lipid-based gels for delivery of 3-O-ethyl L-ascorbic acid in topical applications. Pharmaceutics. 2024;16(9):1197. doi:10.3390/pharmaceutics16091197.