One of the most complex issues Formula Botanica students come up against is deciding not only on the best form of Vitamin C for skin but also how to use it in their various natural skincare formulations. Vitamin C is one of the most well-known, beneficial active ingredients in skincare and has been on trend for some time now.
In our first post in this series on vitamin C, we looked at the benefits of Vitamin C in high-performance skincare reviewing its action, among other uses, as a brightening agent and as an antioxidant able to scavenge free radicals. Vitamin C comes in many forms each of which has a different use and place in skincare products. As natural skincare formulators we need to understand our options to ensure we use the correct form to provide the maximum benefits in our end products.
In this post on vitamin C in natural skincare, we go over some of the most suitable and commonly-available vitamin C ingredients and also do a bit of a deep dive into their chemistry to help you understand which is best suited to your aims.
Forms of vitamin C in natural skincare
As we all know, we can’t be chopping up vitamin C-rich fruit and vegetables or squeezing orange juice for use in our formulations. While this may be possible for DIY recipes for immediate use, we can’t create long-lasting, high-performance skincare formulations in this manner. And certainly not skincare that will pass the required safety and stability tests. Of course, the vitamin C in natural skincare products won’t come directly from raw, unprocessed fruit or vegetable sources. We need to use vitamin C processed in a lab.
Even though most natural cosmetics’ formulators accept this, it is one of the shades of natural that is subject to debate in the natural skincare world. To make up your own mind on what natural means to you, listen to our podcast – what does natural skincare mean?.
Some vitamin C chemistry
L-ascorbic acid (LAA) is a weak sugar acid structurally related to glucose. In our bodies, it is found both in its acidic and ionised forms (as mineral ascorbates). It acts as an antioxidant by donating an electron, which converts it to an oxidised state. Ascorbic acid is oxidised to dehydroascorbic acid, which is recycled back to ascorbic acid and reused. Ascorbic acid is the most biologically active form of vitamin C, but also very unstable as it quickly oxidises when exposed to light, oxygen, or heat. There are other, more stable forms of vitamin C, which are available to us as formulators. We’ll cover some of them soon.
Common forms of vitamin C used in skincare
1. Ascorbic acid (water soluble)
Ascorbic acid is the most well-researched vitamin for skincare use. Its main use in skincare is as a brightening and rejuvenating agent. It achieves this by inhibiting melanin formation, reducing hyperpigmentation, and acting as an antioxidant. Also, it has a relevant role in collagen production, helping regulate and promote it, and stabilising this protein’s structure. It is used, for example, in products directed to mature skin or designed to address hyperpigmentation.
Disadvantages of ascorbic acid
Ascorbic acid is highly unstable, which is problematic and an aspect of huge concern to us as natural skincare formulators. When exposed to light, heat and air, ascorbic acid not only becomes inactive, but also oxidises extremely fast to become dehydroascorbic acid (DHAA). This reaction is reversible, but if the oxidation process continues, DHAA can degrade irreversibly and generate various compounds, including erythrulose. Erythrulose is considered a self-tanning agent, which reacts with skin proteins. That is one of the reasons why oxidated vitamin C can stain your skin an orange-reddish tone, which won’t go away just by rinsing off the product. To be more effective and to be able to penetrate the skin, ascorbic acid requires a low (acidic) pH of less than 3.5. At this pH, the molecule has fewer ionic charges, favouring its transport across the stratum corneum.
The natural form of vitamin C, ascorbic acid, might be the most effective when applied topically, but is also the least stable version. Beware that some efficacy claims need to be professionally tested and may classify the product as a drug or a cosmetic subject to more strict rules. So, it is essential to learn the regulations applied in your country. We cannot stress enough that in using ascorbic acid you need to be fully aware of what you are doing as this ingredient requires very advanced formulating skills. Never forget that as a formulator you have a responsibility towards your customers.
2. Vitamin C derivatives: stabilised Vitamin C
Instead of focusing only on finding ways to extend the shelf life of products containing ascorbic acid, the industry has been investing in developing more stable vitamin C derivatives. A derivative is a compound structurally related to and derived from another; in this case, ascorbic acid. By combining ascorbic acid with other molecules, these derivatives are able to protect ascorbic acid from oxidation and help prevent the degradation of vitamin C. Theoretically, these derivatives would be converted back to ascorbic acid on the skin. The most common vitamin C derivatives are esters, which are compounds derived from the reaction between an acid and usually an alcohol. There are other types of derivatives too, such as glucosides, for example. Derivatives have advantages for us as skincare formulators as they:
- are not as sensitive to oxidation as ascorbic acid and so are more stable;
- work at higher pH ranges than ascorbic acid; and
- are less irritating to your skin.
Their main disadvantages relate to the fact that as they still need to be converted back to ascorbic acid on the skin, they turn out to be less effective. Also, fewer studies support their action.
Possible derivatives include:
- magnesium ascorbyl phosphate
- sodium ascorbyl phosphate
- ascorbyl glucoside
- ascorbyl palmitate
- ascorbyl tetraisopalmitate
We know that many of our students start by experimenting with oil-based formulations. Although ascorbic acid and most of its derivatives are water-soluble, there’s no need to worry. If you were hoping to create some butters or balms with a focus on vitamin C, you will be happy to know that you still can. Ascorbyl palmitate and ascorbyl tetraisopalmitate are esterified forms of vitamin C that are soluble in oil. However, if you feel confident formulating water-based products, one of the best forms of vitamin C you can choose from is ascorbyl glycoside, which we’ll look at in more detail below.
3. Ascorbyl glucoside: a promising vitamin C derivative
All forms of vitamin C present pros and cons, and it is hard to find an ingredient that offers a good balance between stability and efficacy. Also, while ascorbic acid has been extensively researched, studies about its derivatives still have a long way to go. Among the naturally-derived options of stabilised vitamin C, ascorbyl glucoside, also known as AA2G, seems to be one of the most promising so far. It presents fairly good stability and has some evidence backing up its use. What we know about its effects:
- It has better antioxidant activity than other vitamin C derivatives but not as much as ascorbic acid.
- It has been demonstrated to convert into ascorbic acid both in vitro and in vivo.
- It stimulates collagen synthesis in vitro.
- It reduces UV-induced damage in vitro.
- AA2G has presented beneficial properties in volunteers, but combined with other high-performance ingredients.
Now let’s take a look at some characteristics of ascorbyl glucoside:
- INCI: ascorbyl glucoside
- A stable derivative of ascorbic acid.
- It is produced by an enzymatic process that combines ascorbic acid with starch glucose.
- White to off-white powder.
- It is effective at a pH between 5 – 7, which means it is gentler for people with sensitive skin.
- It is naturally derived: Ecocert/COSMOS approved.
Application dosage: Check with your chosen supplier as usage information can vary. Usually, the recommended usage rates are between 0.1 – 5 %.
Formulation advice: Ascorbyl glucoside is easy to work with. It needs to be dissolved in water and the solution’s pH should be adjusted before being added to the rest of the formulation in the cool-down phase.
Note: because this active is more stable at a near-neutral pH range, the preservative of choice must be effective at this pH too.
Keep in mind that the best choice of vitamin C, in fact, depends on the type of formulation you are making. Take into account each option’s particularities and weigh its pros and cons. Look for what fits best to the purpose of your product, considering the other ingredients you’ll be using in your formulation.
Let’s conclude with some wise words from Walt Disney: “I suppose my formula might be: dream, diversify and never miss an angle”. In our case, as natural formulators, we need never miss out on vitamin C’s many benefits by choosing the optimal form suited to our product formulas.
Further reading and references on vitamin C
Enescu CD et al., 2022. A review of topical vitamin C derivatives and their efficacy.
Jacques C et al., 2021. Ascorbic acid 2-glucoside: An ascorbic acid pro-drug with longer-term antioxidant efficacy in skin.
Stamford NPJ, 2012. Stability, transdermal penetration, and cutaneous effects of ascorbic acid and its derivatives.
This post was updated on 11.10.22 by Beatriz Amaral, Formula Botanica technical research coordinator
Vitamin C, L-ascorbic acid (LAA), is the most biologically active form of vitamin C. However, it is notoriously unstable and prone to oxidising. This makes it unsuitable for most natural cosmetic formulations. There are various choices of stabilised vitamin C derivatives, and ascorbyl glucoside seems to be one of the most promising options. While it presents fairly good stability, it also has some evidence backing up its action. It offers antioxidant properties and can be used in high-performance skincare directed to mature skin.
Ascorbic acid presents properties that make it an interesting choice for high-performance skincare. It acts as a strong antioxidant and participates in collagen production and stabilisation. It has a brightening action, evening the skin tone, and also helps prevent the signs of ageing. There are stable vitamin C derivatives, which present similar properties, although less effective than ascorbic acid. From these, ascorbyl glucoside seems one of the most promising options. These ingredients, when added to well-formulated products, can be of great benefit in high-performance skincare.
Professionally formulated products use specific vitamin C ingredients designed for cosmetic use. Vitamin C and its derivatives can be used in high-performance skincare to target issues such as hyperpigmentation and ageing signs. Crushing and hydrating readily available forms of vitamin C, such as food supplements in tablet or powdered form, or using raw vitamin C-laden fruits on your skin, is not advisable. Cosmetic-grade ingredients are always the best choice for your skincare products. As a cosmetic ingredient, vitamin C and its derivatives must be formulated professionally to work as desired and in synergy with other ingredients in the cosmetic formulation.
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Jilly Schechter is a Tutor at Formula Botanica, where she helps our students to become better organic cosmetic formulators. Jilly lives in Belgium and loves writing tutorials on how to make skincare and haircare.