About the author: John Su is an established skin care expert and aspiring dermatologist. He also runs a blog, The Triple Helix Liaison, dedicated to providing unbiased, meaningful, and insightful information about skin care. For his full bio, please visit our About page.
L-ascorbic acid (vitamin C) is the father of all topical treatments, found to do everything from brighten to stimulate/enable collagen production. USDA photo. Image Number K3644-12. (Photo credit: Wikipedia)
I’ve been on such a kick talking about tretinoin recently, that I figured I might as well talk about the other elephant in the room. If tretinoin is the mother of all topical treatments, L-ascorbic acid would undoubtedly be its father. Together, these two ingredients form the cornerstone of modern-day skin care. Though several other classes of ingredients have gained prominence in recent times such as polyphenols, flavonoids, and hydroxy acids; none can rival the combined preventative and corrective effects of these two giants.
This post will be limited to the discussion of just L-ascorbic acid. Its derivatives like magnesium/sodium ascorbyl phosphate and ascorbyl (tetraiso)palmitate/acetate will not be addressed simply because Nicki beat me to the punch [Read more: Ascorbyl Glucoside, Magnesium Ascorbyl Phosphate, and L-ascorbic acid: What are the differences between different forms of vitamin C?]
What is L-ascorbic acid, anyway?
Chemical structure of ascorbic acid, (aka vitamin C) (Photo credit: Wikipedia)
L-ascorbic acid is chemically a hydrophilic monovalent hydroxyl compound; colloquially it is basically a water-loving (or water-soluble) molecule that possesses many singly covalently-bonded hydroxyl groups, which largely determine its function and role, such as those in ionization and various hydrogen bonding scenarios.
Many people know that L-ascorbic acid is beneficial, but don’t know the reason why it enjoys such attention. So I’m going to lay it out for you!
How L-Ascorbic Acid Fights Hyperpigmentation
Structure of eumelanin. Vitamin C limits melanin formation. (Photo credit: Wikipedia)
L-ascorbic acid inhibits melanin production, so it can help with irregular hyperpigmentation such as melasma. Specifically, it reduces o-DOPAquinone back to DOPA, thereby, avoiding melanin formation (1). It however, has not been shown to significantly lighten the skin for example, from NC40 to NC30.
UV Damage: Being an excellent electron donor, L-ascorbic acid acts as a potent antioxidant against reactive oxygen species (ROS) like the superoxides and hydroxyl radical from peroxides because it interferes and “scavenges” the lone electrons that all radicals possess (2).
Collagen Production: Because the L-ascorbic acid ion is a cofactor for the enzymatic activity of prolyl hydroxylase, which binds aspects of procollagen prior to triple helix formation (like my blog name!), it is essential for collagen synthesis (3). The introduction of L-ascorbic acid to fibroblast cultures have been shown to upregulate collagen production because it increases the transcription rate of genes that code for procollagen as well as elevating procollagen mRNA levels (4). In other words, the presence of L-ascorbic acid increases the rate at which genetic information instructing the creation of additional collagen is manufactured while adding additional “messengers” to deliver these instructions, resulting in more finished “product,” or in this case, collagen.
What to look for in “Vitamin C” products
In vitamin C products, look for:
1.) Packaging. Vitamin C is sensitive to light and air, so small, dark bottles and airtight pumps are best.
2.) Low pH. Look for vitamin C in acidic form, as with Skinceuticals CE Ferulic.
3.) Vitamin C with vitamin E or alpha lipoic acid, both of which are found to increase vitamin C’s strength.
L-ascorbic acid is notoriously difficult to stabilize because it is such an excellent antioxidant, and therefore electron donor. It will gladly donate electrons to the oxygen content in air (to form water) and become doubly oxidized, forming dehydro-L-ascorbic acid (DHAA), which contains an aromatic (lactone specifically) ring. If further oxidized, the ring will open and the molecule (now diketogulonic acid) will become completely useless. All of this happens within hours after initial exposure. Therefore, a Vitamin C product needs to be properly packaged. Ideally, tube packaging or an airless pump bottle would be best. The packaging also needs to be opaque since UV radiation such as sunlight will degrade the L-ascorbic acid and any other antioxidants present.
Furthermore, being an acid with a pKa(1) of 4.2, L-ascorbic acid needs to be incorporated into a vehicle that has a low pH (less than about 3.5) in order to function and more effectively penetrate the stratum corneum.
Finally, several other antioxidants have been shown to work in-tandem or synergistically with Vitamin C, such as vitamin E and alpha lipoic acid. For example, vitamin C can reduce oxidized vitamin E, effectively recycling the latter for further use (5). Therefore, products with more than just L-ascorbic acid as their primary antioxidants are recommended. Chemical penetration enhancers wouldn’t hurt either.
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About Author
John Su describes himself as eccentric—you might find him having a conversation with himself. He’s a stickler for accuracy, so you might find him correcting one thing or another! His goal is to answer questions and provide unbiased, meaningful, and insightful information when it comes to skin care. His underlying motivations stem from a need to inform people who have doubts, questions, or even prayers for solutions to their problems. He has his own skin care blog, The Triple Helixian.
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jeff
Philosphy has a vitamin C powder that you mix with any serum or cream? But what about the PH of the serum or cream your using? dos tham matter?
Nicki
@Jeff – Thanks for the great question! We talk a lot about what delivery systems are “best” or “optimal” for products. Yes, the vitamin C powder from philosophy will work at any pH, but it will work best if it is added to a solution that is at an acidic pH (less than 3.5). Hope this helps!
Karen K
Is there any ingredient we should avoid when using vitamin c products? A few sources say we need to avoid sodium benzoate. The reason why I’m asking is because I like to layer products and I would like to avoid layering on ingredients that would make vitamin c ineffective.
John Su
@Karen K
If the vitamin C form is present as L-ascorbic acid, the pH needs to be less than 3.5 to allow it to penetrate, protonate, and exfoliate the skin. So you’ll want to avoid ingredients that either change the pH or do not work optimally at low pH environments. For example, retinol.
As for your questions about sodium benzoate, the reason to avoid using that with L-ascrobic acid, is not because it will make the latter ineffective. Rather, and more importantly, it’s to avoid forming a known carcinogenic compound. When you mix the two compounds together, they form benzene, which is highly carcinogenic. However, please note that the amounts formed are significantly lower than the amount necessary to deem something as “toxic.” This has been ruled by the FDA, so I’m sure most manufacturers will know not to use these two compounds together. Here’s the link for the interaction (which was shown in beverages).
http://www.fda.gov/Food/FoodSafety/FoodContaminantsAdulteration/ChemicalContaminants/Benzene/ucm055815.htm
I hope that helped!
Soi Dog
Can Ascorbyl Glucoside be used with GHK-CU copper peptide?
Thankyou
John Su
@Soi Dog
Sure! Because the copper is bound and not present as a free ion, it won’t have any significant deleterious effect on the L-ascorbic acid content that eventually forms from the ascorbyl glucoside. And its high affinity for copper may even reduce the overall environmental levels of free copper ions.
Kitty
Regarding vitamin C serums oxidising – we know they use potency that way, but could they do your skin any harm? I’ve read on various beauty blogs that oxidised vitamin C can “create free radicals”. I’ve been searching and searching and I can’t find any scientific back up for this, is it just a myth?
Another thing I was wondering was, how long does it take vitamin C to fully oxidise and become dehydroascorbic acid? Because in all my googling I came across people asking how they could make their own DHA, and the answers were a lot more complicated than just “leave vitamin C lying around getting air to it”!
Also, am I right in thinking that it’s best to use distilled water for the mix because that has less oxygen in it than plain old tap water, or is there a other reason? I’ve also been told that mixing it with a metal spoon oxidises it…?
John Su
@Kitty
Of course all antioxidants have the potential to act as pro-oxidants! See, antioxidants have the capacity to donate electrons to reactive oxygen species (ROS). But after they do so, they themselves can become pro-oxidant via intermediate radical phases. Therefore, they either have to be regenerated (such as how vitamin E regenerates vitamin C) or they will decay. The effects of that decay is dependent in-part by the oxidized antioxidant’s pathway of decay: is it destructive or degradative? This means is it more likely to interact with surrounding structures or with itself? For example, after donating electrons, alpha lipoic acid tends to interact with surrounding tissues, while L-ascorbic acid is less reactive and tends to bind to itself. Check out this post for more info: http://thetriplehelixian.com/2013/02/11/spotlight-on-thioctic-acid-or-alpha-lipoic-acid/ So no, it’s not a myth.
As for how long it takes vitamin C to oxidize to DHAA, I can’t give an accurate number, but it happens within hours of exposure to air. Keep in mind that DHAA is not the final oxidized endproduct of L-ascorbic acid. LAA bcomes DHAA after it donates two electrons. At this point, it can be regenerated. But if it donates more electrons (or more are taken away), the lactone ring will open and DHAA will become diketogulonic acid, which cannot be regenerated and is physiologically inactive. Therefore, you wouldn’t want to make DHAA products anyways… Why would you want an oxidized antioxidant that has to be regenerated, and is one electron away from becoming inactive?
If you must make you own Vitamin C serum, it is best to distilled water because the minerals in tap water will reduce the antioxidant potential of vitamin C, since it will chelate the free metal ions and thereby become inactive. But you don’t have to worry about not using a metal spoon because the amount of free metal ions formed is irrelevant.
Finally, keep in mind that unless you have sophisticated equipment, technique and/or you make a new batch everyday, I wouldn’t personally recommend making a DIY vitamin C serum.
Does that all make sense?