Let’s start with Vitamin C—it’s an appealing ingredient for skin care products because it has several biological roles in skin health. It’s an antioxidant, it’s is required for collagen synthesis, and it turns off an enzyme called tyrosinase that cause your skin to discolor.
The problem with vitamin C is that it’s water soluble and can’t penetrate your skin’s top layer which is made up of fats and dead skin cells. So, if it can’t penetrate your skin, it won’t get into cells and your dermis where it can actually help your skin look better by creating more collagen and dealing with oxidative damage. The other problem with vitamin C is that it’s really unstable, which you’re about to learn about. So, several vitamin C derivatives, which are really just chemically modified versions of vitamin C, have been designed to maximize skin penetration, stability, and effectiveness. You’ve probably seen these on the labels of some vitamin C serums or lotions.
Let’s start with L-ascorbic acid (L-AA). It’s is the most biologically active form of vitamin C. But, it’s also the least stable and penetrates your skin barrier the least. It requires really low pH’s in order to be stable enough to work on helping your skin out. What that means is that if your product has L-AA as the vitamin C ingredient, it’s likely kind of harsh and may be irritating to your skin if overused.
Magnesium ascorbyl phosphate AND sodium L-ascorbyl-2-phosphate are esterified forms of vitamin C that’s are the most stable versions, but have really poor skin penetration. They’re generally better tolerated than L-AA because they’re stable in neutral pH’s. You’re you’re better off finding a different vitamin C derivative.
Ascorbic 2-phosphate 6-palmitate (APPS) it both stable AND has good skin penetration because it’s stabilized with a phosphate group and it’s lipophilic, unlike L-AA which is hydrophilic. One study actually showed that it’s a better antioxidant than L-AA. That said, once it penetrates cells, it is directly converted into L-AA, so it’s not entirely clear how to interpret this information.
Ascorbyl tetraisopalmitate and tetrahexyldecyl ascorbate are stable vitamin C versions that have the best skin penetration known. They’re proven to protect skin from UV damage and are very effective antioxidants.
Ascorbyl 2-glucoside is a glycated vitamin C with good stability but doesn’t have great penetration because it’s less lipophilic.
Lastly, 3-O-ethyl Ascorbic Acid is similar to L-ascorbic acid but may be slightly more lipophilic and have better skin penetration.
So, which one should you choose? Based on effectiveness, stability, and cost/availability, I’d recommend 2: L-ascorbic acid or Tetrahexyldecyl ascorbate
We are actively working on a vitamin C containing all natural anti aging product so stay tuned for that.
Reference: J Cosmet Dermatol. 2022;21:2349–2359.