Ingredient Library
Vitamin C
L-Ascorbic Acid
The gold standard your formula has to earn.
It’s the most studied antioxidant in skincare — and the most misformulated. Here’s the oxidation chemistry, the delivery reality, and what the concentrations actually mean. No shortcuts, no workarounds.
INCI
Ascorbic Acid
Solubility
Water soluble
pH Range
2.5–3.5
Effective Range
10–20%
01 — What Is It
The Antioxidant That Oxidises
L-Ascorbic Acid is the only form of Vitamin C with direct, well-documented skin activity. Every other derivative — Ascorbyl Glucoside, SAP, MAP — needs to convert to L-AA once it’s absorbed. That conversion is slow, incomplete, and varies by skin. When you use L-AA, you skip the middleman.
It’s a small, acidic molecule — which is why it works best at a pH below 3.5. It donates electrons to neutralise free radicals, regenerates Vitamin E, and stimulates collagen synthesis via a separate pathway. Three jobs. One ingredient.
Why It Matters
Not all Vitamin C is the same. L-Ascorbic Acid is not interchangeable with its derivatives — it’s the reference compound everything else is measured against.
02 — Mechanism
How It Protects and Builds
Two mechanisms, distinct but synergistic. The antioxidant action is immediate; the collagen stimulation takes weeks. Both are happening.
One
Antioxidant defence
L-AA donates an electron to a free radical, neutralising it and becoming a semi-dehydroascorbic acid radical. That radical is relatively stable and either gets recycled back to L-AA by glutathione and Vitamin E, or oxidises further to dehydroascorbic acid (DHA). Think of it as a sacrifice play: L-AA takes the hit so collagen and lipid membranes don’t have to.
Two
Collagen synthesis
L-AA is a required cofactor for prolyl and lysyl hydroxylase — the enzymes that stabilise the collagen triple helix. Without adequate ascorbate, the helix doesn’t form properly. This is the mechanism behind scurvy. In formulation, it means L-AA isn’t just protecting collagen — it’s actively required to build it.
Three
Melanin inhibition
L-AA suppresses tyrosinase — the enzyme at the top of the melanin synthesis pathway. It also reduces already-formed melanin intermediates. Where niacinamide intercepts the transfer of melanosomes, L-AA works earlier, upstream at the production step. Together, they cover the full pathway.
Why It Matters
Antioxidant and collagen synthesis are separate mechanisms. A formula can deliver one without the other. Know which you’re targeting.
03 — Concentrations
Stability Is the Real Variable
Percentage matters less than oxidation state. L-AA is notoriously unstable — it oxidises to DHA and then to diketogulonic acid, which has no activity. A 20% serum that’s been sitting on a warm shelf for six months may do less than a fresh 10% formula. Formulation conditions matter more than the number on the label.
5–10%
Entry-level antioxidant protection. Appropriate for sensitive formulas or layering under actives.
10–15%
The clinical sweet spot for both antioxidant and collagen benefits. Formulate here unless there’s a brief-specific reason not to.
15–20%
Hyperpigmentation and advanced photoageing. Harder to stabilise — requires careful pH and packaging decisions.
Above 20%
No meaningful additional benefit. Increases irritation risk and accelerates oxidation. Avoid.