Sodium acetylated hyaluronate is hyaluronic acid modified by attaching acetyl groups to the molecule. Sometimes marketed as super hyaluronic acid, which is marketing rather than chemistry.
What the modification does
Standard hyaluronic acid is strongly hydrophilic, meaning it loves water and has little affinity for oil. That is what makes it an effective humectant and also what limits it: a highly water-loving molecule does not readily interact with a lipid-rich barrier, and it rinses away easily.
Adding acetyl groups makes the molecule partly lipophilic. The result is amphiphilic, with affinity for both water and oil.
Why that matters practically
Two consequences.
Being more compatible with skin lipids, it adheres to the surface more persistently than standard hyaluronic acid, so the hydrating effect lasts longer through the day rather than dissipating.
And the amphiphilic character means it interacts more readily with the barrier rather than sitting entirely on top of it, though how far it actually travels remains subject to the same size constraints as any hyaluronic acid.
How it holds water
The underlying mechanism is unchanged. Hydrogen bonding along the polysaccharide chain binds water molecules, drawing moisture from the environment when humidity is high and from deeper skin layers when it is not.
That second route is why humectants generally work better applied to damp skin and sealed with an emollient.
Worth knowing
Like all hyaluronic acid ingredients, molecular weight is not disclosed on ingredient lists and varies considerably between suppliers. The INCI name tells you the molecule has been acetylated. It does not tell you the chain length, which affects behaviour at least as much.
