Ask a Chemist: What is L-ascorbic Acid? Are There Other Forms of Vitamin C in Skincare?

Our Head of Chemistry, Lizzy Trelstad, weighs in on your most pressing skincare questions.

L-ascorbic acid is the active form of vitamin C. There are other derivative forms of vitamin C that are more stable and easier to formulate with but do not have the robust research behind them that L-ascorbic acid does.

Other forms of vitamin C are technically derivatives—they have the same identifying molecular skeleton as vitamin C, but with a slight modification to one of their functional groups. The "best" form of vitamin C is the form/derivative of ascorbic acid that can work most directly and specifically with your skin to provide a plethora of benefits. All the clinical evidence points to L-ascorbic acid as the most efficient and effective form of vitamin C for the promotion of skin health.

"L-" is a special piece of nomenclature chemists and biologists use to distinguish enantiomers. Note: instead of an R (or D) or an L, you might see a d- and an l-, or just a + or - sign; all mean the same thing. Enantiomers are, very simply, the same molecular skeleton arranged differently in 3D space. Specifically, it describes if parts of a molecule stick out to your right or to your left in 3D space. L and R enantiomers are mirror images of each other, like your hands. Enantiomers have the same structure in 2D, but they are 3D, nonsuperimposable mirror images of each other. This is key for biologists because the body's biochemical systems are mostly set up to "read," or chemically interact with, only chemicals, hormones, proteins, etc. that are geometrically in the "L-" configuration. 

Other forms of vitamin C are less effective in skin but are far easier to formulate with—that's why they're generally more popular in the marketplace. Consumers can still see great skin results with other forms of vitamin C, but formula-stabilized L-ascorbic acid can't be beat.