Sodium Ascorbyl Phosphate
Sodium Ascorbyl Phosphate (SAP) is the trisodium salt form of ascorbic acid (vitamin C), with CAS number 66170-10-3. It is a stable vitamin C derivative that maintains stability up to pH 7, making it more shelf-stable than pure ascorbic acid. Skin penetration is considered limited compared to pure ascorbic acid, and conversion to active ascorbic acid in the skin has not been confirmed by available data.
SAP has demonstrated in-vivo photo-protective (antioxidant) properties, though less potent than pure ascorbic acid. In-vivo data from a trade publication indicates it can fade brown spots, supporting a skin-brightening effect. Clinical studies show that 5% SAP significantly reduces both inflammatory and non-inflammatory acne lesions, with results comparable to or slightly better than 5% benzoyl peroxide, and further improvement when combined with 0.2% retinol.
Skin penetration is described as poor compared to pure ascorbic acid, which may limit efficacy for some benefits such as collagen boosting. In-vitro collagen-boosting data exists but SAP appears less effective than the MAP (magnesium ascorbyl phosphate) derivative. No conversion-to-ascorbic-acid data is available to confirm or deny this mechanism in skin.
