Vitamin C (sodium ascorbyl phosphate)

Ruamrak, C., N. Lourith, et al. International journal of cosmetic science, 2009, 31(1), 41-46.

This randomized, double-blind study compared the efficacy of a topical formulation containing sodium ascorbyl phosphate (SAP) 5% and retinol 0.2% alone and in combination. The results indicate that the combination of SAP and retinol significantly reduced inflammatory lesions compared with use alone and can be used to effectively treat acne vulgaris.
Experimental design and results
· The study involved 45 participants with grade II-III facial acne. They were randomly divided into three groups: 15 used a 5% SAP lotion with a control base cream, 15 used a 0.2% retinol cream with a control base lotion, and 15 used both the 5% SAP lotion and the 0.2% retinol cream. Those using the SAP lotion applied it twice daily for 8 weeks to all facial areas, while the retinol cream was applied only at night. Participants in the combination group applied the SAP lotion twice daily and the retinol cream once daily, following the same guidelines as the separate treatments.
· Results indicated that the SAP lotion reduced inflammatory lesions by 20.14% in 4 weeks and 48.82% in 8 weeks. The retinol cream showed a slight improvement, with lesions decreasing by 21.79% after 4 weeks and 49.50% after 8 weeks. The combination treatment was more effective, leading to a 29.28% reduction after 4 weeks and 63.10% after 8 weeks of use.

Alma Fočo, et al. International Journal of Pharmaceutics, 2005, 291(1-2), 21-29.

A liposome-encapsulated sodium ascorbyl phosphate (SAP) formulation was developed to improve its ability to penetrate the stratum corneum into the deeper layers of the skin. Two multilamellar vesicles were prepared by the thin film method, and their upper limit of SAP encapsulation efficiency was 8-10%. The study showed that the liposome carrier enabled greater penetration of SAP through the epidermal membrane compared to application of SAP in aqueous solution to the skin surface. SAP that penetrates the epidermis reflects active compounds, which can slow down the complex process of skin phototoxicity.
Preparation of liposome-encapsulated SAP
· Multilamellar vesicles (MLVs) were constructed using non-hydrogenated (NS) or hydrogenated (HS) soybean lecithin combined with 30% (w/w) cholesterol, utilizing the thin film technique. The organic solvent was removed through evaporation, and any remaining solvent traces were eliminated by subjecting the lipid films to a vacuum overnight.
· SAP was incorporated into the liposomes during the hydration process at concentrations of 1% and 2%. This hydration was carried out at temperatures above the phase transition temperature (Tm) of the phospholipids, which is 23 °C for NS and 80 °C for HS.
· The liposome dispersions were then reduced in size through sonication, with a sonication time of 150 seconds at an amplitude of 35%.