Stability of L-ascorbic acid was >90% and dl-a-tocopherol was 100% in the formulation containing 0.50% ferulic acid. Figure 2 [below] shows the marked protection against erythema (eightfold) provided by the ferulic acid-stabilized formulation in comparison to control, vehicle, ferulic acid alone and vitamins C and E without ferulic acid.
[Alternatively, see the Skinceuticals Antioxidant Protection - Serums Comparison Graph.]
Figure 3a [below] shows colorimeter readings of the protection provided by each of the solutions. Colorimetric measurements of combination of vitamins C, E, and ferulic acid were statistically better than control and vehicle at all MEDs tested; different from ferulic acid alone at 2x, 6x, and 8x MEDs; and different combination vitamins C+E at 4x and 6x MEDs.
Sunburn counts (Figure 3b) [below] of combination of vitamins C, E, and ferulic acid were statistically different from control and vehicle at all MEDs tested and different from ferulic acid alone as well as from the combination of vitamins C+E at 2x, 4x, 6x, and 8x MEDs.
[Alternatively, see the Skinceuticals Sunburn Cell Reduction - Serums Comparison Chart.]
Figure 4 [below] demonstrates dose-response protection against thymine dimer formation.
At 4x MEDs, control and vehicle-treated skin showed virtually uniform nuclear fluorescence in both epidermis and papillary dermis (a).
After 8x MEDs ferulic acid-treated (b) and C+E-treated skin (c) were both; positive but, skin treated with Skinceuticals C E Ferulic acid was completely negative (d).