Many currently marketed antioxidant formulations claim to contain stabilized forms of vitamin C, such as ascorbyl-2-glucoside and magnesium ascorbyl phosphate, or stabilized forms of glutathione, such as acyl-glutathione. While these molecules are stable, they are not antioxidants. They are antioxidant-precursors that must be enzymatically modified following skin application to yield L-ascorbic acid and glutathione respectively.4,5 While conversion to functional antioxidants has been demonstrated in cell culture, where it is relatively easy to introduce large amounts of these stable precursors, conversion following topical application is an inefficient process.4 Other skin care products claim to contain antioxidant fruit or herb extracts; however, any antioxidant originally present in the fruit or herb is no longer active when the extract is prepared for addition to a cosmetic formulation. This research examined a novel antioxidant formulation of L-ascorbic acid and L-glutathione manufactured using antioxidant stabilization technology originally developed for organ/tissue preservation products. The primary cause of operating room transplant organ damage is oxidative damage. The organ preservation solution must contain active and stable antioxidants to optimize the viability of the harvested organ. Development of these solutions requires proof of the presence and stability of antioxidants prior to regulatory clearance. Manufacturing must also occur under GMP conditions. This same preservation technology has been used to stabilize the L-ascorbic acid and L-glutathione in the tested cosmetic formulation.
The total ascorbate in the cosmetic formulation and a competitor product labelled as containing 7.5% L-ascorbic acid was measured using a UV spectrophotometric method. Wavelength scans were performed on a PerkinElmer Lambda 35 Spectrophotometer, (PerkinElmer Corp., Hopkinton, MA) and measurement of ascorbate was taken at 243 nm, the wavelength of maximum absorbance for ascorbic acid under the assay conditions. Ascorbate concentrations in product samples were determined by interpolation; plotting measured values on a concentration curve generated by ascorbic acid standards. The method was verified for all products using ascorbic acid spike recovery assays.
Functional Antioxidant Assay
10 mLs of an 8.8 μM thionin solution prepared in Hanks Balanced Salt Solution (pH 3) was aliquoted to control and test flasks. 250 μl of the study product or the comparator ascorbic acid-containing cosmetic was added to separate thionin-containing