FORMULATING FOR MILDNESS Retinyl palmitate (0.1%)
75.000 65.000 55.000 45.000 35.000 25.000 15.000 5.000 0
Retinol/retinal 10.000
95.000 85.000 75.000 65.000 55.000 45.000 35.000 25.000 15.000 5.000 0
Retinyl linoleate (0.1%) 95.000
Triplicate skin discs EpiDerm, 24h Etthylacetate extraction, LC/MS/MS
33
1 Figure 2: Chromatograms of retinyl esters and metabolites extracted from tissue treated as shown
in keratinocytes cultured from neonatal foreskin are notably high.6 While the expression of RA binding protein
CRABP2 was elevated in both the treated and control tissues, it is nonetheless noteworthy to see that the ligand-inducible retinoic acid receptor alpha (RARA) is up-regulated almost threefold by the R-LIN treatment. While the CRAPB2 protein binds RA, this complex is ultimately recognized by the receptor complex RARA upon its transfer to the nucleus.7 The differential regulation of this particular
retinoic acid receptor suggests that indeed the liberated retinol is being converted to RA in the cells and transported to the nucleus to participate in downstream gene regulation. Overall, up-regulation of specific retinoid
marker genes supports the role of R-LIN in a retinoid biochemical cascade when applied topically to cultured skin. Both the cellular retinol binding protein CRBP3 and the retinoic acid receptor alpha (RARA) are up-regulated by the R-LIN treatment, indicating that retinol is indeed being liberated from the retinyl ester by hydrolysis, bound by cellular binding proteins and subject to further enzymatic transformation to retinoic acid in the cultured cells.
Permeation and hydrolysis of retinyl esters in a skin model Results comparing the retinoids extracted from tissue treated with either retinyl palmitate or mixed retinyl esters are presented in the chromatograms in Figure 2. The retinyl esters used in the treatment are detected by the LC/ MS/MS analysis, indicating that they were able to permeate into the tissue of the skin model. In the panel on the left, the peaks
corresponding to retinyl palmitate are in dark green. In the panel on the right, the peaks corresponding to retinyl linoleate are blue-green, while the peaks corresponding to retinyl oleate are in pink. The analytical method does not distinguish retinyl linoleate from retinyl CLA. According to the LC/MS/MS results, the
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April 2023 PERSONAL CARE
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