94 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS O . O ' 8•.o i i ! Figure 8. Stability of vitamin E in receptor solution without contacting skin: Chromatograms of samples in UV and radioanalysis at 24 hours. CONCLUSION Percutaneous absorption of vitamin E has been investigated. The radiolabeled vitamin E promptly penetrated the skin while nonlabeled vitamin E appeared after a long time lag. HPLC analysis in line with UV and a liquid scintillation counter showed that vitamin E was extensively metabolized to ot-tocopherol quinone and more hydrophilic metabolites in the hairless mouse skin. Since vitamin E undergoes significant metabo- lism during skin permeation, the data with radiolabeled vitamin E does not necessarily represent the characteristics of intact vitamin E itself. Total radioactivity has to be identified from the possible metabolites. ACKNOWLEDGMENTS The authors express thanks to Professor Richard Chang and Dr. Allan Cooney in the Chemical Biology Laboratory, College of Pharmacy, Rutgers University, for their valu- able discussions and kindness in providing HPLC in line with LSC for this study. The radiolabeled ot-tocopherol and ot-tocopherol quinone standaMs offered by Dr. L.J. Machlin of Hoffmann-La Roche, Nutley, New Jersey, are greatly appreciated. A grad-

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