GLYCOLIC ACID AND SKIN PENETRATION 31 10 glycolic acid •. 2 + gel with glycolic acid 0 0 1 2 3 4 time (hours) Figure 2. Skin penetration by vitamin A palmitate along time in a gel formulation. 10 0 1 2 3 4 -.-e,-- gel cream without glycolic acid gel cream with glycolic acid time (hours) Figure 3. Skin penetration by vitamin A palmirate along time in a gel cream formulation. 10 t I 0 1 2 3 4 + cream without glycolic acid --lB--cream with glycolic acid time (hours) Figure 4. Skin penetration by vitamin A palmirate along time in a cream formulation. lation showed that the behavior of the latter did not differ significantly in the presence or absence of glycolic acid (Figure 4). CONCLUSION Skin penetration tests showed that, under the present experimental conditions, the gel

32 JOURNAL OF COSMETIC SCIENCE formula behaved differently in terms of vitamin A palmitate penetration when the vitamin was combined with glycolic acid, whereas the behavior of the cream and gel cream formulas were not affected, also showing the well known fact that vehicle inter- feres with the skin penetration of active principles. ACKNOWLEDGMENT The research in this article was supported by FAPESP. REFERENCES (1) R. Hermitte, Aged skin, retinoids and alpha hydroxy acids, Cosmet. Toiletr., 107, 63-67 (1992). (2) B. Idson, Vitamins and the skin, Cosmt. Toiletr., 108, 79-94 (1993). (3) P.M. B. G. Maia Campos, Estudos da Estabilidade Quoemica e da Absoffcio "In Vivo" da Vitamina A em Prepara•-•es Cosmgticas Para a Pele, Ribeirgo Preto, 1994, 120pp. Tese (Doutorado) Faculdade de Ci&ncias FarmacSuticas de Ribeirgo Preto, Universidade de Sgo Paulo. (4) P.M. B. G. Maia Campos, S. A. Benetton, and G. M. Eccleston, The influence of the vehicle in the penetration of vitamin A into the skin, Cosmet. Toiletr. (in press). (5) A. Nilson, "Efectos Cosmeto16gicos de las Vitaminas," in: Congresso Latino Americano e Ibmrico de Qu micos Cosm6ticos, 10, Caracas, 1991. Anais, Caracas, Sociedade Venezolana de CiSncias Cosm&i- cas, 1991, pp. 2-16. (6) M. I. R. Santoro, P.M. B. G. Maia Campos, and E. R. M. Hackman, Determining vitamins A, D3 and E in creams: High performance liquid chromatography, Cosmet. Toiletr., 108, 71-74 (1993). (7) W. P. Smith, Hydroxy acids and skin aging, Cosmet. Toiletr., 109, 41-48 (1994). (8) J. Van Scott and R.J. Yu, Alpha hydroxy acids: Procedures for use in clinical practice, Cutis., 93, 222-228 (1989). (9) D. F. Counts, F. F. Skreko, J. Mcbee, and G. Wich, The effect ofretinyl palmirate on skin composition and morphometry, J. Soc. Cosmet. Chem., 39, 235-240 (1988). (10) B. Idson, Vitamins and the skin, Cosmet. Toiletr., 108, 79-94 (1993). (11) P.M. B. G. Maia Campos, Vitaminas lipossolfiveis em cosm&icos, Cosmet. Toiletr., 4, 30-33 (1992). (12) H. Shaefer and A. Zesch, Penetration of vitamin A acid into human skin, Acta Dermatol. Venerol., 55, 50-55 (1975). (13) M.J. Stiller et al., Topical 8% glycolic acid and 8% L-lactic acid creams for the treatment of photodamaged skin, Arch. Dermatol., 132, 631-636 (1996). (14) E.J. Van Scott and R.J. Yu, Alpha hydroxy acids: Therapeutic potentials, Can. J. Dermatol., 1, 108-112 (1989). (15) D. D. Munro, The relationship between percutaneous absorption and stratum corneum retention, Br. J. Dermatol., 81, 92-97 (Suppl. 4). (16) P.M. B. G. Maia Campos, G. Ricci, et al., "Avaliaggo da Estabilidade e Estudo, s Histopatol6gicos e Estereo16gicos de Formulag6es Dermocosm&icas Contendo Vitamina A e/ou Acido Glic61ico," in: Congresso Latino Americano e Ibmrico de Qu•micos Cosm&icos, 12, Sgo Paulo, 1995. Anais, Sgo Paulo, Associaggo Brasileira de Cosmetologia, pp. 46-70 (1995). (17) G. Maia Campos, G. M. C. Software Verscio 6.1, Ribeirgo Preto, Departamento de Estomatologia, Faculdade de Odontologia de Ribeirgo Preto, Universidade de Sgo Paulo. (18) J. Boehnlein, A. Sakr, J. L. Lichtin, and R. L. Bronaugh. Characterization of esterase and alcohol dehydrogenase activity in skin: Metabolism of retinyl palmirate to retinol (vitamin A) during percu- taneous absorption, Pharm. Res., 11, 1155-1159 (1994).