Address of Corresponding Author

Skin Pharmacol Physiol 2004;17:274-282 (DOI: 10.1159/000081112)

  Key Words

• Co-drug
• Retinyl ascorbate
• Retinoic acid
• Keratin
• Pig ear skin
• Callus

  Abstract

Retinyl ascorbate (RA-AsA), an ester co-drug of vitamins A (RA) and C (AsA), is proposed as a topical antioxidant/cell division regulator for reducing UV-induced generation of free radicals and disrupted dermal cell growth. The efficacy of dermatological agents is influenced by their retention within the skin, which is increased by the interaction with skin components. Keratin is the major protein (~95%) in the skin, and this paper reports the binding of RA-AsA, RA, AsA, retinol, ascorbic acid palmitate and retinol palmitate to three tissues - human callus, pig ear skin and bovine horn keratin. Tissue samples were incubated with solutions of compounds and the uptake measured as the ratio of bound/free compound at equilibrium. Binding to keratin was assessed using delipidised tissue, and was much higher for the polar compounds, suggesting dipolar/H-bonding interaction. Binding strength was ranked as human > porcine > bovine, but there was no distinction for highly lipophilic compounds. The binding characteristic of native tissues was complicated by lipid content of the tissues. There seemed to be a dual effect. The binding of very lipophilic materials increased with lipid content, implying that a substantial amount is dissolved in the lipid matrix. For highly polar AsA, lipid content decreased the binding, suggesting that the lipid reduced the strong polar interactions with skin protein/keratin.

Copyright © 2004 S. Karger AG, Basel

  Author Contacts

C.M. Heard
Welsh School of Pharmacy
Cardiff University
Cardiff CF10 3XF (UK)
Tel./Fax +44 29 2087 5819, E-Mail heard1@cf.ac.uk

  Article Information

Received: March 1, 2004
Accepted after revision: July 29, 2004
Number of Print Pages : 9
Number of Figures : 5, Number of Tables : 2, Number of References : 45