ODOR INHIBITION 139 Table 1 Deposition of Zn-GLY Onto Stratum Corneum •mol Zn-GLY/g stratum corneum [Zn-GLY] Trial 1 Trial 2 Average 0.01 mM 0.3 0.3 0.3 50.0 mM 82.0 108.0 95.0 This study indicates that the formation of Zn-GLY is proceeding in the solution and that the Zn from Zn-GLY binds appreciably to hair from solutions where Zn-GLY concen- tration exceeds approximately 1 raM. When Zn-GLY expressed as [Zn] exceeds about 10 mM in solution, binding is about 50 I.•mol/g. SUBSTANTIVITY OF Zn-GLY TO SKIN Table 1 shows that stratum corneum exposed to 50 mM Zn-GLY binds approximately 90 I.•mol Zn/g. Exposure to 0.01 mM Zn-GLY produces binding of less than 1 I.•mol/g. 6O 50 lO o. oo mM Zn • 0.85 mM Zn 3.4 mM Zn 10 20 30 40 50 60 time, min. Figure 4. Beta-G reactions in the presence of hair treated with Zn-GLY. 7O

140 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Interestingly, the binding to stratum corneum is about the same as the binding to hair apparently, the keratins of both are similar with respect to chemical features recognized during zinc glycinate binding. INHIBITORY ACTIVITY OF RESIDUES The above studies show that exposure to a solution of 100 mM Zn-GLY is required to produce a residue of approximately 100 }xmol/g of Zn on hair or skin. This concentra- tion of Zn-GLY is probably attainable in a cosmetic preparation. We wanted to deter- mine whether the residue left by such solutions was an effective inhibitor of the enzymes responsible for axillary odor generation. Figure 4 shows the time courses for beta-G reactions in the presence of the hair samples that had been exposed to various concentrations of Zn-GLY. Figure 5 is a similar plot for AS reactions. In both, it is obvious that the inhibition of the reactions is dependent on the concentration of bound Zn. Replotted as enzyme activity vs [Zn] (Figure 6), the data show that hair exposed to Zn-GLY at less than 15 mM inhibits AS by more than 90%, and that hair exposed to less than 10 mM Zn-GLY inhibits beta-G almost completely. 50 4O 30 20 10 0.00 mM Zn III mM Zn' 13.3 rnM Zn ß I ' I ' I ' I ' I ' I 0 10 20 30 40 50 60 time, min. Figure 5. Aryl sulfatase reactions in the presence of hair treated with Zn-GLY. 7O