Abstract: The effect of pyrolidine (L) or its copper-complex © on rabbit melanocytes tyrosinase were studied. The results revealed that (L) appeared to be a non competitive inhibitor of tyrosinase for about 30% , while ( C ) was an activator for about 4.6 fold. In addition, general effects of (L) or ( C ) on rabbit were studied via serum parameters. The obtained data afforded an additional biological effect of the tested compounds .