early study on the structural modifications of clioquinol, more 8-hydroxyquinoline-derived Mannichbases were synthesized and examined for growth-inhibitory effect. Taken Mannich base 1 as our lead compound, upon replacement of either sulfonyl group with methylene group or piperazine ring with ethylenediamine group resulted in an appreciable increase in potency. On the other hand, as 8-hydroxyquinoline