*Introduction to Schiff Base DOI: http://dx.doi.org/10.5772/intechopen.108289*

simple iron chelators and requires oxygen. This is in agreement with the experimental observations and the reaction is reversible, as reported by them. In the enzyme, there must be a hydrophobic pocket or patch with which the aromatic system interacts, which indicates that methylation on the aromatic ring of 2-formyl pyridine thiosemicarbazone renders this compound more active. It proves that 1-formyl isoquinoline thiosemicarbazone inhibits more strongly ribonucleotide reductase than 2-formyl pyridine thiosemicarbazone. It was identified by Agrawal et al. [75] while searching for an optimum bulk for the aromatic fragment, the most active compound found in the quinoline series was 2-formyl-4-(3-amino) phenyl pyridine thiosemicarbazone instead 1-formyl-5-aminoisoquinoline thiosemicarbazone (**Table 1**) [75–77].
