Biodistribution (as determined by the radiolabelled equivalent) of a gold(III) bis(pyrrolide‐imine) Schiff base complex: a potential chemotherapeutic

The biodistribution of an N 2 N 2 ′ tetradentate gold(III) chelate, which is known to be cytotoxic towards a range of human cancer cell lines, was determined by a radiolabelled equivalent of the compound. The 198 Au‐labelled gold(III) chelate of a bis(pyrrolide‐imine) Schiff base ligand with a three‐carbon di(azomethine) linkage was successfully synthesised with a high radiochemical yield of 73% and radiochemical purity of >95%. The high energy γ‐ray emitted by the 198 Au nucleus was used to follow the biodistribution of the compound in vivo in six male Sprague Dawley rats on a gamma camera. The log P o/w value of the nat Au analogue, −1.92(2), showed that the compound is hydrophilic and therefore likely to largely remain in the blood pool. This was confirmed by the biodistribution study, which showed 21% of the injected dose (ID) remained in the blood pool 4.5 h after injection. This decreased to 10.8% over a 24‐h period. The activity measured in the lungs, 1.48%ID/g, remained relatively constant over a 24‐h period suggesting that the complex had accumulated in the lungs in the form of particulates, and could not be cleared by the test subjects. The t ½ for the heart and lungs was greater than 24 h. Excretion of the test compound is seemingly via the kidneys, but is slow with approximately 30% of the ID excreted within 24 h.