Background: Uric acid is the end product of purine metabolism in humans and its
increased level in serum leads to hyperuricemia. Among the different regulatory factors to control
the level of uric acid in humans, xanthine oxidase (XO) is a well-established pharmacological target,
as it is directly involved in uric acid production.
Methods: The aim of the study was to present a systematic approach to analyze the xanthine
oxidase inhibition studies from in vitro leading to in vivo.
Results: Initially, dinuclear cyclam complex 1 was evaluated for in-vitro XO inhibitory activity
using a spectrophotometric assay. Significant results were obtained in XO inhibition assay (IC50 =
3.70 ± 0.07 μM), in comparison to the standard drug, allopurinol (IC50 = 2.00 ± 0.01 μM). Complex
1 showed a non-competitive type of inhibition in kinetic studies. Complex 1 was also found to be
non-cytotoxic in MTT assay, as it did not affect the viability of 3T3-cell line. Based on these
results, compound 1 was further evaluated for the in-vivo xanthine oxidase inhibitory activity. An
in-vivo model was used to evaluate the XO inhibitory activity in plasma samples of male Wistar
rats. Complex 1 showed a significant inhibition of xanthine oxidase activity (50%), in comparison
to the standard inhibitor allopurinol (100%). Therefore, non-cytotoxic compound 1 could be
considered as an anti-hyperurecemic lead for further studies.
Conclusion: Our studies concluded that complex 1 is a non-cytotoxic inhibitor that decreases the
activity of XO in a non-competitive manner. It can serve as a potential anti-hyperurecemic lead
after further pre-clinical and clinical studies.