Antioxidant properties of new heterocycle nitrogen compounds

Abstract

The imbalance between intracellular reactive oxygen species (ROS) and the cells’ antioxidant defence systems is generally called oxidative stress and has been clearly associated with several pathologies. The search for new substances with the ability to act against excessive intracellular free radicals has been increasing in the last few years, with the objective of developing new drugs with pharmacological potential. In this study we further evaluated the free radicals’ scavenging capacity of new nitrogen compounds (FMA762 and FMA796), from organic synthesis. The compounds proved to be non toxic for L929 cells and showed high antiradical activities (IC50 values for DPPH discoloration of 3.4μM and 3.7μM for FMA762 and FMA796, respectively) superior to that obtained for the traditional antioxidants Trolox and α-Tocopherol. The partition coefficients obtained are indicative of the compounds liposoluble profile, which enables them to permeate cells and act intracellularly. Indeed, a high protective role on ascorbate/iron-induced intracellular ROS formation could be observed in PC12 cells, at concentrations around 3 - 4μM, as monitored by flow cytometry, using the fluorescent probe H2DCF-DA. These compounds are also effective in protecting cells from lipid peroxidation (TBARS assay), induced by the same oxidant pair. On both tests, the protection levels observed are higher than the ones presented by traditional antioxidant Trolox and similar to α-Tocopherol. We also investigated the compounds protective role on some apoptotic features. Both of them were found to decrease the levels of staurosporine-induced DNA fragmentation, assessed by the TUNEL assay, at the above mentioned IC50 concentrations. However, no effects were observed on the reversal of caspase-3 activation, even for concentrations of about 100 μM. This fact may be indicative of a non involvement of these compounds in the intracellular cascade of events conducting to cell death but rather a direct effect on ROS scavenging. The data obtained with these nitrogen heterocycle structures clearly indicate that the presence of three OH groups improves their radical scavenging properties making them interesting as potent antioxidants. However when compared with similar previously tested compounds (1) they failed in preventing the caspase signalling pathway involved in cell death.