Comparative EPR Study on the Scavenging Effect of Methotrexate with the Isomers of Its Photoswitchable Derivative

The scavenging effect of the antimetabolite dihydrofolate reductase inhibitor methotrexate (MTX) and the isomers of its photoswitchable derivate, cis- and trans-phototrexate (PHX), have been compared by ESR spectroscopy, with the application of a cyclic hydroxylamine spin probe. The results showed the most pronounced scavenging effect in the presence of trans-phototrexate (trans-PHX). At a low concentration (100 µM) cis-PHX also showed a greater scavenging effect than the parent molecule MTX. Direct antioxidant properties of the investigated molecules were measured by ABTS scavenging assay, which showed no significant difference between trans-PHX and cis-PHX, but both of the isomers of PHX showed a higher antioxidant capacity than MTX. These findings imply that trans-PHX may have more pronounced anti-inflammatory and tissue-protective effects than MTX, despite the lack of its cytotoxic, antineoplastic effect.