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.
Keywords: electron paramagnetic resonance (EPR); methotrexate; photopharmacology; photoswitchable; phototrexate; scavenger.