Kynuramine compounds, such as AFMK and its de-formylated form (AMK), are molecules produced during tryptamine degradation. The redox activity and antioxidative properties of AFMK have been evaluated in several experimental models. Unlike antioxidants, such as vitamin C and vitamin E, AMFK can donate more than one electron
[41][7]. In particular, Rosen and colleagues showed that AFMK can donate four electrons leading to the production of indolinone derivatives, such as Z-, E- isomers of N-(1-formyl-5-methoxy-3oxo-2,3-dihydro-1H-indol-2-ylidenemethyl)-acetamide and N-(1-formyl-2-hydroxy-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylmethyl)-acetamide
[42][8]. However, AFMK was reported to be a less effective free radical scavenger than AMK and melatonin
[43,44,45,46][9][10][11][12]. The antioxidant properties of AFMK were demonstrated also in biological models. In particular, Tan and colleagues showed that the addition of AFMK to calf thymus DNA in presence of a mixture of prooxidant agents strongly reduced in a dose-dependent way the levels of 8-OH-dG (an indicator of DNA damage)
[41][7]. Moreover, in rat liver homogenates incubated with H
2O
2 and Fe
2+, 100 µM AFMK inhibited lipid peroxidation (LPO) and improved cell viability, although Fe
2+ chelation was not observed
[41][7].