Physicochemical Study of the Redox State Reversibility of Ommochromes in Insect Eyes

The aim of this study was to thoroughly investigate the physicochemical properties, including changes in antioxidant and biochemical properties, of ommochromes from insect eyes undergoing biological reversibility during their redox reactions. The biological function of ommochromes in the complex ocular structures of insects and other invertebrates may be related to their antioxidant properties due to reversible redox processes. In this study, we examined the reversible redox processes of ommochromes isolated from the eyes of the black soldier fly (Hermetia illucens) and the eyes of the tobacco hawk moth (Manduca sexta). Reversible changes in the spectral and fluorescent properties, as well as the composition of ommochromes during redox reactions, were investigated using IR spectroscopy, CARS spectroscopy, and fluorescence spectroscopy. Nearly complete reduction of oxidized ommochromes from fly eye was demonstrated using HPLC chromatography and mass spectrometry. Changes in the redox properties of ommochromes lead to structural changes that affect their ability to exhibit antioxidant properties—reduced ommochromes exhibited significantly higher antioxidant activity compared to oxidized ommochromes. The reversibility of redox transitions of ommochromes is important for regulating the spectral sensitivity and antioxidant status of the invertebrate eye.