Antiradical capacity of ommochromes.

Ommochromes are colored substances that apparently function as biological signals among arthropods and insects. These substances may prevent oxidative stress by scavenging free radicals. Two principal mechanisms exist for scavenging free radicals: the electron transfer and hydrogen atom transfer. In this investigation, a theoretical study of the antiradical capacity of five ommochromes was performed within the density functional theory framework. Vertical ionization energy and vertical electron affinity were used to study the electron transfer mechanism between ommochromes and four free radicals: CH3O•, NO2•, HO•, and HOO•. For the hydrogen transfer mechanism, dissociation energy (D0) and Gibbs free energy were calculated, taking into account hydrogen atoms at different positions in the ommochromes. Both mechanisms are thermodynamically possible. The best antiradical is ommatin D. The UV/VIS spectra for ommochromes were obtained with ommatin D registering as the ommochrome with the greatest λmax value. In summary, ommatin D is the best antiradical and also the redder molecule. These results are important and may help to elucidate the function of these molecules in the animal kingdom. Graphical abstract Ommochromes are red and yellow substances present in arthropods and insects. According with computational chemistry, these substances present the capacity of prevent oxidative stress since they scavenge free radicals. These results may help to elucidate the function of these molecules in the animal Kingdom.