ommochrome
Ommochrome (or filtering pigment) refers to several biological pigments that occur in the eyes of crustaceans and insects. The eye color is determined by the ommochromes. Ommochromes are also found in the chromatophores of cephalopods, and in spiders.{{Cite journal
| last1 = Oxford | first1 = G. S.
| last2 = Gillespie | first2 = R. G.
| doi = 10.1146/annurev.ento.43.1.619
| title = Evolution and Ecology of Spider Coloration
| journal = Annual Review of Entomology
| volume = 43
| pages = 619–643
| year = 1998
| pmid = 15012400
| pmc =
| s2cid = 6963733
}}
Ommochromes are metabolites of tryptophan, via kynurenine and 3-hydroxykynurenine. They are responsible for a wide variety of colors, ranging from yellow over red and brown to black. Lighter colors tend to be generated by ommatins, while mixtures of ommatin and ommins are responsible for darker colors.{{Cite journal
| last1 = Casas | first1 = J. R. M.
| last2 = Casas | first2 = M.
| doi = 10.1098/rstb.2008.0212
| title = The multiple disguises of spiders: Web colour and decorations, body colour and movement
| journal = Philosophical Transactions of the Royal Society B: Biological Sciences
| volume = 364
| issue = 1516
| pages = 471–480
| year = 2009
| pmid = 18990672
| pmc =2674075
}}
In spiders, ommochromes are usually deposited as pigment granules within the cells of the hypodermis, immediately beneath the cuticle.
A study on various insects showed that ommochromes in their eyes have high antioxidant activity. The ommochromes were found to have the ability to suppress the Maillard reaction.{{Cite journal |last1=Dontsov |first1=A. E. |last2=Yakovleva |first2=M. A. |last3=Ostrovsky |first3=M. A. |date=2021 |title=Ommochromes of Insect Compound Eyes: Antiglycation Action |url=https://link.springer.com/10.1007/s11055-021-01141-y |journal=Neuroscience and Behavioral Physiology |language=en |volume=51 |issue=6 |pages=837–841 |doi=10.1007/s11055-021-01141-y |s2cid=254862128 |issn=0097-0549}}
Anti-radical capacity
Due to the chemical properties exhibited in the chromophoric groups of ommochromes, these substances have been proven to be satisfactory in functioning as free radicals.{{Cite journal |last=Figon |first=Florent |last2=Casas |first2=Jérôme |date=2018 |title=Ommochromes in invertebrates: biochemistry and cell biology |url=https://onlinelibrary.wiley.com/doi/10.1111/brv.12441 |journal=Biological Reviews |language=en |volume=94 |issue=1 |pages=156–183 |doi=10.1111/brv.12441 |issn=1464-7931|doi-access=free }} In testing the anti-radical capacity of ommochromes, their electron transfer and hydrogen transfer mechanisms were examined, and it was shown that ommochromes possesses the ability to prevent oxidative stress by scavenging free radicals. Results regarding this study were quantified using a full-electron donor acceptor map (FEDAM) which allowed for optimal discretion in evaluating anti-radical capacity. {{Cite journal |last=Romero |first=Yanet |last2=Martínez |first2=Ana |date=2015 |title=Antiradical capacity of ommochromes |url=http://link.springer.com/10.1007/s00894-015-2773-3 |journal=Journal of Molecular Modeling |language=en |volume=21 |issue=8 |doi=10.1007/s00894-015-2773-3 |issn=1610-2940}}