Isolation of ommochromes and 3-hydroxykynurenine from the tobacco hornworm,Manduca sexta

A complex of the two red pigments was prepared from epidermis of the fifth instar larvae of the black mutant of the tobacco hornworm according to the method generally available for ommochromes. The primary component, a brick-red pigment (II), was shown to be identical with synthetic l-dihydroxanthommatin by various physico-chemical tests. The other red pigment (I) was similar to pigment (II), except in the i.r. spectra in 1000–1150 cm⁻¹ region and is thought to be also an ommatin. A red pigment identical with pigment (I) was obtained during the chemical oxidation of 3-hydroxy-l-kynurenine. These same two pigments were found in the red epidermis underlying the black cuticle of larvae either allatectomized or neck-ligatured before the critical period for juvenile hormone action during the last larval molt. Also, they were found in the dorsal epidermis of wandering stage larvae. 3-Hydroxykynurenine, the immediate precursor of the ommochrome pigments, was found to accumulate in the epidermis before the synthesis of the ommochromes began.