Homocatechol in an Insect Cuticle

Abstract

DURING the course of an investigation into the hardening of the cuticle of the desert locust Schistocerca gregaria, 4-methyl-catechol, a substance not previously recorded from insect cuticles, was identified chromatographically in abundant amounts from fully hardened cuticles after acid hydrolysis as well as after alkaline hydrolysis under reducing conditions. This substance, although absent from the soft cuticles newly exposed on moulting, is readily detected after they have been artificially tanned with B-(3 : 4-dihydroxyphenyl)acetic acid, indicating decarboxylation of the tanning agent. If B-(3 : 4-dihydroxyphenyl)propionic acid is used in place of the acetic derivative to tan the cuticles a compound with similar properties is recovered from the cuticles. This latter compound, which is also present in aqueous extracts of naturally tanned cuticles, has an R _F value, in benzene/acetic acid/water, slightly higher than that of 4-methyl-catechol. It can only be presumed to be 4-ethyl-catechol similarly formed by decarboxylation. B-(3 : 4-dihydroxyphenyl)acetic acid and 4-methyl-catechol have also been detected after tanning cuticles with B-(3 : 4-dihydroxyphenyl)-propionic acid, and the formation of these compounds seems a clear indication that degradation of ortho-diphenolic compounds in an insect cuticle¹ to compounds having shorter side-chains may be accompanied by decarboxylation. Hackman and Todd² have already demonstrated the decarboxylation in vitro of 3 : 4-dihydroxybenzoic acid in the presence of a plant phenolase.