Identification of catecholamine β-glucosides in the hemolymph of the tobacco hornworm, Manduca sexta (L.), during development

Abstract

Catecholamine conjugates were isolated from the hemolymph of larval, pupal and adult stages of the tobacco hornworm, Manduca sexta, and their identities were determined by synthesis from 14C-labeled precursors, HPLC analysis, 1H-NMR and FAB-mass spectrometry, and GLC analysis of the sugar moieties. β-Glucosides of N-acetyldopamine (NADA) and N-β-alanyldopamine (NBAD) were the primary conjugates identified and their relative abundance depended on the stage of development. NADA glucosides were the predominant conjugates in hemolymph of pharate or newly ecdysed fifth stadium larvae with 86% as the 3- O-glucoside and 14% as the 4- O-glucoside. Low concentrations of dopamine (DA) 3- O-glucoside and NBAD 3- O-glucoside also were found. In pharate or newly ecdysed pupal hemolymph, NBAD 3-O-glucoside was the major conjugate (98%) along with small amounts of NBAD 4- O-glucoside, DA 3- O-glucoside and NADA 3- O-glucoside. In hemolymph of pharate or newly ecdysed adults, NADA 4- O-glucoside (67%) was more abundant than NADA 3- O-glucoside. Only traces of NBAD 3- O-glucoside were found. Therefore, a preponderance of catecholamine 3- O-glucoside occurred in larval and pupal hemolymph as storage precursors for cuticle sclerotization agents, whereas the 4- O-glucoside of NADA predominated in adult hemolymph. The role of catecholamine glucosides in hemolymph in relation to cuticle sclerotization is discussed.