Two Isomeric α and β Aspartyl Dodecapeptides and Their Cyclic Amino Succinyl Analogue From the Australian Green Tree Frog Litoria gilleni

Abstract

Three related peptides, caeridins 1.1-1.3, have been isolated from the green tree frog Litoria gilleni. Caeridins 1.1 and 1.2 are dodecapeptides differing only in having α and β Asp at residue 4 [viz. Gly Leu Leu Asp Gly Leu Leu Gly Thr Leu Gly Leu (NH₂)]. Caeridin 1.3 is the corresponding cyclic amino succinyl derivative derived formally by cyclization of Asp(4) and Gly (5). Hydrolysis of caeridin 1.3 yields caeridin 1.1 and 1.2 in the ratio 3:1. This constitutes a rare case of the isolation of three such related peptides from a natural system.