Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2004
Publication Date: 12/30/2004
Citation: Krasnoff, S.B., Reategui, R., Wagenaar, M.M., Gloer, J.B., Gibson, D.M. 2004. Cicadapeptins i and ii: new aib-containing peptides from the entomopathogenic fungus cordyceps heteropoda. Journal of Natural Products. 68(1):50-55. Interpretive Summary: Fungi are known to be prolific producers of structurally diverse, biologically active compounds, especially those fungi that are found in close association with other organisms, such as insect pathogenic fungi. We detected antimicrobial activity in an extract of Cordyceps heteropoda, a fungus originally isolated from cicadas and deposited in the ARS Collection of Entomopathogenic Fungi. The known antifungal active compound myriocin was produced by the fungus, as well as a complex mixture of a novel peptide family having antibacterial and limited antifungal activity. Two major forms of the peptide family, named cicadepeptin I and II, were purified and characterized. This manuscript provides additional evidence that the insect pathogenic fungi have untapped potential as producers of novel, biologically active compounds.
Technical Abstract: Fermentation extracts of Cordyceps heteropoda (ARSEF# 1880), an entomopathogenic fungus isolated from an Australian cicada, yielded a known antifungal compound, myriocin, and a complex microheterogeneous family of novel non-ribosomal peptides containing two residues of alpha-aminoisobutyric acid (Aib). Structure elucidation of two major components of the peptide mixture, cicadapeptins I and II (1 and 2), was accomplished by amino acid analysis, and various MS, 1-D NMR, and 2-D NMR experiments. Both compounds are acylated at the N-terminus by n-decanoic acid,and amidated at the C-terminus by 1,2-diamino-4-methylpentane. The amino acid sequence of cicadapeptin I is N-terminus-Hyp-Hyp-Val-Aib-Gln-Aib-Leu-C-terminus. Ile substitutes for Leu in cicadapeptin II. To our knowledge, this is the first report from fungi of consecutive Hyp or Pro residues in a non-ribosomal linear peptide. ROESY data indicated that the cicadapeptins adopt a helical conformation. Cicadapeptins I and II displayed antibacterial activity and limited antifungal activity.