Identification and characterization of a library of microheterogeneous cyclohexadepsipeptides from the fungus Isaria

Sabareesh, V and Ranganayaki, RS and Raghothama, Srinivasarao and Bopanna, MP and Balaram, Hemalatha and Srinivasan, MC and Balaram, P (2007) Identification and characterization of a library of microheterogeneous cyclohexadepsipeptides from the fungus Isaria. In: Journal of Natural Products, 70 (5). pp. 715-729.

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Abstract

Ten new cyclic hexadepsipeptides, six isariins and four isaridins, from the fungus Isaria have been identified and characterized by high-performance liquid chromatography, coupled to tandem electrospray ionization mass spectrometry (LC-ESIMS/MS). The isariins possess a beta-hydroxy acid residue and five alpha-amino acids, while isaridins contain a beta-amino acid, an alpha-hydroxy acid, and four alpha-amino acids. One- and two-dimensional NMR spectroscopy confirmed the chemical identity of some of the isariin fractions. Mass spectral fragmentation patterns of [M + H](+) ions reveal clear diagnostic fragment ions for the isariins and isaridins. Previously described cyclic depsipeptides, isarfelins from Isaria felina (Guo, Y. X.; Liu, Q. H.; Ng, T. B.; Wang H. X. Peptides 2005, 26, 2384), are now reassigned as members of the isaridin family. Examination of isaridin sequences revealed significant similarities with cyclic hexadepsipeptides such as destruxins and roseotoxins. The structure of an isariin (isariin A) investigated by NMR spectroscopy indicated the presence of a hybrid alpha beta C-11 turn, formed by the beta-hydroxy acid and glycine residues and a (D)Leu-(L)Ala type II' beta-turn. Additionally, the inhibitory effect of isariins and an isaridin on the intra-erythrocytic growth of Plasmodium falciparum is presented.

Item Type:	Journal Article
Publication:	Journal of Natural Products
Publisher:	American Chemical Society
Additional Information:	Copy right of this article belongs to American Chemical Society.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	30 Apr 2010 05:09
Last Modified:	19 Sep 2010 06:01
URI:	http://eprints.iisc.ac.in/id/eprint/27401

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